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GENERAL SCIENCE for Competitive Exams FOR MORE JOIN ~ MISSION SSC / BANKING / UPSC

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CONTENTS PHYSICS 1.

Mechanics

1 - 11

Properties of matter

12 - 16

Heat

17 - 22

Sound

23 - 25

Optics

26 - 31

Electricity

32 - 38

Magnetism

39 - 42

Semiconductor Electronics

43 - 48

CHEMISTRY 1.

Nature of Matter

49 - 52

Structure of Atom

53 - 56

Classification of Elements and Periodicity in Properties

57 - 61

Acids, Bases and Salts

62 - 66

Metals & Non-Metals

67 - 72

Environmental Pollution

73 - 78

General Concepts of Chemistry

79 - 83

Some Important Man-Made Materials

84 - 88

General Organic Chemistry

89 - 92

BIOLOGY 1.

Diversity in Living Organisms

93 - 99

Cells and Tissues

100 - 104

Plant Physiology

105 - 110

Human Physiology

111 - 117

Genetics and Evolution

118 - 122

Biology in Human Welfare

123 - 126

Diseases and their defence mechanism

127 - 130

Ecology & Environment Awareness

131 - 136

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Mechanics

Physical Quantities Those quantities which can describe the laws of physics and possible to measure are called physical quantities. The physical quantities which do not depend upon other physical quantities are called fundamental quantities. In Standard International (S.I.) system the fundamental quantities are mass, length, time, temperature, luminous intensity, electric current and amount of substance. The physical quantities which depend on fundamental quantities are called derived quantities e.g. speed, acceleration, force, etc.

Units

The unit of a physical quantity is the reference standard used to measure it. Types of Units 1. Fundamental Units The units defined for the fundamental quantities are called fundamental or base units. Fundamental Mass (M) Physical quantity

Length (L)

Time (T)

kilogram (kg)

metre (m)

second (s)

Fundamental unit

Temperature (q or K) kelvin (K)

Electric current (I)

Luminous intensity

Amount of substance

ampere (A)

Candela (Cd)

mole (mol)

Derived Units The units defined for the derived quantities are called derived units. e.g. unit of speed or velocity (metre per second), acceleration (metre per second2) etc.

Dimensions

The limit of a derived quantity in terms of necessary basic units is called dimensional formula and the raised powers on the basic units are dimensions. S. No.

Physical Quantity

Formula

Dimensional Formula

SI Unit

Length × breadth Length × breadth × height Mass/volume Distance/time Mass × velocity

L × L = L2 = M0L2T0

m2 m3 kg/m3 m/s kg m/s

1. 2. 3. 4. 5.

Area Volume Density Speed or velocity Linear momentum

Acceleration

7. 8. 9. 10.

Force Impulse Pressure Work

11.

Energy

12. 13.

Power Moment of force

Change in velocity time Mass × acceleration Force × time Force/area Force × displacement 1 mgh or mv2 2 Work/time Force × distance

14.

Universal gravitational

15. 16.

constant Surface tension Surface energy

Force/length Energy/area

Fr 2 m1m2

L × L × L = L3 = M0L3T0 M/L3 = ML–3T0 L/T = M0LT–1 MLT–1 LT -1 T–2 = M0LT T MLT–2 MLT–2 × T = MLT–1 MLT–2/L2 = ML–1T–2 MLT–2 × L = ML2T–2

newton (N) Ns N/m2 joule (J)

ML2T–2 ML2T–2/T = ML2T–3 MLT–2 × L = ML2T–2

J watt (W) N-m

MLT-2 ´ L2

M2 –1 = M L3T–2 MLT–2/L = ML0T–2 ML2T–2/L2 = ML0T–2

m/s2

Nm2/kg2 N/m J/m2

C-2

MLT–2/L2 = ML–1T–2

GENERAL SCIENCE newton (N) N/m2

Change in configuratrion Initial configuration

M0L0T0 (dimensionless)

No unit

Modulus of elasticity Radius of gyration Moment of inertia Angle

Stress/strain Length Mass × (distance)2 Length/radius

ML–1T–2 M0LT 0 ML2T0 M0L0T 0

N/m2 m kg m2 radian

Angular velocity

Angular displacement Time

1 = M 0 L0 T -1 T

rad/s

M 0 L0 T -1 = M0 L0 T -2 T ML2T–1

rad/s2 kg m2/s

ML2T–2

N-m

M0LT 0

17. 18.

Thrust, Tension Stress

Force Force/area

19.

Strain

20. 21. 22. 23. 24.

MLT–2

25.

Angular acceleration

26.

Angular momentum

27.

Torque

28.

Wavelength

Angular velocity Time Moment of inertia × angular velocity Moment of inertia × angular acceleration Length

29.

Frequency

No. of vibrations/s

1 = M 0 L0 T -1 T

s –1

30.

Velocity gradient

Velocity/distance

LT -1 = M 0 L0 T -1 L

s –1

Rounding Off

Speed and Velocity

Rules of Rounding off uncertain Digits (a) The preceding digit is raised by 1 if the uncertain digit to be dropped is more than 5 and is left unchanged if the latter is less than 5. Example : x = 5.686 is rounded off to 5.69 (as 6 > 5) x = 3.462 is rounded off to 3.46 (as 2 < 5) (b) If the uncertain digit to be dropped is 5, the preceeding digit raised by 1 if it is odd and is left unchanged if it is even digit. Example : 7.735 is rounded off to three significant figures becomes 7.74 as preceeding digit is odd. 7.745 is rounded off to 7.74 as preceeding digit is even. Path Length or Distance The length of the actual path between initial and final positions of a particle in a given interval of time is called distance covered by the particle. Displacement The shortest distance from the initial position to the final position of the particle is called displacement.

Speed =

Distance travelled Time taken

Average speed V =

Instantaneous speed = Velocity =

Displacement

Distance

It has single value between two points.

It may have more than one value between two points.

May be +ive, –ive or zero.

It is always > 0 (+ive)

It can decrease with time.

It can never decrease with time.

It is a vector quantity It is a scalar quantity.

Lim

Dt ® 0

Dx dx = Dt dt

Displacement Time interval

Average velocity =

Displacement Total time taken ®

Dx d x = Instantaneous velocity V = Dt Lt ® 0 Dt dt

Acceleration ® ®

Acceleration ( a ) =

Comparative Study of Displacement and Distance S. No.

Total distance travelled Total time taken

Change in velocity = v '- v Time interval t '- t

Average acceleration = ®

a inst

Total change in velocity Total time taken ®

Dv d v = Lim = dt Dt ® 0 Dt

Kinematic Equations for Uniformly Accelerated Motion Motion under uniform acceleration is described by the following equations. v = u + at ; s = ut +

1 2 at and v2 = u2 + 2as 2

FOR MORE JOIN ~ MISSION SSC / BANKING / UPSC Mechanics Distance Travelled in nth Second of Uniformly Accelerated Motion S

n th

So,

= Sn – Sn–1 = (u n +

1 1 a n2) – [u(n–1) + a(n–1)2 2 2

a = u + (2n - 1) 2

nth

Relative Velocity ®

If v A and vB be the respective velocities of object A and B then relative velocity of A w.r.t. B is ®

v AB = v A – vB

Similarly, relative velocity of B w.r.t. A is ®

v BA = v B – v A

Scalars and Vectors The physical quantities which require only magnitude to express, are called scalar quantities. Ex. Mass, distance, time, speed, volume, density, pressure, work, energy, power, charge, electric current, temperature, potential, specific heat, frequency, etc. Certain physicsl quantities have both magnitude and direction, they are called vector quantities. Ex. Displacement, velocity, acceleration, force, momentum, impulse, electric field, magnetic field, current density, etc.

Cross Product or Vector Product of Two Vectors ®

Cross product of A and B inclined to each other at an angle q is defined as : ®

A B sin q nˆ = A ´ B ®

nˆ ^ to plane of A and B .

The vector product of unit orthogonal vectors iˆ, ˆj and kˆ have the following relations in the right-handed coordinate system. (a)

iˆ ´ ˆj = kˆ ˆj ´ kˆ = iˆ

ˆj ´ iˆ = - kˆ kˆ ´ ˆj = -iˆ

kˆ ´ iˆ = ˆj

iˆ ´ kˆ = - ˆj

(b) iˆ ´ iˆ = 0

ˆj ´ ˆj = 0 ®

If q is the angle between A and B . ®

Then A (B cos q) = A • B , A and B are the magnitudes of ®

Inertia Inertia is the property of a body due to which it opposes the change in its state. Inertia of a body is measured by mass of the body. It is directly proportional to the mass of the body i.e., Inertia µ mass. Momentum r The linear momentum of a body ( p) is defined as the product of r r r the mass of the body (m) and its velocity (v ) . i.e., p = mv . Relation between momentum and kinetic energy : Consider a body of mass m moving with velocity v. Linear momentum of the body, p = mv. KE of a particle can be expressed as p2 E= and p = 2mE 2m 2nd law : The rate of change of momentum of a body is directly proportional to the unbalanced external force applied on it. r r dpr r dp i.e., F µ or, F = k dt dt r r or F = ma Impulse : If a large force acts on a body or particle for a smaller time, then impulse = product of force and time. r Impulse = F Dt 3rd law : According to this law, every action has equal and opposite reaction. Action and reaction act on two different bodies and they are simultaneous. There can be no reaction without action.

Law of Conservation of Linear Momentum

If the total external force acting on a system is equal to zero, then the final value of the total momentum of the system is equal to the initial value of the total momentum of the system. r r r p = constant or p f = pi Motion in a Lift Let a man of weight W = Mg be standing in a lift. Case (a) : If the lift is moving with constant velocity v upwards or downwards.

a=0

kˆ ´ kˆ = 0

Scalar Product or Dot Product of Two Vectors ®

C-3

vectors A and B .

iˆ • ˆj = 0, ˆj • kˆ = 0, kˆ • iˆ = 0 iˆ • iˆ = 1, ˆj • ˆj = 1, kˆ • kˆ = 1

Newton's Laws of Motion 1st law : Every body continues to be in its state of rest or of uniform motion in a straight line unless compelled by an external force to change its state. This fundamental property of the body is called inertia. This law is known as Newton’s first law of motion or law of inertia.

In this case there is no accelerated motion hence no pseudo force experienced by observer 'O' inside the lift. So apparent weight, W' = actual weight W Case (b) : If the lift is accelerated i.e., a = constant and in upward direction. Then net forces acting on the man are (i) weight W = Mg downward (ii) fictitious force F0 = Ma downward. So apparent weight, W' = W + F0 = Mg + Ma = M (g + a)

W¢ = Mg

W¢ = M(g + a)

C-4

GENERAL SCIENCE

Case (c) : If the lift is accelerated downward with acceleration a < g :

a MB. t = Ia Two forces equal in magnitude but opposite in direction form a couple which tends to rotate the body. If B is upthrust of air on balloon, and a is downward acceleration, then Mg – B = Ma

V rair g Mg - B =gM V rCO2

Vrair æ = ç1 ç VrCO 2 è

n esc = 2gR , where R is radius of the planet.

Hence escape velocity is independent of m. 47. (b) g ' = g - w2 R cos 2 l . 50. (b) The orbital speed of satellite is independent of mass of satellite, so the ball will behave as a satellite and will continue to move with the same speed in the original orbit. 51. (b) Since orbital velocity of satellite is GM , it does not depend upon the mass of the r satellite. Therefore, both satellites will move with same speed. 52. (b) Due to inertia of motion it will move tangentially to the original orbit with same velocity. v0 =

v0 = gR i.e., v0 independent of mass of the satellite. 54. (c) From Kepler's 2nd law – The straight line joining the sun and the planet sweeps out equal areas in equal 53. (a)

dA = const; area swept) dt Areal velocity of the satellite is given by

time intervals (

dA 1 2 L = wr = const. = dt 2 2m where w = angular velocity of the satellite L = mvr = mwr2 = const, showing that Kepler's 2nd law is a consequence of the conservation of angular momentum. 55. (c) The weightlessness inside a satellite is due to the fact that the surface does not exert any force on the body and hence its apparent weight is zero. 56. (b) At the centre of earth, weight is zero as g = 0 at center of earth. weight = mg = 0 and Potential energy = mgh But mass ¹ 0 as mass is the quantity of matter.

ö æ 28.8 ö 2 ÷ ´ 9.8 m / s ÷÷ g = ç1 44 ø è ø

= 3.4 m/s2

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C-12

GENERAL SCIENCE

Properties of Matter

Elasticity and Plasticity The property of the body to regain its original configuration (length, or shape) when the deforming forces are removed is called elasticity. On the other hand, if the body does not have any tendency to regain its original configuration on removal of deforming force the body is called plastic body and this property is called plasticity. Perfectly elastic body : A body which regains its original configuration immediately and completely after the removal of deforming force from it, is called perfectly elastic body. Quartz and phosphor bronze, are closed to perfectly plastic body. Perfectly plastic body : A body which does not regain its original configuration at all on the removal of deforming force, however small the deforming force may be is called perfectly plastic body. Putty and mud are closed to perfectly plastic body.

Stress The internal restoring force acting per unit area of a body is called stress. i.e., Stress = Restoring force/ Area

(ii)

Brittle materials : The materials which have very small range of plastic extension are called brittle materials. These materials break as soon as the stress is increased beyond the elastic limit. e.g., glass, ceramics, cast iron, etc. (iii) Elastomers : The materials which can be stretched to large values of strain are called elastomers. e.g., rubber, elastic tissue of aorta, etc. Young’s modulus of elasticity (Y) : It is defined as the ratio of normal stress to the longitudinal strain within the elastic limit. Thus, Y = or,

Normal stress Longitudinal strain

F / p r 2 MgL0 = Dl / L0 pr 2 Dl

Thermal Stress

When a rod is rigidly fixed at its two ends and its temperature is changed, then a thermal stress is set up in the rod. And the corresponding strain developed is called thermal strain. F Force = = Y a Dq. A Area of cross section

Strain

Thermal stress =

The ratio of change in configuration to the original configuration is called strain. Change in configuration i.e., Strain = Original configuration Strain being the ratio of two like quantities has no units and dimensions.

where a = coefficient of linear expansion of the rod Dq = change in temperature.

Elastic Limit Elastic limit is the upper limit of deforming force up to which, if deforming force is removed, the body regains its original form completely and beyond which, if deforming force is increased, the body loses its property of elasticity and gets permanently deformed.

Hooke’s law It states that within the elastic limit stress is directly proportional to strain. i.e., Stress µ strain or Stress = E × strain Stress = E = constant Strain Here E is the coefficient of proportionality and is called modulus of elasticity or coefficient of elasticity of a body.

Materials-Ductile, Brittle and Elastomers (i)

Ductile materials : The materials which have large range of plastic extension are called ductile materials. They can be drawn into thin wires, e.g., copper, silver, aluminium, iron, etc.

Fluids Fluids are the substances that can flow. Therefore liquids and gases both are fluids. The study of fluids at rest is called fluid statics or hydrostatics and the study of fluids in motion is called fluid dynamics or hydrodynamics. Both combined are called fluid mechanics. Density (r) Mass per unit volume is defined as density. So density at a point of a fluid is represented as Dm dm r = lim = dV DV ®0 DV where m is the mass and v is the volume of the fluid. Relative Density It is defined as the ratio of the density of the given fluid to the density of pure water at 4°C. Relative density (R.D). =

Density of given liquid Density of pure water at 4°C

The density of water is maximum at 4°C and is equal to 1.0 × 103 kgm–3

Pressure If a uniform force is exerted normal to an area (A), then average pressure (pav) is defined as the normal force (F) per unit area. i.e., pav =

F A

Properties of Matter DF In limiting sense, pressure p = lim . Pressure is a scalar DA D A ® 0 quantity. SI unit : pascal (Pa), 1 Pa = 1 N/m2 Practical units: atmospheric pressure (atm), bar and torr 1 atm = 1.01325 × 105Pa = 1.01325 bar = 760 torr = 760mm of Hg column pressure.

Pascal's Law of Transmission of Fluid Pressure Pascal's law is stated in following ways : • The pressure in a fluid at rest is same at all the points if gravity is ignored. • A liquid exerts equal pressures in all directions. • If the pressure in an enclosed fluid is changed at a particular point, the change is transmitted to every point of the fluid and to the walls of the container without being diminished in magnitude. Applications of Pascal's law : Hydraulic machines, lifts, presses and brakes, are based on the Pascal's law.

Atmospheric Pressure Force exerted by air column on unit cross-section area of sea level is called atmospheric pressure (P0) F = 101.3 kN / m2 A Barometer is used to measure atmospheric pressure which was discovered by Torricelli. Atmospheric pressure varies from place to place and at a particular place from time to time. P0 =

Buoyancy and Archimed Principle If a body is partially or wholly immersed in a fluid, it experiences an upward force due to the fluid surrounding it. This phenomenon of force exerted by fluid on the body is called buoyancy and force is called buoyant force or upthrust. Archimedes’ Principle : It states that the buoyant force on a body that is partially or totally immersed in a fluid equal to the weight of the fluid displaced by it.

Bernoulli’s Principle When incompressible, non-viscous, irrotational liquid i.e., ideal liquid flow from one position to other in streamline path then in its path at every point, the sum of pressure energy, kinetic energy and potential energy per unit volume remains constant. 1 2 1 2 i.e., P1 + rgh1 + r v1 = P2 + rgh2 + rv2 2 2 2 rv \ P + rgh + = constant 2

Viscosity

The property of a fluid due to which it opposes the relative motion between its different layers is called viscosity (or fluid friction or internal friction) and the force between the layers opposing the relative motion is called viscous force. According to Newton, the frictional force or viscous force between two layers depends upon the following factors : dv FµA dy dv or F = -h A dy where, h is a constant called coefficient of viscosity or simply viscosity of fluid.

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Factors Affecting Viscosity (1) Effect of temperature : On increasing temperature viscosity of a liquid decreases. While it increases in the case of gases. (2) Effect of pressure : On increasing pressure viscosity of a liquid increases but viscosity of water decreases. Viscosity of gases is independent of pressure.

Stoke’s Law According to stoke’s law, the viscous drag force F on a spherical body of radius r moving through a fluid of viscosity h with a velocity called terminal velocity v is given by F=6 phrv

Terminal Velocity It is maximum constant velocity acquired by the body while falling freely in a viscous medium. VT =

2r 2 (r - s) g 9h

Surface Tension Surface tension is basically a property of liquid. The liquid surface behaves like a stretched elastic membrane which has a natural tendency to contract and tends to have a minimum possible surface area. This property of liquid is called surface tension. Surface tension T =

Force F Length L

Examples of surface tension (i) Raindrops are spherical in shape. (ii) The hair of a shaving brush cling together when taken out of water. (iii) Oil spread on cold water but remains as a drop on hot water etc.

Angle of Contact (q) The angle enclosed between the tangent plane at the liquid surface and the tangent plane at the solid surface at the point of contact inside the liquid is termed as the angle of contact. Angle of contact of various solid-liquid pairs Solid - liquid pair qC Glass -normal water 8° Glass -distilled water 0° Acute angle Glass - alcohol Glass - mercury Paraffin wax - water Silver - water

0° 135° Obtuse angle 108° 90° Right angle

Capillarity A glass tube with fine bore and open at both ends is known as capillary tube. The property by virtue of which a liquid rise or fall in a capillary tube is known as capillarity. Rise or fall of liquid in tubes of narrow bore (capillary tube) is called capillary action. Rise of kerosene in lanterns, rise of ink in fountain pen etc. are due to capillary action.

C-14

Kerosene oil rises up in a wick of a lantern because of (a) diffusion of the oil through the wick (b) surface tension (c) buoyant force of air (d) the gravitational pull of the wick 2. Two pieces of metal when immersed in a liquid have equal upthrust on them; then (a) both pieces must have equal weights (b) both pieces must have equal densities (c) both pieces must have equal volumes (d) both are floating to the same depth 3. If the force on the surface is doubled and area is reduced to half, pressure will (a) become 2 times (b) become 3 times (c) become 4 times (d) remain unchanged 4. Pressure at a point inside a liquid does not depend on (a) the depth of the point below the surface of the liquid (b) the nature of the liquid (c) the acceleration due to gravity at that point (d) the shape of the containing vessel 5. The bulk modulus for an incompressible liquid is (a) zero (b) unity (c) infinity (d) between 0 and 1 6. An egg when placed in ordinary water sinks but floats when placed in brine. This is because (a) density of brine is less than that of ordinary water (b) density of brine is equal to that of ordinary water (c) density of brine is greater than that of ordinary water (d) None of these 7. Water is flowing through a horizontal pipe in streamline flow. At the narrowest part of the pipe (a) Velocity is maximum and pressure is minimum (b) Pressure is maximum and velocity is minimum (c) Both the pressure and velocity are maximum (d) Both the velocity and pressure are minimum 8. The following four wires are made of the same material. Which of these will have the largest extension when the same tension is applied ? (a) Length = 50 cm , diameter = 0.5 mm (b) Length = 100 cm, diameter = 1 mm (c) Length = 200 cm, diameter = 2 mm (d) Length = 300 cm, diameter = 3 mm 9. A man is sitting in a boat which is floating in pond. If the man drinks some water from the pond, the level of water in the pond will (a) rise a little (b) fall a little (c) remain stationary (d) None of these 10. In solids, interatomic forces are (a) totally repulsive (b) totally attractive (c) combination of (a) and (b) (d) None of these

GENERAL SCIENCE

11. A body floats in a liquid containing in a beaker. The whole system as shown in Fig. is falling under gravity. The upthrust on the body due to liquid is

12.

13.

14.

15.

16.

17.

18.

19.

20.

(a) zero (b) equal to weight of body in air (c) equal to weight of liquid displaced (d) equal to weight of immersed part of the body A water tank of height 10 m, completely filled with water is placed on a level ground. It has two holes one at 3 m and the other at 7 m from its base. The water ejecting from (a) both the holes will fall at the same spot (b) upper hole will fall farther than that from the lower hole (c) upper hole will fall closer than that from the lower hole (d) more information is required The lift of an air plane is based on (a) Torricelli’s theorem (b) bernoulli’s theorem (c) law of gravitation (d) conservation of linear momentum The rain drops falling from the sky neither injure us nor make holes on the ground because they move with (a) constant acceleration (b) variable acceleration (c) variable speed (d) constant terminal velocity Two soap bubbles are held by a tube. What will happen ? (a) Air will travel from bigger to smaller bubble (b) Air will not travel (c) Air will travel through tube (d) Nothing can be said With the increase of temperature, the surface tension of the liquid (a) may increase or decrease depending on the density of liquid (b) remains the same (c) always increases (d) always decreases According to Hooke’s law of elasticity, if stress is increased, then the ratio of stress to strain (a) becomes zero (b) remains constant (c) decreases (d) increases Liquid pressure at a point in a liquid does not depend on the (a) density of liquid (b) shape of the vessel in which the liquid is kept (c) depth of the point from the surface (d) acceleration due to gravity A container partly filled in a liquid is suspended from a spring balance. A small body is gently dropped in the container. The pointer of spring balance will (a) read less (b) oscillate (c) read the same (d) read more Small droplets of a liquid are usually more spherical in shape than larger drops of the same liquid because (a) force of surface tension is equal and opposite to the force of gravity (b) force of surface tension predominates the force of gravity

FOR MORE JOIN ~ MISSION SSC / BANKING / UPSC Properties of Matter (c) force of gravity predominates the force of surface tension (d) force of gravity and force of surface tension act in the same direction and are equal 21. Which of the following materials is most elastic ? (a) Rubber (b) Lead (c) Wood (d) Steel 22. A stretched rubber has (a) increased kinetic energy (b) increased potential energy (c) decreased kinetic energy (d) decreased potential energy 23. The load verses elongation graph for four wires is shown. The thinnest wire is Load

a b c

Elongation

(a) a (b) b (c) c (d) d 24. Elastomers are the materials which (a) are not elastic at all (b) have very small elastic range (c) do not obey Hooke’s law (d) None of these 25. The lift in an aeroplane is based on (a) Law of gravitation (b) Theorem of continuity (c) Pascal’s low (d) Bernoulli’s theorem 26. In the figure below is shown the flow of the liquid through a horizontal pipe. Three tubes A, B and C are connected to the pipe. The radii of the tubes A, B and C at the junction are respectively 2 cm, 1 cm and 2 cms. It can be said that A

C-15

30. Water is flowing through a horizontal pipe line having a restriction. Then (a) pressure will be the same throughout the length of the pipe. (b) pressure will be greater at the restriction. (c) pressure will be greater in the wider portion. (d) None of these 31 Paint-gun is based on (a) Bernoulli’s theorem (b) Archemedes’ principle (c) Boyle’s law (d) Newton’s laws of motion 32. A tank filled with water has a hole at a certain height from its bottom. The volume of water emerging out per second from the hole does not depend on (a) the height of the level of liquid above the hole. (b) the area of a hole. (c) the density of a liquid. (d) the acceleration due to gravity. 33. A boy carries a fish in one hand and a bucket of water in the other hand. If he places the fish in the bucket, the weight now carried by him. (a) is less than before (b) is more than before (c) is the same as before (d) depends upon his speed 34. A drop of oil is placed on the surface of water. Which of the following statements is correct? (a) It will remain on it as a sphere (b) It will spread as a thin layer (c) It will partly be a spherical droplet and partly a thin film (d) It will float as a distorted drop on the water surface 35. For a fluid which is flowing steadily, the level in the vertical tubes is best represented by

(a)

(b)

(a) the height of the liquid in the tube A is maximum (b) height of the liquid in the tube A and tube B is the same (c) height of the liquid in all the three tubes is the same (d) height of the liquid in tube A and C is the same 27. Houses far from the municipal water tank find it difficult to get water on the top floor even if their ceilings are lower than the level of water filled in tank. Its reason is (a) pipes are more wide. (b) pipes are less wide. (c) when water flows there is loss of pressure. (d) None of these 28. Working of atomizer is based on (a) Boyle’s law (b) Bernoulli’s law (c) Newton’s laws of motion (d) Archimedes’ principle 29. Ideal liquid is that liquid (a) whose density is zero (b) whose viscosity is zero (c) which is compressible (d) None of these

(c)

(d) 36. Surface tension of a liquid is due to (a) gravitational force between molecules (b) electrical force between molecules (c) adhesive force between molecules (d) cohesive force between molecules 37. A liquid rises in a capillary tube higher than water does. The difference may be due to the fact that (a) diameter of the capillary may be different in the two cases (b) temperature of liquid is higher than that of water (c) surface tension of water is less than that of the liquid (d) both (a) and (c)

C-16

GENERAL SCIENCE (c) Pressure of water increases with depth (d) Temperature of water increases with depth 41. Hydraulic lift is based on the principle of (a) Pascal’s law (b) Bernoulli’s theorem (c) Toricelli’s theorem (d) Stoke’s law 42. A and B are two wires. The radius of A is twice that of B. They are stretched by the same load. Then the stress on B is (a) equal to that on A (b) four times that on A (c) two times that on A (d) half that on A

38. Construction of submarines is based on (a) Archimede's principle (b) Bernoulli's theorem (c) Pascal's law (d) Newton's laws 39. The action of a nib split at the top is explained by (a) gravity flow (b) diffusion of fluid (c) capillary action (d) osmosis of liquid 40. Why the dam of water reservoir is thick at the bottom? (a) Quantity of water increases with depth (b) Density of water increases with depth

ANSWER KEY 1 2 3 4 5 6 7

(b) (c) (c) (d) (c) (c) (a)

8 9 10 11 12 13 14

(a) (c) (c) (a) (a) (b) (b)

15 16 17 18 19 20 21

(a) (d) (b) (b) (d) (b) (d)

(b) (b) (c) (d) (d) (c) (b)

22 23 24 25 26 27 28

29 30 31 32 33 34 35

(b) (c) (a) (c) (c) (b) (a)

36 37 38 39 40 41 42

(d) (c) (a) (c) (c) (a) (b)

HINTS AND SOLUTIONS 5.

Pressure Pressure = Volume Strain 0

Bulk modulus = ¥ [As liquid is uncompressible, ΔV = 0 ] (c) Brine due to its high density exerts an upthrust which can balance the weight of the egg. (a)

T/A Dl / l

T ´l T l Dl = = ´ A´ Y Y A Hence,

T l is constant. Therefore, Dl = Y A

l is largest in the first case. A 12. (a) Velocity of water from hole A = v1 = 2 gh Velocity of water from hole B = v2 = 2 g ( H 0 - h) Time of reaching the ground from hole B

= t1 =

2( H 0 - h) / g

Time of reaching the ground from hole A = t2 = 2h / g 13. (b) Apply Bernoulli’s theorem.) 15. (a) The excess pressure inside a soap bubble is given by,

4T . As the excess of pressure is less in bigger bubble r means pressure is more inside bigger bubble. So, air travels from bigger bubble to smaller. 16. (d) Surface-Tension is the property of liquid at rest. As we increase temperature, due to gain in kinetic energy of molecules, surface tension decreases. 17. (b) The ratio of stress to strain is always constant. If stress is increased, strain will also increase so that their ratio remains constant. p=

19. (d) The pointer of spring balance will read more. The increased reading will be equal to the upthrust given by Archimedes principle. 24. (c) Elastomers do not obey Hooke’s law. 26. (d) The rise of water in capillary tube is inversely proportional to radius, h =

2T . It is given that radius of A rrg

and C are same. So, height of the liquid in tube A and C is the same. 30. (c)

A v P (Area A, Velocity v, Pressure P)

32. (c) Volume per second = A 2gh 34. (b) The surface tension of oil is less than that of water, so the oil spreads as a thin layer. 35. (a) From continuity equation, velocity at cross-section (1) is more than that at cross-section (2). Hence, P1 < P2. 36. (d) Surface tension of a liquid is due to force of attraction between like molecules of a liquid i.e. cohesive force between the molecules. 37. (c) The height to which liquid rises in a capillary is given by, h =

2T . Thus, if height to which liquid rises is more, rrg

the liquid have greater surface tension than water. Option (a) is not suitable because diameter of capillary tube containing liquid should be smaller than the capillary in which water rises. This is not mentioned clearly in the option (a). 40. (c) A torque is acting on the wall of the dam trying to make it topple. The bottom is made very broad so that the dam will be stable. 41. (a) Hydraulic lift is based on the principle of Pascal’s law. 42. (b) Stress =

force 1 \ Stress µ 2 Area πr 2

SB æ rA ö = ç ÷ = (2)2 Þ S B = 4S A S A è rB ø

Heat

Temperature and Heat

Absolute Temperature

Temperature is defined as the degree of hotness or coldness of a body. It is a scalar quantity. Its S.I. unit is kelvin (K). Heat is a form of energy which causes sensation of hotness or coldness. The flow of heat is always from higher temperature to lower temperature. No heat flows from one body to other, when both the bodies are at the same temperature. The two bodies are said to be in thermal equilibrium. The SI unit of heat is joule. Its CGS unit is calorie, 1 cal = 4.2 joule

The lowest temperature of –273.16 °C at which a gas is supposed to have zero volume and zero pressure and at which entire molecular motion stops is called absolute zero temperature. A new scale of temperature starting with –273.16°C by Lord Kelvin as zero. This is called Kelvin scale or absolute scale of temperature. T(K) = t°C + 273.16

Measurement of Temperature

The increase in the dimensions of a body due to the increase in its temperature is called thermal expansion.

A branch of science which deals with the measurement of temperature of a substance is called thermometry. Thermometer is a device used to measure the temperature. Thermometer used for measuring very high temperatures are called pyrometer.

Relationship Between Different Scales of Temperature C–0 F - 32 K - 273.16 = = 100 212 - 32 373.16 - 273.16 R -0 Ra - 460 = 80 - 0 672 - 460 T°(K) = (t°C + 273.16) Normal temperature of human body is 310.15 k (37°C = 98.6°F) STP or NTP implies 273.15 K (0°C = 32°F) =

Ideal-gas Equation and Absolute Temperature The equation, PV = nRT where, n = number of moles in the sample of gas R = universal gas constant; (its value is 8.31 J mol–1 K–1), is known as ideal-gas equation It is the combination of following three laws (i) Boyle's law : When temperature is held constant, the pressure is inversely proportional to volume. 1 i.e., P µ ( at constant temperature) V (ii) Charle's law : When the pressure is held constant, the volume of the gas is directly porportional to the absolute temperature. i.e., V µ T (at constant pressure) (iii) Avogadro's law : When the pressure and temperature are kept constant, the volume is directly proportional to the number of moles of the ideal gas in the container. i.e., V µ n (at constant pressure and temperature)

Thermal Expansion

Linear expansion : The fractional increase in length per ºC rise in temperature is called coefficient of linear expansion. æ Dl ö çè ÷ø dl l Coefficient of linear expansion, a = = l.dT DT

Superficial expansion : On increasing the temperature of a solid, its area increases. This increase in area is referred as superficial expansion. Coefficient of superficial expansion is defined as the fractional increase in area per ºC rise in temperature. i.e., Coefficient of a real expansion b =

DA / A dA = DT A.dT

Cubical expansion : On increasing the temperature of a solid, its volume increases. This increase in volume with increase in temperature is called cubical or volume expansion. Coefficient of volume expansion is defined as the fractional increase in volume per ºC rise in temperature. DV / V dV = DT V.dT Relation between coefficient of linear expansion (a), coefficient of superficial expansion (b) and coefficient of cubical expansion (g) b g a= = Þ a : b : g = 1: 2 :3 2 3

i.e., Coefficient of volume expansion, g =

Anomalous Expansion of Water Almost all liquids expand on heating but water when heated from 0°C to 4°C its volume decreases and hence density increases until its temperature reaches 4°C. Its density is maximum at 4°C on further heating its density decreases. This behaviour of water is called anomalous behaviour of water.

C-18

GENERAL SCIENCE

Specific Heat Capacity It is the amount of heat energy needed to raise the temperature of unit mass of substance by 1ºC (or 1K). It is denoted by s or c. 1 dQ m. dT Unit of specific heat capacity : SI unit of specific heat capacity is joule/kg K For example, the specific heat capacity of water is : Cwater = 1 cal/g °C = 1 cal/g K = 1 kcal/kg K=4200 joule/kg K c=

Latent Heat or Hidden Heat When state of a substance changes, change of state takes place at constant temperature (m.pt. or b.pt.) heat is released or absorbed and is given by, Q = mL where L is latent heat. The SI unit of latent heat is J/kg

Conduction : Conduction is that mode of transmission of heat in which heat is transferred from a region of higher temperature to a region of lower temperature by the aid of particles of the body without their actual migration. Conduction requires material medium. Convection : Convection like conduction requires a material medium. It is the process in which heat is transferred from one place to other by actual movement of heated material particles. Radiation : When a body is heated and placed in vacuum, it loses heat even when there is no medium surrounding it. The process by which heat is lost in this case is called radiation. This does not require the presence of any material medium. It is by radiation that the heat from the sun reaches the earth.

The Electromagnetic Spectrum Frequency, (in Hz) 10°

Microwaves

ac power

Gamma rays Visible

Change of State

Any state of a substance (solid/ liquid/ gas) can be changed into another by heating or cooling. The transition of a substance from one state to another is called a change of state. Some common changes of states : (i) Melting : When heat is supplied, solid substance changes into liquid, this change of state of substance is called melting. Heat

Solid ¾¾¾ ® Liquid The temperature at which the solid and the liquid states of a substance coexist in thermal equilibrium with each other is called its melting point. (ii) Freezing : When heat is released, liquid changes into solid, this change of state of substance is called freezing. Cool

Liquid ¾¾¾ ® Solid (iii) Condensation : When vapour is cooled, it changes into liquid, this change of state is called condensation Cool

Vapour ¾¾¾ ® liquid (iv) Evaporation : Conversion of liquid into gaseous state at all the temperatures is called evaporation or boiling. Heat

(v)

x-rays

FM T.V. radio

Liquid ¾¾¾ ® Vapour The temperature at which the liquid and vapour states of a substance coexsist in thermal equilibrium with each other is called its boiling point. It is a phenomenon that occurs at the surface of liquids. The rate of evaporation increases with rise in temperature. Heat required to change unit mass of liquid into vapour at a given temperature is called heat of evaporation at that temperature. Sublimation : It is the conversion of a solid directly into vapours. Heat

Solid ¾¾¾ ® Vapour Sublimation takes place when boiling point is less than the melting point. Heat transfer : Heat energy transfer from a body at higher temperature to a body at lower temperature by three different methods. They are conduction, convection and radiation.

109

106

103

Infrared 10°

–3

Ultraviolet –6

–9

–12

–15

Wavelength, (in m)

Perfectly black body : A black body is defined as one that will completely absorb all the radiations of whatever wavelength which falls on it. For perfectly black body, al = 1. Properties of perfectly black body : (i) A perfectly black body absorbs all the radiant heat incident upon it. (i.e. a = 1) (ii) A perfectly black body does not reflect or transmit the radiant heat incident upon it. (i.e. t = 0, r = 0) (iii) The coefficient of emission of a perfectly black body is 1. It is very good emitter of heat. Wien's displacement law. According to Wien’s displacement law lm × T = b Here, constant b is known as Wien's constant

Newton's Law of Cooling The rate of cooling of a body (rate of loss of heat) is directly proportional to the excess of temp. of the body over the surroundings, provided that this excess is small and loses of heat by radiation only. If q and q0 are the temperatures of the body and its surroundings respectively, then according to Newton’s law of cooling, Rate of loss of heat, –

dQ µ (q - q0 ) dt

Thermodynamics The thermodynamics is the branch of science in which the conversion of heat into mechanical work and vice versa is studied. Triple point of water : The triple point of water represents the coexistence of all the three phases of water ice, water and water vapour in equilibrium. The pressure corresponding to triple point of water is 6.03 × 10–3 atmosphere or 4.58 mm of Hg and temperature corresponding to it is 273.16 K.

Heat

C-19

Zeroth Law of Thermodynamics

Heat Engines

If objects A and B are separately in thermal equilibrium with a third object C then objects A and B are in thermal equilibrium with each other. Heat : It is energy in transit between two objects or system due to temperature difference between them. It exists in the form of translational, rotational and vibrational motion of molecules of a substance. It depends on processess. For constant pressure process Q = nCP DT and For constant volume process Q = nCv DT For any other process Q = nC DT, where C is called molar specific heat for that process. Internal energy : Internal energy of a system is the energy possessed by the system due to molecular motion and molecular configuration. The energy due to molecular motion is called internal kinetic energy (Uk ) and that due to molecular configuration is called internal potential energy (Up). dU = dUk + dUp If there is no intermolecular forces, then dUp = 0. \ dU = dUk = mCv dT Work : Work is energy transfer brought about by other means, such as moving the piston of a cylinder containing the gas, by raising or lowering some weight connected to it etc.

Heat engine is a device which converts heat energy into work. A heat engine, in general, consists of three parts :

First Law of Thermodynamics If some quantity of heat is supplied to a system capable of doing external work, then the quantity of heat absorbed by the system is equal to the sum of the increase in the internal energy of the system and the external work done by the system. i.e., dQ = dU + dW The first law of thermodynamics is essentially a restatement of the law of conservation of energy, i.e., energy can neither be created nor be destroyed but may be converted from one form to another.

T1 Source or high temp. reservoir Q1

Working substance Q2

T2 Sink or low temp. reservoir

Efficiency of heat engine, h =

Work done (W ) Heat taken from soruce (Q1 )

T1 - T2 Q1 - Q2 Q2 = 1= T1 Q1 Q1

Refrigerators and Heat Pumps A refrigerator is the reverse of a heat engine. A heat pump is the same as a refrigerator. 1

T1 Source or high temp. reservoir Q1

Working 2 substance

W=Q1 – Q2 Q2

Different Types of Thermodynamic Processes Quasi-static process : It is infinitely slow. So its variables (P, V, T) remains in thermal and mechanical equilibrium with its surroundings. Isochoric or isometric process : It is a thermodynamic process that takes place at constant volume of the system, but pressure and temperature varies for change in state of the system. Isobaric process : It is a thermodynamic process that takes place at constant pressure, but volume and temperature varies for change in state of the system. Isothermal process : It is a thermodynamic process in which the pressure and volume of system change but temperature remains constant. Adiabatic process : It is that thermodynamic process in which pressure, volume and temperature of the system change but there is no exchange of heat between the system and the surroundings. A process has to be sudden and quick to be adiabatic. Equation of state : PV = µRT Equation for adiabatic process PVg = constant

W=Q1 – Q2

T2 Sink or low temp. reservoir

The coefficient of performance of a refrigerator or heat pump. Q2 Q2 = W Q1 – Q2

[Q W = Q1 – Q2 ]

Carnot Theorem No irreversible engine (I) can have efficiency greater than Carnot reversible engine (R) working between same hot and cold reservoirs. T Q i.e., hR > hI or 1 - 2 > 1 - 2 T1 Q1

C-20

Woollen clothes are used in winter season because woollen clothes (a) are good sources for producing heat (b) absorb heat form surroundings (c) are bad conductors of heat (d) provide heat to body continuously 2. Water has maximum density at (a) 0°C (b) 32°F (c) –4°C (d) 4°C 3. Expansion during heating (a) occurs only in solids (b) increases the weight of a material (c) decreases the density of a material (d) occurs at the same rate for all liquids and solids 4. When a copper ball is heated, the largest percentage increase will occur in its (a) diameter (b) area (c) volume (d) density 5. If a liquid is heated in condition of weightlessness, the heat is transmitted through (a) conduction (b) convection (c) radiation (d) None, because the liquid cannot be heated in weightlessness 6. Heat travels through vacuum by (a) conduction (b) convection (c) radiation (d) both (a) and (b) 7. A bimetallic strip consists of brass and iron. When it is heated it bends into an arc with brass on the convex and iron on the concave side of the arc. This happens because (a) brass has a higher specific heat capacity than iron (b) density of brass is more than that of iron (c) it is easier to bend an iron strip than a brass strip of the same size (d) brass has a higher coefficient of linear expansion than iron 8. The earth radiates in the infra-red region of the spectrum. The spectrum is correctly given by (a) Wien’s law (b) Rayleigh's law (c) Planck’s law of radiation (d) Stefan’s law of radiation 9. Good absorbers of heat are (a) poor emitters (b) non-emitters (c) good emitters (d) highly polished 10. Which of the following qualities suit for a cooking utensil? (a) High specific heat and low thermal conductivity (b) High specific heat and high thermal conductivity (c) Low specific heat and low thermal conductivity (d) Low specific heat and high thermal conductivity 11. 5g ice at 0ºC is mixed with 5g of steam at 100ºC . What is the final temperature? (a) 50ºC (b) 100ºC (c) 80ºC (d) 150ºC

GENERAL SCIENCE

12. 13.

14.

15. 16.

17.

18.

19.

20.

21.

By the first law of thermodynamics, for solids (a) dQ = dU + dW (b) dQ = dU (c) dQ = dW + dU (d) dQ = dU / dW There are four objects A, B, C and D. It is observed that A and B are in thermal equilibrium and C and D are also in thermal equilibrium. However, A and C are not in thermal equilibrium. We can conclude that – (a) B and D are in thermal equilibrium (b) B and D could be in thermal equilibrium but might not be A and D (c) B and D cannot be in thermal equilibrium (d) the zeroth law of thermodynamics does not apply here because there are more than three objects According to the kinetic theory of gases (a) all the atoms move horizontally with equal speeds (b) an atom moves faster during its downward motion than its upward motion (c) at any instant one-third of the total atoms are moving along x-axis (d) None of these The fastest mode of transfer of heat is (a) conduction (b) convection (c) radiation (d) None of these The wavelength of radiation emitted by a body depends upon (a) the nature of its surface (b) the area of its surface (c) the temperature of its surface (d) All of the above The sprinkling of water slightly reduces the temperature of a closed room because (a) temperature of water is less than that of the room (b) specific heat of water is high (c) water has large latent heat of vaporisation (d) water is a bad conductor of heat Which of the following is not close to a black body? (a) Black board paint (b) Green leaves (c) Black holes (d) Red roses A solid cube and a solid sphere of the same material have equal surface area. Both are at the same temperture 120°C , then (a) both the cube and the sphere cool down at the same rate (b) the cube cools down faster than the sphere (c) the sphere cools down faster than the cube (d) whichever is having more mass will cool down faster At a given temperature the internal energy of a substance (a) in liquid state is equal to that in gaseous state (b) in liquid state is less than that in gaseous state (c) in liquid state is more than that in gaseous state (d) is equal for the three states of matter Consider two identical iron spheres , one which lie on a thermally insulating plate, while the other hangs from an insulatory thread. Equal amount of heat is supplied to the two spheres

Heat

22.

23.

24.

25.

26.

27.

28.

29.

30.

(a) Temperature of A will be greater than B (b) Temperature of B will be greater than A (c) Their temperature will be equal (d) Can’t be predicted Air conditioner is based on the principle of (a) Carnot cycle (b) refrigerator (c) first low of thermodynamics (d) None of these Gases exert pressure on the walls of the container because the gas molecules (a) possess momentum (b) collide with each other (c) have finite volume (d) obey gas laws Food in the pressure cooker is cooked faster, as (a) the boiling point increases due to an increase in pressure (b) the boiling point decreases due to an increase in pressure (c) more steam is available at 100°C (d) more pressure is available at 100°C A metal sheet with a circular hole is heated. The hole (a) gets larger (b) gets smaller (c) remains of the same size (d) gets deformed When water is heated from 0ºC to 10ºC, its volume (a) increases (b) decreases (c) does not change (d) first decreases and then increases A : At high altitude regions the cooking of food becomes difficult. B : Water boils at lower temperature when the pressure is low. (a) Both A and B are wrong. (b) A and B are correct and B is not the correct explanation of A. (c) A and B are correct and B is the correct explanation of A. (d) A is correct but B is wrong. When vapour condenses into liquid (a) it absorbs heat (b) it liberates heat (c) its temperature rises (d) its temperature decreases The temperature of the sun is measured with (a) Platinum thermometer (b) Gas theromometer (c) Pyrometer (d) Vapour pressure thermometer Two spheres of same size are made of the same metal but one is hollow and the other is solid. They are heated to same temperature, then (a) both spheres will expand equally (b) hollow sphere will expand more than the solid one (c) solid sphere will expand more than the hollow one (d) None of the above

C-21

31. Heat is transmitted from higher to lower temperature through actual mass motion of the molecules in (a) conduction (b) convection (c) radiation (d) none of these 32. The temperature of a room is 77°F. What would it be on the Celsius scale? (a) 25°C (b) 45°C (c) 60°C (d) 350°C 33. Ventilators are provided at the top of room (a) to bring oxygen for breathing (b) so that sunlight may enter the room (c) to maintain conventional currents to keep the air fresh in the room (d) to provide an outlet for carbon dioxide 34. What temperature is the same on celsius scale as well as on Fahrenheit scale? (a) – 212°C (b) – 40°C (c) – 32°C (d) 32°C 35. Two holes of unequal diameters d1 and d2 (d1 > d2) are cut in a metal sheet. If the sheet is heated,

36.

37.

38.

39.

40.

(a) both d1 and d2 will decrease (b) both d1 and d2 will increase (c) d1 will increase, d2 will decrease (d) d1 will decrease, d2 will increase At 0°C a body emits (a) no radiation (b) only visible light (c) only microwave radiation (d) all wavelengths. Triple point is the temperature at which (a) matter may simultaneously exist in liquid and gaseous state. (b) matter may simultaneously exist in liquid and solid state. (c) matter may simultaneously exist in solid and gaseous state. (d) matter may simultaneously exist in all the three forms. In order that the heat flows from one part of a solid to another part, what is required? (a) Uniform density (b) Temperature gradient (c) Density gradient (d) Uniform temperature At a common temperature, a block of wood and a block of metal feel equally cold or hot. The temperatures of block and wood are (a) equal to the temperature of the body (b) less than the temperature of the body (c) greater than temperature of the body (d) either (b) or (c) The bulb of one thermometer is spherical, while that of other is cylindrical. If both of them have equal amount of mercury, which thermometer will respond quickly to the temperature? (a) spherical bulb (b) cylindrical bulb (c) elliptical bulb (d) both (a) and (c)

C-22

GENERAL SCIENCE (b) length of the rod. (c) temperature difference across the rod. (d) All of these 43. Which of the following represents convection ? (a) Land breeze (b) Exhaust fan (c) Heating water by keeping the vessel on a flame (d) All of these

41. Consider the following statements. (A) Some bodies may contract on heating (B) Water shows anamolous expansion. (a) (A) is true and (B) is false (b) (A) is false and (B) is true. (c) Both (A) and (B) are true. (d) Both (A) and (B) are false. 42. The rate of flow of heat through a rod depends on: (a) thermal conductivity of the rod.

ANSWER KEY 1 2 3 4 5 6 7 8

9 10 11 12 13 14 15 16

17 18 19 20 21 22 23 24

25 26 27 28 29 30 31 32

(a) (d) (c) (b) (c) (a) (b) (a)

33 34 35 36 37 38 39 40

41 42 43

HINTS AND SOLUTIONS 1.

(c) In winter, the temperature of surrounding is low compared to the body temperature (37.4°C). Since, woollen clothes are bad conductors of heat, so they keep the body warm. 2. (d) Water has maximum density at 4°C. 3. (c) Solids, liquids and gases all expand on being heated as a result density ( = mass/volume) decreases. 4. (c) When a copper ball is heated, it’s size increases. As volume µ (radius)3 and Area µ (radius)2, so percentage increase will be largest in it’s volume. Density will decrease with rise in temperature. 5. (a) Convection is not possible in weightlessness. So the liquid will be heated through conduction. 6. (c) Heat radiations are electromagnetic waves of high wavelength. 7. (d) It is so because brass has a higher coefficient of linear expansion. 9. (c) Good absorbers are always good emitters of heat. 11. (b) Heat required by ice to raise its temperature to 100ºC, Q1 = m1L1 + m1c1Dq1 = 5 × 80 + 5 × 1 × 100 = 400 + 500 = 900 cal Heat given by steam when condensed, Q2 = m2L2 = 5 × 536 = 2680 cal as Q2 > Q1. This means that whole steam is not even condensed. Hence temperature of mixture will remain at 100ºC. 13. (c) Thermal equilibrium means same temperature. 19. (b) Rate of cooling of a body R = ÞRµ

A Area µ m Volume

Dq Aes(T 4 - T04 ) = t mc

[ m = r ´ V]

1 Volume Q Volume of cube < Volume of sphere Þ Rcube > RSphere i.e., cube, cools down with faster rate.

Þ For the same surface area. R µ

21. (b) Temperature of B will be higher because, due to expansion, centre of mass of B will come down. Same heat is supplied but in B, Potential energy is decreased therefore internal energy gain will be more. 34. (b)

35. (b)

36. (d) 37. (d) 38. (b) 39. (a) 40. (b)

41. (c) 42. (d)

C F - 32 = Here C = F 5 9 C F - 32 = Þ 9C = 5C – 160 5 9 4C = – 160 Þ C = – 40°C. Thus at –40°C and –40° F the temperture is same. When a body is heated, the distance between any two points on it increases. The increase is in the same ratio for any set of two point. At any temperature other than zero K, each body emits all wavelengths. Triple point is the temperature where three states of matter can exist simultaneously. As heat flows from higher temperature to lower temperature, so a temperature gradient is required. The temperatures of the block and wood are equal to the temperature of the body as both feel equally hot or cold. As the surface area of cylindrical bulb is larger than a spherical bulb, heat will be transmitted quickly through a cylindrical bulb and it will respond quickly to the temperature. Some bodies like wood, rubber etc. have negative value of coefficient of thermal expansion, hence they contract on heating, hence (A) is true. (B) is also true. Rate of flow of heat through a rod,

kA DT 2 43. (d) All the given phenomena are caused due to convection.

4 Periodic Motion Any motion that repeats itself in equal intervals of time is called periodic motion. A periodic motion can be represented in terms of sines and cosines, so it is called a harmonic motion. The uniformly rotating earth represents a periodic motion that repeats itself at every 24 hours.

Simple Harmonic Motion (S.H.M.)

Oscillatory motion in which the acceleration of the particle is directly proportional to the displacement and directs towards a fixed point in a direction opposite to displacement is called simple harmonic motion abbreviated as S.H.M. If a particle performs oscillatory motion such that its acceleration (a) and displacement (x) are related as below a µ – x, then the motion of particle is simple harmonic. An oscillatory motion is always periodic but a periodic motion may not be oscillatory. Examples of S.H.M. (i) clock pendulum, (ii) oscillating liquid in a U-tube, (iii) oscillating block in a liquid, (iv) oscillating frictionless piston fitted in a cylinder filled with ideal gas, etc.

Sound

Sound is a form of energy which produces a sensation of hearing in our ears.

Source of Sound and its Propagation

A source of vibration (vibration means a kind of rapid to and fro motion of an object) is normally a source of sound. When we pluck a string of guitar or sitar or veena it produces sound. Similarly vibrations of wings of bee or mosquito. Sound is emitted by vibrating source and is transmitted through a material medium producing sensation of hearing in our ears. The motion of a vibrating source sets up waves in the surrounding medium.

Sound Needs a Material Medium for its Propagation

In the absence of medium (air) around the source, sound is not being propagated and light (electromagnetic) waves travel through the vacuum.

Mechanical Waves

A mechanical wave is a periodic disturbance which requires a material medium for its propagation. The properties of these waves depend on the medium so they are known as elastic waves, such as sound-waves, water waves, waves in stretched string. On the basis of motion of particles the mechanical waves are classified into two parts.

Sound (a)

Transverse wave : When the particles of the medium vibrate in a direction perpendicular to the direction of propagation of the wave, the wave is known as the transverse wave. For example, waves produced in a stretched string, waves on the surface. These waves travel in form of crests and troughs. These waves can travel in solids and liquids only. (b) Longitudinal wave : When the particles of the medium vibrate along the direction of propagation of the wave then the wave is known as the longitudinal wave. For example sound wave in air, waves in a solid rod produced by scrabbing etc. These waves travel in the form of compressions and rarefactions. These waves can travel in solids, liquids and gases. Electromagnetic Waves The waves which do not require medium for propagation are called electromagnetic waves. This means that these waves can travel through vacuum also. For example, light waves, X-rays, grays, Infrared waves, radio waves, microwaves, etc. These waves of transverse type. Difference between sound waves and electromagnetic waves (i) Sound waves are longitudinal and electromagnetic waves are transverse. (ii) Sound waves travel at a speed of 340 m/s whereas electromagnetic waves travel at a speed of 3 × 108 m/s (iii) Sound waves do not pass through a vacuum but electromagnetic waves (light) do. Characteristics of Sound Waves Sound is characterised by three parameters : (i) Pitch (ii) Loudness (iii) Quality (i) Pitch : Pitch is the sensation (brain interpretation) of the frequency of an emitted sound and is the characteristic which distinguishes a shrill (or sharp) sound from a grave (or flat) sound. (ii) Loudness : Loudness or softness of a sound wave is the sensation that depends upon its amplitude. The loudness of sound is a measure of the sound energy reaching the ear per second. The loudness of sound is measured in ‘decibel dB’. The loudness of sound of people talking quietly is about 65 dB, the loudness of sound in a very noisy factory is about 100 dB. (iii) Quality (Timber) : Quality or timber of a sound wave is that characteristic which helps us in distinguishing one sound from another having same pitch and loudness. We recognise a person (without seeing) by listening to his sound as it has a definite quality.

C-24

GENERAL SCIENCE A pure sound of single frequency is called a tone. An impure sound produced by mixture of many frequencies is called a note. It is pleasant to listen.

Reflection of Sound

When sound waves strike a surface, they return back into the same medium. This phenomenon is called reflection. Laws of reflection of sound waves (i) Angle of incidence is equal to the angle of reflection. (ii) The incident wave, the reflected wave and the normal all lie in the same plane.

Echo

Phenomenon of hearing back our own sound is called an echo. It is due to successive reflection from the surface of obstacles of large size. Conditions for the formation of Echoes (i) The minimum distance between the source of sound and the reflecting body should be 17.2 metres. (ii) The wavelength of sound should be less than the height of the reflecting body. (iii) The intensity of sound should be sufficient so that it can be heard after reflection.

Ultrasonic waves have frequency (a) below 20 Hz (b) between 20 and 20,000 Hz (c) only above 20,000 Hz (d) only above 20,000 MHz Voice of your friend can be recognized by its (a) pitch (b) quality (c) intensity (d) velocity The ratio of the speed of a body to the speed of sound is called (a) Sonic index (b) Doppler ratio (c) Mach number (d) Refractive index The velocity of sound is largest in (a) water (b) air (c) metal (d) vacuum An underwater explosion is caused near the sea-shore. There are two observers, X under water and Y on land, each at a distance of 1 km from the point of explosion then (a) X will hear the sound earlier (b) Y will hear the sound earlier (c) Both will hear the sound at the same time (d) Y will not hear the sound at all If you are at open-air concert and someone’s head gets between you and the orchestra, you can still hear the orchestra because (a) sound waves pass easily through a head (b) a head is not very large compared with the wavelength of the sound

Reverberation Persistence of sound after its production stopped, is called reverberation. When a sound is produced in a big hall, its wave reflect from the walls and travel back and forth. Due to this energy does not reduce and the sound persist. A short reverberation is desirable in a concert hall (where music is being played) because it gives ‘life’ to sound. Speed of sound Speed of sound through any medium depends upon elasticity and density of medium. (i)

In solids, v = Y d

(ii)

In liquids, v = B r

(iii) In gases, v =

gRT g = CP gP , v= ; Cv M r

(c) the sound is reflected from the head (d) the wavelength of the sound is much smaller than the head 7. A thunder clap is heard 5.5 second after the lightening flash. The distance of the flash is (velocity of sound in air = 330 m/s) (a) 1780 m (b) 1815 m (c) 300 m (d) 3560 m 8. Which of the following is carried by the waves from one place to another ? (a) Mass (b) Velocity (c) Wavelength (d) Energy 9. Human ears can sense sound waves travelling in air having wavelength of (a) 10–3 m (b) 10–2 m (c) 1m (d) 102 m 10. The frequency of a wave travelling at a speed of 500 ms–1 is 25Hz. Its time period is (a) 20 s (b) 0.05 s (c) 25 s (d) 0.04 s 11. The velocity of sound in any gas depends upon (a) wavelength of sound only (b) density and elasticity of gas (c) intensity of sound waves only (d) amplitude and frequency of sound 12. What is the effect of humidity on sound waves when humidity increases? (a) Speed of sound waves is more (b) Speed of sound waves is less (c) Speed of sound waves remains same (d) Speed of sound waves becomes zero

Sound 13. Which of the following is used to find the depth of sea? (a) RADAR (b) SONAR (c) ECHO (d) None of these 14. Echo is a type of (a) reflected sound (b) refracted sound (c) neither reflected sound nor refracted sound (d) None of these 15. A shrill sound has a ______ pitch and a dull sound has a _____ pitch. (a) high, low (b) low, high (c) low, low (d) high, high 16. _____ is the characteristic of a musical sound by which a loud sound can be distinguished from a faint sound even though both have the same pitch. (a) Loundness (b) Pitch (c) Quality (d) None of these 17. If you go on increasing the stretching force on a wire in a guitar, its frequency. (a) increases (b) decreases (c) remains unchanged (d) None of these 18. A vibrating body (a) will always produce sound (b) may or may not produce sound if the amplitude of vibration is low (c) will produce sound which depends upon frequency (d) None of these 19. The wavelength of infrasonics in air is of the order of (a) 100 m (b) 101 m –1 (c) 10 m (d) 10–2 m 20. When a sound wave goes from one medium to another, the quantity that remains unchanged is (a) frequency (b) amplitude (c) wavelength (d) speed

C-25

21. Resonance is an example of (a) tuning fork (b) forced vibration (c) free vibration (d) damped vibration 22. A hollow sphere is filled with water. It is hung by a long thread. As the water flows out of a hole at the bottom, the period of oscillation will (a) first increase and then decrease (b) first decrease and then increase (c) go on increasing (d) go on decreasing 23. If a tunnel is dug along the diameter of earth and a piece of stone is dropped into it, then the stone will (a) come out of the another end of the earth and will escape out in space (b) come to rest at the centre of the earth (c) start oscillating about the centre of the earth (d) stop at another end of the earth 24. Which of the following statements is incorrect regarding the time period of a simple pendulum oscillating with small amplitude? The time period of the pendulum (a) is inversely proportional to

(b) is directly proportional to l (c) does not depend upon the amplitude (d) depends upon its mass, material and shape 25. Range of audio-frequencies is (a) 1 – 15 Hz (b) 20 – 20, 000 Hz (c) 103 – 105 Hz (d) 106 – 108 Hz 26. The marching soldiers break steps while crossing a bridge because of (a) damped oscillations (b) resonance (c) echo (d) reverberation

ANSWER KEY 1 2 3 4 5

6 7 8 9 10

(b) (b) (d) (c) (d)

11 12 13 14 15

(b) (a) (b) (a) (a)

16 17 18 19 20

(a) (a) (c) (b) (a)

21 22 23 24 25

(b) (a) (c) (d) (b)

(b)

HINTS AND SOLUTIONS [i.e distance between centre of suspension and centre of gravity of bob] Initially, centre of gravity is at the centre of sphere. When water leaks the centre of gravity goes down until it is half filled; then it begins to go up and finally it again goes at the centre. That is effective length first

11. (b) Velocity of sound in any gas depends upon density and elasticity of gas. 12. (a) Velocity of sound =

gRT M

When water vapour are present in air average molecular weight of air decreases and hence velocity increases.

increases and then decreases. As T µ l , so time period first increases and then decreases.

æl ö

22. (a) Time period of simple pendulum T = 2p çç ÷÷ µ l g è

where l is effective length.

24. (d)

T = 2p

l g

C-26

GENERAL SCIENCE

5 Optics The branch of physics which deals with the propagation, nature and behaviour of light is known as optics.

Light

Light is a form of energy which enables human beings and creatures to ‘see’ things. When light emitted from an object or reflected from the object enters our eyes we are able to see the object. We can’t see an object in dark even if we are in light because there is no light coming from the object to our eyes. Light is an electromagnetic radiation which exhibits properties like a wave as well as a particle. It always propagates in a straight line. Light travels with a speed nearly equal to 3 × 108 m/s. According to current theories, no material particle can travel at a speed greater than the speed of light.

Luminous and Non-luminous Objects Luminous objects are those which emit its own light e.g., sun, glowworm, burning candle, electric lights. Non-luminous objects do not give out its own light but are visible only when light from a luminous object falls on it. e.g., moon, earth, table, paper, etc.

Transparent Translucent and Opaque materials Transparent materials are those which allow most of light to pass through them. Example : Glass, water, air. Translucent materials allow only a part of light to pass through it. We cannot see distinctly through them. Example : greased paper, paraffin wax, etc. Opaque materials do not allow any light to pass through it. They reflect or absorb all the light that falls on them. Example : Books, desk, stone, rubber, trees, etc.

Reflection of Light When light hits an opaque material, the light may be absorbed by the material and converted into heat energy. If light is not absorbed, it is bounced back or reflected at the surface of material. The turning back of light in the same medium is called reflection of light. Laws of reflection 1. The angle of incidence ‘i’ is equal to the angle of reflection ‘r’. 2. At the point of incidence, the incident rays, the normal to the surface and the reflected ray all lie in the same plane.

Optics Reflection by Plane Mirrors Plane mirror is a looking glass which is highly polished on one surface and is silvered on the other surface. When a light ray strikes the polished surface, it is reflected by the silvered surface. An ‘image’ is defined as the impression of an object carried over and formed by light reflected from it. Use of plane mirrors (a) Plane mirrors are primarily used as looking glasses. (b) Since, a combination of mirrors can produce multiple images, they are used to provide false dimensions in showrooms. (c) They are also used as reflectors in solar cookers. (d) Plane mirrors are used in the construction of a periscope. Images and their properties An ‘image’ is defined as the impression of an object carried over and formed by light reflected from it. An image is said to be a real image if it can be caught on a screen, and a virtual image if it cannot be caught on the screen. For example, the image on the screen in a theatre is a real image and the image observed in a plane mirror is a virtual image. Real image 1. When the rays of light actually meet, the image so formed is known as real image. 2. A real image can be caught on a screen since it is formed by actual meeting of rays. 3. A real image is always inverted. 4. A real image is formed by a convergent reflected beam. 5. In ray diagrams, for real image, the rays are represented by full lines. Virtual image 1. When the rays of light appear to meet, the image so formed is known as virtual image. 2. A virtual image cannot be caught on a screen since it is formed by meeting of imaginary rays. 3. A virtual image is always erect. 4. A virtual image is formed by a divergent reflected beam. 5. In ray diagrams, for virtual image, the rays are generally represented by dotted lines. Characteristics of images formed by a plane mirror The image formed by a plane mirror is (a) virtual (the image cannot be formed on a screen) (b) upright (c) laterally inverted (the left side of an image is formed by the right side of an object) (d) the same size as the object (e) the same distance behind the mirror as the object is in front of the mirror

Optics

C-27

Concave and Convex Mirror Concave mirror : If the reflection takes place from the inner surface of a spherical mirror, then the mirror is called concave mirror. Convex mirror : If the outer surface of the spherical mirror acts as a reflector then the mirror is called convex mirror. Uses of concave mirrors : (i) In torches, search-lights and vehicles headlights to get powerful beams of light. (ii) As a shaving mirror to see a large image of the face. (iii) As a dentists mirror to see large images of the teeth of patients. (iv) Large sized concave mirror is used to concentrate sunlight to produce heat in solar furnaces. Uses of convex mirrors : (i) As a rear -view mirrors in vehicles. (ii) For security purposes.

Mirror Formula If an object is placed at a distance u from the pole of a mirror and its image is formed at a distance v (from the pole) then, 1 1 1 + = v u f

(+ve means erect image) (–ve means inverted image)

Lens A lens is a piece of transparent material with two refracting surfaces such that atleast one is curved and refractive index of used material is different from that of the surroundings.

Refraction through a thin lens (lens formula) If an object is placed at a distance u from the optical centre of a lens and its images is formed at a distance v (from the optical centre) and focal length of this length is f then 1 1 1 - = v u f This is called lens formula.

1 . The unit of power f (in m)

is diopter. Focal length of a lens (lens maker’s formula) é1 1 1 ù - ú ê = ( m –1) m l f ë R1 R2 û where mml refractive index of lens with respect to medium. R1 = radius of curvature of first surface of lens, R2 = radius of curvature of second surface of lens.

(|m| >1 means large image)

Total Internal Reflection

(|m| < 1 means small image)

When the object is placed in an optically denser medium and if the incident angle is greater than the critical angle then the ray of light gets reflected back to the originating medium. This phenomenon is called total internal reflection. Critical angle (ic) : When a ray passes from an optically denser medium to an optically rarer medium, the angle of refraction r is greater than the corresponding angle of incidence i. From Snell’s law. Let m1 = m and m 2 = 1 and let for i = ic, r = 90º then sin i c = 1/ m

Refraction of Light When a ray of light passes from one medium to another medium it bends – towards the normal when goes from rarer to denser and away from the normal when goes from denser to rarer medium. This phenomenon is called refraction of light. Twinkling of stars, sun is visible to us about 2 minutes before the actual sunrise, and about 2 minutes after actual sunset etc. due to atmospheric refraction. Refractive index Refractive index of medium II with respect to medium I Speed of light in medium I Speed of light in medium II

Laws of Refraction (i)

Real depth Virtual depth

The power of a lens is defined as P =

If a thin object linear size O situated vertically on the axis of a mirror at a distance u from the pole and its image of size I is formed at a distance v (from the pole), magnification (transverse) is defined as

m 21 =

Refractive index µ =

Power of a lens

Magnification

é I ù évù m= ê ú = ê ú ëO û ëu û

sin i =constant, where i = incidence angle, r = refraction sin r angle. (ii) The incident ray, the refracted ray and the normal at the incident point all lie in the same plane. When object is in denser medium and observer is in rarer medium: i.e.,

Snell’s law : For any two media and for light of a given wavelength, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant.

1 ; i is called the critical angle. m c This phenomenon takes place in shining of air bubble, sparkling of diamond, mirage, looming, in optical communication, endoscopy using optical fibre. \ i c = sin -1

Dispersion of Light When a white ray of light or sunlight passes through a prism it breakes into its seven constituents colours violet, indigo, blue, green, yellow, orange and red (VIBGYOR). This phenomenon is called dispersion of light. The band of seven constituents colours is called spectrum. The deviation is maximum for violet colour and least for red colour.

C-28

GENERAL SCIENCE

The Rainbow A rainbow is a spectrum of white light from the sun. This is a phenomenon due to combined effect of dispersion, refraction and reflection of sunlight by spherical water droplets of rain. (i) Primary rainbow: It is formed due to two refractions and one total internal reflection of the light incident on the droplet. Sunlight is first refracted as it enters a raindrop which cause different colours of light to separate. The observer sees a rainbow with red colour on the top and violet on the bottom. (ii) Secondary rainbow: It is formed due to two refractions and two total internal reflection of light incident on the water droplet. It is due to four - step process. The intensity of light is reduced at the second reflection and hence the secondary rainbow is fainter than the primary rainbow.

Scattering of Light As sunlight travels through the earth’s atmosphere it gets scattered by the small particles present in the atmosphere. According to Rayleigh law, the amount of scattering is inversely æ 1 proportional to the fourth power of the wavelength ç è l4

ö ÷. ø

Phenomenon based on scattering of light (i) Blue colour of sky: Blue colour has a shorter wavelength than red colour therefore blue colour is scattered strongly. Hence the bluish colour predominates in a clear sky. (ii) White colour of clouds: Clouds contain large dust particles, water droplets or ice particles. These large sized Particles do not obey Rayleigh law of scattering. All wavelengths are scattered nearly equally. Hence clouds are generally white. (iii) Sun looks reddish at the Sunset or Sunrise: At sunset or sunrise, the sun’s rays have to pass through a larger distance in the atmosphere. Most of the blue and other shorter wavelengths are scattered. The least scattered light reaching our eyes, therefore the sun looks reddish.

Power of Accomodation of Eye The ability of the lens to change its shape to focus near and distant objects is called accommodation. A normal human eye can see objects clearly that are between 25 cm and infinity.

Defects of Vision and Their Correction Nearsightedness: If the eyeball is too long or the lens too spherical, the image of distant objects is brought to a focus in front of the retina and is out of focus again before the light strikes the retina. Nearby objects can be seen more easily. Eyeglasses with concave lenses correct this problem by diverging the light rays before they enter the eye. Nearsightedness is called myopia. Farsightedness: If the eyeball is too short or the lens too flat or inflexible, the light rays entering the eye — particularly those from nearby objects— will not be brought to a focus by the time they strike the retina. Eyeglasses with convex lenses can correct the problem. Farsightedness is called hypermetropia.

Astigmatism : Astigmatism is the most common refractive problem responsible for blurry vision. Most of the eyeball’s focusing power occurs along the front surface of the eye, involving the tear film and cornea (the clear ‘window’ along the front of the eyeball). The ideal cornea has a perfectly round surface. Anything other than perfectly round contributes to abnormal corneal curvature– this is astigmatism. Cylindrical lens is use to correct astigmatism.

Microscope It is an optical instrument used to see magnified image of a tiny objects. Resolving power (R.P.) of a microscope Resolving power of a microscope is defined as the reciprocal of the least separation between two close objects, so that they appear just separated, when seen through the microscope. Resolving power of a microscope =

1 2m sin q = l d

q = half angle of the cone of light from the point object m sin q = numerical aperture Telescope (Astronomical) It is an optical instrument used to increase the visual angle of distant large objects. It is used to see far off objects clearly. Resolving power (R.P.) of a telescope Resolving power of telescope is defined as the reciprocal of the smallest angular separation between two distant objects, so that they appear just separated, when seen through the telescope. Resolving power of telescope =

D 1.22l

Interference of Light Waves The phenomenon of redistribution of light energy in a medium due to superposition of light waves from two coherent sources is called interference of light. Conditions for sustained interference: (i) Two sources must be coherent. (ii) Amplitudes of waves should be either equal or approximately equal. (iii) Light should be monochromatic. Polarisation It is the phenomenon of restricting the vibration of light in a particular plane. Light waves are transverse in nature i.e., the electric field vector associated with light wave is always at right angles to the direction of propagation of the wave. When unpolarised light is incident on a polaroid (Nicol Prism), the light wave gets linearly polarised i.e., the vibration of electric field vector are along a single direction.

Optics

10.

11.

When the distance between the object and the plane mirror increases (a) the image remains same (b) the size of the image will become less than the size of the object (c) the distance between the image and the plane mirror increases (d) the distance between the image and the plane mirror decreases In lateral inversion (a) right side of the object will be right side of the image. (b) left side of the object will be left side of the image. (c) upside of the object will be down side of the object. (d) right side of the object will be left side of the image. The sun is seen before the actual sunrise because of (a) reflection (b) refraction (c) scattering of light (d) rectilinear propagation of light Butter paper is an example for ............. object. (a) a transparent (b) a translucent (c) an opaque (d) a luminous Power of accommodation of eye implies (a) control intensity (b) prevent internal reflection of light (c) change of focal length of eye lens (d) All of the above Which of the following parts of eye protects the eye and gives it shape? (a) Choroid (b) Sclera (c) Yellow spot (d) Ciliary muscles The human eye forms the image of an object at its (a) cornea (b) iris (c) pupil (d) retina Rainbow is caused due to (a) reflection of sun light from air particles (b) dispersion of sun light from water drops (c) interference of light (d) diffraction of sun rays from water drops In the visible spectrum the colour having the shortest wavelength is (a) green (b) red (c) violet (d) blue The splitting of white light into seven colours on passing through a glass prism is due to (a) refraction (b) reflection (c) interference (d) diffraction At sunrise or at sunset the sun appears to be reddish while at mid-day it looks white. This is because (a) scattering due to dust particles and air molecules causes this phenomenon

C-29

12.

13.

14.

15.

16.

17.

18.

(b) the sun is cooler at sunrise or at sunset (c) refraction causes this phenomenon (d) diffraction sends red rays to the earth at these times A person cannot see objects clearly which are nearer than 75 cm from his eyes, the disease he is suffering from is (a) astigmatism (b) myopia (c) hypermetropia (d) presbyopia For seeing a cricket match, we prefer binoculars to the terrestrial telescope, because (a) binoculars give three-dimensional view (b) terrestrial telescope gives inverted image (c) to avoid chromatic aberration (d) to have larger magnification Dispersion is the term used to describe (a) the propagation of light in straight lines (b) the splitting of a beam of light into component colours (c) the bending of a beam of light when it strikes a mirror (d) the change that takes place in white light after passage through red glass Consider telecommunication through optical fibres. Which of the following statement is not true? (a) Optical fibres can be of graded refractive index (b) Optical fibres have extremely low transmission loss (c) Optical fibres are subject to electromagnetic interference from outside (d) Optical fibres may have hom*ogeneous core with a suitable cladding An optician while testing the eyes finds the vision of a patient to be 6/12. By this he means that (a) the person can read the letters of 6 inches from a distance of 12 m (b) the person can read the letters of 12 inches from 6 m (c) the person can read the letters of 6 m which the normal eye can read from 12 m (d) the focal length of eye lens had become half that of the normal eye A mirage occurs because (a) the refractive index of atmosphere increases with height (b) the refractive index of atmosphere decreases with height (c) the hot ground acts like a mirror (d) refractive index remains constant with height A well cut diamond appears bright because (a) of reflection of light (b) of dispersion of light (c) of the total internal reflection (d) of refraction of light

C-30

GENERAL SCIENCE

19.

Twinkling of stars is on account of (a) large distance of stars and storms in air (b) small size of stars (c) large size of stars (d) large distance of stars and fluctuations in the density of air

20.

A coin in a beaker filled with water appears raised. This phenomenon occurs because of the property of (a) reflection of light (b) refraction of light (c) total internal reflection of light (d) interference of light A spherical air bubble is embedded in a piece of glass. For a ray of light passing through the bubble, it behaves like a (a) converging lens (b) diverging lens (c) plano-converging lens (d) plano-diverging lens ‘The stars seem to be higher on the sky than they actually are’. This can be explained by (a) atmospheric refraction (b) dispersion of light (c) total internal reflection (d) diffraction of light Yellow colour light is used as fog light because yellow colour (a) light is most scattered by fog (b) has the longest wavelength among all colours (c) has the longest wavelength among all colours except red and orange but the red colour is already used for brake light and stop light whereas orange colour is avoided due to its similarity with red (d) has the shortest wavelength among all colours The mirror used for the head light of a car is (a) spherical concave (b) plane (c) cylindrical (d) parabolic concave Soap bubble looks coloured due to (a) dispersion (b) reflection (c) interference (d) Any one of these A star is emitting yellow light. If it is accelerated towards earth then to an observer on earth, it will appear (a) shinning yellow (b) gradually changing to violet (c) gradually changing to red (d) unchanged What should be refractive index of a transparent medium to be invisible in vacuum? (a) 1 (b) < 1 (c) > 1 (d) None of these When a drop of oil is spread on a water surface, it displays beautiful colours in daylight because of (a) dispersion of light (b) reflection of light (c) polarization of light (d) interference of light Smoke emerging from a campfire at the bottom of a hill is being observed by a person at some distance, as shown in the figure. It is evening and the sun has just set behind the hill. Consider regions I and II of the smoke going up the sky

21.

22.

23.

24.

25.

26.

27.

28.

29.

30.

31.

32.

33.

34.

35.

36.

(a) region I will be slightly brighter than the hill and region II will be slightly brighter than the sky (b) region I will be slightly darker than the hill and region II will be slightly brighter than the sky (c) region I will be slightly brighter than the hill and region II will be slightly darker than the sky (d) region I will be slightly darker than the hill and region II will be slightly darker than the sky The ability of an optical instrument to show the images of two adjacent point objects as separate is called (a) dispersive power (b) magnifying power (c) resolving power (d) None of these Total internal reflection can take place only if (a) light goes from optically rarer medium to optically denser medium (b) light goes from optically denser medium to rarer medium (c) the refractive indices of the two media are close to different (d) the refractive indices of the two media are widely different The least distance of distinct vision of a normal eye of an adult is (a) 25 m (b) 25 cm (c) 25 mm (d) None of these Rear-view mirror used in a vehicle is a (a) concave mirror (b) convex mirror (c) plane mirror (d) None of these Magnification produced by a rear view mirror fitted in vehicles (a) is less than one (b) is more than one (c) is equal to one (d) can be more than or less than one depending upon the position of the object in front of it A child is standing in front of a magic mirror. She finds the image of her head bigger, the middle portion of her body of the same size and that of the legs smaller. The following is the order of combinations for the magic mirror from the top. (a) Plane, convex and concave (b) Convex, concave and plane (c) Concave, plane and convex (d) Convex, plane and concave When a CD (compact disc used in audio and video systems) is seen in sunlight, rainbow like colours are seen. This can be explained on the basis of the phenomenon of (a) reflection and diffraction (b) reflection and transmission (c) diffraction and transmission (d) refraction, diffraction and transmission

Optics 37. A watch shows times as 3 : 25 when seen through a mirror, time appeared will be (a) 8 : 35 (b) 9 : 35 (c) 7 : 35 (d) 8 : 25 38. The fine powder of a coloured glass is seen as (a) coloured (b) white (c) black (d) that of the glass colour

C-31

39.

40.

For which wavelength of light is our eye most sensitives (a) 3.00 nm (b) 555 nm (c) 200 nm (d) 800 nm The acronym for LASER is (a) Light Amplification by Stimulated Emission of Radiation (b) Low Amplitude Stimulated Emission of Radiation (c) Low Amplitude Short Energy Radiation (d) Light Amplification by Short Energy Radiation

ANSWER KEY 1 2 3 4 5 6 7

8 9 10 11 12 13 14

(b) (c) (a) (a) (c) (a) (b)

15 16 17 18 19 20 21

(a) (c) (d) (c) (b) (a) (d)

22 23 24 25 26 27 28

29 30 31 32 33 34 35

36 37 38 39 40

(d) (a) (b) (b) (a)

HINTS AND SOLUTIONS 10. 20.

(a) Disperssion arises because of basic phenomenon refraction. (b) We know that, the apparent depth is m times less than the actual depth. i.e.,

dapparent = 21. 22. 23. 24.

25. 26.

27. 28.

30. 31.

dactual m

(b) Bubble will behave as diverging lens because refrective index of air is less than that of a glass. (a) Due to atmospheric refraction the twinkling of star, and their position appear higher than the normal. (c) Yellow colour is used as fog light because of its longest wavelength it 63.33 penetrates well through dense fog. (d) Parabolic reflectors are used to collect energy from a distant source (for example sound waves or incoming star light) and bring it to a common focal point, thus correcting spherical aberration found in simpler spherical reflectors. Since the principles of reflection are reversible, parabolic reflectors can also be used to project energy of a source at its focus outward in a parallel beam, used in devices such as spotlights and car headlights. (c) Interference at thin films causes colouring of soap bubble. (b) As the star is accelerated towards earth, its apparent frequency increases, apparent wavelength decreases. Therefore, colour of light changes gradually to violet. (a) To be invisible in vacuum, µ of medium must be equal to µ of vacuum, which is 1. (d) The colours are seen due to interference of light. The colours seen in reflected light are complementary with the colours seen in transmitted light.

36.

(d)

37. 38. 39.

(a) (b) (b)

where r = 90º for particular incidence angle called critical angle. When the incidence angle is equal to or greater then ic, then total internal reflection occurs. It take place when ray of light travels from optically denser medium (µ1 > µ2)to optically rarer medium. The reason CDs reflect rainbow colors is because they have a clear plastic coating on top of a mirrorized surface. Light refracts (bends) when it moves from one medium (such as air) to another with a different optical density (such as the clear plastic surface of a CD). Different wavelengths of light (every color has a different wavelength) travel at different speeds, so that full spectrum appears when white light passes from the air through the plastic surface of a CD, separated light rays which are then reflected back to us by the mirrorized center surface of a CD. Here the diffraction and transmission also takes place because diffraction of light rays occur when it strikes the surface of CD and transmission is obvious when light enters from one medium to another. The thickness of the different optical media, angle of source light, and brightness of source light all affect which rainbow patterns are visible on a CD. Subtract the given time from 11: 60. All colours are reflected. Our eye can see wavelength of light range 4000Å to 7800Å

C-32

GENERAL SCIENCE

Electricity

Electric Charges

The S.I. unit of electric field intensity is N/coul or volt/metre.

Charge is something associated with matter due to which it produces and experiences electric and magnetic effects. The study of charges at rest is called static electricity or electrostatics while the study of charges in motion is called current electricity. There are two types of electric charge : (i) Positive charge and (ii) Negative charge The magnitude of elementary positive or negative charge is same and is equal to 1.6 × 10–19 C. Charge is a scalar quantity and its SI unit is ampere second or coulomb (C). Basic Properties of Electric Charge (1) Similar charges repel and opposite charges attract. (2) A charged body attracts light uncharged bodies. (3) Accelerated charge radiates energy.

Electric Lines of Force

Conductors and Insulators The materials which allow electric charge (or electricity) to flow freely through them are called conductors. Metals are very good conductors of electric charge. Silver, copper and aluminium are some of the good conductors of electricity. The materials which do not allow electric charge to flow through them are called nonconductors or insulators. For example, most plastics, rubber, non-metals (except graphite), dry wood, wax, mica, porcelain, dry air etc., are insulators.

Coulomb's Law It states that, the electrostatic force of interaction (repulsion or attraction) between two electric charges q1 and q2 separated by a distance r, is directly proportional to the product of the charges and inversely proportional to the square of distance between them. qq F = k 1 22 i.e., F µ q1 q2 and F µ 1/r2 or r K=

Nm 2 coul2 1 –12 Þ e = 8.85× 10 = 9 × 109 0 4 pe 0 coul2 Nm 2

Electric Field The region surrounding an electric charge or a group of charges in which another charge experiences a force of attraction or repulsion is called 'electric field'. r r r F r F E = , E = qlim 0 ®0 q q0 0

An electric line of force is that imaginary smooth curve drawn in an electric field along which a free isolated unit positive charge moves. Two lines of force never intersect. If they are assumed to intersect, there will be two directions of electric field at the point of intersection, which is impossible.

Electric Flux ( f ) The total number of electric lines of force through a given area is called the electric flux. r r (a) For open surface, f0 = df = E . ds r r (b) For closed surface, fc = E . ds

z z z

Gauss’s Law æ 1 ö The total electric flux linked with a closed surface is ç e ÷ è 0ø times the charge enclosed by the closed surface (Gaussian r r q surface). i.e. Ñ ò E.ds = e0

Electrostatic Potential Potential at a point can be physically interpreted as the work done by the field in displacing a unit + ve charge from some reference point to the given point. i.e., V =

w q0

r r dv V = – ò E.ds i.e. E = – dr

O q

It is a scalar quantity. Its dimensions : [M L2 T–3 A–1] Its SI unit is volt or joule coulomb–1. Equipotential Surfaces For a given charge distribution, locus of all points having same potential is called equipotential surfaces.

Capacitors and Capacitance A capacitor or condenser is a device that stores electrical energy. It consists of conductors of any shape and size carrying charges of equal magnitude and opposite signs and separated by an insulating medium

Electricity The symbol of a capacitor is or The net charge on a capacitor is zero. Capacitance or capacity of a capacitor is a measure of ability of the capacitor to store charge on it. When a conductor is charged then its potential rises. The increase in potential is directly proportional to the charge given to the conductor.

C-33

Resistance, Conductance and Resistivity Resistance (R) : It is the property of a substance due to which it opposes the flow of current through it. Its SI unit volt/ampere called ohm (W).

Capacitance of the conductor depends upon : (i) Size of conductor (ii) Surrounding medium (iii) Presence of other conductors nearby

1 L L so, R µ or R = r A A A where L = length, A = area of cross-section of wire and r is called resistivity or specific resistance. 1 The reciprocal of specific resistance is conductance i.e. s = r Superconductors At a very low temperature, the resistance of the conductor may vanish completely. When it happens, the conductor is called a superconductor. For example, helium is a super conductor at 4.2 K (– 268.8°C).

Equivalent Capacitance of Capacitors

Ohm’s Law

Q V The constant C is known as the capacitance of the conductor. Its SI unit is farad (F) or coulomb/volt

i.e.,

Q µ V or Q = CV or, C =

1 1 1 1 = + + ....... + In series : Ceq C1 C2 Cn In parallel : Ceq = C1 + C2 + ....... + Cn

Van de Graff Generator (H igh Voltage Generator) R.J. Van de Graff in 1931 designed an electrostatic generator capable of generating very high potential of the order of 5 × 106 V, which was then made use of an accelerating charged particles so as to carry out nuclear reactions. Principle : It is based on the following two electrostatic phenomena (i) The electric discharge takes place in air or gases readily at pointed conductors. (ii) If a hollow conductor is in contact with an other conductor, then as charge is supplied to the conductor, the hollow conductor continues accepting the charge irrespective of the fact, howsoever large its potential may grow.

Electric Current

R µ L and R µ

It states that if the physical state i.e. temperature, nature of material and dimensions of a conductor remain unchanged then the ratio of potential difference applied across its ends to current flowing through it remains constant. V i.e., V µ I or V = I R, where R = is the resistance of I conductor.

Combination of Resistors – Series and Parallel Series Combination of Resistors Resistances are said to be connected in series between two points if they provide only a single path between two points. Rs = R1 + R2 + R3 + ......... + Rn Parallel Combination of Resistors Resistances are said to be connected in parallel between two points, if it is possible to proceed from one point to another along different paths.

1 1 1 1 1 = + + + .... + R p R1 R2 R3 Rn

The time rate of flow of charge through any cross-section is called electric current. If Dq charge passes through a crossDq section in time Dt then, average current I av = Dt Dq dq Instantaneous current I = lim = Dt ® 0 Dt dt Electric current is measured in ampere (A).

Electrical Energy, Power

Types of electric current : (a) Direct current : The current whose magnitude and direction does not vary with time is called direct current (dc). The various sources are cells, dc dynamo, etc.

V2 I 2 RT t joule = calorie R 4.2 This is the joule’s law of heating 1 unit of electrical energy = 1 Kilowatt hour (1 KWh) = 3.6 × 106 joule

(b)

+ – It’s symbol is Alternating current : The current whose magnitude continuously changes with time and periodically changes its direction is called alternating current. It has constant amplitude and has alternate positive and negative halves. It is produced by ac dynamo. It’s symbol is

When a current is passed through a resistor energy is wasted in overcoming the resistance of the wire. This energy is converted into heat. The heat generated (in joule) when a current of I ampere flows through a resistance of R ohm for T second is given by : H = I2RT = VIt =

This is known as Board of trade (B.O.T) unit of electrical energy. Energy liberated per second is called its power. The electrical power P delivered or consumed by an electrical device is given by P = VI, where V = Potential difference across the device and I = current.

C-34

Ammeter

GENERAL SCIENCE Transformation ratio of the transformer,

An ammeter is a low resistance galvanometer used to measure strength of current in an electrical circuit. An ammeter is always connected in series in a circuit because, when an ammeter is connected in series it does not appreciably change the resistance of circuit and hence the main current flowing through the circuit. Conversion of galvanometer into ammeter : A galvanometer can be converted to an ammeter by connecting a low resistance or shunt in parallel to coil of galvanometer.

Voltmeter A voltmeter is a high resistance galvanometer used to measure potential difference. A voltmeter is connected in parallel to a circuit element because, when connected in parallel it draws least current from the main current. So it measures nearly accurate potential difference. Conversion of galvanometer into voltmeter : A galvanometer is converted to a voltmeter by connecting a high resistance in series with the coil of galvanometer.

Alternating Current When an alternating voltage is applied across a coil or a bulb, it sends a similar varying current (i.e., of the same nature as that of voltage) through the coil. The current is called alternating current (A.C.). The current flowing in only one direction in a circuit is called direct current (D.C.). Batteries, thermocouples and solar cells are some of the sources of direct current. Advantages of Alternating Current Over Direct Current (i) A.C. can be obtained over a wide range of voltages. These voltages can be easily stepped up or stepped down with the help of transformers. (ii) The generation of A.C. is found to be economical than that of D.C. (iii) Alternating current can be controlled by using a choke coil without any significant wastage of electrical energy. (iv) Alternating current may be transmitted at a high voltage from the power house to any place where it can again be brought down to low voltage. The cost in such a transmission is low and energy losses are minimized. Transformers cannot be used for D.C. Hence the cost of D.C. transmission from one place to other is quite high. (v) A.C. equipments such as electric motors etc are more durable and convenient as compared to D.C. equipments.

Transformers It is a device used for transforming a low alternating voltage of high current into a high alternating voltage of low current and vice versa, without increasing power or changing frequency. Principle : It works on the phenomenon of mutual induction. If a low voltage is to be transformed into a high voltage, then the number of turns in secondary is more than those in primary. The transformer is called a step up transformer. If a high voltage is to be transformed into a low voltage, then the number of turns in secondary is less than those in primary. The transformer is called a step-down transformer.

Number of turns in sec ondary ( N s ) Number of turns in primary ( N p )

K > 1, for step-up transformer. K < 1, for step-down transformer. input power = output power i.e., Ep × Ip = Es × Is or,

E N = s = s Is E p N p

Uses of Transformer A transformer is used in almost all ac operation. (i) In voltage regulators for TV, refrigerator, computer, air conditioner etc. (ii) In the induction furnaces. (iii) Step down transformer is used for welding purposes. (iv) In the transmission of ac over long distance. (v) Step down and step up transformers are used in electrical power distribution. Transmission lines G

Low V

Power Station

Step up transformer

High V

Low Load House or factory V

Step down transformer

(vi) Audio frequency transformers are used in radiography, television, radio, telephone etc. (vii) Radio frequency transformers are used in radio communication.

Faraday's Laws of Electromagnetic Induction Faraday gave two laws of electromagnetic induction. First law : Whenever there is change in the magnetic flux associated with a circuit, an e.m.f. is induced in the circuit. This is also known as Neumann’s law. Second law : The magnitude of the induced e.m.f. (e) is directly proportional to the time rate of change of the magnetic flux through the circuit. Df Df or, e = k Dt Dt df In the S.I. system, emf ‘e’ is measured in volt and in Wb/sec. dt

i.e., e µ

Lenz’s law and Conservation of Energy According to Lenz’s law, the direction of the induced current is such that it opposes the change in the magnetic flux that causes the induced current or e.m.f. i.e., induced current tries to maintain flux. df dt The Lenz’s law is consistent with the law of conservation of energy.

On combining Lenz’s law with Faraday’s laws e = -

Electricity

C-35

Eddy Currents

Mutual Inductance

The induced circulating current produced in a metal itself due to change in magnetic flux linked with the metal are called eddy current. The direction of eddy currents is given by Lenz’s law.

Production of induced e.m.f. in a coil due to the changes of current in a neighboring coil, is called mutual induction. Coefficient of mutual induction or mutual inductance : Let fs= magnetic flux linked with the secondary coil when a current Ip flows through the primary coil. Then, fs µ Ip or fs = M Ip .......(1) M = constant of proportionality called mutual inductance or coefficient of mutual induction.

Applications of Eddy Currents (1) Dead beat galvanometer. (2) Energy meter. (3) Speedometer. (4) Electric brakes. (5) Single phase AC motor. (6) Induction furnace.

Self Inductance Production of induced e.m.f. in a coil due to the changes in current in the same coil, is called self induction. The magnetic flux (f) linked with the coil is directly proportional to the current (I) flowing through it. i.e. f µ I \ f= LI The constant L is called coefficient of self induction or self inductance of the coil. The S.I. unit of self inductance or inductance is henry (H). Self-Inductance of a Solenoid L=

µ0 N 2 A l

Factors on which self inductance depends : If no iron or similar material is nearby, then the value of selfinductance depends only on the geometrical factors (length, crosssectional area, number of turns and magnetic permeability of free space).

The charge given to any conductor resides on its outer surface, because (a) the free charge tends to be in its minimum potential energy state (b) the free charge tends to be in its minimum kinetic energy state (c) the free charge tends to be in its maximum potential energy state. (d) the free charge tends to be in its maximum kinetic energy state Two identical conducting balls having positive charges q1 and q2 are separated by a distance r.If they are made to touch each other and then separated to the same distance, the force between them will be (a) less than before (b) same as before (c) more than before (d) zero

AC Generator/Dynamo/Alternator An electrical machine used to convert mechanical energy into electrical energy is knownm as AC generator/alternator or dynamo. Principle : It works on the principle of electromagnetic induction, i.e., when a coil is rotated in uniform magnetic field, an induced emf is produced in it.

DC Motor A D.C. motor converts direct current energy from a battery into mechanical energy of rotation. Principle : It is based on the fact that when a coil carrying current is held in a magnetic field, it experiences a torque, which rotates the coil. Efficiency of the d.c. motor : h=

EI E Back e.m. f . = = VI V Applied e.m. f .

Uses of D.C Motor 1. The D.C. motors are used in D.C. fans (exhaust, ceiling or table) for cooling and ventilation. 2. They are used for pumping water. 3. Big D.C. motors are used for running tram-cars and even trains.

Potential at any point inside a charged hollow sphere (a) increases with distance (b) is a constant (c) decreases with distance from centre (d) is zero Three bulbs of 40 W, 60 W and 100 W are connected in series to a current source of 200 V. Which of the following statements is true ? (a) 40 W bulb glows brightest (b) 60 W bulb glows brightest (c) 100 W bulb glows brightest (d) All bulbs glow with same brightness A voltmeter essentially consists of (a) a high resistance, in series with a galvanometer (b) a low resistance, in series with a galvanometer (c) a high resistance in parallel with a galvanometer (d) a low resistance in parallel with a galvanometer

C-36

Eddy currents are produced when (a) a metal is kept in varying magnetic field (b) a metal is kept in steady magnetic field (c) a circular coil is placed in a magnetic field (d) through a circular coil, current is passed An AC generator of 220 V having internal resistance r = 10W and external resistance R = 100W. What is the power developed in the external circuit? (a) 484 W (b) 400 W (c) 441 W (d) 369 W Choke coil works on the principle of (a) transient current (b) self induction (c) mutual induction (d) wattless current In an a.c. circuit, the r.m.s. value of current, Irms is related to the peak current, I0 by the relation (a)

I rms = 2 I 0

(b)

I rms = p I 0

1 1 I0 (c) I rms = I 0 (d) I rms = p 2 10. The frequency of A.C. mains in India is (a) 30 c/s (b) 50 c/s (c) 60 c/s (d) 120 c/s 11. A bulb and a capacitor are connected in series to a source of alternating current. If its frequency is increased, while keeping the voltage of the source constant, then bulb will (a) give more intense light (b) give less intense light (c) give light of same intensity before (d) stop radiating light 12. In an A.C. circuit with voltage V and current I the power dissipated is

(a)

13.

14.

15.

16.

(b)

1 VI 2

2 (c) V I (d) dependent on the phase between V and I Alternating current cannot be measured by D.C. ammeter because (a) average value of current for complete cycle is zero (b) A.C. changes direction (c) A.C. cannot pass through D.C. ammeter (d) D.C. ammeter will get damaged The core of a transformer is laminated because (a) the weight of the transformer may be reduced (b) rusting of the core may be prevented (c) ratio of voltage in primary and secondary may be increased (d) energy losses due to eddy currents may be minimised When a body is charged by induction, then the body (a) becomes neutral (b) does not lose any charge (c) loses whole of the charge on it (d) loses part of the charge on it If a body is positively charged, then it has (a) excess of electrons (b) excess of protons (c) deficiency of electrons (d) deficiency of neutrons

17.

18.

19.

20.

21.

22.

23.

24.

25.

26.

27.

GENERAL SCIENCE On charging by conduction, mass of a body may (a) increase (b) decreases (c) increase or decrease (d) none of these Coulomb’s law is true for (a) atomic distances (= 10–11 m) (b) nuclear distances (= 10–15 m) (c) charged as well as uncharged particles (d) all the distances Which of the following is the best insulator of electricity? (a) Carbon (b) Paper (c) Graphite (d) Ebonite Two spheres A and B of exactly same mass are given equal positive and negative charges respectively. Their masses after charging (a) remains unaffected (b) mass of A > mass of B (c) mass of A < mass of B (d) nothing can be said What happens when some charge is placed on a soap bubble? (a) Its radius decreases (b) Its radius increases (c) The bubble collapses (d) None of these If a body is charged by rubbing it, its weight (a) remains precisely constant (b) increases slightly (c) decreases slightly (d) may increase slightly or may decrease slightly Electric flux at a point in an electric field is (a) positive (b) negative (c) zero (d) none of these The length of a wire is doubled and the radius is doubled. By what factor does the resistance change? (a) 4 times as large (b) Twice as large (c) Unchanged (d) Half as large According to international convention of colour coding in a wire (a) live is red, neutral is black and earth is green (b) live is red, neutral is green and earth is black (c) live is brown, neutral is blue and earth is black (d) live is red, neutral is black and earth is green The resistivity of a wire depends on (a) length (b) area of cross-section (c) material (d) all of these In the circuits shown below the ammeter A reads 4 amp. and the voltmeter V reads 20 volts. The value of the resistance R is R A

(a) slightly more than 5 ohms (b) slightly less than 5 ohms (c) exactly 5 ohms (d) None of these 28. Gases are good conductors of electricity at (a) high pressure (b) low pressure (c) low temperature (d) high temperature

Electricity 29. The resistance of a thin wire in comparison of a thick wire of the same material (a) is low (b) is equal (c) depends upon the metal of the wire (d) is high 30. Conductivity increases in the order of (a) Al, Ag, Cu (b) Al, Cu, Ag (c) Cu, Al, Ag (d) Ag, Cu, Al 31. Kilowatt-hour is the unit of (a) potential difference (b) electric power (c) electrical energy (d) charge 32. An electric bulb is filled with (a) hydrogen (b) oxygen and hydrogen (c) ammonia (d) nitrogen and argon 33. When current is passed through an electric bulb, its filament glows, but the wire leading current to the bulb does not glow because (a) less current flows in the leading wire as compared to that in the filament (b) the leading wire has more resistance than the filament (c) the leading wire has less resistance than the filament (d) filament has coating of fluorescent material over it 34. From a power station, the power is transmitted at a very high voltage because – (a) it is generated only at high voltage (b) it is cheaper to produce electricity at high voltage (c) electricity at high voltage is less dangerous (d) there is less loss of energy in transmission at high voltage 35. When a fuse is rated 8A, it means (a) it will not work if current is less than 8A (b) it has a resistance of 8 ohm (c) it will work only if current is 8A (d) it will burn if current exceeds 8A 36. Fuse wire is made of (a) platinum (b) copper (c) aluminium (d) alloy of tin and lead 37. Which is not a device based on the heating effect of electricity? (a) Heater (b) Toaster (c) Refrigerator (d) Press 38. The primary cell which is used in daily life is (a) Leclanche cell (b) Dry cell (c) Daniel cell (d) Simple voltaic cell 39. The filament of an electric bulb is of tungsten because (a) its resistance is negligible (b) it is cheaper (c) its melting point is high (d) filament is easily made 40. Which one of the following heater element is used in electric press? (a) Copper wire (b) Nichrome wire (c) Lead wire (d) Iron wire 41. What should be the characteristic of fuse wire? (a) High melting point, high specific resistance (b) Low melting point, low specific resistance (c) High melting point, low specific resistance (d) Low melting point, high specific resistance

C-37

42. The heating element of an electric heater should be made with a material, which should have (a) high specific resistance and high melting point (b) high specific resistance and low melting point (c) low specific resistance and low melting point (d) low specific resistance and high melting point 43. In charging a battery of motor car, the following effect of electric current is used (a) magnetic (b) heating (c) chemical (d) induction 44. For electroplating a spoon, it is placed in the voltameter at (a) the position of anode (b) the position of cathode (c) exactly in the middle of anode and cathode (d) anywhere in the electrolyte 45. Electroplating does not help in (a) fine finish to the surface (b) shining appearance (c) metals to become hard (d) protect metals against corrosion 46. Faraday’s laws are consequence of conservation of (a) energy (b) energy and magnetic field (c) charge (d) magnetic field 47. Lenz’s law is a consequence of the law of conservation of (a) charge (b) mass (c) energy (d) momentum 48. The laws of electromagnetic induction have been used in the construction of a (a) galvanometer (b) voltmeter (c) electric motor (d) generator 49. Whenever, current is changed in a coil, an induced e.m.f. is produced in the same coil. This property of the coil is due to (a) mutual induction (b) self induction (c) eddy currents (d) hysteresis 50. Alternating current is converted to direct current by (a) rectifier (b) dynamo (c) transformer (d) motor 51. To convert mechanical energy into electrical energy, one can use (a) DC dynamo (b) AC dynamo (c) motor (d) (a) & (b) 52. Transformers are used (a) in DC circuits only (b) in AC circuits only (c) in both DC and AC circuits (d) neither in DC nor in AC circuits 53. The essential difference between an AC generator and a DC generator is that (a) AC generator has an electromagnet while a DC generator has permanent magnet (b) DC generator will generate a higher voltage (c) AC generator will generate a higher voltage (d) AC generator has slip rings while the DC generator has a commutator 54. At the time of short circuit, the current in the circuit (a) reduces substantially (b) does not change (c) increases heavily (d) vary continuously

C-38

55. In an electric motor, conversion takes place of (a) chemical energy into electrical energy (b) electrical energy into mechanical energy (c) electrical energy into light energy (d) electrical energy into chemical energy 56. The current in a generator armature is AC because (a) the magnetic field reverses at intervals (b) the current in the field coils is AC (c) the rotation of the armature causes the field through it to reverse (d) the commutator feeds current into it in opposite directions at every half cycle

1 2 3 4 5

(a) 6 (c) 7 (b) 8 (a) 9 (a) 10

(a) (b) (b) (d) (b)

11 (a) 12 (d) 13 (a) 14 (d) 15 (b)

16 (c) 17 (c) 18 (d) 19 (d) 20 (c)

21 22 23 24 25

GENERAL SCIENCE 57. The current in the armature of a motor is reversed at every half cycle due to the action of a(n) (a) armature (b) field coil (c) brush (d) commutator 58. For dynamo which one of the following statements is correct? (a) It converts the electrical energy into light energy (b) It converts the kinetic energy into heat energy (c) It converts the mechanical energy into electrical energy (d) It converts the electrical energy into mechanical energy

ANSWER KEY (b) 26 (c) 31 (c) (d) 27 (a) 32 (d) (c) 28 (b) 33 (c) (d) 29 (d) 34 (b) (d) 30 (b) 35 (a)

36 37 38 39 40

46 (a) 47 (c) 48 (d) 49 (b) 50 (a)

51 52 53 54 55

(d) (b) (d) (c) (b)

56 57 58

HINTS AND SOLUTIONS 3.

dV dV or, 0 = dr dr because electric field inside a charged hollow sphere is zero. or, v = constant (a) Current through each bulb is same because these are connected in series.

(b) As, E = -

æ V2 ö since ç R = P ÷ , resistance of 40 W bulb is more, hence è ø

greater heat is produced in the 40 W bulb, it glows brightest H = I2 R t (a) For conversion of a Galvanometer to a voltmeter, we connect a large resistance R in series with the galvanometer. (b) V = 200V; r = 10W R¢ = 10 + 100W = 110W V 220 = = 2A R¢ 100 P = I2R = 4 × 100 = 400 W (d) Power dissipated = Erms. Irms = (Erms) (Irms) cosq Hence, power dissipated depends upon phase difference. (a) D.C. ammeter measures average current in AC current, average current is zero for complete cycle. Hence reading will be zero. (d) When there is change of flux in the core of a transformer due to change in current round it, eddy current is produced. The direction of this current is opposite to the current which produces it, so it will reduce the main current. We laminate the core so that flux is reduced resulting in the reduced production of eddy current. (b) Charging by induction involves transfer of charges from one part to the other of the body. No loss of charge is involved. I=

12. 13.

14.

15.

16. (c) Positive charge is due to deficiency of electrons. 17. (c) On charging by conduction, body may gain mass, if it acquires negative charge. It may lose mass, if it acquires positive charge. 18. (d) Coulomb’s law is true for all distances small and large. Hence it is called a long range force. 19. (d) Ebonite is the best insulator. 20. (c) A loses electrons and B gains electrons. Therefore, mass of A < mass of B. 21. (b) The radius of soap bubble increases because of outward force acting on the bubble due to charging. 22. (d) The weight can be increased slightly, if it acquire negative charge & weight can be decreased slightly, if it acquires positive charge. 23. (c) As area of a point is zero, \ f = E (ds) cos q = E cos q ´ 0 = Zero. 30. (b) Silver is the best conductor of electricity. 41. (d) Fuse wire should be such that it melts immediatley when strong current flows through the circuit. The same is possible if its melting point is low and resistivity is high. 42. (a) A heating wire should be such that it produces more heat when current is passed through it and also does not melt. It will be so if it has high specific resistance and high melting point. 43. (c) Chemical effect of current is used in charging a car battery. 44. (b) In electroplating, the metallic ions are positive, which are deposited on cathode. 45. (c) Electroplating does not help in making the metals become hard. 46. (a) Faraday’s laws are based on the conversion of electrical energy into mechanical energy; which is in accordance with the law of conservation of energy.

Magnetism

Magnetism The phenomenon of attracting magnetic substances like iron, cobalt, nickel etc. is called magnetism. A body possessing the property of magnetism is called magnet. Lodestone or magnetite is natural magnet. Earth is also a natural magnet. In magnetised substance all the atomic magnets are aligned in same direction and thus resultant magnetism is non-zero.

Bar Magnet A bar magnet consists of two equal and opposite magnetic poles separated by a small distance. Poles are not exactly at the ends. The shortest distance between two poles is called effective length (Le) and is less than its geometric length (Lg). For bar magnet Le = 2l and Le =(5/6) Lg.

N Le = 2l Lg Bar magnet

Properties of Magnet (i) Attractive property : When a magnet is dipped into iron fillings it is found that the concentration of iron filings, i.e., attracting power of the magnet is maximum at two points near the ends and minimum at the centre. The places where its attracting power is maximum are called poles. (ii) Directive property : When a magnet is suspended its length becomes parallel to N-S direction. The pole pointing north is called the north pole while the other pointing in the geographical south is called the south pole of the magnet. The line joining the two poles of a magnet is called magnetic axis and the vertical plane passing through the axis of a freely suspended or pivoted magnet is called magnetic meridian. (iii) Poles of a magnet always exist in pairs : In a magnet the two poles are found to be equal in strength and opposite in nature. If a magnet is broken into number of pieces, each piece becomes a magnet with two equal and opposite poles. This shows that monopole do not exist. (iv) Repulsive property : A pole of a magnet attracts the opposite pole while repels similar pole. Demagnetisation of Magnet A magnet gets demagnetised, i.e., loses its power of attraction if it is heated, hammered or alternating current is passed through a wire wound over it.

Permanent and (Electromagnets)

Temporary

Magnets

The permanent artificial magnets are made of some metals and alloys like Carbon-steel, Alnico, Platinum-cobalt, Alcomax, Ticonal etc. The permanent magnets are made of ferromagnetic substances with large coercivity and retentivity The temporary artificial magnets like electromagnets are prepared by passing current through coil wound on soft iron core. These cannot retain its strength for a long time. These are made from soft iron, non-metal and alloy. Electromagnets are stronger than permanent magnet. Some Applications of Electromagnets (i) Electric motors (ii) Doorbells (iii) In scrapyards to separate iron from other metals

Coulomb's Law in Magnetism If two magnetic poles of strengths m1 and m2 are kept at a distance r apart then force of attraction or repulsion between the two poles is directly proportional to the product of their pole strengths and inversely proportional to the square of the distance between them

mm µ mm i.e., F µ 1 2 or F = 0 12 2 2 4p r r µ0 where F = = 10 -7 Wb A -1 m -1 = 10 -7 henry/m 4p µ0 is permeability of free space or absolute permeability Magnetic Field The space around a magnet (or a current carrying conductor) in which its magnetic effect can be experienced is called the magnetic field. If a magnet is cut into two equal parts along the length then pole strength is reduced to half and length remains unchanged. m M ´ 2l = 2 2 If a magnet is cut into two equal parts transverse to the length then pole strength remains unchanged and length is reduced to half. 2l M New magnetic dipole moment M ' = m æç ö÷ = è 2 ø 2 Magnetic Lines of Force Magnetic line of force is an imaginary curve tangent to which at a point gives the direction of magnetic field at that point or the magnetic field line is the imaginary path along which an isolated north pole will tend to move if it is free to do so.

New magnetic dipole moment M' = m' (2l) =

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GENERAL SCIENCE

Magnetic lines of force do not intersect each other. Because if they do, there will be two directions of magnetic field which is not possible.

Gauss’s Law in Magnetism

r The surface integral of magnetic field B over a closed surface S is always zero. ® ®

Mathematically,

Ñò B . da = 0 S

The Earth’s Magnetism The branch of Physics which deals with the study of earth's magnetic field is called terrestrial magnetism. William Gilbert suggested that earth itself behaves like a huge magnet. (a) A freely suspended magnet always comes to rest in N-S direction. (b) A piece of soft iron buried in N-S direction inside the earth acquires magnetism. Geographic meridian : It is a vertical plane passing through geographic north and south pole of the earth. Geographic equator : A great circle on the surface of the earth in a plane perpendicular to geographical axis is called geographic equator. All places on geographic equator are at equal distances from geographical poles. Magnetic meridian : It is a vertical plane passing through the magnetic north and south pole of the earth. Magnetic equator : A great circle on the surface of the earth in a plane perpendicular to magnetic axis is called magnetic equator. All places on magnetic euqator are at equal distance from magnetic poles. Magnetic Elements The physical quantities which determine the intensity of earth's total magnetic field completely both in magnitude and direction are called magnetic elements. Angle of declination (f) : The angle between the magnetic meridian and geographical meridian at a place is called angle of declination. Angle of dip or inclination (q) : The angle through which the N pole dips down with reference to horizontal is called the angle of dip. At magnetic north and south pole angle of dip is 90°. At magnetic equator the angle of dip is 0°. Horizontal component of earth's magnetic field : The total intensity of the earth's magnetic field makes an angle q with horizontal. It has (i) component in horizontal plane called horizontal component BH. (ii) component in vertical plane called vertical component BV. BV = B sin q BH = B cos q B so, V = tan q and B= B 2 +B 2 H V BH Intensity of Magnetisation It is defined as the magnetic dipole moment developed per unit volume when a magnetic material is subjected to magnetising field.

Intensity of magnetisation, I=

Magnetic dipole moment M = Volume V

Magnetic Susceptibility The magnetic susceptibility of a magnetic substance is defined as the ratio of the intensity of magnetisation to magnetic intensity. I H The value of cm depends on nature of material and temperature.

i.e., cm =

Magnetic Permeability The magnetic permeability of a magnetic substance is defined as the ratio of the magnetic induction to the magnetic intensity. i.e., µ =

B H

Hysteresis The lagging of intensity of magnetisation (I) or magnetic induction (B) behind the magnetising field (H) during the process of magnetisation and demagnetisation of a ferromagnetic material is called hysteresis. Retentivity : The value of I (or B) of a material when the magnetising field is reduced to zero is called retentivity or residual magnetism of the material. Coercivity : The value of reverse magnetising field required to reduce residual magnetism to zero is called coercivity of the material. Comparison of properties of soft iron and steel : (1) The area of hysteresis loop for soft iron is much smaller than for steel, so energy loss per unit volume per cycle for soft iron is smaller than steel. (2) The retentivity of soft iron is greater than that of steel. (3) The coercivity of steel is much larger than that of soft iron. (4) The magnetisation and demagnetisation is easier in soft iron than steel. (5) Soft iron acquires saturation magnetisation for quite low value of magnetising field than in case of steel or soft iron is much strongly magnetised than steel. Diamagnetic Substances : The substances which when placed in a magnetic field are feebly magnetised in a direction opposite to that of the magnetising field are called diamagnetic substances. Some diamagnetic substances are Cu, Zn, Bi, Ag, Au, Pb, He, Ar, NaCl, H2O, marble, glass, etc. Paramagnetic Substances : The substances which when placed in a magnetic field are feebly magnetised in the direction of magnetising field are called paramagnetic substances. Some paramagnetic substances are Al, Na, Sb, Pt, CuCl2, Mn, Cr, liquid oxygen, etc. Ferromagnetic Substances : The substances which when placed in a magnetic field are strongly magnetised in the direction of the magnetising field are called ferromagnetic substances. Iron, cobalt, nickel, etc. are some examples of ferromagnetic substance.

Magnetism

The magnetism of magnet is due to (a) the spin motion of electron (b) earth (c) pressure of big magnet inside the earth (d) cosmic rays 2. Which of the following is the most suitable material for making permanent magnet ? (a) Steel (b) Soft iron (c) Copper (d) Nickel 3. The permanent magnet is made from which one of the following substances? (a) Diamagnetic (b) Paramagnetic (c) Ferromagnetic (d) Electromagnetic 4. Demagnetisation of magnets can be done by (a) rough handling (b) heating (c) magnetising in the opposite direction (d) All of the above 5. Which of the following is most suitable for the core of electromagnets? (a) Soft iron (b) Steel (c) Copper-nickel alloy (d) Air 6. A magnetic needle is kept in a non-uniform magnetic field. It experiences (a) neither a force nor a torque (b) a torque but not a force (c) a force but not a torque (d) a force and a torque 7. Out of the following, diamagnetic substance is (a) iron (b) copper (c) lead (d) silver 8. The magnetic compass is not useful for navigation near the magnetic poles. Since (a) R = 0 (b) V = 0 (c) H = 0 (d) q = 0º 9. Metals getting magnetised by orientation of atomic magnetic moments in external magnetic field are called (a) diamagnetics (b) paramagnetics (c) ferromagnetics (d) antimagnetics 10. At magnetic poles, the angle of dip is (a) 45º (b) 30º (c) zero (d) 90º 11. Curie temperature is the temperature above which (a) a ferromagnetic material becomes paramagenetic (b) a paramagnetic material becomes diamagnetic (c) a ferromagnetic material becomes diamagnetic (d) a paramagnetic m aterial becomes ferromagnetic

C-41

12. Electromagnets are made of soft iron because soft iron has (a) low retentivity and high coercive force (b) high retentivity and high coercive force (c) low retentivity and low coercive force (d) high retentivity and low coercive force 13. To shield an instrument from external magnetic field, it is placed inside a cabin made from (a) wood (b) ebonite (c) iron (d) diamagnetic substance 14. The force which makes maglev move (a) gravitational field (b) magnetic field (c) nuclear forces (d) air drag 15. A conducting wire can give magnetic poles when it (a) bent into the form of a circular ring (b) placed in an external magnetic field (c) suspended freely in air (d) All of the above 16. Which of the following is an artificial magnet? (a) Bar magnet (b) Horse-shoe magnet (c) Magnetic needle (d) All of the above 17. The distance between two magnetic poles is doubled and their pole-strength is also doubled. The force between them (a) increases to four times (b) decreases by half (c) remains unchanged (d) increases to two times 18. Earth’s magnetic field always has a horizontal component except at (a) magnetic equator (b) magnetic pole (c) geographical north pole (d) at an altitude of 45° 19. When an iron bar is moved over a bar magnet along its length the attractive force (a) increases first and then decreases (b) decreases first and then increases (c) remains same (d) cannot say 20. When the S–pole of a magnet is placed near an unknown pole of another magnet, the two magnets (a) repel each other because the unknown pole is N–pole (b) repel each other because the unknown pole is S–pole (c) attract each other because the unknown pole is S–pole (d) can either attract or repel

C-42

Two magnets A and B are placed with like poles having one above another. What will happen? 23.

A 24.

(a) A will stuck to B (b) A will remain as in figure (c) A will move side ways (d) Can't say 22. A compass which is allowed to move in a horizontal plane is taken to a geomagnetic pole. It (a) will stay in north-south direction only

25.

26.

GENERAL SCIENCE (b) will stay in east-west direction only (c) will stay in any position (d) None of these Magnetic meridian is a (a) point (b) horizontal plane (c) vertical plane (d) line along N-S Due to the earth's magnetic field, charged cosmic ray particles (a) require greater kinetic energy to reach the equator than the poles (b) require less kinetic energy to reach the equator than the poles (c) can never reach the equator (d) can never reach the poles Which one of the following is a non-magnetic substance? (a) Iron (b) Cobalt (c) Nickel (d) Brass The universal properties of all substances is (a) diamagnetism (b) ferromagnetism (c) paramagnetism (d) All of these

ANSWER KEY 1 2 3 4 5

(a) (a) (c) (d) (a)

6 7 8 9 10

(d) (b) (c) (b) (d)

11 12 13 14 15

(a) (d) (c) (b) (a)

16 17 18 19 20

(d) (b) (b) (b) (b)

21 22 23 24 25

(b) (c) (c) (c) (d)

(a)

HINTS AND SOLUTIONS 5. 6.

7. 8. 9.

(a) Soft iron is highly ferromagnetic. (d) A magnetic needle kept in non uniform magnetic field experience a force and torque due to unequal forces acting on poles. (b) Copper has negative susceptibility (i.e. c = –0.96). Hence, it is diamagnetic. (c) Near the magnetic poles, H = 0, therefore, magnetic compass will not work. (b) In paramagnetic metals, magnetism is acquired by orientation of atomic dipoles.

10. (d) At poles, d = 90º. 12. (d) Soft iron has high retentivity and low coercive force. 13. (c) The cabin is made up of iron because maximum magnetic lines of forces pass through it. 14. (b) The magnetic force will pull the vehicle. 21. (b) Unlike poles repel. The repulsive magnetic force will not allow the like poles to get stuck. 22. (c) At geomagnetic poles, there is no horizontal component of earth field and so compass needle may stay at any position.

8 Metals, Semiconductors and Insulators On the basis of electrical conductivity (s) or resistivity (r = 1/s) the solids are classified as (i) Metals – have low resistivity r ~ 10–2 to 10–8 Wm s ~ 102 to 108 Sm–1 (ii) Semiconductors – have intermediate resistivity r ~ 105 to 100 Wm s ~ 10–5 to 100 Sm–1 (iii) Insulators – have high resistivity r ~ 108 Wm s ~ 10–8 Sm–1 i.e. the Semiconductors are the materials whose conductivity is more than insulators but less than conductors. Types of Semiconductors Intrinsic semiconductors or Pure semiconductors In semiconductors forbidden energy gap Eg is more than metals or conductors and less than insulators. Silicon (Si) and Germanium (Ge) are the examples of pure semiconductors. In pure or intrinsic semiconductor, ne = nh = ni where, ne = no. of electrons; nh = no. of holes and ni = no. of intrinsic carrier concentration. Impurity like pentavalent (As, Sb, P) or trivalent (In, B, Al) are added to increase conductivity. Depending on doping type we have (a) n – type semiconductor and (b) p – type semiconductor (a) n – type semiconductor: Si or Ge with pentavalent doping. An atom of valency +5 occupies the position of parent atom in crystal lattice. Four valence electrons form 4 covalent bonds but 5th electron is free and weakly bound to parent atom. The ionisation energy (~ 0.01V for Ge and 0.05V for Si) is small and even at room temperature the electron jumps to conduction band. The dopant is called donor impurity (positively charged). (b) p - type semiconductor: Si or Ge with trivalent doping means one less electron in the 4 covalent bonds, so the 4 th neighbour has a vacancy or hole that can be occupied by an electron from another site. Thus a hole is available for conduction. The trivalent atom is negatively charged as it acquires an electron and is called acceptor atom or impurity. Formation of p – n junction: Part of p-type can be converted into n – type by adding pentavalent impurity. There is concentration gradient between p and n sides, holes diffuse from p side to n

Semiconductor Electronics side (p ® n) and electrons move from (n ® p) creating a layer of positive and negative charges on n and p side respectively called depletion layer. External bias is applied to cause charges to flow.

W – – – –

– – – –

+ + + +

n metallic contact

metallic contact

depletion layer Symbol of p-n junction diode

p – n junction under forward bias: When p – side is connected to positive terminal and n – side to negative terminal of external voltage, it is said to be forward biased. V W – – – –

+ + + +

The applied voltage V is opposite to built in potential V0, hence depletion layer width decreases and barrier height is reduced to (V0 – V). There is minority carrier injection, hence charges begin to flow. Current is in the order of mA. (c) p – n junction under reverse bias: When p-side of p-n junction is connected to –ve terminal and n-side to +ve terminal of the battery, the diode is said to be reverse biased. The direction of applied voltage is same as direction of barrier potential, so barrier height increases to (V0 + V). This suppresses flow of electrons from n ® p and holes from p ® n. Diffusion current decreases but drift of electrons and holes under the electric field affect remains. This drift current is few mA. The current under reverse bias is independent of applied voltage upto a critical value known as breakdown voltage (Vbr) when V = Vbr diode reverse current increases sharply. If the reverse current is not limited below this, the diode gets destroyed due to overheating.

– – – –

+ + + +

C-44

GENERAL SCIENCE

Special purpose p – n junction diode:

Junction Transistor:

Zener diode: It is fabricated by heavy doping of p and n sides of p – n junction. Depletion region is thin < 10–6 m. Electric field of junction is high ~ 5 × 106 V/m. Reverse bias ~ 5V. It is used as voltage regulator. p-n junction diode is used as a rectifier. Rectifier is a device which converts A.C. into D.C. Inverter converts D.C. into A.C.

Types: (i) n-p-n type, (ii) p-n-p type. Structure: (i) Emitter (E), (ii) Base (B), (iii) Collector (C) Symbol:

Optoelectronic junction devices: (a) Photodiode: It is a p – n junction fabricated with a transparent window to allow light photons to fall on it. These photons generate electron hole pairs upon absorption. The generation of electron hole pair is near the junction and due to junction field they remain separated till external load is connected. The electron are collected on n–side and holes on p–side near junction and give rise to an emf. When external load is connected, current flows. The magnitude of current depends on intensity of incident radiation. (b) Light emitting diode (LED) : It consists of heavily doped p – n junction in forward bias. Electrons move from n ® p and holes from p ® n (minority carriers). Thus, near junction, minority carrier concentration increases (under no bias it is less) and they combine with majority carriers near the junction to release energy in form of photons with energy equal to or less than band gap energy. As forward bias increases, current increases till light intensity reaches maximum.

In a p-n junction (a) the potential of p & n sides becomes higher alternately (b) the p side is at higher electrical potential than n side (c) the n side is at higher electric potential than p side (d) both p & n sides are at same potential Barrier potential of a p-n junction diode does not depend on (a) doping density (b) diode design (c) temperature (d) forward bias The energy band gap is maximum in (a) metals (b) superconductors (c) insulators (d) semiconductors The part of a transistor which is most heavily doped to produce large number of majority carriers is (a) emmiter (b) base (c) collector (d) can be any of the above three

E C

B npn type n-p-n type AC parameters: (i)

Input resistance = Þ ri =

(ii)

B pnp type p-n-p type Change in base-emitter voltage Base current

ΧVBE ® dynamic resistance ΧI B

æ ΧVCE ö÷ ÷ Output resistance, r0 = ççç çè ΧIC ø÷÷ I

(iii) Current amplification factor (b) æ ΧI ö α ac < ççç C ÷÷÷ çè ΧI B ø÷ V

; αdc
(Eg)Si > (Eg)Ge (d) (Eg)C = (Eg)Si = (Eg)Ge 11. In an unbiased p-n junction, holes diffuse from the p-region to n-region because (a) free electrons in the n-region attract them. (b) they move across the junction by the potential difference. (c) hole concentration in p-region is more as compared to n-region. (d) all the above 12. For a transistor amplifier, the voltage gain (a) remains constant for all frequencies. (b) is high at high and low frequencies and constant in the middle frequency range. (c) is low at high and low frequencies and constant at mid frequencies. (d) none of the above 13. p-n junction diode works as a insulator, if connected (a) to A.C. (b) in forward bias (c) in reverse bias (d) None of these 14. In an n-type silicon, which of the following statement is true? (a) Electrons are majority carriers and trivalent atoms are the dopants. (b) Electrons are minority carriers and pentavalent atoms are the dopants. (c) Holes are minority carriers and pentavalent atoms are the dopants. (d) Holes are majority carriers and trivalent atoms are the dopants. 15. Which of the statements is true for p-type semiconductos? (a) Electrons are majority carriers and trivalent atoms are the dopants. (b) Electrons are minority carriers and pentavalent atoms are the dopants. (c) Holes are minority carriers and pentavalent atoms are the dopants. (d) Holes are majority carriers and trivalent atoms are the dopants. 16. When a forward bias is applied to a p-n junction, it (a) raises the potential barrier. (b) reduces the majority carrier current to zero. (c) lowers the potential barrier. (d) None of these

C-45

17. The potential barrier, in the depletion layer, is due to (a) ions (b) holes (c) electrons (d) both (b) and (c) 18. Zener diode is used as (a) half wave rectifier (b) full wave rectifier (c) A.C. voltage stabilizer(d) D.C. voltage stabilizer 19. For a transistor amplifier, the voltage gain (a) remains constant for all frequencies (b) is high at high and low frequencies and constant in the middle frequency range (c) is low at high and low frequencies and constant at mid frequencies (d) None of these 20. In a semiconductor, the concentration of electrons is 8 × 1014/cm3 and that of the holes is 5 × 1012 cm3. The semiconductor is (a) p-type (b) n-type (c) intrinsic (d) Cannot say 21. When a semiconductor is heated, its resistance (a) decreases (b) increases (c) remains unchanged (d) either (b) or (c) 22. The forbidden gap in the energy bands of germanium at room temperature is about (a) 1.1 eV (b) 0.1 eV (c) 0.67 eV (d) 6.7 eV 23. To obtain a p-type germanium semiconductor, it must be doped with (a) arsenic (b) antimony (c) indium (d) phosphorus 24. Which impurity is doped in Si to form n-type semiconductors? (a) Al (b) B (c) As (d) None of these 25. In extrinsic semiconductors (a) the conduction band and valence band overlap (b) the gap between conduction band and valence band is more than 16 eV (c) the gap between conduction band and valence band is near about 1 eV (d) the gap between conduction band and valence band will be 100 eV and more 26. Function of rectifier is (a) to convert A.C. into D.C. (b) to convert D.C. into A.C. (c) Both (a) and (b) (d) None of these 27. Zener breakdown takes place if (a) doped impurity is low (b) doped impurity is high (c) less impurity in n-part (d) less impurity in p-part

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28. Which one of the following is not a correct statement about semiconductors? (a) The electrons and holes have different mobilities in a semiconductor (b) In an n-type semiconductor, the Fermi level lies closer to the conduction band edge (c) Silicon is a direct band gap semiconductor (d) Silicon is has diamond structure 29. The energy band gap is minimum in (a) metals (b) superconductors (c) insulators (d) semiconductors. 30. An oscillator is nothing but an amplifer with (a) positive feedback (b) negative feedback (c) large gain (d) no feedback 31. When a solid with a band gap has a donor level just below its empty energy band, the solid is (a) an insulator (b) a conductor (c) p-type semiconductor (d) n-type semiconductor 32. Regarding a semiconductor which one of the following is wrong? (a) There are no free electrons at room temperature (b) There are no free electrons at 0K (c) The number of free electrons increases with rise of temperature (d) The charge carriers are electrons and holes 33. p-n junction is said to be forward biased, when (a) the positive pole of the battery is joined to the p-semiconductor and negative pole to the n-semiconductor (b) the positive pole of the battery is joined to the n-semiconductor and p-semiconductor (c) the positive pole of the battery is connected to n- semiconductor and p- semiconductor (d) a mechanical force is applied in the forward direction 34. At absolute zero, Si acts as (a) non-metal (b) metal (c) insulator (d) None of these 35. When n-type semiconductor is heated (a) number of electrons increases while that of holes decreases (b) number of holes increases while that of electrons decreases (c) number of electrons and holes remain same (d) number of electrons and holes increases equally 36. To use a transistor as an amplifier (a) The emitter base junction is forward biased and the base collector junction is reverse biased (b) no bias voltage is required (c) both junctions are forward biased (d) both junctions are reverse biased 37. The part of the transistor which is heavily doped to produce large number of majority carriers is (a) emitter (b) base (c) collector (d) any of the above depending upon the nature of transistor

38.

39.

40.

41.

42.

43.

44.

45.

46.

47.

GENERAL SCIENCE When a p-n junction diode is reverse biased the flow of current across the junction is mainly due to (a) diffusion of charges (b) drift of charges (c) depends on the nature of material (d) both drift and diffusion of charges When an n–p–n transistor is used as an amplifier then (a) electrons flow from emitter to collector (b) holes flow from emitter to collector (c) electrons flow from collector to emitter (d) electrons flow from battery to emitter An n-p-n transistor conducts when (a) both collector and emitter are negative with respect to the base (b) both collector and emitter are positive with respect to the base (c) collector is positive and emitter is negative with respect to the base (d) collector is positive and emitter is at same potential as the base Reverse bias applied to a junction diode (a) increases the minority carrier current (b) lowers the potential barrier (c) raises the potential barrier (d) increases the majority carrier current In semiconductors, at room temperature (a) the conduction band is completely empty (b) the valence band is partially empty and the conduction band is partially filled (c) the valence band is completely filled and the conduction band is partially filled (d) the valence band is completely filled Application of a forward bias to a p–n junction (a) widens the depletion zone. (b) increases the potential difference across the depletion zone. (c) increases the number of donors on the n side. (d) increases the electric field in the depletion zone. A piece of copper and another of germanium are cooled from room temperature to 80 K. The resistance of (a) each of them increases (b) each of them decreases (c) copper increases and germanium decreases (d) copper decreases and germanium increases In an intrinsic semiconductor (a) only electrons are responsible for flow of current (b) both holes and electrons carry current (c) both holes and electrons carry current with electrons being majority carriers (d) only holes are responsible for flow of current If the conductivity of a semiconductor is only due to break up of the covalent bonds due to thermal excitation, then the semiconductor is called (a) intrinsic (b) extrinsic (c) donor (d) acceptor The mobility of conduction electrons is greater than that of holes, since electrons (a) are lighter (b) are negatively charged (c) require smaller energy for moving through crystal lattice (d) undergo smaller number of collisions

Semiconductor Electronics 48. In the symbol of a transistor , the arrow head points in the direction of flow of (a) holes (b) electrons (c) majority carriers (d) minority carriers 49. Transistors are essentially (a) power driven devices (b) current driven devices (c) voltage driven devices (d) resistance driven devices 50. In a transistor (a) emitter is more highly doped than collector (b) collector is more highly doped than emitter (c) both are equally doped (d) None of the above 51. One way in which the operation of an n-p-n transistor differs from that of a p-n-p

C-47

(a) the emitter junction is reverse biased in n-p-n. (b) the emitter junction injects minority carriers into base region of the p-n-p (c) the emitter injects holes into the base of the p-n-p and electrons into the base region n-p-n (d) the emitter injects holes into the base of n-p-n 52. n-p-n transistors are preferred to p-n-p transistors because: (a) they have low cost (b) they have low dissipation energy (c) they are capable of handling large power (d) electrons have high mobility than holes and hence high mobility of energy 53. An alternating current can be converted into direct current by a (a) rectifier (b) transformer (c) dynamo (d) motor

ANSW ER KEY 1

(b )

(c)

(a)

(d )

(c)

(b )

(c)

(a)

(c)

(d)

(c)

(a)

(c)

(a)

(c)

(d)

(d )

(d)

(c)

(d )

(b)

(a)

(c)

(a)

(b )

(a)

(b)

(a)

(c)

(d )

(c)

(b )

(a)

(c)

(a)

(b)

(c)

(b)

(a)

(c)

(a)

HINTS AND SOLUTIONS 1.

3. 5. 6. 7.

(b) [Hint : For easy flow of current the p-side must be connected to +ive terminal of battery i.e., it is connected to higher potential in comparison to n. This connection is called forward biased. In this case the input resistance is very low. In reverse-biased, the p-side is connected to –ive terminal & n-side to (+ive) terminal to battery. In this case input resistance is very high. n ow I d k e forward ea ag Br volt biased VB V VT reverse biased (b) [Hint : Barrier potential depends on, doping density, temperature, forward/reverse bias but does not depend on diode design.] (c) Maximum in insulators and overlaping in metals. (d) Holes move from base to emitter. (a) The phase difference between output voltage and input signal voltage in common base transistor circuit is zero (b) Inverter converts a.c. into d.c.

13. 18.

20. 22. 23. 24.

(a) Distance between conduction band and valence band = Fermi gap energy = 1eV. Since there is a small gap between the conduction and valence band so it is semiconductor. (c) In reverse bias no current flows. (c) For a wide range of values of load resistance, the current in the Zener diode may change but the voltage across it remains unaffected. Thus the output voltage across the Zener diode is a regulated voltage. (b) Since, ne > nh, the semiconductor is n-type. (c) DEg(Germanium) = 0.67 eV. (c) For p-type semiconductor the doping impurity should be trivalent. (c) Because As is pentavalent impurity.

26. (a) AC ® Rectifier ® DC 27. (b) Zener breakdown can occur in heavily doped diodes. In lightly doped diodes the necessary voltage is higher, and avalanche multiplication is then the chief process involved. 28. (c) Silicon is an indirect-band gap semi-conductor. CB Donor level VB

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29. (a) Maximum in insulators and minimum in metals. 30. (a) A positive feedback from output to input in an amplifier provides oscillations of constant amplitude. 31. (d) Donor level close to energy band is in case of n-type semi-conductor. 32. (a) At room temperature, few bonds breaks and electron hole pair generates inside the semiconductor. 33. (a) For forward biasing of p-n junction, the positive terminal of external battery is to be connected to p-semiconductor and negative terminal of battery to the n-semiconductor. 34. (c) Semiconductors are insulators at room temperature. 35. (d) Due to heating, when a free electron is produced then simultaneously a hole is also produced. 36. (a) To use a transistor as an amplifier the emitter base junction is forward biased while the collector base junction is reverse biased. 37. (a) The function of emitter is to supply the majority carriers. So, it is heavily doped. 38. (b) When p-n junction is reverse biased, the flow of current is due to drifting of minority charge carriers across the junction. 39. (a) In an n-p-n transistor, the charge carriers, are free electrons in the transistor as well as in external circuit; these electrons flow from emitter to collector. 40. (c) When the collector is positive and emitter is negative w.r.t. base, it causes the forward biasing for each junction, which causes conduction of current. 41. (c) In reverse biasing, the conduction across the p-n junction does not take place due to majority carriers but takes place due to minority carriers if the voltage of external battery is large. The size of the depletion region increases thereby increasing the potential barrier.

GENERAL SCIENCE 42. (c) In semiconductros, the conduction is empty and the valence band is completely filled at 0 K. No electron from valence band can cross over to conduction band at 0K. But at room temperature some electrons in the valence band jump over to the conduction band due to the small forbidden gap, i.e. 1 eV. 43. (c) PN

Number of donors is more because electrons from – ve terminal of the cell pushes (enters) the n-side and decreases th e number of uncompen sated pentavalent ion due to which potential barrier is reduced. The neutralised pentavalent atom are again in position to donate electrons.

CHEMISTRY

1 1.

Nature of Matter

Substance (or chemical substance) : A “substance” is a kind of matter that can not be separated into other kinds of matter by any physical process. e.g. gold, silver, iron, sodium chloride, calcium carbonate etc. Pure substance: is one that is a single substance and has a uniform composition. Such a substance always have the same texture and taste. e.g. water, salt, sugar etc.

Testing the purity of a substance : The purity of substance can easily be checked by checking its melting points in case of a solid substance or by checking its boiling points in case of a liquid substance.

Types of pure substances : Two different types of pure substances are (i) Element: An element is a substance which can not be split up into two or more simpler substances by usual chemical methods of applying heat, light or electric energy. e. g. hydrogen, oxygen, sodium, chlorine etc. (ii) Compound: A compound is a substance made up of two or more elements chemically combined in a fixed ratio by weight e.g. H2O (water), NaCl (sodium chloride) etc.

Mixture Insoluble solid in solvent

2. 3. 4. 5. 6.

Solution of solid in liquid Miscible mixture of liquids. Immiscible mixture of liquids. Mixture of two solids one of which is sublime Mixture of substances in solution.

Mixture : A mixture is a substance which consists of two or more elements or compounds not chemically combined together. e.g. Air is a mixture of nitrogen, oxygen, inert gases, water vapour, carbon dioxide etc. Types of mixtures : Mixtures are impure substances. They are of two types: (i) hom*ogeneous mixture: It has a uniform composition throughout and its components can not be distinguished visually. e.g. a well mixed sample of vinegar. (ii) Heterogeneous mixture: It is one that is not uniform throughout. Different samples of a heterogeneous mixture may have different composition. e.g. a mixture of salt and pepper. Solution : It is a hom*ogeneous mixture of two or more substances whose composition can be varied. e.g. solution of common salt in water, solution of ammonia in water. Some other examples are lemonade, co*ke, pepsi etc. Separating the components of a mixture : Various methods are used for separating the constituents of a mixture. Depending upon the type of mixture (i.e. whether it is a hom*ogeneous mixture or heterogeneous mixture) different methods used are given below :

Separation Method Sedimentation followed by filtration. In case of a fine solid centrifugation is used instead of filtration Evaporation, crystallization, distillation Fractional distillation Separating funnel Sublimation Chromatography

Solute : The component of solution that is dissolved and present in smaller quantities in a solution is known as solute. e.g. common salt in case of solution of common salt in water and ammonia in case of solution of ammonia in water. 10. Solvent : The component of solution in which solute is dissolved is known as solvent. It is always present in larger amount in a solution. e.g. water in case of the solution of common salt or ammonia in water. 11. Saturated Solution : A solution in which no more solute can be dissolved at the same temperature is called

12. 13.

14.

Saturated solution. Unsaturated Solution : It is a solution in which more solute can be dissolved at the same temperature. Super-saturated Solution : It is a solution which contains more mass of the dissolved solute than the saturated solution at the same temperature and pressure. Alloys : Alloys are hom*ogeneous mixtures of metal and can not separated into their components by physical methods. e.g. Brass is a mixture of copper (Cu) and zinc (Zn).

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15. Concentration of a solution : Concentration of a solution is the amount of solute present in a given amount (mass or volume) of a solution or the amount of solute dissolved in a given mass or volume of a solvent. Concentration=

Amount of solute Amount of solvent

16. Solubility : It is defined as the amount of solute dissolved in 100g of solvent to form a saturated solution. 17. Suspension : It is a non-hom*ogeneous mixture in which solids are dispersed in liquids. In it the solute particles do not dissolve but remains suspended through out the bulk of the medium. 18. Colloids or colloidal solution : Colloid is a heterogeneous mixture. The size of particles of a colloid is intermediate between true solutions and suspensions (i.e between 1nm and 100 nm). The particles of a colloid can not be seen with naked eye. 19. Types of colloidal solution : Since colloidal solution is heterogeneous mixture it consists of two phases. These are (i)

dispersed phase (colloidal particles)

(ii) dispersion medium (The medium in which colloidal particles are dispersed.) 20. Emulsion : Emulsions are liquid-liquid colloids. 21. Types of Emulsion : Emulsions are of two types : (i) water in oil

(ii) oil in water

22.

GENERAL SCIENCE Emulsifiers are those substances that help in forming stable emulsions of oil and water, e.g. milk, cod-liver oil, cold creams, vanishing creams, moisturising cream, paints, etc.

23.

Physical change : During such a change no new substances is formed and there is no change in the chemical properties of the substances.

24.

Chemical change : Such a change is accompanied by change in chemical properties and formation of new substances.

25.

Elements are a type of pure substances. An element is a substance that can not be split into two or more simpler substances by usual chemical methods of applying heat, light or electric energy. Types of elements : Elements have been divided into metals and non-metals. All metals (except mercury) are solids. mercury is a liquid, e.g. sodium, potassuim, gold, silver etc. All non-metals are solids or gases (Bromine is an exception as it is a liquid non-metal) e.g. hydrogen, oxygen, carbon, bromine, chlorine, iodine etc.

26.

Compound : A compound is a substance made up of two or more elements chemically combined in a fixed ratio by weight. e.g. water (H2O) is a compound made up of two elements Hydrogen and Oxygen chemically combined in a fixed proportion of 1: 8 by weight.

Nature of Matter

10.

11.

12.

13.

Air is regarded as a mixture because (a) its pressure may very (b) its temperature may change (c) its volume changes under different conditions (d) its composition may vary Which of the following is a compound ? (a) Stainless steel (b) Bronze (c) Graphite (d) Hydrogen sulphide The process used to separate oil and water is (a) distillation (b) sublimation (c) separating funnel (d) chromatography In which of the following the constituents are present in any ratio? (a) Mixture (b) Compound (c) Solution (d) Colloid A mixture of common salt, sulphur, sand and iron filings is shaken with carbon disulphide and filtered through a filter paper. The filtrate is evaporated to dryness in a china dish. What will be left in the dish after evaporation? (a) Sand (b) Sulphur (c) Iron filings (d) Common salt Two substances A and B when brought together form a substance C with the evolution of heat. The properties of C are entirely different from those of A and B. The substance C is (a) a compound (b) an element (c) a mixture (d) none of these. Camphor can be purified by (a) distillation (b) filtration (c) sedimentation (d) sublimation Which one of the following will result in the formation of a mixture? (a) Crushing of a marble tile into small particles (b) Breaking of ice cubes into small pieces (c) Adding sodium metal to water (d) Adding milk in water Purity of a solid substance can be checked by its (a) boiling point (b) melting point (c) solubility in water (d) solubility in alcohol A mixture of ethanol and water can be separated by (a) filtration (b) decantation (c) fractional distillation (d) sublimation Salt can be obtained from sea water by (a) filtration (b) decantation (c) evaporation (d) sublimation A sample contains two substances and has uniform properties. The sample is (a) a compound (b) a heterogeneous mixture (c) an element (d) a hom*ogeneous mixture Which of the following is considered to be a pure substance? (a) Granite (b) Sodium chloride (c) Muddy water (d) Milk of magnesia

C-51

14.

15.

16.

17.

18.

19.

20.

21.

22.

23.

24.

Physical properties of a mixture (a) vary with the amount of substance. (b) depend on the volume of the substance (c) depend on the organization of the substance (d) vary depending upon its components Compounds (a) are the same as mixtures (b) can be separated by their physical properties (c) contain only one type of element (d) are different kinds of atoms chemically combined with each other. White gold is used in jewelry and contains two elements, gold and palladium. A jeweler has two different samples that are both identical in appearance and have a uniform composition throughout. What can be said about the samples? (a) They are hom*ogeneous mixtures and be classified as metallic alloys. (b) The materials are heterogeneous mixtures and can be classified by their components (c) The samples have variable compositions and are classified as metallic solutions. (d) The samples are heterogeneous mixtures that can be separated using magnetic properties. Which of the following is an example of a heterogeneous substance? (a) Bottled water (b) Table salt (c) Pieces of copper (d) Candle Which of the following is an example of a hom*ogeneous substance? (a) Granite (b) Copper sulphate (c) Oil-water solution (d) Muddy water Filtration can be used to separate (a) solids from solids (b) liquids from solids (c) liquids from liquids (d) liquids from gases Melting points can separate materials because (a) substances melt at different temperatures (b) molecules vibrate rapidly when heated (c) heat causes molecules to disintegrate (d) many substances fuse at the melting point Distillation is a good separation technique for (a) solids (b) liquids (c) solid alloys (d) gases Solubility is a good separation technique for (a) pure metals (b) noble gases (c) different salts (d) metallic alloys Magnetism is most beneficial for separating (a) gases and non-metallic liquids (b) magnetic solids and solids such as sulfur (c) non-metallic solids and solids such as sulfur (d) non-magnetic solids from non-magnetic liquids Select the one that is a chemical change. (a) Melting of wax (b) Freezing of water (c) Cooking of food (d) None of these

C-52

25.

26.

27.

28.

29.

30.

Select the one that is a physical change. (a) Digestion of food (b) Growth of plant (c) Rusting of iron (d) None of these On passing through a colloidal solution, the beam of light gets .......... (a) reflected (b) refracted (c) scattered (d) absorbed The size of colloidal particles usually lies in the range (a) 10–5 - 10–7 cm (b) 10–7 - 10–9 cm –3 –5 (c) 10 - 10 cm (d) 10–2 - 10–6 cm Brass is an example of (a) compound (b) element (c) hom*ogeneous mixture (d) heterogeneous mixture Select the one that is not a chemical change ? (a) Dissolution of ammonia in water. (b) Dissolution of carbon dioxide in water. (c) Dissolution of oxygen in water. (d) None of these is a chemical change. A change is said to be a chemical change when (a) it is accompanied by energy change (b) it is accompanied by formation of new substances (c) it is accompanied by change in physical properties (d) All the above are correct

1 2 3 4 5 6

(d) (d) (c) (a) (b) (a)

7 8 9 10 11 12

(d) (d) (b) (c) (c) (d)

13 14 15 16 17 18

31. 32.

33.

34.

35.

36.

GENERAL SCIENCE Solutions with low concentrations of solutes are (a) concentrated (b) dilute (c) solvents (d) None of these Which of the following statements is true about a colloidal system? (a) It carries a net electric charge (b) It consists of one phase only (c) It can be made out of two gases (d) It is electrically neutral as a whole Cloud or fog is an example of colloidal system of (a) liquid dispersed in gas (b) gas dispersed in gas (c) solid dispersed in gas (d) solid dispersed in liquid Normal solution is : (a) inert solution (b) acidic solution (c) one litre containing one equivalent (d) basic solution Which of the following is a colloid ? (a) Sugar solution (b) Urea solution (c) Silicic acid (d) NaCl solution When dispersed phase is liquid and dispersion medium is gas then the colloidal system is called (a) smoke (b) clouds (c) jellies (d) emulsions

ANSWER KEY (b) 19 (d) 20 (d) 21 (a) 22 (d) 23 (b) 24

(b) (a) (b) (c) (b) (c)

25 26 27 28 29 30

(d) (c) (a) (c) (c) (d)

31 32 33 34 35 36

(b) (d) (a) (c) (c) (b)

HINTS AND SOLUTIONS 1.

(d)

(c)

(b)

(a)

(d)

9. 10.

(b) (c)

11.

(c)

12.

(d)

13.

(b)

14.

(d)

15. 16.

(d) (a)

Air is a mixture of different gases like N2, O2, CO2 etc. Its general composition is N2 = 78%, O2 = 21% and traces of few other gases but there may be variation in its composition from place to place and at different height. Hydrogen sulphide (H2S) is a compound of hydrogen and sulphur. Stainless steel and bronze are alloys whereas graphite is allotropic form of element carbon. As oil being less denser than water it forms upper layer. Thus mixture of oil and water can be separated by using separating funnel. Sulphur will left behind. As in given mixture only sulphur gets dissolved in carbon disulphide. C is a compund which is formed as a result of reaction between A and B. Camphor being a sublime substance can be purified by sublimation. Every pure solid has a fixed melting point. Mixture of ethanol and water can be separated by fractional distillation as they have different boiling points. Sea water is a solution of salt and water.During evaporation water gets evaporated off and salt left as a residue. hom*ogeneous mixture is a solution having uniform composition and properties throughout. Sodium chloride being compound is a pure substance. Granite, muddy water and milk of magnesia all are mixtures. Physical properties of mixtures are same as of its components. In a compund the elements are present in a fixed ratio by weight. As they have uniform composition throughout they are considered as hom*ogeneous mixture. Both samples are mixture of two metals (gold and palladium) thus are alloys.

17.

(d)

18. 20.

(b) (a)

21.

(b)

22.

(c)

23.

(b)

24. 25.

26. 27.

28. 29. 31. 33.

34.

(c)

35.

(c)

36.

(b)

Candle is a heterogeneous mixture of wax and thread. Copper is element while bottled water and table salt are compounds. It is a compound. Different pure solid substances melts at a different temperatures. Distillation is a separation technique used for separation of miscible liquids having different boiling point. Different salts have different solubility in a particular solvent. Thus on this basis mixture of different salts can be separated. Magnetism is useful for separation of magnetic and nonmagnetic substances. Chemical changes are irrerversible in nature. Each of the process given in options are irreversible and involve change in chemical properties hence all are chemical changes. This is due to Tyndall effect. The size of colloidal particles usually lie in range of one nm to 100 nm. i.e., 10–5 to 10–7 cm or 1nm = 10–7 \ 100 nm = 10–5cm Brass is an alloy which is a hom*ogeneous substance. Oxygen is insoluble in water. dilute solutions have low concentration of solid. Fog is a colloidal system consisting water droplets dispersed in air. The solution which has one gram equivalent in one litre is called normal solution. Those substances which can not pass through membrane are termed as colloids e.g., silicic acid. Whereas sugar solution, urea and NaCl can pass through the membrane. Clouds consists of fine droplets of water suspended in air.

2 1.

Structure of Atom

Law of conservation of mass :This law was stated by Lavoisier in 1744. It states that “In all physical and chemical changes, the total mass of reactants is equal to total mass of products.” Law of constant proportions (or constant composition) : This law was first stated by Proust in 1797. According to the law “a chemical compound is always found to be made up of the same elements combined together in the same proportions by weight” e.g. the ratio of hydrogen and oxygen in pure water is always 1 : 8 by weight. This law is also called law of definite proportions. Law of multiple proportions : This law was given by John Dalton (1803) and states that "when two elements combine to form two or more compounds, the different mass of one of the elements and the fixed mass of the one with which it combines always form a whole number ratio". This law explains the concept of formation of more than one compound by two elements. Dalton’s Atomic theory : Postulates of Dalton’s Atomic Theory (i) Matter is made up of extremely small indivisible particles called atoms. (ii) Atoms of the same substance are identical in all respects i.e., they possess same size, shape, mass, chemical properties etc. (iii) Atoms of different substances are different in all respects i.e., they possess different size, shape, mass etc. (iv) Atom is the smallest particle that takes part in a chemical reaction. (v) Atoms of different elements may combine with each other in a fixed simple, whole number ratio to form compound atoms. (vi) Atoms can neither be created nor destroyed i.e., atoms are indestructible. Atom : It is the smallest particle of an element which can take part in a chemical change. It may or may not be capable of independent existence. Symbol : The abbreviation used for lengthy names of elements are termed as their symbols. The symbol of an element is the first letter or the first and another letter of English name or Latin name of the element. While writing a symbol, the first letter is always capital and the second is always small.

Molecule : It is the smallest particle of an element or compound that is capable of independent existence and shows all the properties of that substance. [The molecules of an element is made up of only one and same type of atoms, while the molecule of a compound is made up of dissimilar atoms]

Atomicity : The number of atoms present in a molecule of an element or a compound is known as its atomicity. e.g. the atomicity of oxygen is 2 while atomicity ozone is 3.

Ion : It is an electrically charged atom or group of atom. It is formed by the loss or gain of electrons by an atom. Ions are of two types : (i) Cation : It is positively charged ion and is formed by the loss of electron from an atom e.g. H+, Na+, Ca2+, Al3+, NH4+ etc. (ii) Anion : It is negatively charged ion and is formed by the gain of electrons by an atom, e.g. Cl–, O2–, C–, F–, CO32– PO3– 4 etc.

10. 11.

Valency : The combining power (or capacity) of an element is known as its valency.

Formula of simple and molecular compounds Binary compounds are those compounds which are made up of two different elements e.g. NaCl, KBr, CaO etc. Following rules are to be followed for writing the formula. (i) The valencies or charges on the ions must be balanced. (ii) For a compound made up of a metal and a non-metal the symbol of metal is written first. (iii) In compounds formed with polyatomic ions, the ion is enclosed in a bracket before writing the number to indicate the ratio. 12. Sub-Atomic Particles (i) Electrons: Electron was discovered in cathode ray experiment. (ii) The term electron was coined by G.J. Stoney (iii) Protons were discovered in anode ray experiment. Anode rays are also called positive rays or canal rays. Protons was discovered by Wilhelm Wien in 1902. It was identified by J.J. Thomson. (iv) Neutron was discovered by James Chadwick in 1932.

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13. Valency : The electrons present in the outermost shell of an atom are known as valence electrons. These electrons determine the valency of an atom. Valency is equal to the number of valence electrons. In case the number of valence electrons is close to its full capacity. Then, Valency = 8 - valence electrons

If outermost shell is completely filled then valency is zero. Valency is the combining capacity of an atom. 14. Atomic number (Z) : Atomic number of an element is equal to the number of protons present in the nucleus of an atom. Atomic number (Z) = number of protons = number of electrons. 15. Mass number (A) : It refers to the total number of neutrons and protons (i.e., sum of protons and neutrons) called collectively as nucleus, present in an atom. Mass number (A) = number of protons + number of neutron 16. Isotopes : Atoms of the same element having same atomic number but different mass numbers are known as Isotopes e.g.

35 17 Cl

and

36 1 17 Cl , 1 H

and

2 1H

12 6 C

and 14 6 C etc.

17. Applications of Isotopes : Isotopes are used in various fields. For example. (i) Isotope of uranium is used as a fuel in nuclear reactor (ii) Isotope of cobalt is used in treatment of cancer (iii) Isotope of iodine is used in treatment of goitre. 18. Isobars : Atoms of different elements having same mass numbers are known as Isobars, e.g K-40 and Ar-40 19. The discovery of cathode rays was done by J.J. Thomson an English physicist. Properties of cathode rays :

GENERAL SCIENCE • The cathode rays are constituted by fast moving electrons. • These rays travel in a straight line. • These rays posses mechanical energy. • These rays produce heat when focussed on metals. • These rays produce flourescenes when focussed on metals. • They affects the photographic plate. • They are deflected by electric and magnetic field. • They ionize the gases through which they pass. • They travel in a straight line. • They can produce mechanical effects. • Anode rays are positively charged. • The nature of anode rays depends upon the gas taken in the discharge tube. • The mass of anode rays particles is almost equal to the mass of an atom from which it is formed. Sub-atomic Particles : Electron, proton and neutron are subatomic particles. The credit for discovery of these particles goes to Electron — J.J. Thomson and Proton — E. Goldstein Another subatomic particle which is neutral and has a mass approx. equal to that of a proton was called neutron and was discovered by Chadwick. The neutron is a neutral particle found in the nucleus of an atoms. Atom of all elements contain neutron (except hydrogen atom which does not contain neutron). The relative mass of neutron is 1 amu and it carries no charge (i.e., it is neutral)

Properties of atomic particles (Comparative) Particle

Electron e–

(i) Symbol (ii) Nature (iii) (a) Charge (b) Unit charge (iv) Mass (a) amu (b) kg (v) Location

e or Negatively charged (a) – 1.6 × 10–19C (b) –1 (a) 0.0005486 amu (b) 9.1 × 10–31kg Extra nuclear space

(vi) Notation

–1

(vii) Relative mass

1/1840

Proton

Neutron

p Positively charged (a) + 1.6 × 10–19C (b) + 1 (a) 1.00753 amu (b) 1.67265× 10–27 kg nucleus

n neutral (no charge) 0 0 (a) 1.00893 amu (b) 1.67495 × 10–27 kg nucleus

1 p 1

1 0n

Structure of Atom

10.

11.

12.

The formation of SO2 and SO3 explain (a) the law of conservation of mass (b) the law of multiple proportions (c) the law of definite properties (d) Boyle’s law One gram of which of the following contains largest number of oxygen atoms? (a) O (b) O2 (c) O3 (d) All contains same The law of definite proportions was given by – (a) John Dalton (b) Humphry Davy (c) Proust (d) Michael Faraday Molecular mass is defined as the (a) mass of one atom compared with the mass of one molecule (b) mass of one atom compared with the mass of one atom of hydrogen (c) mass of one molecule of any substance compared with the mass of one atom of C-12 (d) None of these The chemical symbol for barium is (a) B (b) Ba (c) Be (d) Bi A group of atoms chemically bonded together is a (an) (a) molecule (b) ion (c) salt (d) element Adding electrons to an atom will result in a (an) (a) molecule (b) anion (c) cation (d) salt When an atom loses electrons, it is called a (an) _____ and has a ______ charge. (a) anion, positive (b) cation, positive (c) anion, negative (d) cation, positive The molecular formula P2O5 means that (a) a molecule contains 2 atoms of P and 5 atoms of O (b) the ratio of the mass of P to the mass of O in the molecule is 2:5 (c) there are twice as many P atoms in the molecule as there are O atoms (d) the ratio of the mass of P to the mass of O in the molecule is 5 : 2 The percentage of copper and oxygen in samples of CuO obtained by different methods were found to be the same. The illustrate the law of (a) constant proportions (b) conservation of mass (c) multiple proportions (d) reciprocal proportions The total number of atoms represented by the compound CuSO4.5H2O is (a) 27 (b) 21 (c) 5 (d) 8 The correct symbol for silver is (a) Ag (b) Si (c) Ar (d) Al

C-55

13.

14.

15.

16.

17.

18.

19.

20.

21.

22.

23.

The cathode ray experiment was done for the first time by (a) J.J. Thomson (b) John Dalton (c) Goldstein (d) Rutherford The nucleus of an atom contains (a) protons (b) electrons (c) protons and neutrons (d) neutrons By whom was neutron discovered? (a) Bohr (b) Chadwick (c) Rutherford (d) Dalton In an atom valence electron are present in (a) outermost orbit (b) next to outermost orbit (c) first orbit (d) any one of its orbit Which of the following statements is incorrect for cathode rays? (a) They move in straight line (b) Their nature depends upon the nature of gas present in the discharge tube. (c) They cost shadow of solid objects placed in their path (d) They get deflected towards positive charge. The isotopes of an element have (a) same number of neutrons (b) same atomic number (c) same mass number (d) None of these Which of the following pairs are isotopes? (a) Oxygen and ozone (b) Ice and steam (c) Nitric oxide and nitrogen dioxide (d) Hydrogen and deuterium Which of the following have equal number of neutrons and protons? (a) Hydrogen (b) Deuterium (c) Fluorine (d) Chlorine The number of electrons in an element with atomic number X and atomic mass Y will be (a) (X – Y) (b) (Y – X) (c) (X + Y) (d) X Which of the following has a charge of +1 and a mass of 1 amu ? (a) A neutron (b) A proton (c) An electron (d) A helium nucleus Which of the following describes an isotope with a mass number of 99 that contains 56 neutrons in its nucleus ? (a)

24.

25.

99 56 Ba

(b)

43 56 Ba

(c) 99 (d) 56 43 Tc 43 Tc Which of the following isotopes is used as the standard for atomic mass ? (a) 12C (b) 16O 13 (c) C (d) 1H Which of the following is not a basic particle of an element? (a) An atom (b) A molecule (c) An ion (d) None of these

C-56

26.

27.

28.

29.

Members of which of the following have similar chemical properties ? (a) Isotope (b) Isobars (c) Allotropes (d) Both isotopes and allotropes While performing cathode ray experiments, it was observed that there was no passage of electric current under normal conditions. Which of the following can account for this observation ? (a) Dust particles are present in air (b) Carbon dioxide is present in air (c) Air is a poor conductor of electricity under normal conditions (d) None of these Which one of the following statement is not true ? (a) Most of the space in an atom is empty (b) The total number of neutrons and protons is always equal in a neutral atom (c) The total number of electrons and protons in an atom is always equal (d) The total number of electrons in any energy level can be calculated by the formula 2n2 Dalton's atomic theory successfully explained (i) Law of conservation of mass (ii) Law of constant composition (iii) Law of radioactivity (iv) Law of multiple proportion

1 2 3 4 5 6

(b) (c) (c) (c) (b) (a)

7 8 9 10 11 12

(b) (b) (a) (a) (b) (a)

13 14 15 16 17 18

30.

31.

32.

33.

34. 35.

GENERAL SCIENCE (a) (i), (ii) and (iii) (b) (i), (iii) and (iv) (c) (ii), (iii) and (iv) (d) (i), (ii) and (iv) Which one of the following laws explains the formation of carbon monoxide and carbon dioxide from carbon and oxygen? (a) Law of conservation of mass (b) Law of multiple proportions (c) Law of reciprocal proportions (d) Law of difinite proportions The atomic weights are expressed in terms of atomic mass unit. Which one of the following is used as a standard? (a) 1H1 (b) 12C6 16 (c) O8 (d) 35Cl17 Which would be the electrical charge on a sulphur atom containing 18 electrons ? (a) 2– (b) 1– (c) 0 (d) 2+ The atomic number of an element is 11 and its mass number is 23. The correct order representing the number of electrons, protons and neutrons respectively in this atom is (a) 11, 11, 12 (b) 11, 12, 11 (c) 12, 11, 11 (d) 23, 11, 23. In an atom valence electron are present in (a) outermost orbit (b) next to outermost orbit (c) first orbit (d) any one of its orbit In a chemical change the total weight of the reacting substances compared to total weight of products is (a) never the same (b) always less (c) always more (d) always the same

ANSWER KEY (a) 19 (c) 20 (b) 21 (a) 22 (b) 23 (b) 24

(d) (b) (d) (b) (c) (a)

25 26 27 28 29 30

(b) (c) (c) (b) (d) (b)

31 32 33 34 35

(b) (a) (a) (a) (d)

HINTS AND SOLUTIONS 1.

(b) In the same weight of SO2 and SO3 weight of oxygen is in the simple ratio of 2 : 3 (c) The no. of atoms in O3 is maximum i.e., 3 (c) 4. (c) 5. (b) (a) In a molecule two or more than two atoms are convalently bonded with each other.

20. 21. 23.

(b) e.g., Cl + e- ¾¾ ® Cl – (anion)

28.

® Na + + e– (b) e.g., Na ¾¾

30.

2. 3. 6.

10.

11. 14. 18.

(cation)

(a) Constant proportions according to which “a pure chemical compound always contains same elements combined together in the same definite proportion of weight.” (b) 1 atom of Cu + 1 atom of sulphur + 9 atoms of oxygen + 10 atoms of hydrogen. Total number of atoms in compound is 21. (c) The nucleus contains protons and neutrons whereas electrons revolves around the nucleus in circular orbits. (b) Isotopes have same atomic number but different mass number e.g., 17Cl35 and 17Cl36.

31. 32. 33. 35.

(b) In 1H2 – no. of p = 1 and no. of n = 2 – 1 = 1 (d) No. of electrons = no. of protons = Atomic number = X (c) Given mass number (Z) = 99 no. of neutrons = 56 \ no. of protons = atomic number = 99 – 56 = 43 i.e., 43Tc99 (b) e.g., In 17Cl35 no. of p = 17 but no. of n = 35 – 17 = 18 (b) Law of multiple proportions explains the formation of CO and CO2, in these same weight of carbon that combines with weights of oxygen are in simple rate of 1 : 2. (b) 12C6 used as a standard in the expression of atomic weights in term of amu. (a) S(16) = 2, 8, 6 hence S(18) need two or more electron to complete its octet i.e S + 2e– ® S– – (a) no. of proton = At no.= number of e– = 11 no. of p + no. of n = Atomic mass \ no. of n = 13 – 11 = 12 (d) Law of conservation of mass.

3 1. 2. 3.

Classification of Elements and Periodicity in Properties

Classification means identifying similar species and grouping them together. Lavoisier divided elements into two main types known as metals and non-metals. Doberiner’s Law of triads: According to this law, “in certain triads (group of three elements) the atomic mass of the central element was the arithmetic mean of the atomic masses of the other two elements.” But in some triads all the three elements possessed nearly the same atomic masses, therefore the law was rejected. e.g., atomic masses of Li, Na and K are respectively 7, 23 and 39, thus the mean of atomic masses of 1st and 3rd element is = 7 + 39 = 23 Limitations of Doberiner’s Triads: He could identify only a few such triads and so the law could not gain importance. In the triad of Fe, Co, Ni, all the three elements have a nearly equal atomic mass and thus does not follow the above law. Newland’s Law of octaves: According to this law “the elements are arranged in such a way that the eighth element starting from a given one has properties which are a repetition of those of the first if arranged in order of increasing atomic weight like the eight note of musical scale.” Drawback of Newland’s law of octaves: (i) According to Newland only 56 elements exists in nature and no more elements would be discovered in the future. But later on several new element were discovered whose properties did not fit into law of octaves. (ii) In order to fit new elements into his table Newland adjust two elements in the same column, but put some unlike elements under the same column. Thus, Newland’s classification was not accepted. Mendeleev’s periodic table : Mendeleev arranged 63 elements known at that time in the periodic table. According to Mendeleev “the properties of the elements are a periodic function of their atomic masses.” The table consists of eight vertical column called ‘groups’ and horizontal rows called ‘periods’. Merits of Mendeleev’s periodic table: (i) At some places the order of atomic weight was changed in order to justify the chemical and physical nature.

(ii) Mendeleev left some gap for new elements which were not discovered at that time. (iii) One of the strengths of Mendeleev’s periodic table was that, when inert gases were discovered they could be placed in a new group without disturbing the existing order. Characteristics of the periodic table : Its main characteristics are : (i) In the periodic table, the elements are arranged in vertical rows called groups and horizontal rows called periods. (ii) There are eight groups indicated by Roman Numerals I, II, III, IV, V, VI, VII, VIII. The elements belonging to first seven groups have been divided into sub-groups designated as A and B on the basis of similarities. The elements that are present on the left hand side in each group constitute subgroup A while those on the right hand side form sub-group B. Group VIII consists of nine elements arranged in three triads. (iii) There are six periods (numbered 1, 2, 3, 4, 5 and 6). In order to accomodate more elements, the periods 4, 5, 6 are divided into two halves. The first half of the elements are placed in the upper left corners and the second half occupy lower right corners in each box. Achievements of Mendeleev’s periodic table (i) The arrangement of elements in groups and periods made the study of elements quite systematic in the sense that if properties of one element in a particular group are known, those of the others can be easily predicted. (ii) Prediction of new elements and their properties : Many gaps were left in this table for undiscovered elements. However, properties of these elements could be predicted in advance from their expected position. This helped in the discovery of these elements. The elements silicon, gallium and germanium were discovered in this manner. (iii) Correction of doubtful atomic masses : Mendeleev corrected the atomic masses of certain elements with the help of their expected positions and properties. Limitations of Mendeleev’s classification : (i) He could not assign a correct position of hydrogen in his periodic table, as the properties of hydrogen resembles both with alkali metals as well as with halogens. (ii) The isotopes of the same element will be given different position if atomic number is taken as basis, which will disturb the symmetry of the periodic table.

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(iii) The atomic masses do not increases in a regular manner in going from one elements to the next. So it was not possible to predict how many elements could be discovered between two elements. 6. Modern periodic law : This law was given by Henry Moseley in 1913. It states, “Properties of the elements are the periodic function of their atomic numbers”. Cause of periodicity : Periodicity may be defined as the repetition of the similar properties of the elements placed in a group and separated by certain definite gap of atomic numbers. The cause of periodicity is the resemblance in properties of the elements is the repetition of the same valence shell electronic configuration. 7. Modern periodic table Moseley proposed this modern periodic table and according to which “the physical and chemical properties of elements are periodic function of their atomic number and not the atomic weight.” (i) The modern periodic table has 18 vertical columns called “groups” and seven horizontal rows called “periods”. The groups have been numbered 1, 2, 3.......18 from left to right. (ii) The elements belonging to a particular group make a family and usually named after the first member. In a group all the elements contain the same number of valence electrons. (iii) In a period all the elements contain the same number of shells, but as we move from left to right the number of valence shell electrons increases by one unit. The maximum number of electrons that can be accommodated in a shell can be calculated by the formula 2n2 where n is the number of the given shell from the nucleus.

GENERAL SCIENCE 8. Trends in modern periodic table : The trends observed in some important properties of the elements in moving down the group (from top to bottom of the table) and across a period (from left to right in a period) are discussed below : (i) Valency : Valency may be defined as “the combining capacity of the atom of an element with atoms of other elements in order to acquire the stable configuration (i.e. 8 electron in valence shell. In some special cases it is 2 electrons).” (ii) Atomic size : It refers to the distance between the centre of nucleus of an isolated atom to its outermost shell containing electrons. The atomic radius decreases on moving from left to right along a period. This is due to an increase in nuclear charge which tends to pull the electrons closer to the nucleus and reduces the size of the atom. In a group atomic size decreases from top to bottom due to increase in number of shells. (iii) Metallic and non-metallic properties : In a period from left to right metallic nature decreases while non-metallic character increases. In a group metallic character increases from top to bottom while non-metallic character decrease. (iv) Electronegativity : The relative tendency of an atom to attract the shared pair of electrons towards itself is called electronegativity. In a period from left to right, the value of electronegativity increases while in a group from top to bottom the value of electronegativity decreases.

Classification of Elements and Periodicity in Properties

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The early attempt to classify elements as metals and nonmetals was made by (a) Mendeleev (b) Lother Meyer (c) Lavoisier (d) Henry Moseley Newlands could classify elements only upto (a) copper (b) chlorine (c) calcium (d) chromium Mendeleev classified elements in (a) increasing order of atomic groups (b) eight periods and eight groups (c) seven periods and eight groups (d) eight periods and seven groups The long form of periodic table consists of (a) seven periods and eight groups (b) seven periods and eighteen groups (c) eight periods and eighteen groups (d) eighteen periods and eight groups All the members in a group in long form of periodic table have the same (a) valence (b) number of valence electrons (c) chemical properties (d) All of these Which of the following properties generally decrease along a period? (a) Atomic size (b) Non-metallic character (c) Metallic character (d) Both (a) and (c) An element ‘M’ has an atomic number 9 and its atomic mass 19. The ion of M will be represented by (a) M (b) M2+ – (c) M (d) M2– The element with smallest size in group 13 is (a) beryllium (b) carbon (c) aluminium (d) boron The elements with atomic numbers 2, 10, 18, 36, 54 and 86 are all (a) halogen (b) noble gases (c) noble metals (d) light metals The number of elements in the third period of periodic table is (a) 2 (b) 8 (c) 18 (d) 32 Which of these choices is not a family of elements? (a) Halogens (b) Metals (c) Inert gases (d) All of these The element which has least tendency to lose electron is (a) H (b) Li (c) He (d) Na

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The most metallic element in the fourth period is (a) Ca (b) K (c) S (d) P The elements of group sixteen are called (a) halogens (b) chalcogens (c) pnicogens (d) noble gases Which of the following is correct set of Dobereiner Triads? (a) Na, Si, Cl (b) Be, Mg, Ca (c) F, Cl, I (d) Li, Na, Be The metal which is hard and has high m.p. and used in electric bulbs is (a) Ni (b) Pt (c) Fe (d) W The lightest liquid metal is (a) Hg (b) Ga (c) Cs (d) Fr Which is not true about noble gases? (a) They are non-metallic in nature (b) They exist in atomic form (c) They are radioactive in nature (d) Xenon is the most reactive among them Elements of which group form anions most readily? (a) Oxygen family (b) Nitrogen family (c) Halogens (d) Alkali metals On moving horizontally across a period, the number of electrons in the outermost shell increases from ...... to ....... . (a) 2, 8 (b) 2, 18 (c) 1, 8 (d) 1, 18 Which of the following is not a representative element? (a) Fe (b) K (c) Ba (d) N The scientist who made maximum contribution towards periodic table was (a) Chadwick (b) Rutherford (c) Dalton (d) Mendeleev Which of the following elements A, B, C, D and E with atomic number 3, 11, 15, 18 and 19 respectively belong to the same group? (a) A, B, C (b) B, C, D (c) A, D, E (d) A, B, E Element A belongs to Group VII in p-block and element B belongs to Group I in s-block of the periodic table. Out of the following assumptions, the correct one is : (a) A and B are metals (b) A and B are non-metals (c) A is a metal and B is a non-metal (d) A is a non-metal and B is a metal The element with atomic number 14 is hard and forms acidic oxide and a covalent halide. To which of the following categories does the element belong? (a) Metal (b) Metalloid (c) Non-metal (d) Left-hand side element

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GENERAL SCIENCE Which of the following properties do not match elements of halogen family ? (a) They have seven electrons in their valence shell (b) They are diatomic in their molecular form (c) They are highly reactive chemically (d) They are metallic in nature Which fact is not valid for Dobereiner's triads? (a) The atomic weight of middle element is roughly average of the other two elements (b) The properties of middle element is roughly average of the other two elements (c) The elements of triads belong to the same group of modern periodic table (d) The elements of triads have same valency electrons. Which of the following statements is incorrect from the point of view of modern periodic table ? (a) Elements are arranged in the order of increasing atomic number (b) There are eighteen vertical columns called groups (c) Transition elements fit in the middle of long periods (d) Noble gases are arbitrarily placed in eighteenth group Which of the following group of elements belongs to alkali metals? (a) 1, 12, 30, 4, 62 (b) 37, 19, 3, 55 (c) 9, 17, 35, 53 (d) 12, 20, 56, 88 Which of the following elements will form acidic oxide? (a) Sodium (b) Magnesium (c) Aluminium (d) Sulphur Which one of the following is most electropositive element? (a) Sodium (b) Calcium (c) Aluminium (d) Silicon The atomic number of an element tells you the number of ................ in a neutral atom. (a) positrons (b) neutrons (c) electrons (d) All of these As you move down the group, the alkali metals become (a) brighter (b) hotter (c) more reactive (d) less reactive

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Which is a metalloid? (a) Pb (b) Sb (c) Bi (d) Zn Which one of the following elements exhibit maximum number of valence electrons? (a) Na (b) Al (c) Si (d) P Which of the following elements does not lose an electron easily? (a) Na (b) F (c) Mg (d) Al To which block is related an element having electronic configuration 1s2 2s22p6 3s23p63d10 4s1 in the periodic table– (a) s–block (b) p–block (c) d–block (d) f–block If the valene shell electronic configuration for an element is ns2np5, this element will belong to the group of – (a) alkali metals (b) inert metals (c) noble gases (d) halogens Which shows variable valency – (a) s–block elements (b) p–block elements (c) d–block elements (d) Radioactive elements The noble gases are unreactive because (a) they react with sodium (b) they have a full outer shell of electrons (c) they have a half outer shell of neutrons (d) they are too thin Which scientist came up with the concept of a periodic table that included all of the known elements? (a) Joseph Priestly (b) Dmitri Mendeleev (c) Antoine Lavoisier (d) Albert Einstein If the two members of a Dobereiner triad are phosphorus and antimony, the third member of this triad is – (a) arsenic (b) sulphur (c) iodine (d) calcium

Classification of Elements and Periodicity in Properties 1 2 3 4 5 6 7 8 9 10

11 12 13 14 15 16 17 18 19 20

(b) (c) (b) (b) (b) (d) (c) (c) (c) (c)

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ANSWER KEY (a) 21 (d) 22 (d) 23 (d) 24 (b) 25 (d) 26 27 (b) 28 (d) 29 (b) 30 (d)

31 32 33 34 35 36 37 38 39 40

(a) (c) (c) (b) (d) (b) (a) (d) (c) (b)

41 42

(b) (a)

HINTS AND SOLUTIONS 3. 5.

8. 9. 11. 12. 13.

14. 16. 17.

(c) Mendeleev’s periodic table consists of seven periods and eight groups. (d) Because of the presence of same number of valence electrons the elements of same group have similar chemical properties. (d) As atomic size decreases along a period valence electrons becomes more firmly held with nucleus. Thus more amount of energy is required to remove valence electrons which reduces metallic character (c) The electronic configuration of M is 2, 7. It needs one electron to complete its octet. It has a strong tendency to gain 1 electron and so its ion will be M–. (d) In group 13, boron is above aluminium. Rest of elements not belong to group 13. (b) All these are noble gases with completely filled outermost shell. (b) A family of elements consists of elements present in a group of the periodic table. (c) He is an inert gas. (b) The fourth period contains elements with atomic number 19 to 36. K (Z = 19) is the first member and so it is most metallic. (b) Elements of oxygen family are known as chalcogens. (d) Tungsten (W) is used in electric bulbs. (c) Cs is a metal. It is liquid at room temperature. It is lighter than Hg (also a liquid metal).

18. 19. 21. 23. 24.

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(c) Only Radon (Rn) is radioactive whereas other noble gases (i.e., He, Ne, Ar, Kr, Xe) are non-radioactive. (c) Halogens are most electronegative elements i.e., they are likely to form anions most readily. (a) Fe is a transition element. (d) A(Z = 3); B(Z = 11) and E(Z = 19) are all alkali metals. (d) Element A belong to halogens (Group VII) group and is a non-metal. While element B belongs to alkali metal group (Group I) and is a metal. (b) The given element belongs to carbon family. (d) The members of the halogen family are non-metallic in nature. However, iodine and astatine are crystalline solids and have lustre just like metals. (b) Alkali metals have 1 electron in valence shell. (d) Oxides of non-metals are acidic. (a) Alkali metals are most electropositive in their respective period. i.e. they have maximum tendency to lose electron and form a cation. (d) P is in group 5 and has 5 valence electron. Number of valence electrons in Na, Al and Si are 1, 3 and 4. (b) F has a tendency to gain an electron. (b). Dmitri Mendeleev is credited with designing the modern periodic table. Joseph Priestly and Antoine Lavoisier were both chemists. Albert Einstein developed theories on photoelectric effect.

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GENERAL SCIENCE

4 1.

2. A.

Acids, Bases and Salts

The term acid, in fact, comes from the latin term acere, which means “Sour”. In everyday life we come across many compounds that chemists classify as acids. Bases are compounds which taste bitter eg. milk of magnesia. Salts also have wide applications for example ammonium chloride is used as electrolyte in dry cells, sodium bicarbonote (baking powder) in the manufacture of glass etc. Properties of acids and bases Properties of acids Chemical properties : (i) Action of metals Metals generally react with dilute acids to form their respective salt and hydrogen.

Strength of Acids and Bases The strength of an acid or a base can be easily estimated by making use of universal indicator which is a mixture of several indicators. The universal indicator show different colours at different concentrations of hydrogen ions in solution. pH Scale : It is a scale that is used for measuring H+ion (Hydrogen ion) concentration of a solution. The term pH stands for “potential” of “hydrogen”. It is the amount of hydrogen ions in a particular solution. For acids pH < 7 For bases pH > 7 For neutral substances pH = 7

Metal + Acid ¾¾ ® Salt + Hydrogen (ii) Action with metal oxides (Basic oxides) Metal oxides are generally basic oxides. These oxides get neutralised when they react with acids. These reactions are mostly carried upon heating e.g.

Importance of pH in Daily Life

® Salt + Water Basic oxide + Acid ¾¾ (neutralisation reaction) (iii) Action with metal carbonates and metal hydrogen carbonates Acids react with carbonates and hydrogen carbonates to form their respective salts, water and carbon dioxide gas. Carbonate/bicarbonate + Acid ¾¾ ® Salt + water + carbon dioxide. Properties of bases Chemical Properties : (i) Reaction of metals with bases : Metals (e.g. Zn, Al, Sn) dissolve in NaOH (an alkali) to liberate hydrogen gas.

® Na2ZnO2 + H2 Zn + 2NaOH ¾¾ Sod. Zincate (ii) Action with acids : Bases combine with acids to form salt and water only. It is a neutralisation reaction. ® Salt + Water Base + Acid ¾¾ Non - metallic oxides react in the same way hence nonmetallic oxides are acidic in nature.

(i)

Blood pH : For proper functioning our body needs to maintain blood pH between 7.35 and 7.45. Values of blood pH greater than 7.8 or less than 6.8 often results in death. (ii) Acid rain : When pH of rain water is less than 5.6, it is called acid rain, when acid rain flows into rivers, it lowers the pH of river water. (iii) pH in our digestive system : We know that hydrochloric acid (HCl) produced in our stomach helps in digestion of food without harming stomach. However excess of acid causes indigestion and leads to pain as well as irritation. To get rid of this people use bases called “antacids”. (iv) pH of the soil : For their healthy growth plants require a specific pH. Soils with high peat content or iron minerals or with rotting vegetation tend to become acidic and the soil pH can reach as low as 4. (v) pH change as the cause of tooth decay : Tooth decay starts when the pH of mouth is lower than 5.5. (vi) Self defence by animals and plants through chemical warfare : Bee-sting leaves an acid (formic acid or methanoic acid, HCOOH) which causes pains and irritation. Use of mild base like baking soda on the stung area gives relley 6. Salts : A salt is an ionic compound which dissociates to yield a positive ion other than hydrogen ion (H+) and negative ion other than hydroxyl ion (OH–) e.g. NaCl Salts are formed by the reaction of acid and base which is also known as neutralisation.

Acids, Bases and Salts (i) Sodium hydroxide (NaOH) or Caustic soda : It is prepared on commercial scale by the electrolysis of strong solution of sodium chloride (NaCl) also called brine. The process is called chlor-alkali process. The overall reaction taking place is : ® H2(g) + Cl2(g) + 2NaOH (aq) 2NaCl (aq) + 2 H2O(l) ¾¾ Uses : (a) Sodium hydroxide is most used base in the laboratory. (b) It is used in many industries, mostly as strong chemical base in manufacture of pulp and paper, textiles, drinking water, soap and detergents etc. (ii) Baking soda, Sodium hydrogen carbonate, (NaHCO3) ® NH4Cl + NaHCO3 NaCl + H2O + CO2 + NH3 ¾¾ When heated the following reaction occurs heat 2 NaHCO3 ¾¾¾ ® Na2CO3 + H2O + CO2 The above reaction occurs when baking soda is heated during cooking. Uses : (a) In baking powder : The most practical use of baking soda is as a leavening agent in baking. (b) As an antacid : Baking soda reacts with acid due to its alkaline nature and neutralizes acidity (i.e. acts as an antacid) (c) In fire extinguishers : It is used in soda-acid fire extinguisher (iii) Washing soda, Na2CO3. 10H2O, Sodium carbonate Sodium carbonate can be obtained by heating baking soda; recrystallisation of sodium carbonate gives washing soda. It is also a basic salt.

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Na 2 CO3 + 10H 2 O ¾¾ ® Na 2 CO 3 ·10H 2O Sodium carbonate

Hydrated sodium carbonate (Washing soda),

Uses : (a) Sodium carbonate (washing soda) is used in glass, soap and paper industries. (b) It is used for removing permanent hardness of water. (iv) Bleaching powder : Calcium hypochlorite is a chemical compound with formula CaOCl2. It is a yellowish powder with smell of chlorine. It is widely used for water treatment and as a bleaching agent (bleaching powder) 2 Ca(OH) 2 + 2Cl 2 ¾¾ ® CaOCl 2 + CaCl2 + 2H 2 O Calcium hypochlorite is used for the disinfection of drinking water or swimming pool water. (v) Plaster of Paris, CaSO4 .1/2 H2O It can be obtained by heating gypsum (CaSO4. 2H2O) 1 3 H2O) + H2O 2 2 Plaster of paris is a white powder and on mixing with water it changes to gypsum once again giving a hard solid mass

(CaSO4. 2H2O) + heat ¾¾ ® (CaSO4.

1 1 H 2 O + 1 H2O ® CaSO4. 2H2O. 2 2 Uses : It is used (a) for making moulds or casts for toys, pottery, cermics etc. (b) in surgical bandages for setting fractured bones.

CaSO4 •

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GENERAL SCIENCE

Bleaching powder is soluble in cold water giving a milky solution due to – (a) available chlorine (b) lime present in it (c) calcium carbonate formation (d) the absorption of carbon dioxide from atmosphere The acid used in making of vinegar is – (a) formic acid (b) acetic acid (c) sulphuric acid (d) nitric acid Reaction of an acid with a base is known as – (a) decomposition (b) combination (c) redox reaction (d) neutralization Antacids contain – (a) weak base (b) weak acid (c) strong base (d) strong acid Bleaching powder gives smell of chlorine because it – (a) is unstable (b) gives chlorine on exposure to atmosphere (c) is a mixture of chlorine and slaked lime (d) contains excess of chlorine Plaster of paris is made from – (a) lime stone (b) slaked lime (c) quick lime (d) gypsum Chemical formula of baking soda is – (a) MgSO4 (b) Na2CO3 (c) NaHCO3 (d) MgCO3 Washing soda has the formula – (a) Na2CO3.7H2O (b) Na2CO3.10H2O (c) Na2CO3.H2O (d) Na2CO3 Plaster of Paris hardens by – (a) giving of CO2 (b) changing into CaCO3 (c) combining with water (d) giving out water A solution reacts with crushed egg–shells to give a gas that turns lime–water milky. The solution contains (a) NaCl (b) HCl (c) LiCl (d) KCl Which of the following is acidic in nature – (a) apple juice (b) soap solution (c) slaked lime (d) lime Which of the following acid is present in sour milk ? (a) glycolic acid (b) lactic acid (c) citrus acid (d) tartaric acid Acid turn blue litmus – (a) green (b) red (c) yellow (d) orange The reaction of metal with acid results in the formation of– (a) only hydrogen gas (b) only salt (c) both salt and hydrogen gas (d) none of these

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‘Alum’ is an example of – (a) single salt (b) double salt (c) acids (d) none of these Which of the following is ‘quicklime’ – (a) CaO (b) Ca(OH)2 (c) CaCO3 (d) CaCl2.6H2O Slaked lime is prepared by adding water to – (a) bleaching powder (b) lime water (c) milk of lime (d) quicklime Plaster of paris has the formula – (a) CaSO4.½H2O (b) CaSO4.H2O (c) CaSO4.1½H2O (d) CaSO4.2H2O Plaster of paris is obtained – (a) by adding water to calcium sulphate (b) by adding sulphuric acid to calcium hydroxide (c) by heating gypsum to a very high temperature (d) by heating gypsum to 373 K. Which of the following is considered a mineral acid ? (a) Oxalic acid (b) Lactic acid (c) Citric acid (d) Phosphoric acid Which of the following is an alkali ? (a) Ca(OH)2 (b) KOH (c) Mg(OH)2 (d) CaCO3 When the stopper of a bottle containing colourless liquid was removed, the bottle gave smell like that of vinegar. The liquid in the bottle could be (a) hydrochloric acid (b) sodium hydroxide solution (c) acetic acid solution (d) saturated sodium hydrogen carbonate solution Which of the following is not required to find the pH of a given sample ? (a) pH paper (b) Litmus paper (c) Universal indicator (d) Standard pH chart Universal indicator solution is named as such because (a) it is available universally (b) it has a universal appearance (c) it can be used for entire pH range (d) all the above are correct Select the one that is having pH < 7. (a) lime juice (b) lime water (c) human blood (d) antacid. Acids and bases are important because of (a) their use in industry (b) their effects on human health (c) their effect on farmer’s crop (d) all the above are correct. Which of the following is a weak base ? (a) NaOH (b) KOH (c) NH4OH (d) none of these

Acids, Bases and Salts 28. Which of the following compounds is basic in nature ? (a) Ca(OH)2 (b) CaCl2.6H2O (c) NaCl (d) CuSO4.5H2O 29. If pH of A, B, C and D are 9.5, 2.5, 3.5 and 5.5 respectively, then strongest acid is (a) A (b) C (c) D (d) B 30. Aqueous solution of which of the following salt will change the colour of red litmus to blue? (a) Na2CO3 (b) Na2CO3.10H2O (c) Both (a) and (b) (d) None of these 31. Which of the following is known as dead burnt plaster? (a) Quick lime (b) Slaked lime (c) Lime stone (d) Gypsum 32. Which of the following pairs of substances are chemically same? (a) Lime water and milk of lime (b) Dead burnt plaster and gypsum (c) Both the above (d) None of the above 33. Baking powder is (a) a mixture (b) a compound (c) an element (d) a salt 34. The chemical name of bleaching powder is (a) calcium chloride (b) calcium oxychloride (c) calcium chloroxide (d) none of above 35. Which of the following is not a hydrated salt? (a) Blue vitriol (b) Baking soda (c) Washing soda (d) Epsom salt 36. Which of the following is a strong acid: (a) Acetic acid (b) Citric acid (c) Nitric acid (d) Tartaric acid 37. The presence of which of the following acid causes indigestion: (a) Citric acid (b) Oxalic acid (c) Acetic acid (d) Hydrochloric acid 38. When few drops of lemon are mixed with milk (i) it turns sour (ii) no change takes place (iii) properties of milk are changed (iv) properties of milk remain same Which of the above statements is/are correct? (a) (ii) and (iii) (b) (i) and (ii) (c) (i) and (iii) (d) (i) only 39. Which of the following is a strong base? (a) Ammonium hydroxide (NH4OH) (b) Sodium hydroxide (NaOH) (c) Water (H2O) (d) Sulfuric acid (H2SO4) 40. Acids are ...................... in taste while bases are .................... in taste (a) sweet, salty (b) sweet, sour (c) sour, salty (d) sour, bitter

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52.

53.

A base which dissolves in water is called (a) soluble base (b) alkali (c) acid (d) oxide Acid rain is caused due to ................... (a) CO2, O2, SO2 (b) CO2, NO2, H2 (c) SO2 N2, O2 (d) CO2, SO2, NO2 Acid contained in the sting of an ant is.................... (a) acetic acid (b) formic acid (c) lactic acid (d) ascorbic acid Natural indicator litmus is extracted from (a) lichens (b) earthworms (c) ants (d) algae When vinegar reacts with baking soda the gas evolved is (a) hydrogen (b) oxygen (c) carbon dioxide (d) nitrogen dioxide On which of the following acid rain has adverse effects? (a) Marble structures (b) Historical monuments (c) Aquatic life (d) All of these pH of human body varies within the range of (a) 6.0 to 6.5 (b) 5.5 to 5.8 (c) 7.0 to 7.8 (d) 7.0 to 11.0 Calamine solution contains (a) zinc hydroxide (b) zinc carbonate (c) sodium hydrogen carbonate (d) magnesium hydroxide Why bases are kept in glass bottles? (a) Bases produce OH– ions in aqueous solutions (b) Basic solutions are conducting in nature (c) Bases are corrosive in nature (d) Basis have soapy texture Which of the following statement regarding bases is false? (a) Bases produce hydroxide ions when dissolved in water (b) Bases are soapy to touch (c) Bases are extremly corrosive in nature (d) Basic solutions are non conducting in nature Which of the following statement is true? (a) Acids are bitter in taste (b) Bases are sour in taste (c) The reaction between acid and a base is exothermic reaction (d) The reaction between an acid and a base is endothermic reaction. Common salt besides being used in kitchen can also be used as the raw material for making (i) washing soda (ii) bleaching powder (iii) baking soda (iv) slaked lime (a) (i) and (ii) (b) (i), (ii) and (iv) (c) (i) and (iii) (d) (i), (iii) and (iv) To protect tooth decay we are advised to brush our teeth regularly. The nature of the tooth paste commonly used is (a) acidic (b) neutral (c) basic (d) corrosive

C-66

GENERAL SCIENCE 1 2 3 4 5 6 7 8 9 10

(b) (b) (d) (a) (b) (d) (c) (b) (c) (b)

11 12 13 14 15 16 17 18 19 20

(a) (b) (b) (c) (b) (a) (d) (a) (d) (d)

21 22 23 24 25 26 27 28 29 30

ANSW ER KEY 31 (b) 32 (c) 33 (b) 34 (c) 35 (a) (d) 36 37 (c) (a) 38 39 (d) (c) 40

(b) (a) (a) (b) (b) (c) (d) (c) (b) (d)

41 42 43 44 45 46 47 48 49 50

(b) (d) (b) (a) (c) (d) (c) (b) (c) (d)

51 52 53

HINTS AND SOLUTIONS 1.

2. 3. 4.

(b) Bleaching powder is actually a mixture of calcium hypochlorite CaOCl2 and the basic chloride CaCl2 with some slaked, Ca(OH)2. (b) 6 - 12% acetic acid is known as vinegar. (d) In a neutralization reaction an acid reacts with a base and forms salt and water. (a) Antacids are weak bases which are given when a patient is suffering from acidity. These antacids neutralises the acid and give relief to patient.

15.

(b)

1 3 CaSO4 . H 2 O + H 2 O ¾¾ ® CaSO4 .2H 2 O 2 2 The egg-shells are made up of calcium carbonate. When it reacts with HCl it liberates CO2 gas which turns lime water milky CaCO 3 + 2HCl ¾¾ ® CaCl2 + H 2 O + CO 2 Soaps are sodium salts of higher fatty acids. 1 ® NaCl + H 2 e.g. Na + HCl ¾¾ 2 K 2 SO 4 + Al2 (SO 4 )3 .24H 2O ¾¾ ® Alum

17.

(d)

CaO + H 2 O ¾¾ ® Ca(OH) 2

19.

(d)

21. 22. 23.

(b) (c) (b)

24. 25.

26. 27.

(d) (c)

29.

(d)

(c)

10.

(b)

11.

(a)

14.

(c)

35. 36. 38.

(b) (c) (c)

1 3 D CaSO4 .2H 2 O ¾¾® CaSO4 . H 2 O + H 2 O 2 2 KOH; Alkali is a base which are water soluble. acetic acid solutions Litmus paper [Hint : Litmus paper does not give any information about the pH values]. It can be for entire pH range. Lime juice [Hint : Lime juice is acidic so its pH < 7.]. All the above are correct. NH4OH as it is not get completely ionized in aqueous solution. Less the pH, more acidic is the solution. The pH of acid B is 2.5 which is minimum. Baking soda is NaHCO3 As HNO3 is a mineral acid. When lemon juice is mixed with milk the milk turns sour and changes into 'paneer'. The properties of milk are completely different from that of 'paneer'.

39.

40.

41.

42.

43.

44.

45.

46.

50.

51. 52.

(b) Sodium hydroxide (NaOH) is a strong base while ammonium hydroxide (NH4OH) is a weak base. Water is neutral in nature, neither acidic nor basic. (d) All acids are sour in taste, like tartaric acid in tamarind and acetic acid in vinegar while all bases are bitter in taste like baking soda. (b) Bases soluble in water are called alkalis. Only the oxides of sodium, potassium, and calcium are soluble in water, so these form sodium hydroxide potassium hydroxide and calcium hydroxide. These are the strongest bases. (d) Acid rain is caused due to increased pollution in the air. The poisonous gases like sulphur dioxide, carbon dioxide and nitrogen dioxide react with water to form sulphuric acid, carbonic acid an d nitric acid respectively. (b) The sting of an ant contains formic acid. Its effect can be neutralized by rubbing moist baking soda on the affected part. (a) Natural indicator is obtained from lichens and is purple in colour. It turns acidic solution red and basic solution blue. (c) Vinegar is acetic acid and baking soda is sodium hydrogen carbonate (a base). Whenever an acid reacts with a metal carbonate it produces carbon dioxide gas. ® CH3COONa + H2O + CO2 CH3COOH + NaHCO3 ¾¾ (d) Acid rain effects all of them. Acid rain corrodes historical monuments and marble structures. Acid rain alter the pH of water bodies by making it more acidic thus affects acquatic plants and animals. (d) Basic solutions are conducting in nature. Conduction depends on the number of hydroxide ions produced when dissolved in water. (c) This reaction is exothermic i.e. Heat is evolved HCl + NaOH ® NaCl + H2O + Heat (c) NaCl + H2O + CO2 + NH3 ¾¾ ® NH4Cl + NaHCO3 Baking soda heat 2NaHCO3 ¾¾¾ ® Na2CO3+ H2O + CO2 Na2CO3 + 10 H2O ¾¾ ® Na2CO3.10 H2O Sodium carbonate Hydrated sodium carbonate (washing soda)

Metals and Non-metals (iii) Metals are very important for the economy of a country. Some metals, such as titanium, chromium, manganese and zirconium are strategic metals. These metals and their alloys find wide applications in atomic energy, space science projects, jet engines and high grade steels.

1. Metals and Non-metals : There are more than 114 elements present in the periodic table. These elements can be broadly classified into two categories i.e., metals and non-metals. Out of 114 elements, 22 are non-metals. 2. Physical properties of metals :

(iv) Gold and silver ornaments are obtained from small pieces of metals by hammering.

(i) They are usually shiny i.e. have a metallic luster. (ii) Metals have a high density (iii) Metals are ductile i.e. they can be drawn into wires. (iv) Metals are malleable i.e. they can be founded into thin sheets. (v) Metals are good conductors of electricity. (vi) Metals have high melting point and are generally in solid state at room temperature. (vii)Metals are good conductors of heat and sound. 3. Uses of mxetals : (i) Metals are very important for modern humans it is not possible to imagine our life without them. (ii) Metals are used in manufacturing of bridges, railways, aeroplanes, diesel mobile units (DMU), electric mobile units (EMU), motor cars, electric motors, telephones, televisions, interplanetary space vehicles, or even common articles like cooking utensils and coins.

4. Noble metal : Noble metals are metals that are resistant to corrosion or oxidation, unlike most base metals. Examples include tantalum, gold, platinum, and rhodium. 5. Precious metal : A precious metal is a rare metallic chemical element of high economic value precious metals include the platinum group metals: ruthenium, rhodium, palladium, osmium, iridium, and platinum, of which platinum is the most widely traded. 6. Alloy : An alloy is a mixture of two or more elements in solid solution in which the major component is a metal. Most pure metals are either too soft, brittle or chemically reactive for practical use. Combining different ratios of metals as alloys modify the properties of pure metals to produce desirable characteristics. The aim of making alloys is generally to make them less brittle, harder, resistant to corrosion, or have a more desirable color and luster. Examples of alloys are steel (iron and carbon), brass (copper and zinc), bronze (copper and tin), and duralumin (aluminium and copper).

Alloy

Composition

Uses

Brass

Cu = 80%, Zn = 20%

For making utensils and cartridges.

Bronze

Cu = 90%, Sn = 10%

For making statues, medals, ships, coins and machines

Solder

Sn = 50%, Pb = 50%

For joining metals, solding wire and electronic components etc.

Duralumin

Al = 95.5%, Cu = 3%,

Used in bodies of aircrafts, kitchen ware and automobile

Mn = 1.0%, Mg = 0.5%

parts etc.

German Silver

Cu = 60%, Zn = 20%, Ni = 20%

For making utensils and ornaments

Gun metal

Cu = 90%, Sn = 10%

For Gears and castings etc.

Bell metal

Cu = 80%, Sn = 20%

For bells, gangs etc.

Magnalium

Al = 90%, Mg = 10%

For balance beams, light instruments.

Type metal

Pb = 82%, Sb = 15%, Sn = 3%

For casting type

10.

Stainless steel

Fe, Ni, Cr, C

For utensils, cutlery etc.

C-68

7. Physical properties of non-metals : (i) They are dull, however diamond, graphite and iodine are lustrous. (ii) They are poor conductors of heat and electricity. Graphite is a good conductor. (iii) They are weak and brittle (they easily break or shatter). (iv) They have a low density (they feel light for their size). (v) They do not make a ringing sound when they are hit. (vi) Melting points and boiling points are usually low. (vii) Non-metals are usually soft. (Diamond is an exception, it is quite hard. It is a crystalline solid). (viii) They exist in allotropic forms. 8. Uses of Non-Metals (i) Oxygen is essential for survival of life. (ii) Hydrogen is used to convert vegetable oil into vegetable ghee by hydrogenation. (iii) Nitrogen is used to preserve food and for manufacturing proteins by plants. (iv) Carbon in the form of diamond is used for cutting rocks and in the form of graphite as electrode and in manufacturing of lead pencils. (v) Sulphur is used in vulcanization of rubber, as fungicide and in manufacture of dyes, gun powder etc. (vi) Chlorine is used as water disinfectant and in the manufacture of pesticides like gammaxene. 9. Extraction of Metals (i) Minerals: The natural substance in which the metals or their compounds occur in the earth is called minerals. (ii) Ores: The minerals from which the metals can be conveniently and economically extracted are called ores. (iii) Native ores: These ores contain metals in the free state, e.g., silver, gold, platinum, etc. (iv) Metallurgy: The whole process of obtaining a pure metal from one of its ore is known as metallurgy. (v) Gangue or matrix: Ores usually contain soil, sand, stones and others useless silicates. These undesired impurities present in ores are called gangue or matrix. (vi) The removal of unwanted earthy and silicious impurities from the ore is called ore-dressing or concentration of ores and the process used to concentrate an ore is called the benefication process. (vii) Concentration of ore is achieved by (a) physical methods, and (b) chemical methods

GENERAL SCIENCE (viii) Physical methods are: (a) Hand-picking: It is used in the case when the impurities are quite distinct from the ore so that these may be differentiated by naked eye. (b) Hydraulic washing or Levigation or Gravity separation: The separation is based on the difference in the specific gravities of the gangue particles and the ore particles. (c) Electromagnetic separation: When one component either the ore or impurity is magnetic in nature, this method can be used for separation. (d) Froth floatation process: This method is used for the concentration of sulphide ores. (ix) Chemical method (Leaching) involves the treatment of the ore with a suitable reagent as to make it soluble while impurities remain insoluble. The ore is recovered from the solution by suitable chemical method. (x) Extraction process used to obtain metals in free state from concentrated ores is called extraction. (xi) Extraction of crude metal from the concentrated ore involves following chemical processes. (a) Conversion of ore into metallic oxides. • Calcination involves heating the ore below its fusion temperature in the absence of air. It can remove moisture from hydrated oxide or CO2 from carbonates. It makes the ore porous. • Roasting is the heating of the ore in the presence of air below its fusion temperature. (b) Reduction to free metal: • Smelting: This involves the reduction of the ore to the molten metal at a high temperature. For the extraction of electropositive metals such as Pb, Fe, Sn, powerful reducing agent like C, H2 CO, Al, Mg, etc., are used. • Self reduction process : These processes are also called auto-reduction process. • Electrolytic process: The oxides of highly electropositive metals like Na, K, Mg, Ca, Al, etc., are extracted by electrolysis of their oxides, hydroxides or chlorides in fused state. For example, Al is obtained by the electrolysis of alumina mixed with cryolite. (xii) Refining is the process of purifying the extracted metals. (xiii)Chromatography is based on the principle that the different components of a mixture are adsorbed to different extents on an adsorbent.

Metals and Non-metals

C-69

The table given here lists some common ores of some metals Sl. No.

Name of the ore

Formula of the ore

Type of ore

Metal obtained from the ore

Bauxite

Al 2O3.2H 2 O

Oxide

Aluminium (Al)

Haematite

Fe2 O3

Oxide

Iron (Fe)

Magnetite

Fe3O4

Oxide

Iron (Fe)

Zincite

ZnO

Oxide

Zinc (Zn)

Cuprite

Cu 2 O

Oxide

Copper (Cu)

Litharge

PbO

Oxide

Lead (Pb)

Malachite

CuCO3 .Cu(OH) 2

Carbonate

Copper (Cu)

Magnesite

MgCO3

Carbonate

Magnesium (Mg)

Lime stone

CaCO3

Carbonate

Calcium (Ca)

10.

Cinnabar

HgS

Sulphide

Mercury (Hg)

11.

Chalcopyrite

CuFeS2

Sulphide

Copper (Cu)

12. 13. 14.

Zinc blende Galena Common salt

ZnS PbS NaCl

Sulphide Sulphide Chloride (Halide)

Zinc (Zn) Lead (Pb) Sodium (Na)

15.

Fluorspar

CaF2

Fluoride

Calcium (Ca)

16.

Horn silver

AgCl

17.

Chalcocite

Cu2S

(Halide) Chloride (Halide) Sulphide

10. Corrosion of Metals : Corrosion is an oxidation reaction with atmospheric oxygen in the presence of water on the surface of a metal. Rusting is 3 Fe(s) + O2 (g) + xH 2O(l) ¾¾ ® Fe 2O3 .xH 2O(s) 2 i.e., rust is hydrated iron (III) oxide. 11.

Prevention of Corrosion : Iron and steel (alloy of iron) are most easily protected by paint which provides a barrier between the metal and air/water. Moving parts on machines can be protected by a water repellent oil or grease layer. Other important methods are

Silver (Ag) Copper (Cu) (i)

Alloying : Iron or steel along with other metals can also be protected by ‘alloying’ or mixing with other metals (e.g., chromium) to make non-rusting alloys. (ii) Galvanizing : Coating iron or steel with a thin zinc layer is called ‘galvanizing’.

12.

Purity of Gold : 24-Carat gold : The carat (abbreviation ct or Kt) is a measure of the purity of gold alloys. Carat is used to refer to the measure of mass for gemstones.

C-70

10.

11.

12.

13.

GENERAL SCIENCE

The most abundant metal in the earth’s crust is (a) iron (b) copper (c) aluminium (d) mercury The only metal that is liquid at room temperature is (a) mercury (b) sodium (c) zinc (d) tungsten Chemically rust is (a) hydrated ferric oxide only (b) hydrated ferrous oxide only (c) ferric oxide only (d) ferrous oxide only Alumina is chief ore of which of the following metal? (a) Na (b) K (c) Ca (d) Al Horn silver is (a) an oxide ore of silver (b) a sulphite ore of silver (c) a carbonate ore of silver (d) a chloride ore of silver Naturally occuring substances from which a metal can be profitably (or economically) extracted are called? (a) Minerals (b) Ores (c) Gangue (d) Salts Cinnabar is an ore of (a) Hg (b) Cu (c) Pb (d) Zn Which of the following is not an ore ? (a) Bauxite (b) Malachite (c) Zinc blende (d) Pig iron Which of the following mineral does not contain Al ? (a) Cryolite (b) Mica (c) Feldspar (d) Fluorspar Formula of magnetite is (a) Fe2O3 (b) FeS2 (c) FeCO3 (d) Fe3O4 Which ore contains both iron and copper? (a) Cuprite (b) Chalcocite (c) Chalcopyrite (d) Malachite Calcination is the process of heating the ore (a) in a blast furnace (b) in absence of air (c) in presence of air (d) none of these Which of the following is an oxide ore? (a) Bauxite (b) Cuprite (c) Haematite (d) All of these

14.

15.

16.

17.

18.

19.

20.

21.

22.

23.

24.

Removal of impurities from ore is known as (a) crushing and grinding (b) concentration of ore (c) calcination (d) roasting Which reducing agent is used in chemical reduction? (a) C (b) CO (c) Al (d) All of these Aluminium is used in thermite welding because (a) aluminium is a light metal (b) aluminium has more affinity for oxygen (c) aluminium is a strong oxidising agent (d) aluminium is a reactive metal The process of extraction of metal from its ores, is known as (a) concentration (b) calcination (c) purification (d) metallurgy The process to heat the ore in the presence of excess supply of air below its melting point is called (a) roasting (b) calcination (c) smelting (d) liquation Brass is a mixture of (a) copper and zinc (b) copper and tin (c) copper, nickel and zinc (d) aluminium, copper and traces of Mg and Mn Sodium is obtained by the electrolysis of (a) an aqueous solution of sodium chloride (b) an aqueous solution of sodium hydroxide (c) fused sodium chloride (d) fused sodium sulphate The chief ore of aluminium is (a) bauxite (b) cryolite (c) alunite (d) feldspar One of the constituents of amalgam is (a) aluminium (b) copper (c) iron (d) mercury The metal used to built bridges is (a) gold (b) silver (c) platinum (d) iron Which of the following is a good conductors of heat and electricity? (a) Graphite (b) Oxygen (c) Chlorine (d) Nitrogen

Metals and Non-metals 25. Metals are (a) malleable (b) ductile (c) Both (a) and (b) (d) Neither (a) nor (b) 26. Which of the following have low melting and boiling points? (a) Phosphorus (b) Sodium (c) Iron (d) Both (a) and (b) 27. Which of the following non-metals has shining lustrous surfaces? (a) Graphite and phosphorus (b) Graphite and iodine (c) Iodine and phosphorus (d) Phosphorus and chlorine 28. Metals like Gold, Platinum which do not easily react are called (a) active metals (b) dull metals (c) noble metals (d) bright metals 29. The metalloids include the elements (a) Boron, Silicon (b) Arsenic, Antimony (c) Germanium, Tellurium (d) All of these 30. Select the property that is associated with non-metals. (a) Low density (b) Low melting point (c) Poor conductor of electricity (d) All of the above 31. Which of the following non-metals sublimes on heating ? (a) Fluorine (b) Chlorine (c) Bromine (d) Iodine 32. Which of the following statement regarding metals is true? (a) All metals are solid in nature. (b) Metals can be used to make handle of cooking utensils (c) Generally most of metals have high melting and boiling points. (d) Gold is used generally to make electrical wires. 33. Which of the following statement is false? (a) Metals are good conductors of heat and electricity. (b) Gold, Silver and Zinc are most malleable metals. (c) Mercury is the only liquid metal. (d) Bromine is the only liquid non-metal. 34. Which of the following statement regarding non-metals is true? (a) Non-metals are of two types only solids and gases. (b) Non-metals reacts with oxygen to form basic oxides generally. (c) Non-metals are non-lustrous with dull apppearence. Graphite, an allotrope of carbon and iodine have shining lustrous surfaces. (d) Non-metals replace hydrogen from acids. 35. Which of the following statements regarding non-metals is false? (a) 11 non-metals are in gaseous state. (b) Gas carbon is a good conductor of heat and electricity. (c) The black material inside a pencil is metal lead. (d) All non-metals are non-sonorous in nature. 36. Consider the following elements: (i) Copper (ii) Gold (iii) Platinum (iv) Silver Which of the above elements exist free in nature? (a) (i) and (ii) (b) (ii) and (iii) (c) (i), (ii) and (iv) (d) (iii) and (iv)

C-71

37.

38.

39.

40.

41.

42.

43.

44.

45.

46.

47.

Consider the following statements: Nitrogen is an essential constituent of (i) soils (ii) animals (iii) plants Which of the statements given above is/are correct ? (a) (iii) only (b) (i) and (iii) only (c) (i) and (ii) only (d) (i), (ii) and (iii) When iron is left exposed in open air, it gets rusted. Which constituent(s) of air is /are responsible for rusting iron? (i) Oxygen gas present in air (ii) Moisture present in air (iii) Carbon dioxide gas present in air Select the correct answer using the code given below : (a) (i) only (b) (ii) only (c) (i) and (ii) (d) (ii) and (iii) Aluminium is used for making cooking utensils. Which of the following properties of aluminium are responsible for the same ? (i) Good thermal conductivity (ii) Good electrical conductivity (iii) Ductility (iv) High melting point (a) (i) and (ii) (b) (i) and (iii) (c) (ii) and (iii) (d) (i) and (iv) Silicon is used in – (a) solar energy devices (b) semiconductors (c) transistors (d) all of these Which of the following is not a atomic characteristics of metal – (a) malleable (b) electropositive nature (c) ductile (d) none of these Pure gold is – (a) 24 carats (b) 22 carats (c) 20 carats (d) 18 carats What is anode mud – (a) fan of anode (b) metal of anode (c) impurities collected at anode in electrolysis during purification of metals (d) all of these The best mealleable metal is – (a) aluminium (b) silver (c) gold (d) lead German silver is a mixture of – (a) copper and zinc (b) copper and tin (c) copper, nickel and zinc (d) aluminium, copper and traces of Mg and Mn. Graphite is a/an – (a) alloy (b) metal (c) metalloid (d) non-metal Which of the following metals constitutes the alloy magnalium – (a) Al, Cu (b) Al, Fe (c) Al, Mg (d) Al, Mn

C-72

GENERAL SCIENCE 1 2 3 4 5 6 7 8 9 10

11 12 13 14 15 16 17 18 19 20

ANSWER KEY (a) 21 (d) 22 (d) 23 (a) 24 (c) 25 (d) 26 (b) 27 28 (c) 29 (a) 30 (d)

31 32 33 34 35 36 37 38 39 40

(d) (c) (b) (c) (c) (c) (d) (c) (d) (d)

41 42 43 44 45 46 47

(d) (a) (c) (c) (c) (d) (c)

HINTS AND SOLUTIONS 2. 3. 5. 7. 8.

9. 11.

13. 16. 19. 21. 23. 24. 25.

(a) Mercury is the only element even being metal is liquid at room temperature. (a) As the chemical formula of rust is Fe2O3. xH2O (d) Chemical formula of horn silver is AgCl. (a) Cinnabar (HgS) is a sulphide ore of mercury (d) Pig iron ® It is the most impure form of iron and contains highest proportion of carbon (2.5–4%). Rest all are ore. Malachite ® Cu(OH)2.CuCO3, Zinc blende ® ZnS, Bauxite ® Al2O3.2H2O (d) Fluorspar (CaF2 ), Cryolite (Na 3 AlF6 ), Feldspar (KAlSi3O8) and Mica (K2O.3Al2O3.6SiO2.2H2O) (c) Among cuprite [Cu 2 O], Chalcocite [Cu 2 S], Chalcopyrite [CuFeS2] and Malachite [Cu(OH)2 CuCO3], only Chalcopyrite is an ore which contains both Fe and Cu. (d) Bauxite – Al2O3 Halmatite – Fe2O3 Cuprite – Cu2 O (b) Fe2O3(s) + 2Al(s) ¾¾ ® Al2O3(s) + 2Fe(l) (a) Brass is a maxture of 80% Cu & 20% Zn. (a) Bauxite is Al2O3.2H2O. (d) Steel an alloy of iron and carbon is used for manufacturing bridges. (a) Graphite is the only non-metal, which is a good conductor of heat and electricity. (c) Metals are both melleable and ductile. Metals can be drawn into thin sheets and wires.

26.

27.

28. 29. 31. 32.

33. 35. 36.

37.

38. 41. 45. 47.

(d) Phosphorus is a non-metal and non-metals have low melting and boiling points. Although, sodium is a metal, it has low melting and boiling point. (b) Graphite which is crystalline form of carbon and iodine are the only two non-metals which has shining lustrous surfaces. (c) Noble metals are those metals which do not react easily and lie at the bottom of the activity series. (a) Both boron and silicon are metalloids. (d) Iodine is a sublime substance (c) Mercury being a metal is liquid at room temperature. Metals are good conductor of heat therefore cannot be used to make handle it will result into burns. Gold cannot be used to make electrical wires it is very expensive therefore metals like copper is used for it. (b) Gold and Silver are most malleable metals whereas zinc metal is non-malleable and brittle. (c) The black material inside a pencil is not metal lead. Actually it is graphite, a non-metal. (c) Cu, Au, Ag are known as coinage metals and occur free in nature. Becuase of nobility they are frequently found in their natives state. (d) Nitrogen is a essential constituent of all vegetables and animal proteins. Soil contains nitrogen as ammonium salts. (c) Both oxygen and moisture present in air cause rusting of iron. (d) All are characteristics of metal. (c) German silver is a mixture of Cu (60%), Zn (20%) and Ni (20%). (c) Magnalium is a mixture of 90% Al and 10% Mg.

Environmental Pollution

6 1.

3. (i)

(ii)

The pollutants may be inorganic, biological or radiological in nature. (i) Bio-degradable pollutants are domestic wastes which are rapidly decomposed by micro-organisms. (ii) Non-biodegradable pollutants include chemicals, mercuric salts, lead compounds, pesticides, etc. (iii) Natural pollution is caused by radioactive substances, volcanic eruptions, forests and mines fires floods, etc. (iv) Artificial pollution is caused by industries, thermal plants, automobile, exhausts, sewage, etc. Environment : The conditions existing around animal or human life. Atmosphere: The gaseous envelop surrounding the earth. It has been classified into following regions:(i) Stratosphere : The layer of the earth’s atmosphere above the troposphere and below the mesosphere. (ii) Troposphere : The lowest region of the atmosphere extending from earth’s surface to the lower boundary of the stratosphere. In this region, human beings along with other organisms live. It contains water vapour and is greatly affected by air pollution. Note : The other two layers are Thermosphere and Mesosphere. Air pollution : The major air pollutants are Carbon monoxide (CO) : It is produced by incomplete combustion of gasoline in motor vehicles, wood, coal, inceneration and forest fires. It is treacherous and deadly poisonous gas. It induces headache, visual difficulty coma and death. It blocks the normal transport of oxygen from the lungs to other parts of the body. Sulphur dioxide ( SO 2 ) : It is produced by petrol

It attacks marble, limestone,vegetation, paper and textiles and injurious to human beings. (iii) Oxides of nitrogen : NO 2 and NO, Source - combustion of coal, gasoline, natural gas, petroleum refining, chemical plants, manufacturing explosives and fertilizers, tobacco smoke. Breathing NO 2 causes chlorosis to plants and chronic lung conditions leading to death. NO 2 reacts with moisture to form acids.

¾® HNO 2 + HNO 3 , 2NO2 + H 2 O ¾ ¾® 2NO + HNO 3 + H 2 O 3 HNO 2 ¾ (iv) Smoke, dust : Sources : cement works, iron and steel works, gas works, power generating stations. Smog : It is a mixture of smoke and fog in suspended droplet form. It is of two types : (a) London smog or classical smog : It is coal smoke plus fog. The fog part is mainly SO2 and SO3. It has sulphuric acid aerosol. It causes bronchial irritation and acid rain. It is reducing in nature. (b) Photochemical smog or Los Angeles smog : The oxidised hydrocarbons and ozone in presence of humidity cause photochemical smog. Hydrocarbons + O2, NO2, NO, O, O3 ® Peroxides, formaldehyde, peroxyacetylnitrate (PAN), acrolein etc. It is oxidising in nature and causes irritation to eyes, lungs, nose, asthamatic attack and damage plants. Acid rain : The oxides of C, N and S present in the atmosphere, dissolve in water and produce acids and lower the pH of water below 5.5. ¾® H 2CO 3 H 2 O + CO 2 ¾

combustion, coal combustion, petrol refining and smelting operations. It hinders the movement of air in and out of lungs. It is particularly poisonous to trees causing chlorosis and

2 H 2 O + 2 SO 2 + O 2 ® 2 H 2SO 4

H + + NO3 The acids are toxic to vegetation, react with marble and damage buildings.

2 SO 2 + O 2 (air) ¾ ¾® 2 SO 3

SO 3 + H 2 O (moisture ) ¾ ¾® H 2SO 4

2 H + + SO 24 -

2 H 2 O + 4 NO 2 + O 2 ® 4 HNO 3

dwarfing. In presence of air it is oxidised to SO 3 which is also irritant. In presence of moisture SO 3 is converted into highly corrosive sulphuric acid.

2 H + + CO32 -

(v)

CaCO3 + H 2SO 4 ¾ ¾® CaSO 4 + H 2 O + CO 2 Acids corrode water pipes and produce salts with heavy metals ions viz Cu, Pb, Hg and Al toxic in nature. Green House effect : The retention of heat by the earth and atmosphere from the sun and its prevention to escape into

C-74

the outer space is known as green house effect. Global warming is average increase in the temperature of earth due to increase in concentration of green house gases (CO2, O3, NOx etc). Consequences of global warming : (i) Global warming would result in rise in sea level due to increased rate of melting of glaciers and floods. (ii) Increase in infectious diseases like malaria, dengue, etc. (vi) Ozone layer and its depletion : The ozone layer, existing between 20 to 35 km above the earth’s surface, shield the earth from the harmful U. V. radiations from the sun. The U. V. radiations cause skin cancer, cataract of eye, and harm to vegetation. Depletion of ozone is caused by oxides of nitrogen N2O + h u ¾ ¾® NO + N reactive nitric oxide NO + O 3 ¾ ¾® NO 2 + O 2 , O3 + h u ¾ ¾® O 2 + O, ¾® NO + O 2 NO 2 + O ¾

2 O3 + h u ¾ ¾® 3 O 2 (Net reaction) The presence of chlorofluorocarbons also increase the decomposition of O 3 . C F2 Cl 2 + h u ¾ ¾® CF2 Cl + Cl ¾® CFCl 2 + Cl, CFCl3 + h u ¾

Cl + O 3 ¾ ¾® ClO + O, ClO + O ¾ ¾® Cl + O 2 O3 + O ¾ ¾® 2 O 2 (Net reaction) (vii) Control of air pollution : It can be controlled by 1. 2. 3. 4. 5. 6. 4.

(i)

Dissolving HCl, HF, SiF4 in water and SO 2 , Cl 2 , H 2S in alkaline solution. Adsorbing gas and liquid molecules over activated charcoal and silica gel. Chemical reactions. Use of precipitators to settle charge particles. Use of settling chambers under the action of gravity. Use of natural gas in place of diesel, petrol, etc.

Water pollution : The contamination of water by foreign substances which would constitute a health hazard and make it harmful for all purposes (domestic, industrial or agriculture etc.) is known as water pollution. The polluted water may have offensive odour, bad taste, unpleasant colour, murky oily, etc. Sources of water pollution (a) Domestic sewage : Discharges from kitchens, baths, lavatories, etc. (b) Industrial waters : Wastes from manufacturing processes which includes acids, alkalines, pesticides, insecticides, metals like copper, Zinc, lead, mercury, fungicides, etc. (c) Oil : From oil spills or washings of automobiles.

GENERAL SCIENCE (d) Atomic explosion and processing of radioactive materials. (e) Suspended particles (organic or inorganic) viruses, bacterias, algae, protozoa, etc. (f) Wastes from fertilizer plants such as phosphates, nitrates ammonia, etc. (g) Clay : Ores, minerals, fine particles of soil. (ii) Aerobic and anaerobic oxidation : The oxidation of organic compounds present in sewage in presence of good amount of dissolved or free oxygen (approx. 8.5 ml/l) by aerobic bacterials is called aerobic oxidation. When dissolved or free oxygen is below a certain value the sewage is called stale. Anaerobic bacterias bring out putrefaction producing H2S, NH3, CH4, (NH4)2S, etc. This type of oxidation is called anaerobic oxidation. (iii) Biological Oxygen Demand (BOD) : It is defined as the amount of free oxygen required for biological oxidation of the organic matter by aerobic conditions at 20°C for a period of five days. Its unit is mg/l or ppm. An average sewage has BOD of 100 to 150 mg/l. (iv) Chemical Oxygen Demand (COD) : It is a measure of all types of oxidisable impurities present in the sewage. COD values are higher than BOD values. 5. Soil pollution : The addition of substances in an indefinite proportion changing the productivity of the soil is known as soil or land pollution. Sources of soil pollution : (i) Agricultural pollutants : Chemicals like pesticides, fertilizers, bacteriacides, fumigants, insecticides, herbicides, fungicides. (ii) Domestic refuge and industrial wastes. (iii) Radioactive wastes from research centres, and hospitals. (iv) Soil conditioners containing toxic metals like Hg, Pb, As, Cd, etc. (v) Farm wastes from poultries, dairies and piggery farms. (vi) Improper disposal of human and animal extreta. (vii) Pollutants present in air from chemical works. 6. Pesticides : The chemical substances used to kill or stop the growth of unwanted organisms are called pesticides. They are further classified as (i) Insecticides : They are used to kill insects. The most common insecticides are (i) D.D.T (ii) BHC, 666, game xene (iii) Baygon (iv) Sevin Carbaryl (v) Parathion (vi) Methoxychlor (vii) Aldrin (ii) Herbicides : They are used to kill weeds (i) 2, 4-dichlorophenoxy acid (ii) Triazines (iii)

NaClO3 Sodium chlorate

(iv)

Na 3 AsO 3 Sodium arsenite

The (iii) and (iv) are not used now-a-days. Addition of phosphate fertilizers to water leads to nutrient enrichment (eutrophication).

Environmental Pollution

Dinitrogen and dioxygen are main constituents of air but these do not react with each other to form oxides of nitrogen because __________. (a) the reaction is endothermic and requires very high temperature. (b) the reaction can be initiated only in presence of a catalyst. (c) oxides of nitrogen are unstable. (d) N2 and O2 are unreactive. The pollutants which came directly in the air from sources are called primary pollutants. Primary pollutants are sometimes converted into secondary pollutants. Which of the following belongs to secondary air pollutants? (a) CO (b) Hydrocarbon (c) Peroxyacetyl nitrate (d) NO Which of the following is not a consequence of greenhouse effect? (a) Climatic conditions will be changed (b) Plants in warmer climates with adequate rainfall would grow faster (c) The incidence of infectious diseases is likely to increase (d) Malaria will be controlled as the mosquitoes will not survive. Which of the following gases is not a green house gas? (a) CO (b) O3 (c) CH4 (d) H2O vapour The substance having the largest concentration in acid rain? (a) H2CO3 (b) HNO3 (c) HCl (d) H2SO4 The non-viable particulate is among the following is (a) Dust (b) Bacteria (c) Moulds (d) Fungi Which of the following statements is not true about classical smog? (a) Its main components are produced by the action of sunlight on emissions of automobiles and factories. (b) Produced in cold and humid climate. (c) It contains compounds of reducing nature. (d) It contains smoke fog and sulphur dioxide Which of the following statements about photochemical smog is wrong? (a) It has high concentration of oxidising agents (b) It has low concentration of oxidising agent (c) It can be controlled by controlling the release of NO2, hydrocarbons ozone, etc. (d) Plantation of some plants like pinus helps in controlling photochemical smog.

C-75

10.

11.

12.

13.

14.

15.

16.

Which of the following statements is wrong? (a) Ozone is not responsible for green house effect. (b) Ozone can oxidise sulphur dioxide present in the atmosphere to sulphur trioxide. (c) Ozone hole is thinning of ozone layer present in stratosphere. (d) Ozone is produced in upper stratosphere by the action of UV rays on oxygen. Which of the following statements is correct? (a) Ozone hole is a hole formed in stratosphere from which ozone oozes out. (b) Ozone hole is a hole formed in the troposphere from which ozone oozes out. (c) Ozone hole is thinning of ozone layer of stratosphere at some places. (d) Ozone hole means vanishing of ozone layer around the earth completely. Biochemical Oxygen Demand, (BOD) is a measure of organic material present in water. BOD value less than 5 ppm indicates a water sample to be __________. (a) rich in dissolved oxygen (b) poor in dissolved oxygen (c) highly polluted (d) not suitable for aquatic life Photochemical smog occurs in warm, dry and sunny climate. One of the following is not amongst the components of photochemical smog, identify it. (a) NO2 (b) O3 (c) SO2 (d) Unsaturated hydrocarbon Phosphate pollution is caused by (a) sewage and agricultural fertilizers (b) weathering of phosphate rocks only (c) agriculutral fertilizers only (d) phosphate rocks and sewage The type of pollution caused by spraying of DDT (a) Air and soil (b) Air and water (c) Air (d) Air, water and soil Which among the following statements is false? (a) Oil slick in sea water increases D.O. value. (b) The main reason for river water pollution is industrial and domestic sewage discharge. (c) Surface water contains a lot of organic matter mineral nutrients and radioactive materials. (d) Oil spill in sea water causes heavy damage to fishery. Sewage containing organic waste should not be disposed in water bodies because it causes major water pollution. Fishes in such a polluted water die because of (a) large number of mosquitoes (b) increase in the amount of dissolved oxygen (c) decrease in the amount of dissolved oxygen in water (d) clogging of gills by mud

C-76

17.

18.

19.

20.

21.

22.

23.

24.

Which of the following practices will not come under green chemistry? (a) If possible, making use of soap made of vegetable oils instead of using synthetic detergents. (b) Using H2O2 for bleaching purpose instead of using chlorine based bleaching agents. (c) Using bicycle for travelling small distances instead of using petrol/ diesel based vehicles. (d) Using plastic cans for neatly storing substances. Identify the wrong statement in the following: (a) Chlorofluorocarbons are responsible for ozone layer depletion. (b) Greenhouse effect is responsible for global warming. (c) Acid rain is mostly because of oxides of nitrogen and sulphur. (d) Ozone layer does not permit infrared radiation from the sun to reach the earth. Water is often treated with chlorine to (a) remove hardness (b) increase oxygen content (c) kill germs (d) remove suspended particles The greenhouse effect is because of the (a) presence of gases, which in general are strong infrared absorbers, in the atmosphere (b) presence of CO2 only in the atmosphere (c) pressure of O3 and CH4 in the atmosphere (d) N2O and chlorofluorohydrocarbons in the atmosphere Which of the following is/are the hazardous pollutant(s) present in automobile exhaust gases? (i) N2 (ii) CO (iii) CH4 (iv) Oxides of nitrogen (a) (ii) and (iii) (b) (i) and (ii) (c) (ii) and (iv) (d) (i) and (iii) Green chemistry means such reactions which (a) produce colour during reactions (b) reduce the use and production of hazardous chemicals (c) are related to the depletion of ozone layer (d) study the reactions in plants Which one of the following statement is not true? (a) pH of drinking water should be between 5.5 – 9.5. (b) Concentration of DO below 6 ppm is good for the growth of fish. (c) Clean water would have a BOD value of less than 5 ppm. (d) Oxides of sulphur, nitrogen and carbon are the most widespread air pollutant. Frequent occurrence of water blooms in a lake indicates (a) nutrient deficiency (b) oxygen deficiency (c) excessive nutrient availability (d) absence of herbivores in the lake

25.

26.

27.

28.

29.

30.

31.

32.

33.

34.

GENERAL SCIENCE When rain is accompanied by a thunderstorm, the collected rain water will have a pH value (a) slightly lower than that of rain water without thunderstorm (b) slightly higher than that when the thunderstorm is not there (c) uninfluenced by occurrence of thunderstorm (d) which depends upon the amount of dust in air The smog is essentially caused by the presence of (a) Oxides of sulphur and nitrogen (b) O2 and N2 (c) O2 and O3 (d) O3 and N2 Identify the wrong statement in the following. (a) Chlorofluorocarbons are responsible for ozone layer depletion. (b) Greenhouse effect is responsible for global warming. (c) Ozone layer does not permit infrared radiation from the sun to reach the earth. (d) Acid rain is mostly because of oxides of nitrogen and sulphur. Identify the incorrect statement from the following. (a) Ozone absorbs the intense ultraviolet radiation of the sun. (b) Depletion of ozone layer is because of its chemical reactions with chlorofluoro alkanes. (c) Ozone absorbs infrared radiation. (d) Oxides of nitrogen in the atmosphere can cause the depletion of ozone layer. What is DDT among the following ? (a) Greenhouse gas (b) A fertilizer (c) Biodegradable pollutant (d) Non-biodegradable pollutant The gas leaked from a storage tank of the Union Carbide plant in Bhopal gas tragedy was (a) Methyl isocyanate (b) Methylamine (c) Ammonia (d) Phosgene The substance which is not regarded as a pollutant? (a) NO2 (b) CO2 (c) O3 (d) Hydrocarbons The greatest affinity for haemoglobin is shown by which of the following : (a) NO (b) CO (c) O2 (d) CO2 Which of the following is not involved in the formation of photochemical smog? (a) Hydrocarbon (b) NO (c) SO2 (d) O3 The false statement among the followings : (a) The average residence time of NO is one month (b) Limestone acts as a sink for SOx (c) SOx can be removed from flue gases by passing through a solution of citrate ions (d) Ammonia acts as a sink for NOx

Environmental Pollution 35. The statement which is not correct about control of particulate pollution (a) In electrostatic precipitator, the particulates are made to acquire positive charge which are then attracted by the negative electrode and removed (b) Gravity settling chamber removes larger particles from the air (c) Cyclone collector removes fine particles in the diameter range 5-20 microns (d) Wet scrubbers are used to wash away all types of particulates 36. Which of the following statements about polar stratosphere clouds (PSCs) is not correct? (a) PSCs do not react with chlorine nitrate and HCl (b) Type I clouds are formed at about –77ºC and contain solid HNO3 . 3H2O (c) Type II clouds are formed at about –85ºC and contain some ice (d) A tight whirlpool of wind called Polar Vortex is formed which surrounds Antarctica 37. Minamata disease is due to pollution of (a) aresenic into the atmosphere (b) organic waste into drinking water (c) oil spill in water (d) industrial waste mercury into fishing water

C-77

38.

39.

40.

41.

42.

BOD is connected with (a) microbes and organic matter (b) organic matter (c) microbes (d) None of these Eutrophication causes reduction in (a) dissolved oxygen (b) nutrients (c) dissolved salts (d) All of these Which among the following statements is false? (a) Oil slick in sea water increases D.O. value (b) The main reason for river water pollution is industrial and domestic sewage discharge (c) Surface water contains a lot of organic matter mineral nutrients and radioactive materials (d) Oil spill in sea water causes heavy damage to fishery Presence of which of the following fuel gas in the exhaust fumes shows incomplete combustion of fuel? (a) Sulphur dioxide (b) Carbon monoxide and water vapour (c) Carbon monoxide (d) Nitrogen dioxide Which one of the following statements about ozone and ozone layer is true? (a) Ozone layer is beneficial to us because ozone cuts out the ultraviolet radiation of the sun (b) The conversion of ozone to oxygen is an endothermic reaction (c) Ozone has a triatomic linear molecule (d) None of these

C-78

GENERAL SCIENCE 1 2 3 4 5 6

(a) (c) (d) (a) (d) (a)

7 8 9 10 11 12

(a) (b) (a) (c) (a) (c)

13 14 15 16 17 18

(a) (d) (a) (c) (d) (d)

ANSWER KEY (c) 19 (a) 20 (c) 21 (b) 22 (b) 23 (b) 24

25 26 27 28 29 30

(a) (a) (c) (c) (d) (a)

31 32 33 34 35 36

(b) (a) (c) (a) (a) (a)

37 38 39 40 41 42

(d) (a) (a) (a) (c) (a)

HINTS AND SOLUTIONS 3.

(d) The mosquitoes will increase their population and spread malaria.

(d) Acid rain contains H2SO4 > HNO3> HCl.

(a) Dust

13.

(a) Phosphate pollution is caused by sewage and agricultural fertilizers.

14.

(d) DDT causes water, air and soil pollution.

15.

(a) Oil slick in sea water decreases D.O value.

18.

(d) Ozone layer acts as a shield and does not allow ultraviolet radiation from sun to reach earth. It does not prevent infra-red radiation from sun to reach earth, thus option (d) is wrong statement and so it is the correct answer.

Thus option (c) is wrong statement and so it is the correct answer. 28.

(c) The ozone layer, existing between 20 to 35 km above the earth’s surface, shield the earth from the harmful U. V. radiations from the sun. Depletion of ozone is caused by oxides of nitrogen ¾® NO + N N 2O + h u ¾

reactive nitric oxide NO + O 3 ¾ ¾® NO 2 + O2 O3 + h u ¾ ¾® O 2 + O NO 2 + O ¾ ¾® NO + O 2

19.

¾® 3 O 2 (Net reaction) 2 O3 + h u ¾

20.

(a) Green house gases such as CO2, ozone, methane, the chlorofluorocarbon compounds and water vapour form a thick cover around the earth which prevents the IR rays emitted by the earth to escape. It gradually leads to increase in temperature of atmosphere.

The presence of oxides of nitrogen increase the decomposition of O3. 29.

(d) DDT is a non-biodegradable pollutant.

30.

(a) Methyl isocyanate, CH3 – N = C = O

31.

(b) CO2 is generally not regarded as an pollutant.

32.

(a) Haemoglobin has great affinity for NO.

33.

34.

(a) The average residence time of NO is 4 days.

35.

(a) Particulates acquire negative charge and are attracted by the positive electrode.

36.

(a) PSCs react with chlorine nitrate and HCl to give HOCl and Cl2.

(b) The ideal value of D.O for growth of fishes is 8 mg/ l . 7mg /l is desirable range, below this value fishes get susceptible to disease. A value of 2 mg/ l or below is lethal for fishes.

37.

(d) Minamata is caused by Hg poisoning.

38.

(a) BOD is connected with microbes and organic matter.

39.

(a) Eutrophication causes reduction in D.O.

(a) Normal rain water has pH 5.6 Thunderstorm results in the formation NO and HNO3 which lowers the pH.

40.

(a) Oil slick in sea water decreases D.O value.

41.

21.

22.

(b) Green chemistry may be defined as the programme of developing new chemical products and chemical processes or making improvements in the already existing compounds and processes so as to make less harmful to human health and environment. This means the same as to reduce the use and production of hazardous chemicals. i.e. correct answer is option (b).

23.

25. 26.

(a) Smog is caused by oxides of sulphur and nitrogen.

27.

(c) Ozone layer acts as a shield and does not allow ultraviolet radiation from sun to reach earth. It does not prevent infra-red radiation from sun to reach earth.

General Concepts of Chemistry

7 1.

Definition Chemistry is a branch of science which deals with study of matter and various changes it undergoes. It deals with the preparation, properties, reactions and structures of chemical elements and compounds. For convenience the study of chemistry is sub-divided into various branches such as: (i) Inorganic chemistry (ii) Organic chemistry (iii) Physical chemistry (iv) Analytical chemistry (v) Industrial chemistry Valency During the formation of molecules of compounds, atoms combine in certain fixed proportions. This is because of the fact that different atoms have different combining capacities. The combining capacity of an atom or radical is known as its valency. Ions or radicals In addition to atoms and molecules, a third type of particles occurs in substances. These particles, called ions, or atoms or group of atoms that carry an electrical charge. An ion is formed when electrons are removed from or added to an atoms or group of atoms. When electrons is/are removed the resulting ion is called a cation or basic radical. A cation is positively charged ion. (e.g. Na+ ). When electron is/are added the resulting ion is called an anion or acidic radicals. An anion is negatively charged ion (e.g. , Cl

, O 22- )

An ion or radical is classified as monovalent, divalent, trivalent or tetravalent when the number of charges over it is 1, 2, 3 or 4 respectively. Formula of Elements and Compounds Formula of elements: The molecule of an element is denoted by writing the symbol of the element and, to the right and below it, a number expressing the number of atoms in the molecule. Formula of compound : A molecule of a compound may be made up of atom of different elements linked up together chemically and in definite proportion by weight.

Chemical formula : It is of two types : (i)

Molecular formulae : Chemical formulae that indicate the actual number and type of atoms in a molecule is called molecular formulae.

(ii) Empirical formulae : Chemical formulae that indicate only the relative number of atoms of each type in a molecule is called empirical formulae. 6.

Equivalent weight (i) Equivalent weight of element =

Atomic weight of element Valency of element

(ii) Eq. wt of an acid/base =

Molecular mass Basicityof acid / Acidity of base

(iii) Eq. wt of salts = 7.

Formula mass (Valency of cation) (No.of cations)

Expression of strength /concentration of Solution (i) Mass percent =

(ii) Normality =

Weight of solute (gm) ´ 100 Weight of solution (gm)

Number of gram equivalents of solute Volume of solution (lit.)

(iii) Molarity =

(iv) Molality =

Number of gram moles of solute volume of solution (lit.)

Gram moles of solute Weight of solvent (kg)

(v) Mole fraction : Mole fraction of solute = XA =

nA nA + nB

Mole fraction of solvent = XB = XA + XB = 1

nB nA + nB

C-80

GENERAL SCIENCE

Chemical reaction : The process in which a substance undergoes change to produce new substances with new properties are known as chemical reaction. For example magnesium carbonate when heated produces magnesium oxide and carbon dioxide (i.e. new substances with new properties). A chemical change is generally accompanied by a change of state, change of colour, evolution of a gas or change of temperature etc. 9. Chemical equation : The qualitative representation of a chemical reaction in a short hand or concise form in term of symbols and formulae, is called a chemical equation. 10. Skeletal chemical equation or symbol equation : A chemical equation written in the form of symbols and formulae is called a skeletal chemical equation. 11. Balanced chemical equation : A chemical equation in which number of atoms of each elements on L.H.S. (i.e. reactants) and R.H.S. (i.e.products) is equal is called a balanced chemical equation. 12. Balancing of chemical equations : The process of making the number of different elements on both side of the equation equal is known as balancing of chemical equation. 13. Types of chemical reactions Various types of chemical reactions are :(i) Combination reactions : Combination reactions are those in which one element reacts with another to form a compound. This type of reactions are also known as synthesis reaction. For example, hydrogen combines with oxygen to give water. 2H 2 (g ) + O 2 ( g ) ¾¾ ® 2H 2O(l) (ii) Decomposition reactions : Decomposition reactions are those reactions in which a compound breaks down into simpler compounds (or substances). This type of reaction is simply the reverse of combination reactions. These reactions require energy in the form of heat, light, electricity, etc. (iii) Simple displacement reaction and simple substitutions : A displacement reaction is a reaction in which an atom, or group of atoms, present in a molecule is displaced by another atom. This type of reaction can be represented as follows:

AB + C ¾¾ ® AC + B (Compound) (New compound)

(iv) Double displacement reactions or Double decomposition : The reactions in which mutual exchange of radicals takes place are known as double decomposition reactions. As a result of double decomposition reactions two new substances are formed.

Examples : 2NaCl + H 2SO 4 ¾¾ ® Na 2 SO4 + 2HCl

Double-displacement reactions can be further classified as precipitation, gas formation, and acid-base neutralization reactions.

(v)

Precipitation reactions : A precipitation reaction occurs when two solutions are mixed together and a solid separates from the solution. The solid part that forms and separates form the solutions is called the precipitate the reaction given above is a precipitation reaction. Oxidation-Reduction Reactions Oxidation : Oxidation is defined as a process which involve addition of oxygen or removal of hydrogen. Reduction : The term reduction is defined as a process which involve the removal of oxygen or addition of hydrogen.

(vi) Redox reactions : Those reactions in which oxidation and reduction takes place simultaneously, are known as redox reactions. Example : addition of oxygen (oxidation) heat

CuO + H2

Cu + H2O

Reduction (removal of hydrogen)

(vii) Exothermic and endothermic reaction : Chemical reactions usually proceed with either liberation of heat or the absorption of heat. When a chemical reaction liberates heat to the surroundings, it is said to be 'exothermic reaction' and when it absorbs the heat from the surroundings, it is said to be endothermic reaction. N 2 ( g ) + 3H 2 ( g ) ¾¾ ® 2NH 3 ( g )

+ energy (Exothermic) D

CaCO 3 (s ) ¾¾ ® CaO(s) + CO 2 ( g )(Endothermic)

14.

Corrosion (erosion by chemical action) : Corrosion is the degradation of metals and generally called rust. Corrosion causes damage to car bodies, iron railings, ships and to all objects made of metals, specially those of iron. Corrosion of iron is a serious problem.

15.

Rancidity : The most important cause of deterioration in fats and fatty foods is oxidation of fats. What we perceive is an unpleasant change in the flavour and odour of a food, called rancidity.

General Concepts of Chemistry

C-81

Na2S2O3 represent the compound (a) sodium sulphate (b) sodium sulphite (c) sodium thiosulphate (d) None of these Which one is a bivalent ion? (a) sodium (b) calcium (c) sulphide (d) Both (b) and (c) The chromate and dicharomate ions are respectively (a)

CrO 24

and

Cr2 O27

(b)

Cr2 O72–

and

13.

14.

CrO 4–

2– (d) CrO 2– CrO 4– and CrO5– 4 and Cr2 O 5 The formula of sodium pyrophosphate is (a) Na2P2O7 (b) Na3PO4 (c) Na4P2O7 (d) Na3PO3 The branch of chemistry which deals with study of physical properties and conditions is (a) physical chemistry (b) analytical chemistry (c) nuclear chemistry (d) pharmaceutical chemistry The branch of chemistry which deals with study of the methods of detection and determination of elements and compounds is (a) Physical chemistry (b) Nuclear chemistry (c) Analytical chemistry (d) Bio chemistry Valency of an atom or radicals is (a) ionisation energy (b) electron affinity of atom (c) its combining capacity (d) size of atom When electrons are added the resulting ion is called (a) basic radical (b) acidic radicals (c) neutral radical (d) None of these Which of the following is most unreactive ? (a) Mg (b) Mg+ (c) Mg2+ (d) All above species are inert Chemical formula of Aluminium sulphate is (a) Al2(SO4)3 (b) AlSO4 (c) Al3(SO4)2 (d) None of these Select the one that represents a displacement reaction. ® AgCl + NaNO3 (a) NaCl + AgNO3 ¾¾ ® ZnSO4 + Cu (b) Zn + CuSO4 ¾¾ ® NaCl + H2O (c) HCl + NaOH ¾¾ ® CO2 (d) C + O2 ¾¾ Which one is a combination reaction ? (a) Formation of a mixture of carbon monoxide and hydrogen. When steam is passed over red hot iron. (b) Reaction of water with sodium metal to form sodium hydroxide and hydrogen. ® 2NaOH + CaCO3 ¯ (c) Ca(OH)2 + Na2CO3 ¾¾ (d) Preparation of stannic chloride (Tin (iv) chloride) by passing chlorine gas into molten tin (Sn).

(c)

10.

11.

12.

15.

Which of the following involves combination of two elements? ® CaCO3 (a) CaO + CO2 ¾¾ ® 2Na2O (b) 4Na + O2 ¾¾ ® 2SO3 (c) 2SO2 + O2 ¾¾ ® NH4Cl (d) NH3 + HCl ¾¾ When hydrogen sulphide gas is passed through a blue solution of copper sulphate, a black precipitate of copper sulphide is formed. This is an example of (a) combination reaction (b) displacement reaction (c) decomposition reaction (d) double decomposition reaction Which one is a decomposition reaction ? heat

(a) 2HgO ¾¾¾® 2Hg + O2

heat (b) CaCO3 ¾¾¾ ® CaO + CO2 Electrolysis

16.

17.

18.

19.

20.

21.

® 2H2 + O2 (c) 2H2O ¾¾¾¾¾¾ (d) All the above reactions are decomposition reaction The reactions in which two compounds exchange their radicals to form two new compounds are called (a) displacement reaction (b) decomposition reaction (c) double displacement reaction (d) isomerisation reaction ® Cu + H2O CuO + H2 ¾¾ Above reaction is an example of (a) Redox reaction (b) synthesis reaction (c) neutralisation reaction (d) decomposition reaction In the reaction : PbO + C ¾¾ ® Pb + CO (a) PbO is oxidised (b) PbO is oxidant (c) C is reductant (d) Both (b) and (c) Chemical equations are balanced in accordance with the (a) Dalton’s law (b) Law of conservation of mass (c) Law of definite composition (d) None of these Which is not a balanced equation ? ® NaCl + H2O (a) NaOH + HCl ¾¾ ® MgSO4 + Cu (b) Mg + CuSO4 ¾¾ ® FeCl3 (c) Fe + Cl2 ¾¾ ® Mg(NO3)2 + H2 (d) Mg + 2HNO3 ¾¾ Which of the following statements is true about chemical equation ? (a) Mass is conserved (b) Atoms are conserved (c) Mass as well as atoms are conserved (d) Molecules are conserved

C-82

22. A molal solution is one that contains 1 mole of a solute in (a) one litre of the solvent (b) 1000 g of the solvent (c) one litre of the solution (d) 22.4 litres of the solution 23. The total number of atoms represented by the compound CuSO4.5H2O is (a) 27 (b) 21 (c) 5 (d) 8 24. The molecular formula P2O5 means that (a) a molecule contains 2 atoms of P and 5 atoms of O (b) the ratio of the mass of P to the mass of O in the molecule is 2:5 (c) there are twice as many P atoms in the molecule as there are O atoms (d) the ratio of the mass of P to the mass of O in the molecule is 5 : 2 25. The empirical formula and molecular mass of a compound are CH2O and 180 g respectively. What will be the molecular formula of the compound ? (a) C9H18O9 (b) CH2O (c) C6H12O6 (d) C2H4O2 26. The empirical formula of a compound is CH2. One mole of this compound has a mass of 42 grams. Its molecular formula is : (a) C3H6 (b) C3H8 (c) CH2 (d) C2H2 27. Which of the following statements is not correct? (a) A chemical equations tells us about the substances involved in a reaction. (b) A chemical equations informs us about the symbols and formula of substances involved in a reaction (c) A chemical equations tells us about the atom or molecules of the reactants and products involved in a reaction (d) All are correct 28.

29.

30.

AgNO3 (aq) + NaCl(aq) ¾¾ ® AgCl(s) + NaNO3 (aq) Above reaction is (a) precipitation reaction (b) double displacement reaction (c) combination reaction (d) Both (a) and (b) A redox reaction is one in which (a) both the substance are reduced (b) both the substance are oxidised (c) an acid is neutralised by the base (d) one substance is oxidised while the other is reduced An organic compound containing C, H and N gave the following analysis : C = 40% ; H = 13.33% ; N = 46.67% Its empirical formula would be (a) C2H7N2 (b) CH5N (c) CH4N (d) C2H7N

31.

32.

33.

34.

35.

36.

37.

38.

39.

40.

GENERAL SCIENCE An organic compound containing C, H and O gave on analysis C – 40% and H – 6.66%. Its empirical formula would be (a) C3H6O (b) CHO (c) CH2O (d) CH4O Slow eating away of iron articles in the presence of moist air is called (a) galvanisation (b) crystallisation (c) rusting (d) neutralisation Which of the following reaction is endothermic? ® CO (a) C + O2 ¾¾ 2 ® CaO + CO (b) CaCO3 ¾¾ 2 ® CO + 2H O (c) CH4 + 2O2 ¾¾ 2 2 ® Ca(OH) (d) CaO + H2O ¾¾ 2 The observation that does not indicate a chemical reaction is (a) change of temperature (b) change of colour (c) evolution of a gas (d) None of these Which one of the following is not an exothermic reaction ? (a) Respiration (b) Slaking of lime (c) Burning of a candle (d) Dipping of iron block in water Which of the following statement is not correct ? To prevent food from getting rancid, we (a) store the food in air-tight containers (b) add antioxidants (c) flush bags of chips with an inert gas (d) increase the temperature of the food In the following equations : NaCO3 + xHCl ¾¾ ® 2NaCl + CO 2 + H 2O, the value x is (a) 1 (b) 2 (c) 3 (d) 4 Which of the following is not an endothermic process? (a) Boiling of water (b) Dissolving salts in water (c) Dissolving conc. H2SO4 in water (d) Evaporation of water Rusting of an iron is an example of (a) reduction (b) ionization (c) oxidation (d) dissociation Which of the following does not corrode when exposed to the atmosphere? (a) Iron (b) Copper (c) Gold (d) Silver

General Concepts of Chemistry

1 2 3 4 5 6

7 8 9 10 11 12

C-83

(b) (d) (d) (c) (a) (d)

13 14 15 16 17 18

ANSWER KEY (b) 19 (c) 20 (c) 21 (b) 22 (b) 23 (a) 24

25 26 27 28 29 30

31 32 33 34 35 36

(b) (c) (c) (c)

37 38 39 40

HINTS AND SOLUTIONS 2. 8. 9. 12. 13. 14. 15. 17. 18.

20. 22. 23.

25.

26.

28.

30.

(d) Ca++ and S– – ® Cl– (acidic radicals) (b) Cl + e– ¾¾ ++ (c) Mg (12 – 2 = 10e–) = 2, 8 hence have complete octel hence inert. ® SnCl4. (d) Sn + 2Cl2 ¾¾ (b) Both Na and O2 are elements. ® CuS ¯ + H2SO4 (d) CuSO4 + H2S ¾¾ (Blue) (Black) (d) In all these reactions the reactants decompose to form simpler products. (a) It involves oxidation and reduction. (d) In this carbon reduces PbO to Pb so carbon (C) is reducing agent (reductant) PbO acts as oxidising agent (oxidant) as it oxidises C to CO. ® 2FeCl3 (balanced chemical eqn.) (c) 2Fe + 3Cl2 ¾¾ (b) Molal solution contains 1 mole of solute in 1000 g solvent. (b) 1 atom of Cu + 1 atom of sulphur + 9 atoms of oxygen + 10 atoms of hydrogen. Total number of atoms in compound is 21. n=

(c)

180 180 = Molecular mass of CH 2O 30

Element %

40.00

At. wt. 12

Rel. Number 40 12

= 3.66

46.67

13.33

= 13.33

13.33

3.33

46.67

= 3.33

3.33

Relative number

Ratio

40 = 3.33 12

3.33 =1 3.33

6.66

6.66 6.66 =2 = 6.66 3.33 1

53.34

53.34 3.33 = 3.33 =1 16 3.33

(% of O in organic compound = 100 – ( 40 + 6.66 ) = 53.34 % ) Empirical formula of organic compound = CH2O. (c) Rusting is a process in which iron gets converted into hydrated iron oxide in presence of moisture. 3 2Fe + O 2 + xH 2 O ¾¾ ® Fe 2O3 .xH 2O 2 rust

33.

34. 35. 36.

Ratio 3.66

39. 40.

= 1.09 ~ 1

Element %

37. 38.

3.33

13.33

Hence empirical formula = CH4N 31.

32.

n=6 (a) Empirical formula of compound = CH2 Molecular mass of the compound = 42 \ n = 42/14 = 3 \ Hence molecular formula = C3H6 (d) This reaction is double displacement and precipitation as well because insoluble silver chloride gets precipitated. (c) As the sum of the percentage of C, H & N is 100. Thus it does not contains O atom. Table for empirical formula

(b) Heat is required to decompose calcium carbonate. Thus this reaction proceeds with absorption of heat therefore it is endothermic reaction. (d) A chemical reaction is generally accompanied by a change of temperature, colour or evolution of a gas. (d) No reaction occurs in this case. (d) Increase the temperature of the food. ® 2NaCl + CO2 + H 2O (b) Na 2 CO3 + 2HCl ¾¾ (c) Dissolution of conc. H2SO4 in water produces a lot of heat. (c) Rusting results in formation of iron oxide. (c) Gold is a noble metal.

C-84

GENERAL SCIENCE

Some Important Man made Materials

Chemistry has helped significantly in meeting human needs by providing chemical fertilizers, improved varieties of insecticides and pesticides to increase the yield of crops and fruits. It has given us a large number of life saving drugs. Also chemical industries manufacturing polymers, soaps, detergents, glass, ceramics etc.

Industrially Important Compounds 1.

Glass It consists of a mixture of two or more silicates. Preparation of glass : Common glass (or soft glass) : It is used to make bottles, glass wares etc. and is obtained by heating together silica (in the form of sand), sodium carbonate or sodium sulphate and chalk or lime stone (calcium carbonate). Some broken glass and a little co*ke are usually added. The glass so prepared consists of silicates of sodium and calcium. Na2CO3(s) + SiO2(s) ® Na2SiO3 (s) + CO2 (g) (silica) Na2SO4(s) + SiO2(s) ® Na2SiO3 (s) + SO3 (g) CaCO3(s) + SiO2(s) ® CaSiO3 (s) + CO2 (g) Hard glass : For preparation of hard glass K2CO3 is used in place of Na2CO3. It consists of a mixture of calcium and potassium silicates. Physical properties of glass : Hard, rigid, high viscosity, bad conductor of heat and electricity, brittle, etc. Blowing : It is a method to cast the molten glass into different moulds. There are two different methods of glass blowing (i) Free blowing and ( ii) Mould blowing Free blowing : It involves the blowing of air to inflate the molten glass which is gathered at one end of the blow pipe to give the desired shape. Mould blowing : This method was developed after the technique of free blowing. In this method, molten glass is inflated into a wooden or metal carved mould with the help of blow pipe which gives the molten glass the shape and design of the interior of the mould. Chemical properties of glass (1) It is resistant to action of air and acids except hydroflouric acid. (2) It is alkaline in nature. (3) It slowly reacts with water to form alkaline solution.

Types of Glass (i) Silica glass : For this type of glass the raw material used is 100% pure form of quartz. It is quite expensive. It is used in the manufacture of laboratory apparatus. It has low thermal expansion. Its softening point is very high and it is resistant to a wide variety of chemicals. (ii) Alkali silicate glass : For it the raw materials used are sand and soda. It is also called water glass because it is soluble in water and used only as a solution. It is generally used to make gums and adhesives. (iii) Lead glass : For this type of glass lead oxide is added to ordinary glass. The addition of lead oxide increases the density and also the refractive index. This type of glass is used for the manufacture of ornamental glass ware, decorative articles etc. (iv) Optical glass : This type of glass is used in the manufacture of optical instruments like binoculars, spectacles, lenses, prisons, telescopes, microscopes etc. It is transparent and can be grounded into the required shape. It generally contains phosphorus, and lead silicates with little cerium oxide which absorbs UV radiations. (v) Processed glass : The properties and applications of glass also depend upon the processing of glass. Some types of processed glass and their applications are given here : Processed glass Applications 1. Laminated glass Used for doors and windows of automobiles. (It has high strength). 2. Fibre glass Used for reinforcing purpose (It has enough tensile strength) 3. Foam glass Used for civil construction and insulation purposes (it is light weight). 4. Opaque glass In it non-transparent glass filters the light entering into it. Thus provides an aesthetic look. (vi) Borosilicate glass : It contains silica and Boron oxide and small amount of oxides of sodium and aluminium. It is resistant to a wide variety of chemicals due to this property it is used in the manufacture of laboratory ware.

Fertilizers Fertilizers are chemical compounds which when added to the soil increase their fertility and directly supply the need of essential elements [N, P, K] of primary importance.

Some Important Man Made Materials Classification : Chemical fertilizers are broadly classified into the following three types : (i) Nitrogenous fertilizers : Ammonium sulphate, urea etc. (ii) Phosphatic fertilizers : Super phosphate, ammonium phosphate (iii) Potash fertilizers : Potassium chloride, potassium sulphate. 3. Soaps and detergents Soap : Fatty acid salts of sodium and potassium are known as soaps. These are prepared by the action of fatty acids with sodium hydroxide or potassium hydroxide. Fatty acid + sodium hydroxide ® Soap + glycerol. Detergents are sodium salt of long chain sulphonic acids or alkyl hydrogen sulphate. Advantages of detergents over soaps (i) Detergents can be used for laundering even with hard water as they are soluble even in hard water. (ii) Detergents possess better cleansing properties than soaps. Disadvantages of detergents over soap : Detergents are prepared from hydrocarbons, while soaps are prepared from edible fatty oils. Thus they are non biodegradable. Saponification : It is the process of making of soap by the hydrolysis of fats and oils with alkalis.

C-85

Both soaps and detergents are soluble in water and act as surfactants which reduce the surface tension of water to a great extent. This increases the water - fabric interaction as a consequence of which dirt particles, grease spots etc are washed away effectively. In other words soaps and detergents enhance the cleansing action of water. Portland cement : It was first discovered in England. It is essentially a mixture of lime stone and clay. It was called Portland cement because in presence of water it sets to a hard stone-like mass resembling with the famous Portland rock. The approximate composition of Portland cement is Calcium oxide (CaO) 62% Silica (SiO2) 22% Alumina (Al2O3) 7.5% Magnesia (MgO) 2.5% Ferric oxide (Fe2O3) 2.5% The above compounds are provided by the two raw materials, namely lime stone (which provides CaO) and clay (which provides SiO2, Al2O3 and Fe2O3). In cement, almost entire amount of lime in present in the combined state as calcium silicate (2CaO. SiO2 and 3CaO. SiO2) and calcium aluminates (3CaO. Al2O3 and 4 CaO. Al2O3). (i) Cement containing excess amount of lime cracks during setting; while cement containing less amount of lime is weak in strength. (ii) Cement with excess of silica is slow-setting and that having an excess of alumina is quick-setting. (iii) Cement containing no iron is white but hard to burn.

Cement is manufactured by two processes, viz. wet and dry. A small amount (2–3%) of gypsum is added to slow down the setting of the cement so that it gets sufficiently hardened. Setting of cement is an exothermic process and involves hydration of calcium aluminates and calcium silicates. Lime stone and clay are powdered and mixed Burnt at 1770-1870K in a rotatory kiln

Addition of

Calcium silicates + calcium aluminates

gypsum

Portland Cement

C-86

GENERAL SCIENCE

Important Biomolecules Vitamins Vitamin generic descriptor name

Solublility

Deficiency disease

Overdose disease Hypervitaminosis Drowsiness of music relaxation with large doses

Vitamin A

Fat

Vitamin B1 Vitamin B2

Water Water

Nightblindness and Keratomalacia Beriberi, Wernicke-Korsakoff syndrome Ariboflavinosis

Vitamin B3

Water

Pellagra

Vitamin B5

Water

Vitamin B6 Vitamin B7

Water Water

Vitamin B9 Vitamin B12 Vitamin C Vitamin D

Water Water Water Fat

Vitamin E

Fat

Vitamin K

Fat

Paresthesia Anemia peripheral neuropathy nerve damage (dose > 100 mg/day) Impairment of proprioception Dematitis, enteritis May mask symptoms of vitamine12 associated with Deficiency during pregnancy is birth defects, such as neural deficiency, other effects tube defects Megaloblastic anemia No known toxicity Scurvy Vitamin C megadosage Rickets and Osteomalancia Hypervitamin osis D Deficiency is very rare; mild Increased congestive heart hemolytic anemia in newborn failure seen in one large Increases coagulation in Bleeding diathesis patients taking warfarin.

Deficiency of vitamin A results in (a) lose in apetite (b) skin diseases (c) sterility (d) retarted growth Which one of the following contains cobalt ? (a) Riboflavin (b) Vitamin B12 (c) Vitamin A (d) Vitamin B6 Night-blindness is caused due to the deficiency of (a) Vitamin D (b) Vitamin A (c) Vitamin C (d) Vitamin B Alkaline hydrolysis of esters is known as (a) esterification (b) saponification (c) dehydration (d) alkalination Deficiency of vitamin E causes (a) Beriberi (b) Scurvy (c) Hemolytic anemia (d) None of these Scurvy is caused due to the deficiency of vitamin (a) B1 (b) C (c) K (d) A

Liver damage (doses > 2g/day) and other problems Diarrohea; possibly nausea and heartburn

Which of the following statements, is not correct, about glass? (a) Because of its high viscosity glass exists in solid state (b) There is no definite melting point for glass. (c) The silicate units in glass are arranged in a way that is quite similar to the arrangement found in liquids. (d) Glass is a solid because it has a regular crystalline arrangement. The property of plasticity is shown by clay , when it is (a) mixed with proper proportion of water (b) heated strongly (c) dried at room temperature after kneading (d) glazed One of the properties of glass is its transparency. This property of glass is due to (a) its high viscosity. (b) regular arrangement of silicate units in glass. (c) irregular arrangement of silicate units in glass. (d) its high coefficient of thermal expansion.

Some Important Man Made Materials 10. Washing soaps are potassium and sodium salts of (a) dicarboxylic acids (b) fatty acids (c) mineral acids (d) None of these 11. When glass is heated, it (a) does not melt at a fixed temperature (b) vapourises (c) melts only above 1000°C (d) None of these 12. Glass is a transparent substance obtained by heating silica with oxides or carbonates of metals. Glass is a mixture of (a) phosphates (b) sulphates (c) oxides (d) silicates 13. Potash (Potassium carbonate) is used as a fertilizer. It is also known as (a) azo compound (b) oil of vitriol (c) pearl ash (d) Glauber’s salt 14. Soft soaps are (a) sodium and potassium salt (b) sodium salt of fatty acids (c) potassium salt of fatty acids (d) potassium salt of sulphonic acids 15. Soaps are (a) sodium salts of sulphuric acids containing carbon atoms 10 to 16 (b) sodium salts of fatty acids containing carbon atoms 16 to 18 (c) sodium salts of trihydroxy alcohols (d) none of these 16. Soaps are sodium salts of fatty acids. Which of the following fatty acid does not form soap? (a) Butyric acid (b) Oleic acid (c) Palmitic acid (d) Stearic acid 17. Which one of the following is not contained in portland cement ? (a) Ca3Al2O6 (b) Ca3SiO5 (c) Ca2SiO4 (d) Ca3(PO4)2 18. What is the reason for white cement to be white? (a) It does not contain carbon (b) It does not contain silicon (c) It does not contain iron (d) It does not contain calcium 19. Which one of the following is not present in cement? (a) Clay (b) Alumina (c) Alum (d) Gypsum 20. Which substance is used to retard the setting action of cement? (a) CaO (b) Al2O3 (c) CaSO4, 2H2O (d) Na2O + K2O 21. Which of the statements about glass are correct? 1. Glass is a super-cooled liquid having infinite viscosity. 2. Violet coloured glass is obtained by adding MnO2. 3. Glass is a man-made silicate. 4. Glass is a crystalline substance. Select the correct answer using the codes given below. (a) 1, 2 and 4 (b) 2, 3 and 4 (c) 1, 2 and 3 (d) 1 and 3

C-87

22.

23.

24.

25.

26.

27.

28.

29.

30.

31.

32.

Which one among the following is the main ingredient in cement? (a) Gypsum (b) Limestone (c) Clay (d) Ash Glass is actually (a) a crystalline solid (b) an ionic solid (c) an elastic solid (d) a vitrified liquid The major component used in preparation of different types of glasses is (a) silica (b) sodium borate (c) calcium silicate (d) sodium silicate The reaction that takes place in soap making is called saponification. Basically soap is sodium or potassium salts of (a) long chain monocarboxylic acids (b) glycerol (c) long chain dicarboxylic acids (d) long chain tricarboxylic acids The most important raw materials used in the manufacture of cement are (a) potassium nitrate, charcoal and sulphur (b) limestone, clay and gypsum (c) transition metal oxides, sodium hydroxide or potassium hydroxide (d) limestone, sodium carbonate and silica Given below is an approximate composition of a substance : CaO 60-70% SiO2 20-25% Al2O3 5-10% Fe2O3 2-3% The substance is (a) plaster of Paris (b) cement (c) marble stone (d) quartz The principle of cleaning by soap is (a) surface tension (b) floatation (c) viscosity (d) elasticity By which one among the following mechanisms, soap removes dirt (soil) from cloth? (a) Soap dissolves the soil as such (b) Soap reacts with soil and converts them into soluble silicates (c) Soap takes away the oily part of the soil and thus separates the soil from the cloth (d) The soap molecules bind with the soil, lift the soil and keep it suspended which can then be rinsed away Consider the following statements 1. Soap cannot be used in acidic water. 2 Ionic part of a soap is —COO–· Na+. 3. Soap dissolves in water faster then detergent. Which of the statements given above is/are correct? (a) 1 and 2 (b) 2 and 3 (c) 3 only (d) 1 only What is the composition of nitrolim – a chemical fertilizer ? (a) Nitrogen and limestone (b) Calcium carbide and nitrogen (c) Calcium carbide and carbon (d) None of these Which one of the following correctly defines the state of glass? (a) Crystalline solid (b) Super cooled liquid (c) Condensed gas (d) Liquid crystal

C-88

33.

34.

Flint glass is obtained from which of the following ? (a) Zinc and barium borosilicate (b) Sand, red lead and potassium carbonate (c) Sodium aluminum borosilicate (d) Pure silica and zinc oxide Which of the following statements about vitamin B12 is incorrect ? (a) It has a cobalt atom (b) It occurs in plants (c) It is also present in rain water (d) It is needed for human body in very small amounts

1 2 3 4 5 6

(d) (b) (b) (b) (c) (b)

7 8 9 10 11 12

(d) (a) (c) (b) (a) (d)

13 14 15 16 17 18

35.

36.

37.

ANSWER KEY 19 (c) 20 (c) 21 (d) 22 (b) 23 (c) 24 (a)

GENERAL SCIENCE Washing soap can be prepared by saponification with alkali of which of the following oil (a) Rose oil (b) Paraffin oil (c) Groundnut oil (d) Kerosene oil The aqueous solution of one of the following vitamins is dark in colour (a) B1 (b) B2 (c) B6 (d) B12 Which one of the following is a vitamin? (a) Benzoic acid (b) Ascorbic acid (c) Oxalic acid (d) Formic acid

25 26 27 28 29 30

(d) (b) (b) (a) (d) (a)

31 32 33 34 35 36

(d) (b) (b) (c) (c) (d)

(b)

HINTS AND SOLUTIONS 1.

3. 4.

6. 17.

18. 19.

20. 21. 22.

23. 24.

(d) In childhood, lack of vitamin A retards growth and hence like other vitamins, it is also said to be a growth promoting factor. In mild deficiency it leads to night blindness. Its prolonged deficiency leads to xerophthalmia. (b) Vitamin B12 (Cyanocobalamines) : Cobalamine has by far the most complicated structure of all the vitamins. It has cobalt atom in the centre. It also has – CN groups in its structure. It is a pink coloured crystalline, water soluble vitamin. (b) Night-blindness is caused due to the deficiency of vitamin A. (b) Alkaline hydr olysis of esters is known as saponification. R - COOR '+ NaOH ¾¾ ® R 'OH + RCOONa (b) Scurvy (bleeding of gums) is caused due to deficiency of vitamin ‘C’ (ascorbic acid). (d) A typical composition for portland cement is CaO, SiO2, Al2O3, Fe2O3, CaSO4.2H2O. \ Ca3(PO4)2 is not contained in portland cement. (c) White cement is white since it does not contain iron. (c) Gypsum is added in calculated quantity in order to adjust the rate of setting of cement. Alum is NOT present in cement. (c) CaSO4. 2H2O (gypsum) is added to cement clinker to retard setting action of cement. (d) Glass is an amorphous substance. (b) The composition of cement is CaO (lime) or limestone 62%, silica (SiO2) 22%, alumina (Al2O3) 7.5%, magnesia (MgO) 2.5%, etc. Thus, limestone is the major raw material for cement. (c) Glass is actually an elastic solid. H2O and aqueous NaOH can be differentiated with the help of red litmus. (a) The major component used in the preparation of different types of glasses is silica.

25.

26. 27. 28.

29.

30. 31.

(d) Vegetable oils and animal fats are the main materials that are saponified. These greasy materials, triesters called triglycerides, are mixture derived from diverse long chain tricarboxylic acid. (b) Cement is manufactured with limestone, clay and gypsum. (b) Cement is made up of calcium oxide, silicon dioxide, aluminium tetra oxide and iron tetra oxide. (a) Soaps form surface films, reduce surface tension of solution and help in removing dirt and dust by emulsifying grease. (d) The soap molecules form micelle around the dirt particles prevents them from coming together and form aggregates, which form emulsion in water. The hand rubbing or the agitation cause dispersion of the dirt particles throughout the soapy water. These are washed away with water along with dust particles. In this way dirt are removed from the surface of the cloth. (a) Detergent dissolves in water faster than soap. (d) Calcium cyanamide (CaCN2) mixed with carbon (C) is called nitrolim. CaC2 + N 2 ¾¾ ® CaCN 2 + C 14243 Cal.Carbide

32. 33. 34.

35.

36. 37.

Nitrolim

(b) Glass is an amorphous, hard, brittle, super cooled liquid. (b) Flint glass is obtained from red lead and potatassium carbonate. (c) It is found in liver, egg, milk, meat, and fish. Minute amounts are probably present in all animal cells. Peculiarly, unlike other vitamins, B12 is not found in significant amounts in green plants. (c) Any oils which are good for eating or cooking, can be used in making soap. One of the best is said to be Coconut oil. Groundnut, shea butter, cocoa butter, sun flower and many other vegetable oils are also used. (d) The aqueous solution of vitamin B12 is dark in colour. (b) Vitamin C is chemically ascorbic acid.

General Organic Chemistry

9 1. 2.

Wohler prepared the first organic compound urea while preparing ammonium cyanate. Classification of organic compounds: Organic Compounds

Acyclic or open chain

Alkanes

Cyclic or closed chain or Ring

Alkynes

Alkenes

hom*ocyclic or Carbocyclic

Alicyclic

Hetrocyclic

Aromatic

Benzenoid Non-benzenoid Isomerism. The existence of two or more chemical compounds with the same molecular formula but having different properties owing to different arrangement of atoms within the molecule is termed as isomerism.

ISOMERISM

Structural Isomerism

Stereo Isomerism

Chain

Conformational

Positional

Configurational

Functional Geometrical Metamerism Cis Trans Optical

Enantiomerism Diastereomerism

C-90

4. 5. 6. 7.

GENERAL SCIENCE Hydrocarbons : All those compounds which contain just carbon and hydrogen are called hydrocarbons. Functional group : The atom or group of atoms which determine the properties of a compound is known as functional group. e.g. –OH (alcohol), –CHO (aldehyde), > C = C < (alkene), – C º C – (alkyne), etc. hom*ologous Series : A series of compounds in which the same functional group substitutes hydrogen in a carbon chain is called a hom*ologous series. e.g. CH3Cl and C2H5Cl differ by a –CH2 unit. Nomenclature : Chemists developed a set of rules, for naming organic compounds based on their structures which is known as IUPAC rules. The IUPAC name of an organic compounds consists of three parts. Prefix – word root – Suffix Word root : A word root indicates the nature of basic carbon skeleton. • In case a functional group is present, it is indicated in the name of the compound with either as a prefix or as a suffix. • While adding the suffix to the word root the terminal ‘e’ of carbon chain is removed • If the carbon chain is unsaturated then the final ‘ane’ in the name of the carbon chain is substituted by ‘ene’ or ‘yne’ respectively for double and triple bonds.

Functional group

Prefix/Suffix

Functional group

1. Halogen

Chloro, bromo, Iodo - Cl, - Br, - I

2.Alcohol

- ol

- OH

3. Aldehyde 4. Ketone 5. Carboxylic acid 6. Amine 7. Ester 8. Double bond 9. Triple bond

- al - one - oic acid Amino oate ene yne

- CHO - CO - COOH - NH 2 - COOR

IUPAC Name - Bromopropane

- Ethanol - Butanal - Propanone - Propanoicacid - Amino ethane - Methyl ethanoate - Propene - Butyne

Chemical Properties of Carbon Compounds (i) Combustion : Carbon compound undergo combustion reaction to produce CO2 and H2O with the evolution of heat and light. CH4 + O2 ¾¾ ® CO2 + H2 O + heat and light (ii) Oxidation : alk. KMnO / D

4 ® CH3COOH CH3CH 2OH ¾¾¾¾¾¾

ethanol

ethanoic acid

The substance which are used for oxidation are known as oxidising agent. e.g alkaline KMnO4, acidified K2Cr2O7. (iii) Addition reaction : Unsaturated hydrocarbons (alkenes and alkynes undergo addition reaction in presence of catalysts e.g. R

R C=C

Ni ¾¾¾ ®R H2

H H | | - C- C - R | | H H

(iv) Substitution reaction : Saturated hydrocarbons give substitution reaction e.g. methane in presence of sunlight undergo chlorination.

General Organic Chemistry

10.

11.

12.

13.

14.

Two adjacent members of a hom*ologous series have : (a) a difference of –CH2 in their structure (b) a difference of 14 a.m.u. in molecular mass (c) same general methods of preparation (d) all of the above Alkenes are characterized by (a) C – C bonds (b) C = C bonds (c) C º C bonds (d) cyclic structure Which of the following contains carbonyl group? (a) Ketones (b) Aldehydes (c) Esters (d) All of these The functional group present in CH3COOC2H5 is (a) ketonic (b) aldehydic (c) ester (d) carboxylic Butanone is a four-carbon compound with the functional group (a) carboxylic acid (b) aldehyde (c) ketone (d) alcohol Which of the following is incorrectly matched? (a) Vinegar ® carboxylic acid (b) C2H6 ® alkane (c) Ethanol ® alcohol (d) Methanol ® ketone If a hydrocarbon has any double bond, it is (a) alkyne (b) alkane (c) alkene (d) All the above Alkynes are characterized by – (a) C – C bonds (b) C = C bonds (c) C º C bonds (d) cyclic structure How many different isomers are possible for a hydrocarbon with the molecular formula C4H10? (a) 1 (b) 2 (c) 3 (d) 5 The general formula CnH2nO2 could be for open chain (a) diketones (b) carboxylic acids (c) diols (d) dialdehydes The IUPAC name of CH3CH2COCl is (a) propanoyl chloride (b) ethanoyl chloride (c) acetyl chloride (d) chloroethane General formula of alkenes and alkyl radicals are respectively: (a) CnH2n and CnH2n+1 (b) CnH2n and CnH2n+2 (c) CnH2n–1 and CnH2n (d) CnH2n+1 and CnH2n+2 The IUPAC name of CH3COOC2H5 will be – (a) ethyl acetate (b) ethyl ethanoate (c) methyl propanoate (d) none of these While cooking, if the bottom of the vessel is getting blackened on the outside, it means that (a) the food is not cooked completely. (b) the fuel is not burning completely. (c) the fuel is wet. (d) the fuel is burning completely.

C-91

16.

17.

18.

19.

20.

Which is a general formula of alkenes? (a) CnH2n+2 (b) CnH2n (c) CnH2n–2 (a) None of these Organic compounds will always contain (a) carbon (b) hydrogen (c) nitrogen (d) sulphur Methane, ethane and propane are said to form a hom*ologous series because all are (a) hydrocarbons (b) saturated compounds (c) aliphatic compounds (d) differ from each other by a CH2 group General formula of alkyne is (a) CnH2n+2 (b) CnH2n (c) CnH2n–2 (d) CnHn Which among the following are unsaturated hydrocarbons? (i)

H3C — CH2 — CH 2 — CH3

(ii)

H3C — C º C — CH3

(iii) H3C — CH — CH 3 | CH3 (iv) H3C — C == CH 2 | CH3

21.

22.

23.

(a) (i) and (iii) (b) (ii) and (iii) (c) (ii) and (iv) (d) (iii) and (iv) Pentane has the molecular formula C5H12. It has (a) 5 covalent bonds (b) 12 covalent bonds (c) 16 covalent bonds (d) 17 covalent bonds The heteroatoms present in CH3 — CH2 — O — CH2— CH2 Cl are (i) oxygen (ii) carbon (iii) hydrogen (iv) chlorine (a) (i) and (ii) (b) (ii) and (iii) (c) (iii) and (iv) (d) (i) and (iv) Isomers of a substance must have the same (a) structural formula (b) physical properties (c) chemical properties (d) molecular formula

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GENERAL SCIENCE 1 2 3 4 5 6

(d) (b) (d) (c) (c) (d)

7 8 9 10 11 12

ANSWER KEY (c) 13 (c) 14 (b) 15 (b) 16 (a) 17 (a) 18

(b) (b) (b) (a) (a) (d)

19 20 21 22 23

HINTS AND SOLUTIONS 2.

(b) Alkanes are saturated compounds in which all the four electrons of carbon are covalently bonded with other carbon atoms through single bond (d) All contains carbonyl ( C = O ) compounds.

Ketones ¾ ¾ ®

(c)

O P - C-

O P Aldehydes ¾ ¾ ® - C- H O P Esters ¾ ¾ ® - C- O - H

6. 7.

(c)

10. 18. 20.

O P CH3 - C - 24 O -3 H 14

21.

O P CH 3 - CH 2 - C - CH 3

23.

Butanone or methyl ethyl ketone

(b) CH 3 - CH2 - CH2 - CH3 CH 3 - CH - CH 3 normal butane | CH 3 iso butane (chain isomers)

ester group

(d) Methanol is an alcohol. (c) Alkenes have double bond.

(b) General formula (d) They belong to hom*ologus series as they succesively have a difference of a – CH2 group. (c) Unsaturated hydrocarbons have double or triple bond.

(c)

bonds. (d) Organic compounds having same molecular formula but differ from each other in physical properties or chemical properties or both are known as isomers.

BIOLOGY

1 • •

•

Diversity in Living Organisms

Biodiversity refers number and types of wide variety of plants and animals present on earth. In 1773, Swedish botanist Carolus Linnaeus formulated the system of Binomial Nomenclature in his book ‘Species plantarum’. In binomial system, each name is expressed in two parts i.e., generic name and specific name. Taxonomy is the branch of biology that deals with the framing of laws and principles for classifying the organisms on the basis of their characteristics and evolutionary relationships. The hierarchial system of classification was introduced by Linnaeus. Kingdom ® Phylum or Division ® Class ® Order ® Family ® Genus ® Species Species is defined as “the smallest real basic unit of taxonomy which is reproductively isolated from other group of individuals”. Genus is a group of closely related species that are alike in broad features of their organisation. Family is a group of related genera having several common characters. Generally, Order and other higher taxonomic categories are identified based on the aggregates of characters. A Class is made of one or more related orders.

• •

The term Phylum is used for animals while Division is commonly employed for plants. Kingdom is the highest taxonomic category. All plants are included in Kingdom Plantae. All animals are included in Kingdom Animalia. Herbarium is a collection of pressed and dried plant specimens that are preserved on paper sheets. In Botanical garden, various plants groups are grown for scientific study, conservation, public education, aesthetics, and recreation. The famous botanical gardens are at Kew (England), Indian Botanical Garden, Howrah (India) and National Botanical Research Institute, Lucknow (India). Museum is a building used for the preservation, storage and exhibition of inanimate objects. Zoological park or zoological garden or zoo is a place where wild animals are kept in protected environment under human care. These animals are kept for public exhibition.

History of Classification

Biological classification was first proposed by Aristotle who used simple morphological characters to classify plants and animals. • • Linnaeus initially separated plants and animals in two Kingdoms i.e., Kingdom Plantae and Kingdom Animalia. • • Most accepted System of classification is Five system classification which was given by Whittaker. Basic Features of Whittaker ’s Five Kingdoms Kingdom Cellular Organisation Movement Nutrition Reproduction 1. Monera Unicellular, without By flagella (tubulin- Absorptive or Asexual (All Prokaryotes) nucleus or membranous dynein system) photosynthetic organelle. 2. Protista Unicellular, eukaryote By flagella, cillia, Absorptive, Both sexual and (Protozoans, with nucleus and pseudopodia and photosynthetic & asexual unicellular algae) membranous mucilage holozoic organelles. propulsion Asexual and Heterotrophic Multicellular eukaryote Non-motile 3. Fungi sexual both (saprophytic/ coenocytic, no plastids, (Multicellular parasitic) cells wall of cellulose, decomposers) chitin. Non-motile Autotrophic or Asexual and 4. Plantae Multicellular, higher photosynthetic sexual both (All plants) organisation eukaryotes, cellulosic cell wall, plastids present. 5. Animalia Multicellular, higher Highly motile with Heterotrophic Both sexual and (All animals) organization, all type of motile (holozoic or asexual but in eukaryotes without cell machinery saprozoic) higher forms wall and chlorophyll. only sexual •

•

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GENERAL SCIENCE

Types of Classification • • •

Artificial classification system : It was used by Linneaus. The artificial classification system was based on vegetative characters or on the androecium structure. Natural classification system : It was based on natural affinities among organisms. Both external and internal features were taken into account. It was used by George Bentham and Joseph Dalton Hooker. Phylogenetic classification system : This system of classification is based upon evolutionary relationship and uses morphological characters, origin and evolution of the different organisms. It was proposed by Hutchinson.

Viruses •

The term ‘virus’ has been derived from latin, which means poison or venom or viscous fluid. They are obligate parasites, i.e., can live inside living host only. They have either RNA or DNA. They have character of both living and non-living.

Plant Kingdom TABLE : Divisions of Algae and their Main Characteristics Classes Name

Common

Major Pigments Food

Stored

Cell Wall

Flagellar Number and Position of Insertions

Habitat

Chlorophyceae

Green algae

Chlorophyll a, b

Starch

Cellulose

2-8, equal, apical

Fresh water, brackish and salt water.

Phaeophyceae

Brown algae Chlorophyll a, c, fucoxanthin

Mannitol, laminarin

Cellulose and algin

2, unequal, lateral

Fresh water (rare), brackish water, salt water

Rhodophyceae

Red algae

Floridean starch

Cellulose

Absent

Fresh water (some), brackish water, salt water (most)

Chlorophyll a, d, phycoerythrin

Bryophytes •

•

Bryophytes are also called amphibians of the plant kingdom because these plants can live in soil but are dependent on water for sexual reproduction. They usually occur in damp, humid and shaded localities. Species of Sphagnum, a moss, provide peat that have long been used as fuel, and because of their capacity to hold water as packing material for trans-shipment of living material.

•

Pteridophytes • •

Evolutionarily, they are the first terrestrial plants to possess vascular tissues – xylem and phloem. The main plant body is a sporophyte which is differentiated into true root, stem and leaves. These organs possess welldifferentiated vascular tissues. Examples are Psilotum, Equisetum, Dryopteris, Marsilea, etc.

•

Gymnosperms •

•

Gymnosperms are plants which bear naked seeds i.e., the ovules and the seeds that develop from these ovules after fertilization are not enclosed in fruit wall. Roots in some genera have fungal association in the form of mycorrhiza (Pinus), while in some other (Cycas) small specialised roots called coralloid roots are associated with N2– fixing cyanobacteria.

Angiosperms (Flowering Plants) •

Angiosperms are seed bearing, flowering vascular plants in which seeds are enclosed in fruits.

The flower is the most characteristic structure of the angiosperms. The male sex organ in a flower is the stamen. Each stamen consists of a slender filament with an anther at the tip. The anthers, following meiosis, produce pollen grains. The female sex organ in a flower is the pistil or the carpel. Pistil consists of an ovary enclosing one to many ovules. Within ovules are present highly reduced female gametophytes termed embryo sacs. Each embryo-sac has a seven-celled egg apparatus – one egg cell and two synergids, three antipodal cells and two polar nuclei. The polar nuclei eventually fuse to produce a diploid secondary nucleus. Pollen grain, after dispersal from the anthers, are carried by wind or various other agencies to the stigma of a pistil. This is termed as pollination. The pollen tubes enter the embryo-sac where two male gametes are discharged. One of the male gametes fuses with the egg cell to form a zygote (syngamy). The other male gamete fuses with the diploid secondary nucleus to produce the triploid primary endosperm nucleus (PEN). Because of the involvement of two fusions, this event is termed as double fertilisation, and event unique to angiosperms.

Animal Kingdom •

Animals are the most diverse groups of organisms. Multicellular, heterotrophs characterised by mobility, sensory and nervous systems.

Diversity in Living Organisms

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Phylum-Porifera

Phylum-Chordata

•

Sponges are aquatic, mostly marine, solitary or colonial and sessile. Examples of some sponges are : Sycon (scypha), Spongilla (fresh water sponge) and Euspongia (bath sponge).

Phylum-Coelenterata (Cnidaria) •

•

All are aquatic and are mostly marine (exception-Hydra are found in fresh-water), solitary or colonial, sessile, or freeswimming and radially symmetrical animals. Example-Physalia (Portuguese man of war), Adamsia (Sea anemone), Pennatula (Sea-pen), Gorgonia (Sea-fan) and Meandrina (Brain coral).

Phylum-Ctenophora •

These are diploblastic, radial symmetrical animals with tissue level of organization. Examples–Hormiphora (sea walnut), Pleurobranchia (sea gooseberry), Cestum (venus girdle), Beroe.

•

The fundamental four characters of phylum chordata are presence of notochord, a dorsal hollow nerve cord, paired pharyngeal gill slits and post anal tail either in the embryonic or adult stage. Examples: Herdmania (sea squirt), Branchiostoma.

Subphylum vertebrata is divided into two sections: Section 1 Agnatha (The jawless vertebrates) Class : Cyclostomata • Mouth jawless suctorial and round. • All living members are ectoparasites on some fishes. Ex. Petromyzon (lamprey), Myxine (hag fish). Section 2 Gnathostomata (The jawed vertebrates) Superclass : Pisces (Bear fins)

Phylum-Aschelminthes

Class : Chondrichthyes • They have a cartilagenous skeleton. • Some of them possess electric organs e.g. Torpedo. • Examples: Scoliodon (Dog fish), Trygon (Sting ray). Class : Osteichthyes • They have a bony skeleton. • Examples : Marine – Exocoetus (Flying fish), Hippocampus (Sea horse), Lophius (Angler fish), Fresh water fishes – Labeo (Rohu), Catla (Katla).

•

Superclass : Tetrapoda (Bear Limbs)

•

Phylum-Platyhelminthes •

•

These are mostly endoparasites, bilateral symmetrical, triploblastic and acoelomate animals with organ level of organisation. Examples– Taenia (Tape worm), Fasciola (liver fluke). They may be free-living, aquatic and terrestrial or parasitic in plants and animals. Examples: Ascaris (Round worm), Wuchereria (filarial worm), Ancylostoma (Hook worm), Enterobius (Pin worm).

Phylum-Annelida • •

It is characterised by metameric segmentation forming ring like segments. Example: Neries, Pheretima (Earthworm) and Hirudinaria (Blood sucking leech).

Phylum-Arthropoda • •

They are bilateral symmetry, triploblastic animals, which have organ-system level of organisation. Example: Apis (Honey bee), Bombyx (Silkworm), Laccifer (Lac insect).

Phylum-Mollusca • •

They are aquatic (marine or fresh water), or terrestrial having an organ-system level of organisation. Ex. Pila, Octopus (devil fish), Loligo (sea squid).

Phylum-Echinodermata • •

All existing echinoderms are marine, generally live at sea bottom. Ex. Asterias (star fish), Cucumaria (commonly called as sea cucumber), Antedon (water lily or feather star).

Phylum-Hemichordata • •

They are bilaterally symmetrical, triploblastic, and entrocoelous animals. Ex. Balanoglossus (acorn worm or tongue worm), Saccoglossus.

Class : Amphibia • Adapted for both water and land life. • They are oviparous and development indirect through distinct larval stage called tadpole. Exambles : Bufo (Toad), Rana (Frog), Hyla (Tree frog), Salamandra (Salamander), Ichthyophis (Limbless amphibia). Class: Reptilia • The class name refers to their creeping or crawling mode of locomotion. • They are oviparous ; Development direct. Examples: Crocodilus (Crocodile), Bangarus (Krait) Class: Aves • Birds are bipedal feathered animals. • Endoskeleton is fully ossified (bony) and the long bones are hollow with air cavities (pneumatic). Examples : Corvus (crow), Pavo (Peaco*ck). Class: Mammalia • These are warm blooded (homiothermous) animals having hair and mammary glands. • They are viviparous with few exceptions and development is direct. Example : Oviparous – Tachyglossus = Echidna (spiny Anteater). Viviparous – Pteropus (Flying fox), Camelus (Camel), Macaca (Monkey).

Plant Morphology The Root • It is the underground system, usually below the soil and originates from the radicle. • The primary functions of root are fixation of plant firmly on soil, absorption of water and conduction of mineral nutrients.

C-96

Modified Tap Roots • Fusiform : e.g. radish. • Napiform : e.g. sugar beet. • Conical : e.g. carrot. • Tuberous root : e.g. tapioca. • Nodulated : e.g. Rhizobium. Modified Branched Root • Pneumatophores : Pneumatophores or respiratory roots are short, vertical and negatively geotropic (grow in an upward direction) that occur in certain halophytes, which grow in saline marshes (mangroves). e.g. Rhizophora. Modified for Mechanical Functions • Prop root : e.g. banyan. • Stilt root : e.g. screwpine. • Climbing root : e.g. betel. • Clinging root : e.g. orchid. • Floating root : e.g., Jussiaea. • Contractile root : e.g., onion. • Root thorn : e.g., coconut. Modified Adventitious Root Modified for Physiological Functions • •

Parasitic root : e.g., Cuscuta. Epiphytic root : e.g., Orchids.

•

GENERAL SCIENCE Tuberous root : e.g., sweet potato.

Shoot System • •

It is negatively geotropic and positively phototropic. Stem facilitates conduction of water, mineral and food material. It also produces and supports leaves and reproductive structure.

Modified Stems Underground • Tuber: e.g. potato. • Bulb : e.g. onion. • Rhizome : e.g. ginger. • Corm :e.g. Amorphophallus. Sub-aerial • Runner : e.g. Oxalis. • Offset : e.g. Pistia. • Stolon : e.g. Mentha. • Sucker : e.g. Chrysanthemum. Aerial or Metamorphosed • Thorn : e.g. Duranta. • Stem-tendril : e.g. grape. • Phylloclade : e.g. Opuntia.

Leaf The leaf is a specialised organ of photosynthesis, transpiration and gaseous exchange. Venation Venation is the arrangement of the veins and the veinlets in a leaf. • Reticulate Venation: The veins are arranged in a net like manner, e.g., dicots. • Parallel Venation: Here the veins are arranged parallel to each other, e.g., monocots.

Modifications of Leaves Leaf tendrils e.g. Pisum sativum, Gloriosa

Leaf spines e.g. Opuntia, Barberry

Scale leaves e.g. Asparagus

Phyllode e.g. Australian acacia

Pitcher e.g. Nepenthes

Bladder e.g. Utricularia

Phyllotaxy (Arrangement of Leaves)

Alternate : Only one leaf is borne at each node in alternate manner e.g. Mustard, Sunflower

Opposite : two leaves occur at each node.

Whorled : When more than two leaves occur at a node, e.g. Nerium, Hydrilla.

Inflorescence •

An inflorescence is the mode of arrangement of flowers on peduncle or mother axis. Types of Inflorescence

I. Racemose (Indefinite) (Main axis grows indefinitely bearing flowers in Acropetal order)

II. Cymose (Definite) (Main axis terminates into flower & flowers arise in Basipetal order)

Diversity in Living Organisms Fruit = Ripened Ovary FRUIT ¯ Flesh Simple Fruit (Pericarp fleshy) • Berry : e.g. tomato, guava. • Hesperidium : e.g. lemon, orange • Pepo : Epicarp makes a hard rind, e.g. cucumber, watermelon •

Pome : e.g. apple, pear.

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Dry Simple Fruit (Pericarp dry)

Indehiscent • Achene : e.g., Hogweed (Boerhaavia), Mirabilis jalapa • Caryopsis : e.g., rice, wheat, maize • Cypsela : e.g., sunflower, marigold • Nut : e.g., water chestnut, oak, cashew-nut, litchi

Study of form and structure of organisms is (a) Ecology (b) Taxonomy (c) Anatomy (d) Morphology Group of organisms that closely resemble each other and freely interbreed in nature, constitute a (a) species (b) genus (c) family (d) taxon Herbarium is (a) a garden where medicinal plants are grown (b) garden where herbaceous plants are grown (c) dry garden (d) chemical to kill plants

Dehiscent • Follicle : e.g., Caloptropis. • Legume or Pod : e.g., pea. • Siliqua : e.g. mustard to expose replum with attached seeds (Brassica) • Capsule : e.g., lady finger.

Organisms which display properties of both living and non-living are (a) Viruses

(b) Diatoms

(c) Lichens (d) Bacteria The taxonomic unit ‘Phylum’ in the classification of animals is equivalent to which hierachial level in classification of plants (a) Class (b) Order (c) Division (d) Family Whittaker is famous for (a) Two kingdom classification (b) Four kingdom classification (c) Five kingdom classification (d) Distinguishing in Bacteria & Blue green algae

10.

11.

12.

Schizocarpic Dehiscing into one seeded parts : • Lomentum : e.g., Acacia, Mimosa. • Cremocarp : e.g. Coriander, Fennel. • Regma : e.g. Castor, Geranium • Double samra : e.g. Acer (Maple)

Which bacteria is utilized in gober gas plant? (a) Methanogens (b) Nitrifying bacteria (c) Ammonifying bacteria (d) Denitrifying bacteria Which one of the following statements about viruses is correct? (a) Viruses possess their own metabolic system. (b) Viruses contain either DNA or RNA. (c) Viruses are facultative parasites. (d) Viruses are readily killed by antibiotics. Which one of the following organisms is not an example of eukaryotic cells ? (a) Paramoecium caudatum (b) Escherichia coli (c) Euglena viridis (d) Amoeba proteus Which of the following does not contain chlorophyll? (a) Fungi (b) Algae (c) Bryophyta (d) Pteridophyta Which of the following is called amphibians of plant kingdom? (a) Bryophytes (b) Pteridophytes (c) Gymnosperms (d) Algae The plant group that produces spores and embryo but lacks vascular tissues and seeds is (a) Pteridophyta (b) Rhodophyta (c) Bryophyta (d) Phaeophyta

C-98

13.

14.

15.

16.

17.

18.

19.

20.

21.

22.

23.

24.

25.

26.

27.

28.

A plant having seeds but lacking flowers and fruits belongs to (a) Pteridophytes (b) Mosses (c) Ferns (d) Gymnosperms Agar is commercially obtained from (a) red algae (b) green algae (c) brown algae (d) blue-green algae An alga very rich in protein is (a) Spirogyra (b) Ulothrix (c) Oscillatoria (d) Chlorella The largest flower found is known as (a) Rafflesia (b) Tecoma (c) Musa (d) Cauliflower A common characteristic of all vertebrates is (a) presence of skull (b) division of body into head, neck, trunk and tail (c) presence of two pairs of functional appendages (d) body is covered with an exoskeleton The long bones are hollow and connected by air passages these are characteristics of (a) Mammals (b) Reptiles (c) Birds (d) All land vertebrates In which one of the following sets of animals do all the four give birth to young ones? (a) Platypus, Penguin, Bat, Hippopotamus (b) Shrew, Bat, Cat, Kiwi (c) Kangaroo, Hedgehog, Dolphin, , Loris (d) Lion, Bat, Whale, Ostrich Which of the following animal is not a insect ? (a) Ticks (b) Honey bee (c) Beetle (d) Wasp Which of the following group of animals maintains high and constant body temperature such as mammals ? (a) Reptiles (b) Amphibians (c) Birds (d) Fishes Insects have (a) 2 pairs of legs (b) 3 pairs of legs (c) 4 pairs of legs (d) 1 pair of legs Cymose is (a) thalamus (b) fruit (c) inflorescence (d) ovary Which is not a stem modification ? (a) Rhizome of ginger (b) Corm of Colocasia (c) Pitcher of Nepenthes (d) Tuber of potato A modification of leaf is (a) Tendrils (b) Phylloclade (c) Cladode (d) Corm Artificial system of classification was first used by (a) Linnaeus (b) De Candolle (c) Pliny the Edler (d) Bentham and Hooker Binomial Nomenclature was given by (a) Lamarck (b) Ernst Mayr (c) Carolus Linneaus (d) Cuvier Which of the following is not a pteridophyte? (a) Ginkgo (b) Selaginella (c) Polypodium (d) Azolla

29.

30.

31.

32.

33.

34.

35.

36.

37.

38.

GENERAL SCIENCE The famous botanical garden ‘Kew’ is located in (a) England (b) Lucknow (c) Berlin (d) Australia Which of the following groups of plants play an important role in plant succession on bare rocks/soil? (a) Algae (b) Bryophytes (c) Pteridophytes (d) Gymnosperms Which of the following groups of plants are propagated through underground root? (a) Bryophyllum and Kalanchoe (b) Ginger, Potato, Onion and Zamikand (c) Pistia, Chrysanthemum and Pineapple (d) Sweet potato, Asparagus, Tapioca and Dahlia ICBN stands for (a) International Code of Botanical Nomenclature (b) International Congress of Biological Names (c) Indian Code of Botanical Nomenclature (d) Indian Congress of Biological Names. Leaves of dicotyledonous plants possess ________ venation, while ____________ venation is the characteristic of most monocotyledons. (a) reticulate and parallel respectively (b) parallel and reticulate respectively (c) reticulate and perpendicular respectively (d) obliquely and parallel respectively. In class of Amphibia, respiration occurs through (a) gills (b) lungs (c) skin (d) All of these Which of the following class of algae mostly found in salt water? (a) Phaeophyceae (b) Rhodophyceae (c) Chlorophyceae (d) Both (a) and (b) Which of the following are correctly matched with respect to their taxonomic classification? (a) Centipede, Millipede, Spider, Scorpion-Insecta (b) House fly, Butterfly, Tse tse fly, Silverfish-Insecta (c) Spiny Anteater, Sea urchin, Sea cucumber-Echinodermata (d) Flying fish, Cuttlefish, Silverfish-Pisces During the post-fertilisation period the ovules develop into __________ and the ovary matures into a _________. (a) A – seeds; B – fruit (b) A – fruit; B – seeds (c) A – flower; B – seed (d) A – seeds; B – flower One of the following is a very unique feature of the mammalian body (a) Presence of diaphragm (b) Four chambered heart (c) Rib cage (d) Homeothermy

Diversity in Living Organisms 39. Which one of the following groups of animals is correctly matched with its one characteristic feature without even a single exception ? (a) Reptilia : possess 3 - chambered heart with one incompletely divided ventricle (b) Chordata : possess a mouth provided with an upper and lower jaw (c) Chondrichthyes : possess cartilagious endoskeleton (d) Mammalia : give birth to young one.

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40.

Which of the following plants is growing in swampy areas, where many roots come out of the ground and grow vertically upwards? (a) Potato (b) Opuntia (c) Rhizophora (d) Grass

ANSWER KEY 1

(d)

(a)

(c)

(d)

(a)

(c)

(b)

(a)

(c)

(d)

(c)

(a)

(c)

(d)

(c)

(d)

(a)

(c)

(a)

(c)

(b)

(a)

(c)

(a)

(b)

(c)

(a)

(b)

(c)

(a)

(c)

(a)

(b)

(c)

HINTS AND SOLUTIONS 3. 7.

9. 12.

13.

14.

15. 16.

17.

(c) Herbarium is dry garden. (a) Methanobacillus (methanogen) occurs in marshes and also in dung. It produces CH4 gas under anaerobic condition and is utilized in gobar gas plant. (b) Viruses have either DNA or RNA as the genetic material. Viruses having RNA as the genetic material are known as Retroviruses. (b) E. coli is a prokaryotic celled gram negative bacterium. (c) Bryophytes are the plants which produces spores and embryo but no vascular tissues are present, although primitive type of conducting tissues are present in the form of hadrome and leptome. (d) Gymnosperms are vascular land plants having naked ovules i.e., ovules are not enclosed in a ovary hence, flower is absent. Ovules after fertilization produces naked seeds. Pteridophytes (ferns) and mosses do not produce seeds. (a) The Agar is obtained from several members of red algae such as Gracilaria, Gelidium, Chondrus etc. Agar gels are extensively used for growing microorganisms. (d) Chlorella can be grown to provide human food rich in proteins, lipids, carbohydrates, vitamins and minerals. (a) Rafflesia or Corpse flower is a total root parasite. It obtains the total nourishment from the roots of the host plant. (a) Vertebrates are also known as Craniata due to presence of skull in all its members.

18.

19.

21.

22.

26. 28. 32.

39.

(c) Hollow bones are characteristic adaptive features of birds. It reduces their body weight and is a major flight adaptation. (c) Penguin, kiwi & ostrich all belong to class Aves of chordata (i.e. birds) and they do not give birth to their young ones, they are oviparous while kangaroo, hedgehog, dolphin, loris all belong to class mammalia and are viviparous. (c) Animals which maintain high and constant body temperature are called warm blooded animals. They are also called homeothermic animals. Birds are the first vertebrate to have warm blood. They are homeothermous. (b) Class insecta has 3 pairs of legs located on the thoracic segments. It is the characteristic feature of class Insecta. (c) Pliny the Edler introduced first artificial system of classification in his book Historia Naturalis. (a) Ginkgo is a gymnosperm. (a) ICBN (International Code of Botanical Nomenclature) - It is one of the code of nomenclature which is independent of zoological and bacteriological nomenclature. The code applies equally to names of taxonomic groups treated as plants whether or not these groups were originally so treated. (c) Chondrichthyes are the cartilaginous fish with a flexible skeleton made of cartilage rather than bone.

C-100

GENERAL SCIENCE

Cells and Tissues

Cell is a basic structural and functional unit of life. • Robert Hooke in 1665 coined the word ‘cell’. • Anton von Leeuwenhoek first saw and described a live cell. • Robert Brown later had discovered the nucleus. • Cell theory was proposed by Schleiden and Schwann in 1855 to explain the concept of the cellular nature of living organism.

•

The golgi apparatus principally performs the function of packaging materials to be delivered either to the intra-cellular targets or secreted outside the cell.

Lysosomes •

Lysosomes are popularly called “suicide bags”.

Prokaryotic Cells

Vacuoles

• •

•

Prokaryotic cells are morphologically most primitive. Prokaryotic cells are devoid of membrane bound organelles like plastids, mitochondria and advanced (9+2) flagella. Prokaryotic cells are represented by bacteria, cyanobacteria (blue green algae) mycoplasma and PPLO (pleuropneumonia like organisms).

In plant cells, the vacuoles can occupy up to 90 percent of the volume of the cell. The vacuole is bound by a single membrane called tonoplast. They are responsible for maintenance of turgour pressure.

Mitochondria

Eukaryotic Cells

•

Plastids

A eukaryotic cell consists of the following components:

Cell Wall • The cell wall is a non-living, semi-rigid, external protective covering of the cell. • Cell wall is entirely lacking in animals. • It is made up of cellulose secreted by the cell itself. Cell Mebrane • The cell membrane is a living, thin, elastic and semipermeable membranous covering of plant and animal cells. Fluid mosaic model of plasma membrane • S.J.Singer and G. Nicolson in 1972 proposed the most accepted model of membrane structure. The plasma membrane is a lipid-bilayer with proteins embedded in it. • Lipids are amphipathic, i.e., they are structurally asymmetric with polar hydrophilic and non-polar hydrophobic group. • One of the most important function of plasma membrane is the transport of the molecules across it.

Endoplasmic Reticulum (ER) There are two types of endoplasmic reticulum i.e., • Smooth or agranular ER – They do not have attached ribosomes on their surface. • Rough or granular ER – They bear ribosomes on their surface, for protein synthesis.

Golgi Apparatus • Golgi apparatus or Golgi complex is a stack of flattened, membrane bounded, parallely arranged organelles that occur in the association of endoplasmic reticulum in the cytoplasmic matrix.

•

Mitochondria are also called as powerhouse of cells.

Plastids are found in plants and few protists Euglena.

Ribosomes •

Ribosomes are smallest cell organelles. They are protein synthesising factories. There are two types of ribosomes viz., – Prokaryotic or 70S ribosomes – Eukaryotic or 80S ribosomes

Nucleus •

Nucleus is centrally located, spherical and largest component of the all eukaryotic cell. It contains the genetic material of the cell.

Structure of Nucleus • A typical nucleus consists of four structures: (i) nuclear membrane, (ii) nucleoplasm (iii) chromatin and (iv) the nucleolus. Satellite

Short arm

Secondary constriction

Short arm Centromere

Centromere Long arm Telocentric Acrocentric

Submetacentric

Metacentric

Fig. : Types of chromosomes based on the position of centromere

Cells and Tissues Nucleolus •

It is present inside the nucleus.

•

It is the site of active ribosomal RNA synthesis.

Cell Cycle •

Cell cycle consists of two basic phases.There is a long non-dividing growing I-phase (Inter-phase) and a shortdividing M-phase.

Phases of Cell Cycle Interphase :

C-101

Diplotene : The participating chromatids of the paired hom*ologous chromosomes physically joined at one or more discrete points having X-shaped structure called chiasmata. Diakinesis : During diakinesis, the terminalisation of chiasmata take place. Metaphase I : Spindle fibres attach themselves to chromosomes and chromosomes align at the equator. Anaphase I : hom*ologous chromosome with its two chromatids moves towards the opposite poles of the cell and separate from each other.

•

It has following three sub-phases:

•

G1 phase: It (G stands for gap) includes the synthesis of substrate and enzyme necessary for DNA synthesis.

Meiosis II

•

S phase: During this phase the amount of DNA per cell doubles.

Prophase II : The nuclear membrane and the nucleolus disappear. The chromosomes condense further.

•

G2 phase: Proteins are synthesized in preparation for mitosis while cell growth continues.

Metaphase II : The chromosomes get arranged on the equator of the spindle.

•

G0 phase : Cells that do not divide further exit G1 phase to enter an inactive stage known as G0.

Anaphase II : The daughter chromosomes move towards the opposite poles.

M Phase (Mitosis Phase) It is also called as equational division as the number of chromosomes in the parent and progeny cells is the same. The 4 Stages of M phase are : (usually divided into several stages or phases) Prophase : Initiation of assembly of spindle formation begins. Metaphase : Chromosomes align at the equatorial plate of cells. Anaphase : The two daughter chromatids, now free of each other, move towards their respective poles. Telophase : The nucleolus condense and reappear. The spindle fibres disperse. The nuclear envelope is assembled around the chromatin mass endoplasmic reticulum reform again. Cytokinesis : Karyokinesis (division of nucleus into two) is followed by cytokinesis i.e., division of cytoplasm into two daughter cells.

Meiosis It occurs in reproductive cells and has two parts:

Meiosis I

Telophase I : The nuclear membrane and nucleolus reappear.

Telophase II : Cytoplasm divides and 4 haploid daughter cells arise.

Tissues A group of structurally similar or dissimilar cells that perform a common function and have a common origin is called a tissue.

Simple Permanent Plant Tissue These tissues are of 3 types: Parenchyma : The cell wall is thin and made up of cellulose. It helps in storage of food, conduction of substances, provides turgidity to softer parts of plants. Collenchyma : It provides mechanical support to the organs and resists bending in wind. Sclerenchyma : These are dead, mechanical and act as skeleton in plants. It is hardest plant tissue, madeup of highly thick walled cells with no nucleus and no cytoplasm. This uniform thicknening is made up of mainly lignin and cellulose or both. Conducting tissue in plants •

Xylem cells conduct water and minerals from roots to shoots.

Leptotene : The chromosomes become gradually visible under the light microscope.

•

Phloem cells transport food or photosynthates from leaves to all parts of plants.

Zygotene : The pairing of hom*ologous chromosomes takes place.

Animal Tissues

Pachytene : Crossing over is the exchange of genetic material between two hom*ologous chromosomes.

The structure of the cells vary according to their function. Therefore, the tissues are different and are broadly classified into four types:

Prophase I : It is the longest stage and includes 5 stges : –

C-102

GENERAL SCIENCE

Epithelial Tissue

squamous (alveoli, capillaries) cuboidal (tubules and ducts) simple ciliated columnar microvilli

simple

Covering

keratinised squamous (skin) unkeratinised squamous (lining mouth, vagin*)

stratified Classification

transitional (urinary bladder) endocrine unicellular (goblet cells) simple multicellular compound (tubular and alveolar)

Glandular exocrine

Connective Tissue Connective tissue

loose : general connective tissue of body reticular : supports lymphoid tissue dense fibrous : strong, forms tendons, ligaments, etc. elastic : possesses extension and recoil properties, e.g. lungs composition

Adipose tissue functions as

adipocytes (fat cells) loose connective tissue matrix protective packing material, e.g. kidneys heat insulator (skin) energy store

matrix chondrocytes (cartilage cells) fibres hyaline : covers articular surfaces, forms framework, e.g. larynx elastic, ear.

composition Cartilage type

fibrocartilage, e.g. intervertebral discs Haemopoietic tissue

red bone marrow : produces blood cells circulating blood : blood cells suspended in blood plasma

Blood

Plasma

Formed Elements of blood

Leucocytes (WBC)

Erythrocytes (RBC)

Granulocytes

Eosinophils

Basophils

Blood Platelets

Agranulocytes

Neutrophils

Monocytes

Lymphocytes

Muscle Tissue (i) Skeletal muscle Cells are long, cylindrical fibres Fibres are cross-striated, due to arrangement of contractile proteins

Morphology

Fibres are multinucleated (syncitium) Thick filaments (myosin; M line in centre) Tubular systems actin Thin filaments (Z line in centre) troponin tropomyosin Sarcomere – distance between two Z lines

Cells and Tissues (ii) Cardiac muscle Location : Cardiac wall Function : Pumps blood Contraction : Comparable to skeletal muscle, but slower Regneration : None (iii) Smooth muscle Location : Walls of hollow organs, eye, skin, etc. Function : Contraction of hollow muscular organs

Morphology –

Non-striated fibres shorter with single nucleus Contractile proteins = actin and myosin Visceral smooth muscle

contains pacemaker occurs in hollow organs

Multi-unit smooth muscle

no pacemakers occurs in iris, blood vessels, etc.

Fibre types

10.

C-103

Difference between the prokaryotic and eukaryotic cells is in having (a) cell wall (b) nuclear membrane (c) ribosome (d) None of these The function of nucleolus is the synthesis of (a) DNA (b) m-RNA (c) r-RNA (d) t-RNA Which one of the following has its own DNA? (a) Mitochondria (b) Dictyosome (c) Lysosome (d) Peroxisome Regarding the sequence of cell cycle, which one is correct (a) G1, G2, S and M (b) S, G1, G2 and M (c) G1, S, G2 and M (d) G2, S, G1 and M The exchange of genetic material between chromatids of paired hom*ologous chromosomes during first meiotic division is called (a) transformation (b) chiasmata (c) crossing over (d) synapsis Chloroplast containing parenchyma is called (a) chlorenchyma (b) collenchyma (c) aerenchyma (d) amylanchyma Chromosomes contain hereditary units called (a) genes (b) ribosomes (c) DNA (d) RNA Which cell organelle is known as the control centre of the cell ? (a) Nucleus (b) Chloroplast (c) Mitochondria (d) Endoplasmic reticulum Who observed and coined the word 'cell' for the first time? (a) Robert Cook (b) Robert Brown (c) Robert Hooke (d) Leeuwenhoek What part of the cell serves as the intracellular highway? (a) Endoplasmic reticulum (b) Golgi apparatus (c) Cell membrane (d) Mitochondria

11.

12.

13.

14.

15.

16.

17.

18.

Which of the following would you not find in a bacterial cell ? (a) DNA (b) Cell membrane (c) Golgi apparatus (d) Ribosomes Which of the following could be found in both the nucleus and the cytoplasm? (a) Nucleolus (b) Ribosomes (c) RNA (d) Both RNA & ribosomes Which one of the following structures is an organelle within an organelle? (a) Ribosome (b) Peroxisome (c) ER (d) Mesosome The process of mitosis is divided into 4 phases. Identify the correct order in which these phases appear in mitosis (a) Anaphase, metaphase, telophase and prophase (b) Telophase, anaphase, metaphase and prophase (c) Metaphase, prophase, anaphase and telophase (d) Prophase, metaphase, anaphase and telophase Which of the following cells is found in the cartilagineous tissue of the body? (a) Mast cells (b) Basophils (c) Osteocytes (d) Chondrocytes Survival of plants in terrestrial environment has been made possible by the presence of (a) intercalary meristem (b) conducting tissue (c) apical meristem (d) parenchymatous tissue The tissues that helps in the movement of our body is (a) muscular tissue (b) skeletal tissue (c) nervous tissue (d) All of these The connective tissue that connects muscle to bone is called (a) ligament (b) tendon (c) cartilage (d) areolar

C-104

19.

20.

21.

22.

23.

24.

Cartilage and bone are types of (a) muscular tissue (b) connective tissue (c) skeletal tissue (d) epithelial tissue Intercalated disc is present in (a) striated muscle (b) smooth muscle (c) cardiac muscle (d) Both (b) and (c) Cells which take part in secondary growth are named as (a) phloem (b) xylem (c) cambium (d) medullary ray Which of the following is responsible for mechanical support and enzyme transport ? (a) Dictyosome (b) Cell membrane (c) ER (d) Mitochondria Cell wall in higher plants is made up of (a) Cellulose + lignin (b) Cellulose + pectin (c) Cellulose + suberin (d) Cellulose + lipid ATP molecule is a (a) Nucleosome (b) Nucleoside (c) Nucleotide (d) Deoxyribose sugar

(b)

(c)

25.

26.

27.

28.

29.

30.

GENERAL SCIENCE Which one is not a carbohydrate? (a) Chitin (b) Methionine (c) Glycogen (d) Starch Branches of botany dealing with the internal organization of plants known as (a) Physiology (b) Ecology (c) Anatomy (d) Cytology Xylem functions as a conducting tissue for water and minerals from _________to the ______and__________. (a) roots, stems, leaves (b) stems, roots, leaves (c) leaves, stems, roots (d) leaves, stems, leaves Most diverse macromolecules, found in the cell both physically and chemically are (a) proteins (b) carbohydrates (c) nucleic acids (d) lipids. Lipids are insoluble in water because lipid molecules are (a) hydrophilic (b) hydrophobic (c) neutral (d) zwitter ions Which one is the most abundant protein in the animal world? (a) Trypsin (b) Haemoglobin (c) Collagen (d) Insulin

ANSWER KEY 17 (c) (a)

(d)

(b)

(c)

(a)

(c)

(b)

(a)

(c)

(d)

(c)

(a)

(c)

(a)

(c)

(b)

(a)

(d)

(c)

(a)

(d)

(b)

(a)

(b)

(c)

HINTS AND SOLUTIONS 1.

6. 13.

(b) The prokaryotic cells do not have nuclear membrane while eukaryotic cell have well organised nuclear membrane. (a) Mitochondria has its own DNA. It is as structure within cytoplasm of eukaryotic cells that carries out aerobic respiration. It is the site of Kreb’s cycle and ETS. Therefore, it is also called as cell’s energy production site. (c) The points of attachment between hom*ologous chromosomes after their separation in diplotene are called chiasmata. The process of pairing of hom*ologous chromosomes is called synapsis, the phenomenon by which DNA isolated from one type of cell, when introduced into another type, is able to bestow some of the properties of the former to the latter is known as transformation. (a) Chloroplast containing parenchyma (chlorenchyma) are mostly present in leaf. (a) Ribosomes are small protein complexes made of r-RNA and proteins. Ribosomes are also seen in the organelles like mitochondria and chloroplasts.

27.

28.

29.

30.

(a) Xylem is a complex permanent tissue mainly responsible for conduction of water and minerals from the roots to the top of plants (unidirectional). (a) Proteins are polymers of amino acids. There are only 20 amino acids which can be arranged in different orders in a polypeptide chain to form a wide array of proteins. (b) Water attracting molecules are called hydrophilic. Water repelling molecules are called hydrophobic. Amino acids carry simultaneously positive and negative charges. Such molecules are called zwitter ions. Lipids are compounds of C, H, O but the ratio of H and O is more than 2 : 1 that is the ratio of oxygen is lesser than carbohydrates. Lipids are insoluble in water but soluble in non-polar solvents such as benzene, chloroform etc. Commonest lipid found in a cell is phospholipid. It contains a hydrophilic (polar) head and a hydrophobic (non- polar tail). (c) Collagen is the most abundant protein of animal world. Rubisco (ribulose biphosphte carboxylase - oxygenase) is not only the most abundant protein in plants but also the whole biosphere.

Plant Physiology

Means of Transport •

concentration. Diffusion rates are affected by concentration gradient, membrane permeability, temperature and pressure.

Hypotonic solution : When concentration of outer solution is lower than concentration of cell sap.

Diffusion is a random movement of individual molecules from a region of higher concentration to a region of lower

•

Hypertonic solution : When concentration of outer solution is higher than concentration of cell sap.

Imbibition : It is a type of diffusion by which movement of water

The substance that have a hydrophilic moiety, find it difficult

takes place along a diffusion gradient. Factors influencing the

to pass through membrane. The movement of such

rate of imbibition are nature of imbibant, surface area of imbibant,

molecules are facilitate, for which proteins provide site at

temperature, concentration of solutes, pH of imbibant

which such molecule cross membrane. This is called as

•

facilitated diffusion.

Cohesion Theory :

Active transport uses energy to pump molecules against a

•

Proposed by Henry Dixon 1914.

•

Evaporation of water from the leaf to atmosphere decreases

concentration gradient.

Plants-Water Relations Water Potential : The potential energy of water is referred to as water potential. It is measured in term of pressure. Y w = Ys + Y p

the water potential of the epidermal cells.

Transpiration •

Loss of water in the form of water vapour from plant through the small pores (stomata) present on leaves is called transpiration.

Osmosis : It is the diffusion of water through a semi-permeable membrane. It depends on two factors (i)

concentration of dissolved solutes in a solution

(ii)

pressure difference.

The Pressure Flow or Mass Flow Hypothesis •

It was put forward by Munch (1930). According to this hypothesis, organic substances move from the region of

Plasmolysis : If a turgid cell is placed in a solution that has more

high osmotic pressure to the region of low osmotic pressure

solutes, it exerts a higher osmotic pressure and water will move

in a mass flow due to the development of a gradient of

out.

turgor pressure.

•

Isotonic solution : When concentration of outer solution

•

Hydroponics : The system of growing plants in soilless

(in which cell is placed) is equal to concentration of cell

culture (also called solution culture or tank farming) is known

sap.

as hydroponics.

C-106

GENERAL SCIENCE

Role of Essential Elements (Macro and Micro) and their Deficiency Symptoms S. NAME OF No. ELEMENT 1. Nitrogen

2. Phosphorous

3. Potassium

4. Calcium

5. Magnesium

6. Boron

7. Chlorine

IN WHICH FORM FUNCTIONS DEFICIENCY SYMPTOMS THEYARE ABSORBED Chlorosis (yellowing of older leaves) NO2–, NO3– or NH4+ Major constituent of proteins, nucleic acids, vitamins and minerals. Constituent of cell Delay in seed germination (H2PO42–, membrane, nucleic acids, purple or red spots on leaves or HPO42–) nucleotides and some proteins. K+ Involved in protein Chlorosis in intervernial synthesis, closing & area, loss of apical opening of stomata. dominance Maintenance of turgidity of cells. Ca++ Used in synthesis Stunted growth, necrosis of of cell wall (middle meristematic regions. lamella) Mg++ Activate enzymes Chlorosis between leaf veins, in respiration, photo necrosis on older leaves. -synthesis, DNA and RNA synthesis. Constituents of the porphyrin ring of chlorophyll structure. Death of root and shoot tips, BO33– and B4O72– Necessary for uptake and utilization of Ca2+, abscission of flowers. pollen generation. – Cl Determine solute Stunted root growth, reduced fruiting. concentration (with Na+ and K+) and anioncation balance in cells, essential for photolysis of water.

Metabolism of Nitrogen : Fixation of N2 • Ammonia is rapidly converted first to nitrites (by Nitrobacter) by the process nitrification. 2NH3 + 3O2 ® 2NO2– + 2H+ + 2H2O 2NO2– + O2 ® 2NO3– • Nitrate is then either available to the plant, or converted to nitrogen gas in the process of denitrification (by Pseudomonas). • Fixation is done by both free living e.g. Azotobacters, Clostridium, Cyanobacteria like Nostoc, Anabaena and symbiotic bacteria Rhizobium. • Nodules act as the site for N 2 fixation. It contains leghaemoglobin (a pink pigment) and enzyme nitrogenase (Mo-Fe protein). • During this process, the N 2 atmospheric(dinitrogen) is reduced by the addition of hydrogen atoms to ammonia. N2 + 8e– + 8H+ + 16 ATP ® 2NH3 + H2 + 16ADP + 16Pi Photosynthesis • It is actually oxidation reduction process in which water is oxidised and CO2 is reduced to carbohydrates. • The reduction of CO2 to carbohydrates needs assimilatory powers, i.e., ATP and NADPH2.

•

Photosynthesis occurs particularly in specialised cells called mesophyll cell. These cells contain chloroplast, which is the actual sites for photosynthesis. • The two forms of chlorophyll ‘a’ are chl a 683 (P680) and chl a 703 (P700) with peak absorption at 683 and 703 respectively are anchored in thylakoids membranes. They are the reaction centres. Electron Transport : It was first formulated by Hill (1939). It is a series of electron carrier over which electrons pass in a downhill journey releasing energy at every step that is used in generating an electrochemical proton gradient which helps in synthesising ATP. Photorespiration : Light stimulated oxidation of photosynthetic intermediates to CO2 is known as photorespiration. The course of photorespiration is related to chloroplasts, peroxisomes and mitochondria. This is a wasteful process & occurs in C3 plants. Respiration : The phenomenon of breaking of the C–C bond of complex organic molecules through oxidation and releasing of energy for cellular use, is called respiration. C6H12O6 + 6O2 ® 6CO2 + 6 H2O + energy ( 2870 kg) Glycolysis : The scheme of glycolysis was given by Gustav Embden, Otto Meyerhof and J. Parnas, hence it is referred to as the EMP pathway. It occurs in the cytoplasm of the cell.

Plant Physiology ATP

C-107

Growth

Glucose (6C)

•

ADP Glucose-6-phosphate (6C)

Fructose-6-phosphate (6C) ATP ADP Fructose1, 6- bisphosphate (6C) Triose phosphate (Dihydroxy acetone phosphate) (3C)

Triose phosphate (glyceraldehyde-3-phosphate) (3C) NAD+ NADH 2 ´ Triose bisphosphate (1, 3-bisphosphoglyceric acid) (3C) ADP ATP 2 ´ Triose phosphate (3-phosphoglyceric acid) (3C)

2 ´ 2-phosphoglycerate

It can be broadly defined as “permanent and irreversible increase in size of living structure which is accompanied by an increase in dry weight and the amount of protoplasm”. • Growth rate can show two types of increase i.e., arithmatic increase and geometrical growth. Arithmatic Increase Lt = L0 + rt where, Lt = length at time ‘t’; L0 = length at time ‘zero’; r = growth rate /elongation per unit time; t = time of growth. Geometrical Growth W1 = W0 ert where, W1 = Final size (weight, height, number etc.); W0 = Initial size at the beginning of the period; e = base of natural logarithms; r = growth rate; t = time of growth. Development is growth accompanied by differentiation. Differentiation: The cells are derived from root apical and shoot apical meristems and cambium differentiate and mature to perform specific functions. Dedifferentiation : The living differentiated cells loose their capacity of division. These cells may regain their capacity to divide under certain conditions. Redifferentiation : The products of dedifferentiated cells which lose the capability to divide but mature to perform specific functions are called redifferentiated cells.

Plant Growth Regulators

H2O 2 ´ phosphoenolpyruvate ADP ATP 2 ´ Pyruvic acid (3C)

Fig. Steps of Glycolysis

Fermentation : When O2 is limiting, NADH and pyruvic acid begin to accumulate. Under this condition, plants carry out fermentation (anaerobic respiration), leading to the formation of CO2 and either ethanol or lactic acid. Citric acid cycle or tricarboxylic acid cycle or kreb’s cycle : It occurs in mitochondrial matrix. Pyruvate (3C)

Acetyl coenyme A (2C)

Oxaloacetic acid (4C) +

NADH+H

Citric acid (6C) CO2 + NAD

NAD

Malic acid (4C)

CITRIC ACID CYCLE

NADH+H a-ketoglutaric acid (5C)

CO 2 + NAD FADH 2

NADH+H

FAD

Succinic acid (4C)

ADP ATP

Fig. The Citric acid cycle

Auxins • Auxins induce elongation in shoot cells and inhibition of elongation of root cells. • Synthetic auxins are indole butyric acid (IBA), indole propionic acid (IPA), 2,4- dichlorophenoxy acetic acid(2,4 D); naphthalene acetic acid (NAA). • At the removal of apical bud the lateral buds grow vigorously. It shows that apical bud suppresses the growth of lateral bud (axillary bud) just below it. This is known as apical dominance. • Initiating and promoting cell division in certain tissues such as cambium. • Promotes elongation of stem and coleoptile. • Auxin generally inhibits flowering but in case of pineapple spray of auxins induces early flowering. Gibberellins • GA3 was one of the first gibberellin to be discovered and remains the most intensively studied form. All GAs are acidic in nature. They occur in various plant organs such as roots, stems, leaves, buds, immature seeds and callus tissues of higher plants. • The most typical and striking effect of gibberellin is on the elongation of stem. The internodes increase in length. • Gibberellin causes the plants to bolt and flower. • Gibberellins have been found be more effective than auxins in causing parthenocarpic development of fruits e.g., tomatos, apples and pears. Cytokinins • Miller in 1954 isolated the first crystals of a ‘cell division inducing substance’ from the autoclaved herring sperm DNA. Since this substance has specific effect on cytokinesis it is called as kinetin (a modified form of adenine).

C-108

GENERAL SCIENCE

Permanent cell division occurs only in presence of cytokinins. It also plays important role in causing expansion of cells. • Cytokinins not only breaks dormancy but also promotes the germination of seeds. Abscisic Acid • Carns and Addicott (1963) isolated two substances Abscisin I and Abscisin II from the cotton balls, that were responsible for accelerated abscission of leaves. • ABA inhibits seed germination and growth of excised embryos. • ABA stimulates stomatal closure by inhibiting the K+ uptake by guard cell. • ABA increases tolerance of plants to various kinds of stresses. Ethylene • Ethylene is only gaseous hormone (CH2 = CH2) that is synthesized in large amounts by tissues undergoing senescence and ripening fruits. • Ethylene inhibits elongation of stem, causes swelling of nodes and nullifies geotropism. • It is highly effective in inducing fruit ripening when it is produced in large amount which coincides with respiratory climactric i.e., a brief rise to a very high level of respiration. This rise indicates the beginning of senescence and death. Photoperiodism • The term photoperiodism is used by Garner and Allard, 1920 for the ability of plant to detect and respond the relative length of day and night to which the plant is exposed. The site of perception of light/dark duration are leaves. • Most of the plants are short day plants that include Cosmos, Dahlia, Chrysanthemum, rice, etc. The long day plants are wheat, barley, sugar beat, larkspur, etc. Cucumber, sunflower, tobacco, tomato etc. are some examples of intermediate day plants.

Vernalisation • In some plants early flowering is induced by pretreatment of seeds with a certain low temperature. Seed Dormancy • Dormancy may be defined as the inactive state of the seed in which the growth of the embryo is temporarily suspended for a specific length of time. Flower • Flowers are highly modified shoots, bearing nodes and modified floral leaves, which are meant essentially for sexual reproduction in plant. • A typical mature embryo sac of angiosperm is 7-celled, 8 nucleate structure i.e., 3 antipodal cells, 3-egg apparatus cells (consists of 2 synergids and 1 egg cell) and one central cell (2 polar nuclei). Double Fertilization • Fusion of male and female gametes is called fertilization. • One of these male gametes fuses with egg to form diploid zygote (2n) while the other fuses with two polar nuclei of the central cell to produce triploid primary endosperm nucleus (PEN) (3n). Since, the latter involves fusion of three haploid nucleus, therefore it is called triple fusion. • In some angiosperms, two types of fusion occur in the same embryo sac “syngamy” leading to the formation of zygote & “triple fusion” forming primary endosperm cell, this phenomenon is called “double-fertilization”. • Endosperm is the nutritive tissue which provides nourishment to the embryo in seed plant. • Seed is a fertilized ovule. After fertilization ovary begins to grow and gradually matures into fruit. • Polyembryony - Given by Leeuwenhoek (1917) in Orange More than one embryo in a seed.

•

The physical process involved in the release of molecular oxygen from leaves is (a) diffusion (b) transpiration (c) osmosis (d) capillarity If a cell swells, after being placed in solution, the solution is (a) neutral (b) hypotonic (c) hypertonic (d) isotonic Chlorophyll is present (a) in the grana of chloroplasts (b) on the surface of chloroplasts (c) dispersed through out the chloroplasts (d) in the stroma of chloroplasts Translocation of carbohydrate nutrients usually occurs in the form of (a) glucose (b) maltose (c) starch (d) sucrose

Hydroponics is a technique in which plants are grown in (a) green house (b) water saturated sand (c) balanced nutrient solution (d) purified distilled water Respiration in plants (a) occurs only during day (b) results in the formation of vitamins (c) is characteristic of all living cells (d) often requires CO2 Chief function of leaves are (a) transpiration and photosynthesis (b) respiration and photosynthesis (c) respiration and digestion (d) respiration and transpiration

Plant Physiology 8. Which element is required in comparatively least quantity for the growth of plant? (a) Zn (b) N (c) P (d) Ca 9. End product of glycolysis is (a) acetyl CoA (b) pyruvic acid (c) glucose-1-phosphate (d) fructose-1-phosphate 10. The ultimate gain of light reaction is (a) ATP and NADPH2 (b) NADPH2 (c) only ATP (d) only O2 11. End product of fermentation of sugars is (a) H2O and CO2 (b) CO2 (c) alcohol and CO2 (d) alcohol 12. Stomata open and close due to (a) circadian rhythm (b) genetic clock (c) pressure of gases inside the leaves (d) turgor pressure of guard cells 13. Which of the following plant is found to have minimum transpiration ? (a) Cactus (b) Hydrilla (c) Mango (d) Guava 14. Photosynthetically active radiation is represented by the range of wavelength of (a) 340 – 450 nm (b) 400 – 700 nm (c) 500 – 600 nm (d) 400 – 950 nm 15. Which of the following is not performed by root hairs ? (a) Water uptake (b) Oxygen uptake (c) Mineral uptake (d) CO2 uptake 16. In rainy season, door gets swelled due to (a) imbibition (b) diffusion (c) transpiration (d) respiration 17. The force responsible for upward conduction of water

C-109

23.

24.

25.

26.

18.

Light (d) 6CO2 + 12H2O ¾¾¾¾¾ ® Chlorophyll

27.

28.

19.

20.

21.

22.

(b) translocation

(c) respiration (d) photosynthesis Double fertilization means (a) fusion of male gametes and ovum (b) fusion of two polar bodies (c) a male gamete fused with egg and second male gamete fused with secondary nucleus (d) all the above Which of the following is not caused by deficiency of mineral nutrition? (a) Necrosis (b) Chlorosis (c) Etiolation (d) Shortening of internodes Generally plants absorbed N2 in the form of (b) NO3– (a) NO2– (c) N º N (d) HNO2 Which of the following element is a constituent of protein ? (a) Sulphur (b) Potassium (c) Lead (d) Phosphorus Haploid, diploid and triploid conditions respectively can be traced in (a) egg, nucellus, endosperm (b) antipodal, egg, endosperm (c) endosperm, nucellus, synergids (d) antipodal, synergids and integuments

The above equation refers to (a) ammonification (b) nitrification (c) nitrogen fixation (d) denitrification In PS-I the reaction centre Chl a has absorption maxima at _____________, while in PS-II the reaction centre Chl a has absorption maxima at ___________. (a) P680, P700 (b) P700, P680 (c) P800, P600 (d) P700, P900 Ethylene gas is used for (a) growth of plants. (b) delaying fruit’s abscission. (c) ripening of fruits. (d) stopping the leaf abscission. Which one is the correct summary equation of photosynthesis? (a) C6H12O6 + 6O2 ¾¾ ® 6CO2 + 6H2O + energy ® (b) C6H12O6 + 6O2 + 6H2O ¾¾ 6CO2 + 12H2O + energy Light ® (c) 6CO2 + 6H2O ¾¾¾¾¾ Chlorophyll 6H2O + C6H12O6

against gravity comes from (a) transpiration

N2 + 8e– + 8H+ + 16 ATP ® 2NH4 + H2 + 16ADP + 16Pi

29.

30.

31.

32.

33.

34.

6O2 + C6H12O6 + 6H2O Which one of the following is primarily concerned with cell division ? (a) GA3 (b) IAA (c) Cytokinin (d) Ethylene Growth is primarily affected by two climatic factors which are – (a) Light and temperature (b) Temperature and relative humidity (c) Light and wind (d) Rainfall and temperature The hormone reducing transpiration rate by inducing stomatal closure is (a) ABA (b) ethylene (c) cytokinin (d) auxin Which part of the plant do not perform photosynthesis? (a) Cactus stem (b) Guard cell of stomata (c) Mesophyll cells of leaf (d) Leaf epidermis Effect of low temperature which shortens vegetative period and hasten flowering is (a) photoperiodism (b) transpiration (c) vernalization (d) photolysis Which of the following elements is not required by plants for their normal healthy growth? (a) Calcium (b) Magnesium (c) Lead (d) Iron The hormone responsible for phototropism is (a) Ethylene (b) Abscisic acid (c) Auxin (d) Gibberellic acid In which part of a flower do both meiosis and fertilization occur? (a) Ovule (b) Stigma (c) Anther (d) Petal

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35.

36.

37.

Bidirectional translocation of minerals takes place in (a) Xylem (b) Phloem (c) Parenchyma (d) Cambium Soil can easily become deficient in____________ because these ions are negatively charged and do not stick to negatively charged clay particles. (a) Nitrate (b) Calcium (c) Ammonium (d) Magnesium In an anaerobic condition, yeast cells breakdown glucose to (a) CO2 + H2O (b) C2H5OH and CO2 (c) CO2 + Lactic acid (d) CO2 + Pyruvic acid

1 2 3 4 5

(a) (b) (a) (d) (c)

6 7 8 9 10

11 12 13 14 15

16 17 18 19 20

38.

39.

40.

GENERAL SCIENCE Two pigment system theory of photosynthesis was proposed by or Concept of evidence for existence of two photosystems in photosynthesis was given by (a) Hill (b) Blackman (c) Emerson (d) Arnon Which mineral nutrients are called critical element for crops? (a) N, P, K (b) C, H, O (c) N, S, Mg (d) K, Ca, Fe Which of the following would not have an effect on flowering of a particular plant species? (a) Plant age (b) Nutritional status (c) Temperature (d) Prevailing wind

ANSWER KEY (a) 21 (a) (a) 22 (a) (c) 23 (c) (c) 24 (b) (b) 25 (c)

26 27 28 29 30

(d) (c) (a) (a) (d)

31 32 33 34 35

36 37 38 39 40

(a) (b) (c) (a) (d)

HINTS AND SOLUTIONS 2. 3. 4.

7. 9.

(b) If a cell swells, after being placed in solution, the solution is called Hypotonic. (a) Chlorophyll is present in the grana of chloroplasts. (d) Translocation of organic solutes occur through sieve tubes in the form of sucrose. Transportable form of sugar is sucrose. (a) Leaves show transpiration & photosynthesis. (b) Pyruvic acid is the end product of glycolysis. glucose

12.

ATP ADP

glucose-6P

13.

Fructose-6P

14. Fructose-1, 6 diphosphate 3PGA

DHAP

16.

Series of reaction

Pyruvic Acid

10. 11.

(a) The ultimate gain of light reaction is ATP & NADPH2. (c) The end product of fermentation of sugars is alcohol and CO2. Sugars are the most common substrate of fermentation, and typical examples of fermentation products are ethanol, lactic acid, and hydrogen. However, more exotic compounds can be produced by fermentation, such as butyric acid and acetone. Yeast carries out fermentation in the production of ethanol in beers, wines and other alcoholic drinks, along with the production of large quantities of carbon dioxide. Fermentation occurs in mammalian muscle during periods of intense exercise where oxygen supply becomes limited, resulting in the creation of lactic acid.

18.

32. 36. 38.

(d) Turgor pressure is the pressure that develops in a cell due to osmotic diffusion of water inside it and is responsible for pushing the membrane against cell wall. Stomata open under conditions of increased turgor pressure of guard cell and stomata get closed under conditions of decreased turgor pressure of guard cells. When turgid, they swell and bend outward. As a result, the stomatal aperture opens. When they are flaccid, the tension from the wall is released and stomatal aperture closes. (a) Cactus is a xerophytic plant and have sunken stomata to reduce the rate of transpiration, confined to lower epidermis. (b) Photosynthesis takes place only in th e visible part (400 – 700 nm wavelength) of electromagnetic radiations. Hence this component comprises the photosynthe-tically active radiation. (a) In rainy season, door gets swelled due to the phenomenon of imbibition. It is the process of absorption of water without forming a solution. (c) Double fertilization means, a male gamete fused with egg and second male gamete fused with secondary nucleus. (c) Lead are toxic even in smaller concentration. (a) NO3–, is negatively charged and not tightly bound to soil particles. (c) The discovery of Emerson effect stated that one group of pigments absorbs light of both shorter and longer wavelengths (more than 680 nm) and another group of pigment absorbs light on only shorter wavelengths (less than 680 nm). These two groups of pigments are known as pigment systems or photosystem.

4 •

Human Physiology

The food that we consume must be broken down into simpler absorbable forms so that they can be easily absorbed and transported to various parts of our body through blood. This task is accomplished by the digestive system.

Dental formula for adult human

Digestion of Food Name of the Digestive Saliva Pancreatic iuice Intestinal juice Gastric iuice Pancreatic iuice Intestinal juice

Name of the enzymes Ptyalin (Salivary amylase) Amylopsin (pancreatic amylase) Sucrase (invertase), Maltase, Lactase Pepsin, Rennin

Substrate Starch Starch, Glycogen Sucrose; Maltose, Lactose

Trypsin, Chymotrypsin, Carboxyl peptidases Amino peptidase, Dipeptidase

Proteins, Proteins Peptides

Proteins, Casein

Peptides

End product Maltose Maltose and Glucose Glucose and fructose, Glucose, Glucose and galactose Proteoses and peptones, Calcium caseinate Proteoses and peptides Peptides Amino acid. Amino acids, Amino acids

Vitamin required by the body Vitamin

Chemical Name Thiamine pyrophosphate

Function In Body Part of coenzyme for respiration

Deficiency Disease Beri-beri: nerve and heart disorders

Riboflavin

Part of coenzyme FAD needed for respiration

Ariboflavinosis: skin and eye disorders

B12

Cyanocobalamin

Pernicious anaemia

Nicotinic acid ('niacin')

Ascorbic acid

Coenzyme needed for making red blood cells, bone, blood and nerve changes Part of coenzymes NAD, NADP used in respiration Not precisely known

Retinol

Cholecalciferol

E K

Tocopherol Phylloquinone

B1 B2

Pellagra: skin, gut and nerve disorders Scurvy: degeneration of skin teeth and blood vessels. Xeropthalmia: 'dry eyes'

Not fully known but forms part of visual pigment, rhodopsin Stimulates calcium absorption by small intestine, Rickets: bone deformity needed for proper bone growth Not precisely known Infertility Involved in blood clotting Possible haemorrage

Inorganic Elements in the Human Diet Element Calcium

Common ions

Phos phorus

H 2PO4

Potas sium Sodium Chlorine

K+ ü ï Na + ý - ï Cl þ

Iron

Fe , Fe

Iodine

Copper M anganes Zinc

Cu 2 + ü 2+ ï Mn ý Zn 2 + ïþ

–

Functions in human body Calcium ions are needed for stability of cell membranes , as cofactors for s ome enzymes and are involved in mus cle contraction and blood clotting. Bones component of many organic molecules like DNA , RNA and A TP. These ions are important in determining the balance of electrical charges in body fluids.

Component of haemoglobin and cytochrome molecules . Component of hormone thyroxin. Trace elements as enzyme cofactors , for example, Cu oxidase.

is co-factor for cytochrome

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•

GENERAL SCIENCE

Marasmus is produced by a simultaneous deficiency of proteins and calories. In Marasmus, protein deficiency impairs growth and replacement of tissue proteins; extreme emaciation of the body and thinning of limbs results, the skin becomes dry, thin and wrinkled. Growth rate and body weight decline considerably. Kwashiorkar is produced by protein deficiency unaccompanied by calorie deficiency. Like marasmus, kwashiorkor shows wasting of muscles, thinning of limbs, failure of growth and brain development.

Human Respiratory System •

Human respiratory system consists of external nostrils, nasal cavity, nasopharynx, larynx, trachea, bronchiole and lungs. Transport of gases • 97% of oxygen is transported from the lungs to the tissues in combination with haemoglobin (Hb + O2 ¾¾® HbO2, oxyhaemoglobin). 3% is transported in dissolved condition by the plasma. There are three ways of transport of CO2. • • •

5%–7% (approximately) of CO2 is transported, being dissolved in the plasma of blood. CO2 react with the water to form carbonic acid (H2CO3) by the enzyme carbonic anhydrase (present in RBC). CO2 reacts with amine radicals (NH2 ) of haemoglobin molecule and forms a carbamino–haemoglobin (HbCO2) molecule. Nearly 23% of CO2 is transported through this mode.

Disorders of respiratory system Bronchial Asthma : It is characterised by the spasm of smooth muscles of the wall of bronchiole. Emphysema : It is an inflation of bronchiole, which results into loss of elasticity of these parts. Occupational Lung Disease : It is caused because of the exposure of potentially harmful substances persuntion in the environment, where people work. Two common occupational diseases are – silicosis and asbestosis. Blood Groups • ABO grouping : It is based on the presence or absence of two surface antigens on the RBCs namely A and B. Table : Blood Groups and Donor Compatibility Blood

Antigens

Antibodies

Donor's

Group on RBCs

in Plasma

Group

A B

anti-B anti-A

A, O B, O

A, B

nil

AB, A, B, O

nil

anti-A, B

Rh Grouping : Another antigen, the Rh antigen are also observed on the surface of RBCs of majority of humans (Rh + individuals). A special case of Rh incompatibility has been observed between Rh– blood of a pregnant mother with Rh+ blood of foetus.

Circulatory Pathways The circulatory patterns are of two types – • Open circulatory system is present in arthropods and molluscs in which blood pumped by the heart passes through large vessels into open spaces or body cavities called sinuses. Annelids and chordates have a closed circulatory system in which the blood pumped by the heart is always circulated through a closed network of blood vessels. All vertebrates possess a muscular chambered heart. Fishes have a 2-chambered heart with an atrium and a ventricle. Amphibians and the reptiles (except crocodiles) have a 3-chambered heart with two atria and a single ventricle, whereas crocodiles, birds and mammals possess a 4-chambered heart with two artia and two ventricles. Heart Beat and Pulse • The human heart beats at the rate of about 72-80 per minute in the resting condition. Electrocardiograph • ECG is the graphic record of electronic current produced by the excitation of cardiac muscles. • A normal electrocardiogram is composed of a P wave, QRS complex and T wave. P wave indicate the depolarisation of the atria. QRS complex expresses the ventricular depolarisation. T wave indicate an repolarisation of ventrcle.

Disorders of Circulatory System Hypertension • A continuous or sustained rise in arterial pressure is known as hypertension. High blood pressure compels heart to work excessive and then can tend to congestive heart disease. Atherosclerosis •

In this, calcium salts precipitated with cholesterol of the forming or formed opaque making the wall of arteries stiff and rigid and is referred to as the hardening of the arteries. It may lead to heart attack and death.

Excretion •

The process of excreting ammonia is -Ammonotelism. Kidney plays a minor role in the elimination of ammonia e.g., teleost fishes, tadpoles, aquatic soft bodied invertebrates. Organism undergoing ammonotelism are called ammonotelic.

•

The process of excreting urea is - Ureotelism. Examples are mammals, many terrestrial adult amphibians and cartilaginous fishes (shark).

•

The process of elimination of uric acid is -Uricotelism Examples are land snails, insects, birds and many reptiles. • Each kidney has nearly one million complex tubular structures called nephrons, which are the functional units of kidney. These filter the blood to produce urine. Disorders of the Excretory System • Malfunctioning of kidneys can lead to accumulation of urea in blood, a condition called uremia, which is highly harmful and may lead to kidney failure.

Human Physiology • In such patients, urea can be removed by a process called hemodialysis. Blood drained from a convenient artery is pumped into a dialysing unit called artificial kidney. • Renal calculi : Stone or insoluble mass of crystallized salts (oxalates, etc.) formed within the kidney. • Glomerulonephritis : Inflammation of glomeruli of kidney.

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•

Skeletal System Human Skeleton (comprising 206 bones) divided into

Skull

Vertebral Sternum column

made up of Ribs

Girdles

Limbs

Axial Skeleton : Skeleton which occurs in the mid axial or longitudinal part of the body. (i) Skull is made up of 29 bones. It is composed of • Cranium (8 bones) : Frontal - 1; Parietal - 2; Occipital - 1; Temporal - 2; Sphenoid - 1; Ethmoid - 1. • Facial bones (14 in number) : Nasal - 2; Maxillae - 2; Zygomatic - 2; Lacrymals - 2; Mandibles - 1; Inferior turbinals - 2; Vomer - 1; Palatines - 2. Hyoid Tongue bone - 1 • Ear ossicles (6 bones) : Malleus -2; Incus - 2; Stapes - 2. (ii) Vertebral column : 33 in babies, 26 in adults. Grouped into 5 categories : Cervical - 7; Thoracic - 12; Lumber - 5; Sacral - 5; Coccygeal - 4 (fused in adults). (iii) Sternum : Composed of 3 parts ® Manubrium, body of sternum and xiphoid process . (iv) Ribs : They are twelve pairs. First seven pairs are true ribs. The 8th, 9th and 10th ribs are called false ribs or vertebrochondrial ribs. The last 11th and 12th pairs are called floating ribs. Appendicular Skeleton : Present laterally or attached to the axial skeleton. (i) Girdles : 2 types - pectoral and pelvic. Pectoral girdle : made of two parts - clavicle and scapula. Pelvic girdle : made of three bones - ilium, pubis and ischium. (ii) Limb bones : Hind limbs and fore limbs - both made up of 30 bones each. Fore limbs : Humerus (1); Radius-Ulna (2); Carpals (8); Metacarpals (5); Phalanges (14); Phalanges formula = 2, 3, 3, 3, 3. Hind limbs : Femur (1); Tibia-Fibula (2); Patella (1); Tarsals (7); Metatarsals (5); Phalanges (14).

Joints •

A joint is a location at which two bones make contact and is essential for all types of movements, involving the bony parts of the body. Synovial Joints - Movable Joints : They are characterised by the presence of a closed space or cavity between the bones.

–

Plane (gliding joint) : Present between carpals. Only sliding motion in all direction is allowed.

–

Hinge joint : Present between Knee joint

–

Pivot joint : Present between atlas and axis

–

Saddle joint : Present between carpal and metacarpal

–

Ball and Socket joint : Present between humerus and pectoral girdle.

Disorders of Muscular and Skeletal System •

Appendicular Skeleton

Axial Skeleton made up of

This kind of joint are classified into six major categories.

•

• • • •

Myasthenia gravis - Autoimmune disorder. It affects neuromuscular transmission. Muscular dystrophy - Progressive skeletal muscle weakness, defects in muscle proteins, the death of muscle cells and tissue. Rheumatoid Arthritis : Inflammation of synovial membrane. Osteoarthritis : Degeneration of articular cartilage. Gout : Caused by excess formation of uric acid and their deposition in the joints. Osteoporosis : Low bone mass, increased fragility and proneness to fracture.

Neural Control and Coordination •

The neural sysem is the control system of the body which consists of highly specialized cells called neurons. • A neuron consists of main cell body and cytoplasmic processes arising from it. The human brain is divisible into three parts: • Forebrain : It comprises the olfactory lobes, cerebrum and diencephalon. Cerebrum is the largest and complex part. It consists of the left and right hemispheres connected by a bundle of myelinated fibres, called corpus callosum. The outer layer of the cerebrum is called the cortex. • Diencephalon : The main parts of the diencephalon are epithalamus, thalamus and hypothalamus. • The hypothalamus is the highest centre of autonomic nervous system. It governs emotional reactions and exercise control over sleep mechanism. •. Midbrain : It is formed of corpora quadrigemina and cerebral peduncles. Cerebral penduncles are bundles of fibres connecting the cerebral cortex with other parts of brain and spinal cord. • Hind brain : It comprises of : – Cerebellum : It controls the balance and posture of the body. – Pons varolii - The pons is concered with maintenance of normal rhythm of respiration. – Medulla oblongata - Medullary centres (reflex centres) are present for controlling the functions of important organs, e.g., cardiac centres (heart), respiratory centre, vasomotor centre (for regulating diameter of blood vessels) and reflex centres (for swallowing, vomiting, peristalsis, secretion and activity of alimentary canal, salivation, coughing etc.)

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GENERAL SCIENCE

Chemical Coordination in Animal (Hormones) Endocrine Gland Thyroid

Hormone Thyroxine (T 4) and Triiodothyronine (T 3 ) Calcitonin

Principal action Maintains calcium level normal in the body.

Disorders Cretinism, myxoedema goiter

Parathyroid

Parathormone (PTH)

Adrenal gland (medulla)

Adrenaline and Noradrenaline

Increases rate of metabolism in the body. Increases plasma calcium Parathyroid tetany osteoporosis Increases heart beat, blood sugar and also constricts blood vessel

Adrenal cortex

Mineralocorticoids (aldosterone)

Increases reabsorption of sodium and excertion of potassium

Hypothalamus

Glucocorticoids (cortisol) Increases blood sugar and affects carbohydrate, fat and protein metabolism ARH Regulates corticotropin secretion

Addison’s disease Adrenal virilism Cushing’s syndrome

TRH SRH

Thyrotropin secretion Stimulates secretion of gonadotropins (Growth hormone releaing Regulates secretion of prolactin factor)

Pituitary gland anterior lobe

(Prolactir releasing hormone) and (Prolactin inhibitory hormone)

Control secretion of MSH

Pituitary gland anterior lobe

Stimulates general growth

Prolactin

Stimulates milk production and secretion Stimulates ovarian follicle and spermatogenesis Stimulates corpus luteum and ovulation in females and interstitial cell in males Stimulates thyroid gland to secrete hormones

(Follicle stimulating hormone) (Lutemizing hormone)

(Thyroid stimulating hormone)

Intermediate lobe Posterior lobe

Adrenocorticotropic hormone Melanocyte stimulating hormone Oxytocin Vasopressin (ADH)

Pituitary dwarfism, gigantism, Acromegaly

Stimulates adrenal cortex to secrete glucocorticoids Growth and development of melanocyte Contraction of uterine muscles and mammary gland cells Promotes reabsorption of water Diabetes insipidus from collecting ducts of kidneys

Pancreas • •

Located posterior to stomach, close to duodenum. Endocrine Pancreas : Consists of islets of Langerhans. The islet of Langerhans have two main types of cells. ENDOCRINE PANCREATIC SECRETIONS : 1. 2.

NAME OF THE CELLS Beta (b) cells Alpha (a) cells

PRODUCT Insulin and Amylin Glucagon

FUNCTION Lower blood sugar level. Raise blood sugar level.

Human Physiology

C-115

Testes

Reproduction

Function : Produces a group of hormones called androgens mainly testosterone.

•

Androgen regulates the development, maturation and functions of the male accessory sex organs.

Ovary Functions : Ovary produces one ovum during each menstrual cycle. It produces 2 groups of steroid hormones called. (i) Estrogen (ii) Progesterone • Stimulating growth and activities of female secondary sex organs. • Supports Pregnancy. • Also regulates female sexual behaviour. • Production of milk.

Which part of the alimentary canal does not secrete any enzyme? (a) Mouth (b) Oesophagus (c) Stomach (d) Duodenum The food that gives more calories per unit mass of food is (a) protein (b) carbohydrates (c) fat (d) water Percentage of oxygen supplied by haemoglobin is (a) 97% (b) 100% (c) 49% (d) 3% Which one of the following correctly represents the normal adult human dental formula ? (a)

3 1 3 1 , , , 3 1 2 1

(b)

10.

11.

12.

2 1 3 3 , , , 2 1 2 3

2 1 2 3 3 1 3 3 , , , , , , (d) 2 1 2 3 3 1 3 3 In expiration, diaphragm becomes (a) flattened (b) relaxed (c) straightened (d) arched Elbow joint is an example of (a) hinge joint (b) gliding joint (c) ball and socket joint (d) pivot joint The toxic effect of CO is due to its greater affinity for haemoglobin as compared to O2 approximately by (a) 2 times (b) 20 times (c) 200 times (d) 1000 times A patient is generally advised to specially, consume more meat, lentils, milk and eggs in diet only when he suffers from (a) Scurvy (b) Kwashiorkor (c) Rickets (d) Anaemia

13.

(c)

14.

15.

16.

It is the ability of living organisms to produce a new offspring similar to themselves. The major reproductive events in human beings are (i) Gametogenesis – Formation of gametes. (ii) Insemination – Transfer of sperms into female genital tract. (iii) Fertilisation – Fusion of male and female gametes leading to formation of zygote. (iv) Implantation – Formation and development of blastocyst and its attachment to the uterine wall. (v) Gestation – Embryonic development; gestation is the time from conception to birth. (vi) Parturition – Delivery of baby (the process of birth).

In which of the following reptiles four chambered heart is present ? (a) Lizard (b) Snake (c) Scorpion (d) Crocodile Melatonin is produced by (a) thymus (b) skin (c) pituitary (d) pineal gland Child death may occur in the marriage between (a) Rh+ man and Rh + woman (b) Rh+ man and Rh – woman (c) Rh– man and Rh – woman (d) Rh– man and Rh + woman Which one of the following organs in the human body is most affected due to shortage of oxygen? (a) Intestine (b) Skin (c) Kidney (d) Brain The pH of blood is (a) between 7-8 (b) between 2-4 (c) between 12-14 (d) between 2-5 Antibodies are (a) carbohydrates (b) immunoglobulins (c) globular proteins (d) extrinsic proteins Air is breathed through (a) Trachea — lungs — larynx — pharynx — alveoli (b) Nose — larynx — pharynx — bronchus — alveoli — bronchioles (c) Nostrils — pharynx — larynx — trachea — bronchi — bronchioles — alveoli (d) Nose — mouth — lungs Which of the following disease is not concerned with disorders of circulatory system? (a) Heart failure (b) Angina (c) Coronary artery disease (d) Uremia

C-116

17.

18.

19.

20.

21.

22.

23.

24.

25.

26.

27.

28.

Neurons receive signals through their __________ and send signals to other neurons through their __________. (a) dendrites ... receptors (b) end feet ... cell bodies and dendrites (c) cell bodies and dendrites ... axons (d) transmitter vesicles ... axons Functional and structural unit of kidney is (a) nephron (b) seminiferous tubule (c) acini (d) None of these Asthma is caused due to (a) Infection of lungs (b) Spasm in bronchial muscles (c) Bleeding into pleural cavity (d) infection of trachea Dialysis is done in the condition when person is suffering from (a) diabetes (b) uremia (c) polyuria (d) haemoptysis Which part of human brain is concerned with the regulation of body temperature? (a) Cerebellum (b) Cerebrum (c) Hypothalamus (d) Medulla Oblongata Which of the following organs can be called as a sort of "blood bank" ? (a) Lungs (b) Heart (c) Liver (d) Spleen Universal blood recipient is (a) blood group O (b) blood group AB (c) blood group A (d) blood group B Bones are mainly made up of (a) calcium and phosphorous (b) calcium and sulphur (c) calcium and magnesium (d) calcium and iron ECG records (a) rate of heart beat (b) potential difference (c) ventricular concentration (d) volume of blood pumped During strenuous exercise, glucose is converted into (a) glycogen (b) pyruvic acid (c) starch (d) lactic acid In human testosterone is produced by (a) tunica albuginea (b) leydig cell (c) seminiferous tubule (d) sertoli cell In adult, normal blood pressure is (a) 80/120 mm Hg (b) 100/80 mm Hg (c) 120/80 mm Hg (d) 100/120 mm Hg

GENERAL SCIENCE 29.

30.

31.

32.

33.

34.

35.

36.

37.

38.

39.

40.

Thoracic cage is made up of (a) ribs, vertebral column & diaphragm (b) ribs, diaphragm & sternum (c) vertebral column, diaphragm & sternum (d) ribs, vertebral column & sternum The junction between an axon and dendrite is called (a) cyton (b) synapse (c) relay (d) conduction zone A certain road accident patient with unknown blood group needs immediate blood transfusion. His one doctor friend at once offers his blood.What was the blood group of the donor? (a) Blood group B (b) Blood group AB (c) Blood group O (d) Blood group A Which one is not a reflex action? (a) Closing of eye lids against fricking (b) Release of saliva on seeing sweets (c) Perspiration due to heat (d) Obeying the order to run Which one is not correct ? (a) Humans - Uriotelic (b) Birds - Uricotelic (c) Lizards - Uricotelic (d) Whale - Ammonotelics Main similarity between hormone and enzyme is (a) both act at particular pH (b) both are proteins (c) both are required in small amounts (d) both can be used again and again Which of the following commonly called emergency gland of body? (a) Thymus (b) Testis (c) Adrenal (d) Pituitary Other function performed by kidney apart from excretion is (a) Osmoregulation (b) Temperature regulation (c) Hormonal regulation (d) Spermatogenesis Appearance of facial hairs in a woman may be due to the effect of (a) temperature (b) ultraviolet radiation (c) hormone (d) pollution Glucagon is secreted by (a) b (beta) cells of islets of langerhans (b) a (alpha) cells of islets of langerhans (c) b cells of pancreas (d) adrenal cortex Parathormone deficiency produces muscle ramps or tetany as a result of (a) lowered blood Ca2+ (b) enhanced blood Na+ (c) enhanced blood glucose (d) enhanced blood Ca2+ Thymosin stimulates (a) milk secretion (b) erythrocytes (c) T-lymphocytes (d) melanocytes

Human Physiology 1 2 3 4 5

(b) (c) (a) (c) (d)

6 7 8 9 10

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(a) (c) (b) (d) (d)

11 12 13 14 15

(b) (d) (a) (b) (c)

16 17 18 19 20

ANSWER KEY 21 (d) 22 (c) 23 (a) 24 (b) 25 (b)

26 27 28 29 30

(d) (b) (c) (d) (b)

31 32 33 34 35

36 37 38 39 40

(a) (c) (b) (a) (c)

HINTS AND SOLUTIONS 3. 4.

10.

11.

12. 13.

14. 15.

(a) About 97% of oxygen is carried in combination with haemoglobin of the erythrocytes to form oxyhaemoglobin. 2 (c) The adult dental formula of human is Incisor , Canine 2 1 2 3 , Premolar , Molar . 1 2 3 (a) Elbow joint is an example of hinge joint. The elbow is a hinge joint; it can open and close like a door. Hinge joint allows angular movement in one plane only, increasing or decreasing the angle between the bones e.g. elbow joint, knee joint etc. (b) A child may have a diet containing sufficient carbohydrates and fats but still suffers a serious form of malnutrition. This form of malnutrition is known as Kwashiorkar. It develops in children whose diets are deficient in protein. (d) Melatonin is secreted by pineal gland present between the cerebral hemispheres. Melatonin concentration in blood follows a diurnal cycle, it rises in the evening and drops at noon. Melatonin lightens skin colour in certain animals and regulates working of gonads. (b) Rh factor was discovered by Karl Landsteiner. A child of Rh+ man will be Rh+ whether the mother is Rh+ or Rh–. If the mother is Rh+ then there will be no problem but if mother is Rh– so when the blood of Rh+ child (in womb) mixes with the blood of Rh– mother then some antibodies in mother’s blood are formed against Rh + factor which coagulate the womb blood causing death. If birth takes place then there is a possibility of child death in early years. This in known as erythroblastosis foetalis. In most cases the first pregnancy may succeed but after that it fails. (d) Brain is the most vital organ. It stops functioning in the absence of O2. (a) Blood is an opaque, mobile connective tissue fluid which has salty taste. pH of blood is between 7-8. Hence, the blood possesses slightly alkaline pH. (b) Antibodies are immunoglobulins (Igs) which are produced in response to antigenic stimulation. (c) The pathway of inhaled air is - Nostrils - pharynx (common passage for food & air) - larynx (voice box) - trachea (the wind pipe) - bronchi (2 for each side lungs) - bronchioles (give arise to alveolar ducts) - alveoli (the exchange site for gases in the form of small sacs or pouches).

17.

23.

24.

29. 30.

31. 32.

33. 35.

36.

39.

(c) Dendrites generally receive inputs and conduct signals toward the cell body, whereas axons conduct signals away from the cell body. (b) Blood group AB individuals have both A and B antigens on the surface of their RBCs, and their blood plasma does not contain any antibodies against either A or B antigen. Therefore, an individual with type AB blood can receive blood from any group with AB being preferable. Hence, blood group AB is known as universal recipient. (a) Bone is the solid rigid strong connective tissue. Its matrix consists of ossein protein and mineralization of matrix occurs by calcium- phosphate salts. This gives rigidity and strength to bones. (d) Rib cage consists of vertebral column (dorsal), sternum (ventral) and ribs (lateral). (b) The junction between an axon and dendrite is known as synapses through which nerve impulse is transmitted from one neuron to other. A synapse consists of swelling at the end of nerve fibre called synaptic knob and small synaptic vesicle containing neuro-transmitter–acetylcholine for the transmission of nerve impulse. (c) Blood group O acts as universal donor. (c) Reflex action is the immediate involuntary response to stimulus. It includes sudden action of body parts due to heat stimulus, burn stimulus, pricking, sneezing, coughing yawning, etc. Perspiration is not a reflex action. It is also known as sweating. Sweating is loss of water from sweat glands of the skin. Sweat includes some salts and urea. Its for temperature regulation. (d) Whale is ureotelic. (c) Adrenal or suprarenal glands are called emergency gland of the body. The medullary portion of these glands secretes hormones adrenaline and nor adrenaline. Their secretion is stimulated by the sympathetic nervous system. These hormones are secreted in emergancy conditions like anger, injury, cold, emotional stress, fear etc, hence also called hormones for fight or flight. (a) Besides removing the metabolic wastes and impurities from the blood the kidney also perform the important function of osmoregulation (regulation of osmolality) by regulating the amount of water in body fluids. (a) Parathormone released by the parathyroid gland elevates the level of Ca2+ in blood. The deficiency of this hormone lowers blood Ca2+. As a result, the excitability of muscles and nerves increases producing tetany sustained contraction.

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GENERAL SCIENCE

Genetics and Evolution

Study of heredity and variation is called genetics. • Term genetics was given by - Bateson. • Father of genetics - Gregor Johann Mendel. • Father of experimental genetics - Thomas Hunt Morgan. • Father of human genetics - Archibald Garrod. Some Terms in Genetics Gene : It is segment of DNA. It is basic unit of heredity. Back cross : It is cross which is performed between hybrid and one of its parents. Test cross : Test cross is crossing of offspring with unknown dominant phenotype with the individual hom*ozygous recessive for the trait. Monohybrid cross : It is a cross between two organisms of a species which is made to study the inheritance of a single pair of alleles or factors of a character. Monohybrid ratio : Monohybrid ratio is usually 3 : 1 (phenotypic ratio) or 1 : 2 : 1 (genotype ratio) in which 25% of the individuals carry the recessive trait, 25% pure dominant and 50% have hybrid dominant trait. Dihybrid cross : It is a cross between two organisms of a species which is made to study the inheritance of two pairs of factors or alleles of two genes. Dihybrid ratio : Dihybrid ratio is 9 : 3 : 3 : 1 (phenotypic ratio) where 9/16 first recessive and second dominant and 1/16 carry both the recessive traits. • Mendel conducted cross hybridization experiments on Garden Pea plant (Pisum sativum). The first was the Principle of segregation, which claimed that each trait was specified by paired hereditary determinants (alleles of genes) that separate from each other during gamete formation. This law is also called Law of purity of gametes or Law of splitting of hybrids. • Gregor Mendel was the first individual to apply a modern scientific approach to the study of heredity. Mendel proposed two basic principles of trasmission genetics. • Mendel’s second basic conclusion was the Principle of independent assortment, which stated that the segregation of one pair of genes-controlling a given trait - was not influenced by the segregation of other gene pairs. The chormosome theory provided a physical basis for the principle of independent assortment. Genes located on different chromosomes move to gametes independently of each other during meiosis.

Human Blood Groups and Multiple Allele • The system of blood groups in humans was discovered by Karl Landsteiner in 1900s. • There are four phenotypes of Blood namely A, B, AB and O produced by three different alleles IA, IB and i of a gene. • The allele IA and IB are equally dominant and do not interfere with expression of each other hence the allele IA IB are said to be co-dominant because both are expressed in the phenotype AB. • Linkage is the phenomenon of certain genes staying together during inheritance through generations without any change or separation due to their being present on the same chromosomes. • Linkage in the genes can be identified by test cross. • The rearrangements of linked genes due to crossing over is known as recombination. Recombination also occurs due to chance separation of chromosomes during gametogenesis and their random coming together during fertilization.

Sex Determination •

•

Henking discovered X body in spermatogenesis of few insects and it was given name of X chromosome. Due to involvment of X and Y chromosomes in determination of sex, they were called sex chromosomes. Rest of the chromosomes which determine other metabolic character of the body are called autosomes.

Mutation •

•

Phenomenon that results in alteration of DNA sequence and consequently results in change in genotype and phenotype of an organism is called mutation. Mutagens are various chemical and physical factors that induce mutations, e.g., UV radiations, carcinogenic chemicals like nicotine, nitric oxide (NO).

Genetic Disorder •

A genetic disorder is a disease that is caused by an abnormality in an individual’s DNA. Haemophilia • A protein involved in clotting of blood is affected in an affected individual; if person gets a cut, will result in nonstop bleeding. • Females are heterozygous and carriers of haemophilia.

Genetics and Evolution Sickle Cell Anaemia

Phenylketonuria

•

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It is due to inheritance of defective allele coding for b-globin. It results in the transformation of HbA into HbS in which glutamic acid is replaced by valine at 6th position in each of two b-chains of haemoglobin. It is an excellent example of single mutation.

•

Affected individual lacks enzyme phenylalanine hydroxylase that converts amino acid phenylalanine to tyrosine. It is characterized by severe mental retardation, hypopigmentation of skin & hair, eczema, etc.

Chromosomal Mutation Name of disorder or syndrome Down’s Syndrome

Chromosomal Alteration involved Trisomy 21

Klinefelter’s Syndrome

XXX (or XXYY, XXXY, etc)

Symptoms or Associated Traits Characteristic facial features, short stature, heart defects, respiratory infections, mental retardation. Sterility, small testes, feminine body contours, normal intelligence or mental retardation.

Turner’s Syndrome

Monosomy X (XO)

Short stature, sex organs do not mature, no secondary sex characteristics, normal intelligence.

Cri du chat Syndrome

Deletion in Chromosome 5

Mental retardation, small head, unusual cry.

Deoxyribonucleic Acid • DNA is a long chain polymer of deoxyribonucleotides. • Nucleotide is made up of 3 chemical groups ® A nitrogen base moiety + pentose sugar 14444444 4244444444 3 Nucleoside

•

• •

•

+ phosphate group Nitrogenous base are of two types – purines (9 membered double rings with nitrogen at 1, 3, 7 & 9th positions) and pyrimidines (6 membered rings with nitrogen at 1 and 3rd position). Purines are of two types – adenine (A) and guanine (G) and pyrimidines are of three types – thymine (T), cytosine (C) and uracil (U). A characteristics that differentiate DNA from RNA is that DNA contains all of the nitrogen bases except uracil and RNA contains all of the nitrogen bases except thymine. Wilkins-Franklin carried out X ray diffraction (X-ray crystallography) on the basis of which Watson and Crick suggested secondary structure of DNA in 1953. 2 DNA strands are organized in antiparallel and complementary arrangement [i.e., 2 strands run in opposite orientation (one in 5' – 3' and allies in 3' – 5')]. Adenine pairs with thymine with 2 hydrogen bonds and guanine pairs with cytosine with three hydrogen bonds. The helix is generally right handed i.e. its turn run clockwise looking along the helix axis. The pitch of helix is 3.4 nm (1 nm = 10–9m) and there are 10bp in each turn. The concept of central dogma in molecular biology was proposed by Francis Crick (1958). It proposes unidirectional or one way flow of information from DNA to RNA & then to protein.

Transcription

Translation

DNA ¾¾¾¾¾¾ ® mRNA ¾¾¾¾¾ ® Polypeptide (protein)

Evolution •

It is the formation of newer types of organisms from the pre-existing ones through modification. Evolution is therefore, often called descent with modification.

•

Earth originated 4600 million years ago.

•

Life appeared 3.7 billion years ago. This is indicated by the discovery of microfossils of cyanobacteria like organisms.

•

Theory of spontaneous generation (Abiogenesis/ autogenesis)

•

–

Given by Aristotle.

–

Life originated from non-living things in spontaneous manner.

Theory of Biogenesis –

Life originated from pre-existing life.

– –

Given by Francesco Redi. Oparin – Haldane theory was supported experimentally by Miller-Urey experiment in 1953. Discharge Apparatus – a large flask containing mixture of CH4, NH3, H2 and H2O with electric source and boiling of water for a week. Miller observed dark condensed liquid which was analysed. Analysis reports concluded, that it was a mixture of amino acids like alanine, glycine, glutamic acid, aspartic acid, valine and leucine and number of other organic compounds like HCN, aldehyde and cyanocompounds.

–

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Theories of Evolution Darwinism • Darwinism is the term coined for the explanation offered by Darwin for the origin of species by Natural selection in 1858. • Darwinism or theory of natural selection is a theory of organic evolution which states that new species evolve over a long period of time through accumulation of small variations which provide the organism with structural and functional superiority over others in their survival and differential reproduction. Genetic Equilibrium (Hardy Weinberg Law) • Law states that “both gene frequency and genotype frequency” will remain constant from generation to generation in an infinitely large interbreeding population in which mating is random and no selection, migration or mutation occurs. • Hardy Weinberg formula or binomial expression is given as p2 + 2pq + q2 = 1 for two alleles A and a. • Genetic drift refers to chance elimination of gene(s) of certain traits when a section of population migrates or dies of natural calamity. It eliminates certain alleles and fixes other alleles. • Genetic drift in a new colony is called founder effect. • Natural calamity like earthquake greatly reduces the size of population, killing the individuals randomly. The genetic pool of surviving population decreases. This condition of reduced genetic variability is called bottleneck effect.

Mutation rates are affected by (a) temperature (b) X-rays (c) gamma and beta radiation (d) All of the above A dihybrid condition is (a) tt Rr (b) Tt rr (c) tt rr (d) Tt Rr In case of incomplete dominance the monohybrid ratio of phenotypes in F2 generation is (a) 1 : 2 : 1 (b) 3 : 1 : 1 (c) 9 : 3 : 3 : 1 (d) 2 : 3 : 1 The number of autosomes in human female ovum is (a) 11 (b) 12 (c) 22 (d) 23 Which one of the following represents a test cross ? (a) Ww × WW (b) Ww × Ww (c) Ww × ww (d) WW × WW How many different kinds of gametes will be produced by a plant having the genotype AABbCC? (a) Nine (b) Two (c) Three (d) Four

GENERAL SCIENCE Vestigial Organs •

The useless and functionless degenerate structures which were large and functional in some other animals. • Examples : Vermiform appendix, coccyx, pinna muscle, wisdom tooth in humans, rudiments of hindlimbs in python. Adaptive radiation • It is a special evolutionary pattern, characterized by a rapid increase in number of kinds of closely related species. • A good example of adaptive radiation is found among the Finches of Galapagos Islands. Another example is Australian Marsupials. Biological evolution • It is the process of change over time, in the heritable characteristics, or traits of a population organisms. • Many experts believe that Australopithecus garhi or a similar species gave rise to the genus hom*o. • Early hominids–members of the genus hom*o–lived contemporaneously with Australopithecines for perhaps a half million years. • The oldest fossil remains of a member of the genus hom*o were discovered in Tanzania. It was named H. habilis. • hom*o erectus is the only other known extinct species of the genus hom*o. • H. erectus was replaced in tropical regions by hom*o sapiens about 200,000 years ago.

10.

How many pairs of contrasting characters in pea pod were chosen by Mendel? (a) 2 (b) 3 (c) 4 (d) 7 From a cross AABb x aaBb, the genotypes AaBB : AaBb : Aabb : aabb will be obtained in the following ratio (a) 1: 1 : 1 : 1 (b) 1: 2 : 1 : 0 (c) 0: 3 : 1 : 0 (d) 1: 1 : 1 : 0 A nucleotide is formed of (a) purine, pyrimidine and phosphate (b) purine, sugar and phosphate (c) nitrogenous bases, sugar and phosphate (d) pyrimidine, sugar and phosphate The process of translation is (a) ribosome synthesis (b) protein synthesis (c) DNA synthesis (d) RNA synthesis

Genetics and Evolution 11. Which one of the following pairs of nitrogenous bases of nucleic acids, is wrongly matched with the category mentioned against it? (a) Thymine, Uracil Pyrimidines (b) Uracil, Cytosine Pyrimidines (c) Guanine, Adenine Purines (d) Adenine, Thymine Purines 12. Ligase helps in (a) removal of few genes (b) translation (c) inserting few genes in DNA (d) bringing transversion in chromosomes 13. A nucleoside differs from a nucleotide in not having (a) phosphate (b) sugar (c) nitrogen base (d) phosphate and sugar 14. Nucleotide arrangement in DNA can be seen by (a) X-ray crystallography (b) Electron microscope (c) Ultracentrifuge (d) Light microscope 15. Scientific name of man is (a) Canis familiaris (b) hom*o habilis (c) hom*o erectus (d) hom*o sapiens 16. The primitive atmosphere of earth contained water vapours, hydrogen, ammonia and (a) CO2 (b) O2 (c) N2 (d) CH4 17. The book ‘Origin of Species’ is written by (a) Aristotle (b) Darwin (c) Watson (d) Lamarck 18. Which was absent in the atmosphere at the time of origin of life ? (a) NH3 (b) H2 (c) O2 (d) CH4 19. hom*ologous organs are (a) wings of insects and bat (b) gills of fish and lungs of rabbit (c) pectoral fins of fish and fore limbs of horse (d) wings of grosshopper and crow 20. The kind of evolution in which two species of different geneology come to resemble one another closely, is termed as (a) progressive evolution (b) convergent evolution (c) parallel evolution (d) retrogressive evolution 21. Which one is linked to evolution? (a) Extinction (b) Competition (c) Variation (d) Reproduction

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22.

23.

24.

Genetic variation in a population arises due to (a) Mutations only (b) Recombination only (c) Mutations as well as recombination (d) Reproductive isolation and selection The first organisms were (a) Chemoautotrophs (b) Chemoheterotrophs (c) Autotrophs (d) Eukaryotes What was the most significant trend in evolution of modern man (hom*o sapiens) from his ancestors ? (a) Upright posture (b) Shortening of jaws (c) Binocular vision (d) lncreasing brain capacity

25. The factors which represent the contrasting pairs of characters are called (a) dominant and recessive (b) alleles (c) hom*ologous pairs (d) determinants 26.

Who proved that DNA is basic genetic material? (a) Griffith (b) Watson (c) Boveri and Sutton (d) Hershey and Chase

27.

28.

29.

The two strands of DNA are held together by (a) peptide bonds (b) phosphodiester bonds (c) hydrogen bonds (d) S – S bonds According to special creation theory the earth is about (a) 4000 yrs old (b) 4.5 M yrs old (c) 4.5 B yrs old (d) 10000 yrs old Which of the following is not a part of Darwin’s theory of evolution? (a) Genetic drift (b) Natural selection (c) Survival of the fittest (d) Struggle for existence

30.

In Down's syndrome of a male child, the sex complement is (a) XO

(b) XY

(d) XXY

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GENERAL SCIENCE 1 2 3 4 5

(d) (d) (a) (c) (c)

6 7 8 9 10

(b) (d) (b) (c) (b)

11 12 13 14 15

ANSWER KEY 16 (d) 17 (c) 18 (a) 19 (a) 20 (d)

(d) (b) (c) (c) (b)

21 22 23 24 25

26 27 28 29 30

(d) (c) (a) (a) (b)

HINTS AND SOLUTIONS 2. 4. 7.

10. 11.

12. 13.

14.

16.

17.

18.

19.

(d) Dihybrid condition involves simultaneous inheritance of two pairs of mendelian factors or genes. (c) In human female ovum, number of autosome are 22 pairs. (d) Mendel in his experiment considered total 7 characters (3 characters of seed i.e., seed shape, seed colour, cotyledon colour, 2 characters of pod i.e., plant height and position of pods on the stem). (b) AABb × aaBb AB Ab AB Ab aB AaBB AaBb AaBB AaBb ab AaBb Aabb AaBb Aabb aB AaBB AaBb AaBB AaBb ab AaBb Aabb AaBb Aabb AaBB : AaBb: Aabb: aabb 4 : 8 : 4 :0 AaBB = 1; AaBb = 2; Aabb = 1; aabb = 0 (c) Nucleotide is a unit of DNA, which is formed of nitrogenous bases (purines & pyrimidines), sugar (pentose) & phosphate. (b) Protein synthesis occurs over ribosomes which are also referred to as protein factories. (d) Purine is an organic nitrogenous base sparingly soluble in water, that gives rise to a group of biologically important derivatives, notably adenine and guanine, which occur in nucleotides and nucleic acids (DNA and RNA). (c) Ligase helps in inserting few genes in DNA. (a) In a nucleotide, purine or pyrimidine nitrogenous base is joined by deoxyribose pentose sugar (D), which is further linked with phosphate (P) group to form nucleotides. (a) In 1953 Wilkins obtained very fin e X-ray crystallographic pictures of DNA from which Watson and Crick developed the double helix model of DNA. (d) The primitive atmosphere of the earth contained : H2O, H2, NH3 & CH4. The ratio was (2 : 2 : 1) of : NH3, CH4 and hydrogen. (b) 'Origin of Species' book was written by Charles Robert Darwin. During his world journey (1831–1936) as a naturalist in H.M.S. Beagle ship, he visitied many parts of the world. On the basis of the observations of this journey, he wrote the book thereby describing his theory of natural selection. (c) Oxygen gas was not present due to reducing atmosphere, it only came to existence after the evolution of photosynthesis process. (c) Organs that are similar in fundamental structure but

20.

(b)

21.

(c)

22.

(c)

23.

(b)

24.

(d)

different in functions are “hom*ologous organs”, Richard Owen, introduced the term hom*ologous. Pectoral fins of fish and fore limbs of horse similar in structure but different in functions are hom*ologous organs. Rest of the organs compared in the question are analogous organs. Progressive evolution is development of organisms with more elaborate and specialized structures from those having less elaborate features e.g. amphibians from reptiles. Retrogressive or degenerative evolution is development of simpler forms from more complex ones. Such evolution has occurred in case of vestigial organs, parasitic forms, and in reduction of overspecialized structures such as wings in flightless birds. Parallel evolution is formation of similar traits in related groups of organisms independently due to similar requirement e.g. running of two toed deer and one toed horse. Evolution of wings in insects and birds serve as example of convergent evolution. Organic evolution is process of cumulative change of living populations and in the descendant populations of organisms. According to Darwin, variations are differences among individuals. Variations which help the individual to fit in its surroundings are passed on to the next generation while others disappear. Thus, variation plays an important role in evolution. Crossing over leads to recombination of genetic material on the two chromosomes. Mutation results in alternation of DNA sequences and consequently results in change in the genotype and the phenotype of an organism. In addition to recombination, mutation is another phenomenon that leads to variation in DNA. Chemoheterotrophs were first organisms. They were prokaryotic like bacteria, anaerobes, as molecular oxygen was absent. They obtained energy by fermentation of some of the organic molecules present in the broth. Thus they absorbed organic molecules from outside for body building and energy. • Chemoautotrophs - Organisms that are capable to synthesize organic molecules from inorganic molecules. E.g., Nitrifying bacteria, sulphur reducing bacteria etc. • Autotrophs are photosynthesizing plants / organisms. The most significant trend in evolution of modern man (hom*o sapiens) from his ancestors is development of brain capacity.

Biology in Human Welfare

6 •

The strategies for enhancement in food production aim at – increasing the amount of food obtained from animals. – increasing the yield of agricultural crops.

Crop 1. Wheat

Variety Himgiri

Animal Husbandry •

2. Cauliflower Pusa snowball K-1 Black rot and curl Pusa shubra 3. Brassica Pusa Swarnim White rust (Karan rai)

Animal husbandry deals with the care, breeding & management of domesticated animals that are useful to humans.

Poultry Farming • •

Poultry is a rearing of domesticated fowls (chickens), ducks, geese, turkeys, guinea fowls and pigeons. Poultry birds exclusively grown for meat are called broilers, layers are for egg production, co*ckerel for young male fowls and rooster are mature male fowls.

4. Cowpea

Pusa Komal

Bacterial blight

5. Chilli

Pusa Sadabahar

Chilly mosaic virus, Tobacco mosaic virus and leaf curl.

Fisheries • •

Pisciculture is the rearing, breeding and catching of fishes. Aquaculture is rearing and management of useful aquatic plants and animals like fishes, oysters, mussels and prawns, etc.

Bee keeping or Apiculture • •

Apiculture is rearing and breeding of honeybees for the production of honey. The commonest species of honeybee is Apis indica.

Animal Breeding •

•

Animal breeding is the production of new breeds of domesticated animals with improved traits. – Inbreeding : Mating between the closely related animals of same breed. – Out-breeding : Mating between the animals which are not closely related. – Out-crossing : Mating between the animals of the same breed which do not have a common ancestor. – Cross-breeding : Mating between the superior animals of different breeds of the same species. MOET (Multiple Ovulation Embryo Transfer) technique is a programme which improves the chances of successful production of hybrids.

Plant Breeding •

Plant breeding refers to the modification and improvement of genetic material of plants resulting in the development of crops which are more beneficial to human beings.

Resistance to diseases Hill bunt & leaf and stripe rust

Table : Crop varieties bred by hybridization and selection for disease resistance to fungi, bacteria and viral disease. • Examples of insect pest resistance crops bred by hybridization are (i) Pusa Gaurav variety of Brassica is resistant to aphids. (ii) Pusa Sawani and Pusa A-4 varieties of Okra (Bhindi) are resistant to shoot and fruit borer. (iii) Pusa sem 2 and Pusa sem 3 varieties of flat bean are resistance to aphids and fruit borer.

Single Cell Protein (SCP) •

Single cell protein refers to the dried microbial cells or total protein extracted from pure microbial cell culture (algae, bacteria, yeasts and filamentous fungi) which can be used as food supplement to humans or animals.

Tissue Culture •

Plant cells and plant organs can be cultured in vitro (e.g., in test tube or any other container) on a suitable medium (e.g., agar medium), is called plant tissue culture. • A plant part excised from its original location and used for initiating a culture is known as explant. The explants, media, vessels and instruments used in tissue culture must be sterilised to make them free from any microbes. Microbes in Human Welfare • Microbes can be grown on culture nutritive media to form colonies which are used for mass production of certain desirable products and for scientific study of metabolism, genetics and structure of micro-organisms.

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• • •

•

Lactobacillus lacti : Milk fermentation Lactobacillus acidophilus : Cheese production Streptococcus thermophilus : Yoghurt production Streptokinase – Streptococcus Dissolution of blood clots Streptodornase Insulin, Interferon Recombinant DNA Human therapy variety of E. coli Baker’s yeast, beer, Saccharomyces Baking and wine, bread cerevisiae brewing industry SCP [single cell S. lipolytica Food protein] supplement Citric acid Aspergillus niger Food product preservative Invertase Mucor Preparation of adhesives, candy making Antibiotics are chemical substances, which are produced by some microbes and can kill or retard growth of other disease causing microbes. Alexander Flemming while working on Staphylococci plates observed that in one of unwashed culture plate, it could not grow because of chemical produced by mould Penicilliun notatum grown on it which produces chemical penicillin.

•

• • • • • • •

•

Microbes in Production of Biogas •

•

Produced by methanogens, which are anaerobic bacteria growing on cellulosic material and produce large amount of methane alongwith CO2 and H2 e.g., Methanococcus, Methanobacterium. Bt Cotton is genetically modified cotton having Bacillus thuringiensis genes. Bacterium Bacillus thuringiensis (Bt) is used as microbial control agent in order to control butterfly caterpillars.

Microbe as Biofertilisers • Rhizobium species in root nodules of leguminous plant. • Azospirillium and Azotobacter are free living species in soil. • Cyanobacteria such as Anabaena, Nostoc and Oscillatoria (autotrophic micorbes) in paddy field. Biotechnology • It deals with large scale production and marketing of products and processes using living organisms, cells or enzymes. • Examples of Biotechnology are GMO [Genetically modified organisms], IVF (in vitro fertilization), Test tube babies, DNA vaccines and gene therapy. • Genetic engineering can be defined as the generation of new combination of heritable material by the insertion of desired genes or DNA sequences, produced by whatever means outside the cell, into any carrier system so as to allow their incorporation into a host organism in which they do not normally occur but in which they are able to perform normal behaviour and propagation.

GENERAL SCIENCE Three techniques of genetic engineering are: (i) rDNA (recombinant DNA technology) (ii) Gene cloning/gene amplification (iii) Gene therapy Tools of (recombinant DNA technology) rDNA technology are (i) Vector – Plasmid, Bacteriophage, Cosmid, BAC, YAC (ii) Host – with Ori C [origin of replication] (iii) Restriction endonuclease – with well defined recognition site Vectors are cloning vehicles required to transfer DNA of interest from one organism to another. Plasmids are extra-chromosomal, circular, double stranded autonomously replicating sequence in bacterial cell. Bacteriophage is virus which infect bacteria. They have special sticky “cos” site to accept foreign DNA. Cosmid can be defined as the hybrid vectors derived from plasmids which contain cos site of phage 1. BAC (Bacterial Artificial Chromosome) : Episome + Foreign DNA. YAC (Yeast Artificial Chromosome) : Yeast DNA + Marker gene from competent bacteria. Marker sequences are the ones whose phenotype gives observable change, e.g., Tetracycline resistance gene, alcohol fermentation gene. Palindromic sequence are the ones which read same in one orientation on both the strands. For e.g., 5' — GAATTC — 3' 3' — CTTAAG — 5' is palindrome as it reads same on both strand in 5' ® 3' direction. Same is true for 3' ® 5' direction.

Restriction Enzymes • Enzymes that recognizes a specific sequence of double stranded DNA and cut the DNA at that site are called restriction enzymes. They are often referred as molecular scissors. • Restriction endonuclease was found by Arber in 1963 in bacteria. First was EcoRI found in colon bacterium Escherichia coli. Recognition sequence of EcoRI is 5' — GAATTC — 3'. • Agrobacterium tumefaciens is cloning vector for plants which is T-DNA (transforming DNA) to transform normal plant cell into tumour and direct them to form mass of cells called galls which start secreting chemical required by bacteria. Applications of Biotechnology are •

GM crop production

•

Transgenics

Animals Plants

• Therapeutics • Gene therapy • Molecular diagnosis GM Crop Production – Genetically Modified Crop (i) Purpose of introduction of GM crop was to minimise use of fertilisers and chemicals so that their harmful effect on environment could be reduced.

Biology in Human Welfare (iii) Examples GM crops are Bt cotton and Pest resistant plants. Bt cotton : It is a pest resistant plant which resist attack of Lepidopterans insects. The plant Bt toxin gene which cause death of insect larvae by causing cell lysis and swelling of epithelium of midgut. • Bt toxin is biologically produced by bacterium called Bacillus thuringiensis (Bt). This toxin is insecticidal protein crystal produced in bacteria (inactive form in bacteria) during a particular phase of growth. • Transgenic plants are organisms containing a foreign gene from a different species received by genetic engineering . • Examples of Transgenic plants are Transgenic plants Character introduced Flavr savr tomato Long shelf life Soyabean, corn Herbicide tolerance Brinjal, tomato Insect resistance Tobacco, potato Viral resistance Golden rice Rich in vitamin A

The animal husbandry deals with the care, breeding and management of (a) Domesticated animals (b) Fishes (c) Honey bees and silk worms (d) All of these Murrah, Mehsana, Jaffarbadi are breeds of (a) Buffalo (b) Cow (c) Cattle (d) Horse The most common species for bee-keeping in India is (a) Apis florae (b) Apis mellifera (c) Apis dorsata (d) Apis indica Blue revolution is related to the following field (a) Dairy products (b) Fisheries (c) Egg production (d) Agriculture Three crops that contribute maximum to global food grain production are (a) Wheat, rice and maize (b) Wheat, rice and barley (c) Wheat, maize and sorghum (d) Rice, maize and sorghum Jaya and Ratna developed for green revolution in India are the varieties of (a) maize (b) rice (c) wheat (d) bajra Yeast Saccharomyces cervisiae is used in the industrial production of (a) butanol (b) citric acid (c) tetracycline (d) ethanol Most of eubacterial antibiotics are obtained from (a) Rhizobium (b) Bacillus (c) Streptomyces (d) Cephalosporium

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Therapeutics Insulin production • Insulin is a hormone used for diabetics patient. • Insulin was extracted from pancreas of cattle, pigs in limited quantity. • PCR is a gene amplification technique that has found wide spread use in medicine & molecular biology. • ELISA is a laboratory test, which can quickly determine antigen or antibody levels in blood or other fluids. •

A single stranded DNA/RNA attached with radioactive molecule is called molecular probe. Molecular probe are used for detection of gene by complementary hybridising in cloned cell, followed by autoradiography.

Biopiracy • Biopiracy is use of bioresource by multinational companies and other organisation without proper authorization from countries and people concerned without compensatory payment.

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Which gas is responsible for the puffed-up appearance of dough ? (a) CO2 (b) O2 (c) SO2 (d) NO2 Streptokinase which is used as a ‘clot buster’ obtained from (a) Streptococcus (b) Staphylococcus (c) Lactobacillus (d) Saccharomyces Ganga and Yamuna action plan is initiated by (a) Ministry of environment and forest. (b) Ministry of agriculture. (c) Ministry of wild-life conservation. (d) None of these BOD refers to (a) Bacteria Oxygen Demand (b) Biochemical Oxygen Demand (c) Biochemical Operation Demand (d) Biological Organism Demand The technology of biogas production was developed in India mainly due to the efforts of (a) Indian Agricultural/ Research Institute (IARI) and Khadi and Village Industries Commission (KVIC) (b) National Botanical Research Institute (NBR1) (c) Indian Council of Medical Research (ICMR) (d) Indian Council of Agricultural Research (ICAR) Cheese and Yogurt are products obtained by (a) distillation (b) pasteurization (c) fermentation (d) dehydration Two microbes found to be very useful in genetic engineering are (a) Vibrio cholerae and a tailed bacteriophage (b) Diplococcus sp. and Pseudomonas sp. (c) Crown gall bacterium and Caenorhabditis elegans (d) Escherichia coli and Agrobacterium tumefaciens

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Domestication of honey bees is called (a) Sericulture (b) Apiculture (c) Tissue culture (d) Pisciculture Silk worm is a (a) fly (b) worm (c) moth (d) beetle Which one of the following statement is true? (a) The greater the BOD of waste water, more is its polluting potential. (b) The greater the BOD of waste water, less is its polluting potential. (c) The lesser the BOD of waste water, more is its polluting potential. (d) The lesser the BOD of waste water, less is its polluting potential. The example of non-renewable source of energy is (a) alcohol fuel (b) petroleum (c) biogas (d) fuel wood The term antibiotic was coined by (a) Alexander Flemming (b) S. Waksman (c) Louis Pasteur (d) Edward Jenner Important objective of biotechnology in agriculture section is (a) to produce pest resistant varieties of plant (b) to increase the nitrogen content (c) to decrease the seed number (d) to increase the plant weight Which of the following is the pair of biofertilizers? (a) Azolla and blue green algae (b) Nostoc and legume (c) Rhizobium and grasses (d) Salmonella and E. coli

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First cloned animal (a) Dolly sheep (b) Polly sheep (c) Molly sheep (d) Dog Which one of the following is not an antibiotic ? (a) Streptomycin (b) Citric acid (c) Griseofulvin (d) Cephalosporin Jatropha is a (a) biodiesel crop (b) biopetro crop (c) fibre crop (d) food crop IPM is (a) International Pest Management Programme. (b) International Pesticide Management Programme. (c) Integrated Pest Management Programme. (d) Internal Pest Management Programme. What are the advantage of gobar gas over conventional utilization? (a) More efficient source of energy (b) Used as good fertilizer (c) Reduces the chances of spreading of pathogens (d) All of the above Organic farming is the technique of raising crops through use of (a) Manures (b) Resistant varieties (c) Biofertilisers (d) All of these Chemically, the silk is (a) Cellulose (b) Resin (c) Protein (d) Lipid Biogas consists of (a) carbon monoxide, methane and hydrogen. (b) carbon dioxide, methane and hydrogen. (c) carbon monoxide, ethane and hydrogen. (d) carbon dioxide, ethane and hydrogen.

ANSWER KEY 16 (a) 17 (b) (a) 18 (c) 19 (d) 20

(b) (c) (a) (b) (b)

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(a) (a) (a) (b) (a)

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HINTS AND SOLUTIONS 5.

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(a) Three crops that contribute maximum to global food grain production are wheat, rice and maize, which belong to the family Poaceae (Graminae). (b) Jaya and Ratna are two rice varieties developed for green revolution in India. (d) Commercial ethanol or ethyl alcohol is produced by yeast Saccharomyces cerevisiae. (b) Bacillus subtilis is used to extract antibiotics substilin or Bacitracin.

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(d) Escherichia coli is a bacterium found in human colon. On this bacterium scientists have made extensive genetic experiments to make some vital chemicals like insulin. Another bacterium is Agrobacterium tumefaciens which causes crown gall in plants. It is extensively used for genetic experiments. (a) Jatropha is a genus of flowering plants in the spurge family, euphorbiaceae. Currently the oil from Jatropha curcas seeds is used for making biodiesel fuel in Phillippines and in Brazil.

Diseases and their Defence Mechanism

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Health is a state of complete physical, social and mental well being and not merely the absence of disease or infirmity.

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Disease is any condition which interferes with the normal structure and function of the body that is manifested by a characteristics sets of symptoms and sign.

DISEASE Communicable Bacterial Examples • T.B. • Diphtheria • Whooping cough • Typhoid • Cholera • Tetanus • Gonorrhoea • Syphilis

Viral Examples • Mumps • Measles • Chicken-pox • Small-pox • Rabies • Hepatitis • AIDS • Influenza • Polio

Protozoal Examples • Amoebiasis • Malaria

Non-communicable Cancers Diabetes Cardiovascular Diseases • Rheumatic heart diseases • Hypertensive diseases • Coronary heart diseases

Helminthic Chlamydial Examples Examples • Ascariasis • Trachoma • Taeniasis • Filariasis

Human genetic disorder Incompatible blood groups ® Rh incompatibility ® ABO incompatibility ® Recessively inherited disorder ® Dominantly inherited disorder

Bacterial Diseases • Typhoid : Typhoid is caused by Salmonella typhi. Typhoid spreads through food, milk and water contaminated with intestinal discharges either directly or through flies and personal hygiene. Typhoid is diagonsed with widal test. • Pneumonia : It is caused by Streptococcus pneumonia or Haemophilus influenza. It infects alveoli of lungs and spread by coughs, sneezes, by sharing drinking glasses and eating utensils with an infected person and contact with used tissue or handkerchiefs. Viral Diseases • Rhinoviruses causes one of the most infectious disease called common cold. Rhinovirus is spread from one person to another by hand to hand contact or from one person sneezing close by another person.

Chromosomal abnormalities ® Autosomal ® Sex chromosomal

Protozoan Diseases Malaria : It is caused by Plasmodium species & spread through female Anopheles mosquito. Primary host are female mosquito of genus Anopheles and humans acts as intermediate host. • Malaria result in anaemia, toxaemia and splenomegaly (enlarged spleen). • Plasmodium enters the human body as sporozoites (infectious form) through the bite of infected female Anopheles mosquito. Plasmodium sporozoites enters the bloodstream and travel to liver where they divide repeatedly & other attack the red blood cells resulting in their rupture. Amoebic Dysentery or Amoebiasis • It is caused by Entamoeba histolytica. It is a protozoan parasite in the large intestine of human.

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Helminthic Diseases Filariasis • Filariasis is caused by Wuchereria bancrofti. Fungal Diseases • Fungi causes diseases and these are known as mycosis. • Microsporum, Trichophyton and Epidermo-phyton are responsible for ringworms, which is characterized by appearance of dry scaly lesions of the skin, nails and scalps. Sexually Transmitted Diseases • Sexually transmitted diseases (STDs) are a group of communicable diseases that are transmitted mainly by sexual contact. STDs are caused by a wide range of bacterial, viral, protozoal and fungal agents. STDs Pathogen Syphilis Treponema pallidum (bacterium) Gonorrhoea Neisseria gonorrhoeae (bacterium) Vaginitis Candida albicans (fungus) AIDS Human immunodeficiency virus (virus) Diabetes mellitus • It is caused by the deficiency of insulin hormone and is characterized by excessive concentration of sugar in the blood and urine. Diabetes insipidus, on the other hand, is characterized by excessive urination, urine being sugar-free and is caused by the deficiency of ADH.

Cancer • •

Cancer is not inheritable. The non-regulated growth of the cells that accompanies cellular transformation produces tumours or neoplasms, each tumour being the product of proliferation of a single abnormal cell. • Tumours are of two types – benign and malignant. • Benign tumour cells is a large localized mass of abnormal tissue enclosed in connective tissue which does not spread to distant sites. • Malignant tumour cells are cancer cells that spread to and take up residence in neighbouring tissues - a condition called metastasis. • Agents that cause cancers are called carcinogens. UV radiations, smoking, mustard gas, soot, viruses, coal tar, aflatoxins and industrial pollutants are known to be carcinogenic. • Cancer can be detected by – biopsy and histopathological studies of the tissue. – blood and bone marrow tests for increased cell counts as in Leukaemia. – use of techniques like radiography, magnetic resonance imaging (MRI) and computed tomography (CT) for cancer of internal organs. Treatment of Cancer • Therapy used in the treatment of cancer are surgery, radiotherapy, chemotherapy, immuno-therapy, hormonal therapy, etc.

AIDS •

AIDS is caused by Human Immunodeficiency Virus (HIV) which is retrovirus.

GENERAL SCIENCE Life Cycle of HIV • The virus after getting into the body of a person, enters the macrophages. • The person becomes easily infected by bacteria like mycobacterium, viruses and even parasites like Toxoplasma. • The person is unable to protect himself/herself against any infection. • AIDS is diagnosed by ELISA (Enzyme Linked Immunosorbent Assay). Prevention of AIDS • World Health Organisation (WHO) has started a number of programmes to prevent spreading HIV infection; some such steps include : – ensuring use of disposable needles and syringes. – checking blood for HIV. – free distributions of condoms and advocating safe sex. – controlling drug abuse. – promoting regular check-up for HIV in susceptible populations, etc. • Treatment with anti-retroviral drugs is only partially effective; they can only prolong the life of the patient and cannot prevent death.

Immunity •

The term immunity refers to the specific resistance exhibited by the host towards infections by micro-organisms (pathogens) and their products. Innate or Natural Immunity • Innate immunity is developed in an individual without having the disease or immunization, e.g., recreation of sweat glands contain certain chemical substances which prevent the entry of micro-organisms. • It is present from birth. • It is the general defence of body including the following four mechanism — (i) Phagocytosis of invaders by leucocytes and macrophages (called cellular barrier). (ii) Resistance of skin to invading micro-organisms (called physical barrier). (iii) Destruction of micro-organisms swallowed with food by the HCl of gastric juice & by digestive enzymes and tear from eye (called physiological barriers). (iv) Virus infected cells secrete proteins (called interferons) which protect non-infected cells from further viral infection (cytokine barriers) Acquired Immunity • It is a third line defence and developed by an animal in response to a disease caused by infections of microbes. • The resistance against infectious disease that an individual acquires during life is known as acquired immunity. Antibody Mediated Immunity • B cells produce specialized proteins called antibodies (immunoglobulin) which are glycoproteins. Classification of Antibodies : (a) Ig A – Protects from inhaled or ingested pathogens. (b) Ig D – Present on lymphocyte surface as receptors, activation of B cells. (c) Ig E – Mediator in allergic response.

Diseases and their Defence Mechanism (d) Ig G – Stimulation of phagocytes and complement system, passive immunity to foetus. (e) Ig M – Activation of B cells.

Immunization • •

Inoculation of vaccines to prevent diseases is called immunization. Vaccines are preparations of living or killed micro-organisms or their products. Vaccines are of two types – live vaccines and killed vaccines.

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•

Genetic vaccines involve one or more genes from diseases carrying agent (pathogen) and splicing these gene into plasmids (closed rings of DNA). These rings are then delivered into small groups of cell, often by infection into muscle cells or by propulsion into via so called ‘gene gun’.

Allergy and Autoimmunity • •

Allergy is an important side effect of immunity. Autoimmune disease result when the immune system attack and destroys ‘self’ cells and molecules. Eg., rheumatoid arthritis.

Drugs and Alcohol Abuse Major groups of psychotrophic drugs, their examples and effects Types of drug 1. Sedatives and transquilizers (depressants) 2. Opiate narcotics

Examples Benzodiazephines (e.g. Valium), Barbiturates Opium, Morphine, Heroin, Penthidine, Methadone

3. Stimulants

Caffeine (very mild), Cocaine, Amphetamines

4. Hallucinogens

LSD, Marijuana, Charas, Bhang, Hashish

Vaccines are (a) treated bacteria or viruses or one of their proteins (b) MHC (major histocompatibility complex) proteins (c) curative medicines (d) monoclonal antibodies Which of the following is a sexually transmitted disease ? (a) Q fever (b) Leprosy (c) Whooping cough (d) Gonorrhoea Which of the following is a pair of viral diseases? (a) Common cold, AIDS (b) Dysentery, common cold (c) Typhoid, tuberculosis (d) Ringworm, AIDS Which of the following is most infectious disease? (a) Hepatitis - B (b) AIDS (c) Amoebiosis (d) Malaria The formation of antibodies within our body is called (a) active immuntiy (b) passive immunity (c) innate immunity (d) acquired immunity ‘Malaria’ a common disease world wide is caused by a (a) bacterium (b) virion (c) protozoa (d) fungi Which of the following diseases is due to an allergic reaction? (a) Goitre (b) Skin cancer (c) Hay fever (d) Enteric fever Which immunoglobin (Ig) is produced in primary immune response? (a) IgA (b) IgE (c) IgG (d) IgM

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Effects (i) Depress brain activity (ii) Produce feelings of calmness, relaxation, and drowsiness (i) Suppress brain function (ii) Relieve intense pain (iii) Causes loss of weight, sterility and lack of interest in work. (i) Stimulates the nervous system (ii) Make a person more wakeful (iii) Increase alertness and activity (iv) Produce excitement (i) Alter th oughts, feelings and perceptions.

Expand ELISA (a) Enzyme Linked Immuno - Sorbent Assay (b) Enzyme Linked Ion Sorbent Assay (c) Enzyme Linked Inductive Assay (d) None of the above Which one of the following is an Indian medicinal plant ? (a) Saccharum officinarum (b) Rauwolfia serpentina (c) Oryza sativa (d) Solanum melongena AIDS is caused by HIV that principally infects (a) all lymphocytes (b) activator B cells (c) cytotoxic T cells (d) T 4 lymphocytes Widal test is used for the diagnosis of (a) malaria (b) pneumonia (c) tuberculosis (d) typhoid Who invented vaccine for small pox ? (a) Robert Koch (b) Robert Hooke (c) Edward Jener (d) Louis Pasteur Which of the following diseases is also known as infantile paralysis? (a) Lock jaw (b) Rabies (c) Polio (d) Chicken pox Which of the following is not a communicable disease ? (a) Typhoid (b) Malaria (c) AIDS (d) Goitre

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GENERAL SCIENCE

Against which of the following does interferon act ? (a) Bacteria (b) Virus (c) Fungi (d) Snake venom Which of the following disease is a hormonal disorder ? (a) Anaemia (b) Cholera (c) Diabetes (d) Goitre AIDS day is (a) June 1 (b) May 1 (c) December 1 (d) December 20 Which one of the following pairs of disease can spread through blood transfusion? (a) Cholera and hepatitis (b) Hepatitis and AIDS (c) Diabetes mellitus and malaria (d) Hay fever and AIDS Which of the following diseases is caused by Protozoa ? (a) Chicken pox (b) Measles (c) Filariasis (d) Sleeping sickness Cancer of blood is called (a) Leukemia (b) Lymphoma (c) Sarcoma (d) Hybridoma DPT vaccine is given for (a) Tetanus, polio, plague (b) Diptheria, whooping cough and leprosy (c) Diptheria, pneumonia, tetanus (d) Diptheria, whooping cough, tetanus Which is an autoimmune disease? (a) Cancer (b) Asthma (c) Erythroblastosis foetalis (d) Rheumatoid arthritis The jaundice is a physiological liver disease. It is caused by a (a) Bacterium (b) Virus (c) Protozoan (d) Helminth A certain patient is suspected to be suffering from Acquired Immuno Deficiency Syndrome. Which diagnostic technique will you recommend for its detection? (a) ELISA (b) MRI (c) Ultra sound (d) Widal test Tobacco smoke contains carbon monoxide which (a) reduces the oxygen-carrying capacity of blood

(b) Causes gastric ulcers (c) Raises blood pressure (d) is carcinogenic In persons addicted to alcohol, the liver gets damaged because it (a) has to detoxify the alcohol (b) stores excess of glycogen (c) is over stimulated to secrete more bile (d) accumulates excess of fats Community health aims at (a) better health and family planning (b) better hygiene and clean environment (c) removing communicable diseases (d) All of the above Tuberculosis is caused by (a) Bacterium (b) Virus (c) Protozoan (d) Malnutrition ‘Plague’ is transmitted by (a) House fly (b) Tse-tse fly (c) Rat flea (d) Mosquito ‘Black death’ is related with (a) Plague (b) Cancer (c) Tuberculosis (d) Measles Cholera, leprosy and diptheria are (a) Bacteria diseases (b) Viral diseases (c) Fungal diseases (d) Functional diseases The group of diseases spread by houseflies is (a) Malaria, Cholera, Scabies (b) Rabies, Rickets, Diarrhoea (c) Typhoid, Dysentery, Tuberculosis (d) Ringworm, Scurvy, Vomiting Which of the following is a communicable disease? (a) Leucoderma (white patches on the skin) (b) Diabetes mellitus (c) Beri-beri (d) Dysentery Which scientist is credited with the development of medical vaccinations? (a) Robert Koch (b) Charles Darwin (c) Edward Jenner (d) William Harvey

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HINTS AND SOLUTIONS 1.

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(a) Vaccine contains dead, attenuated form or antigen of a pathogen which can be injected to provide immunity towards that pathogen. Monoclonal antibodies are hom*ogenous immunological reagents of defined specificity, so that these can be utilized for diagnosis and screening with certainty. (d) A common sexually transmitted disease most often affecting the genitourinary tract and occasionally, the pharynx, conjuctiva, or rectum. (a) We know that HBV causes serum hepatitis. It is most frequently transmitted by blood or by blood contaminated instruments. (c) Hay fever is due to some fungal spores sensitivity, which is an allergic disease with symptoms of bronchial asthma and skin rashes and also with increase in eosinophil (white cells) of blood. (b) Rauwolfia serpentina belong to family Apocynaceae, its roots yield a chemical useful for high blood pressure.

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(d) AIDS virus infects T4 lymphocytes (also called Helper cells). Cytotoxic T cells called T8 lymphocytes. (d) Widal test is used for the diagnosis of typhoid. It is an agglutination test for the presence of antibodies against the Salmonella organisms, which cause typhoid fever. (c) Edward Jenner is known as father of Immunology. (c) Polio results in paralysis of limbs in infants. (d) Goitre is caused due to deficiency of Iodine. (b) The host cell invaded by a virus produces an antiviral protein called interferon which prevents the viral multiplication. (c) Diabetes is caused due to increased glucose level in blood when insulin is not produced by pancreas in required amount. (d) Sleeping sickness is caused by Trypanosoma. (a) ELISA is an fundamental tool of clinical immunology and is used as an initial screen for HIV detection. (c) Edward Jenner was the first person to vaccinate people against disease.

8 • •

Ecology and Environment Awareness

The idea about ecology was first started by Reiter. The term ecology was given and defined by Haeckel as Ecology is the study of the interactions between the organism and their environment. • Population : The collection of individuals of a given species is called population. • Community : The interacting groups of populations of various species constitute a community. • Ecosystem : A biological community and the physical environment associated with its constitute ecosystem. • Biome : A major ecological community or complex of communities that extends over a large geographical area. • Species is a group of organisms that resembles each other more than they resemble to any other organism, and that can breed among themselves and produces fertile offspring. • Habitat : It is a specific place or locality where an organism lives. • Ecotone : It is the marginal vegetation present in between two well established habitat. • Environment : It is the sum total of physical and biotic conditions influencing the behaviour of the organism. • Atmosphere : The multilayered gaseous envelope. It is divided into 5 distinct layers troposphere, stratosphere, mesosphere, ionosphere & exosphere. Water Resource : It is the major component of the hydrosphere and covers about 3/4th of the earth’s surface. • Out of this 97% is sea water which cannot be used directly. Only 3% is fresh water. • Out of 3% about 77% is stored in ice caps, about 22.5% is ground water. Only about 0.5% is present in river & lakes which is available for direct use. • Aquatic animals which can tolerate only a narrow range of salinity are called stenohaline. • Aquatic organisms having wide range of salt tolerance are called euryhaline. Soil : Soil is a mixture of inorganic mineral particles derived from weathering of rock and organic matter consisting of humus. • On the basis of the size of particles, soil is of following types : (i) Clay - upto .062 mm (ii) Silt - .002 to .02 mm (iii) Fine sand - .02 to .2 mm (iv) Coarse sand - .2 to 2 mm (v) Fine gravel - 2 to 5 mm (vi) Coarse gravel - 5 and more • Population : It is the total number of individual of a particular species inhabiting a particular area at a particular time. • Demography : Study of population.

Population Characteristics (1) Population density : It is number of individuals per unit area of environment. (2) Natality : This is addition of individuals in a population due to birth. (3) Mortality : It is the rate of death of individuals in a given population. (4) Population Dispersion (i) Emigration - One way outward movement. (ii) Immigration - One way inward movement. (iii) Migration : It is a cyclical movement with respect to and weather that during life history of an animal at definite intervals, and always includes a return trip from where it began. (5) Age Structure : The proportion of individuals of various age group in a population forms the age structure. Pre reproductive > Reproductive > Post reproductive ® Expanding population Pre reproductive = Reproductive > Post reproductive ® Stable population Pre reproductive < Reproductive < Post reproductive ® Decline population. (6) Biotic Potential : The inherent maximum capacity of an organism to reproduce or increase in number is termed as biotic potential. Nature keeps a check on it. • Carrying Capacity : The maximum population size that can be supported by the environment is called carrying capacity. • Population growth : Current population – Initial population + Birth + Immigration – Death – Emigration. There are two main type of population growth forms (1) J - Shaped : The population values when plotted against time gives a J - shaped growth curve, and at the peak of the population, growth ceases abruptly due to environmental resistance. (2) Sigmoid or S-Shaped form : It shows an initial gradual increase in the population size and then it accelerates and finally slows to a nearly constant level.

Biological Interactions Amensalism : It is a relationship in which one species is harmed whereas the other is unaffected. Competition : It is best defined as a process in which the fitness of one species is significantly lower in the presence of another species.

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Parasitism : Parasitism is a relationship between two species in which one benefits on the host (harm) of the other. It is always an one side relationship for the parasite which is always benefitted from the host. Commensalism : The interaction in which one species benefits and the other is neither harmed nor benefited is known as commensalism. Mutualism : Mutualism interaction is a positive reciprocal relationship between two different species. Anabaena (a nitrogen fixing blue green alga) is associated with water fern Azolla. Predation : Predation is an interaction between members in which one population adversely affects the other by direct attack (capture, kill and eat) but is nevertheless dependent on other. The former is called predators & the latter is called prey Structure of Ecosystem A. Abiotic Components (a) Climatic conditions - Soil, temp, light, water. (b) Inorganic substances - Nitrogen, sulphur, phosphorus (c) Organic substances - Carbohydrate, protein, lipid. B. Biotic Components (a) Producers : The organism which produce their own food. Herbs, shrubs, tree, Phytoplanktons, etc. (b) Consumers : They are the phagocytic heterotrophs which depend for their nutrition on the organic manufactured by producers, the green plants. They are of following 3 types : (i) Herbivores (Primary Consumers) - These animals feed directly on living plants or plant remains. (ii) Carnivore order - 1 (Secondary Consumers) - These carnivores feed on herbivores, e.g. frog, fish. (iii) Carnivore order - 2 (Tertiary Consumers) - These are carnivores feeding on other carnivores. (Eagle feeding on snake) (c) Decomposers : They bring about the decomposition of dead organic matter of producers as well as consumers. They help in returning the mineral elements to the abiotic phase and help in continuing biogeochemical cycle, e.g. - bacteria, fungi. Productivity : The rate of production i.e. the amount of organic matter accumulated in any unit time. It is of following types : (A) Primary Productivity : The rate at which radiant energy is stored by producers. (i) Gross Primary Productivity - It refers to the total rate of photosynthesis including the organic matter used up in respiration. (ii) Net Primary Productivity - It is the rate of storage of organic matter in plant tissue in excess of the respiratory utilization. (B) Secondary Productivity : It is the rate of energy storage at consumer’s level - herbivores, carnivores & decomposers. (C) Net Productivity : It is the rate of storage of organic matter not used by heterotrophs or consumers, i.e. equivalent to net primary production minus consumption by the heterotrophs during unit period (year).

GENERAL SCIENCE

Energy Flow Food Chains : The pattern of eating & being eaten forms a linear chain called food chain, which can always be traced back to the producers. Each step of food chain is known as trophic level. (Plants - 1st trophic level) Producers ® Herbivores ® Small fish ® Large fish Plants ® Grasshopper ® Lizard ® Hawk Ecological Pyramids : Concept of ecological pyramid was given by Elton. • There occurs a regular pattern of change in the properties (like number, energy and biomass) of the organisms across different trophic level. It is the graphical representation of food chain. Types of Ecological Pyramid 1. Pyramid of Number - upright or inverted 2. Pyramid of Biomass - upright or inverted 3. Pyramid of energy - Always upright Lindeman’s ten percent law : The food chain efficiency is only 10% i.e. the organism at a particular trophic level consumes 90% of the total energy which it receives from the preceeding trophic level and passes only the 10% remaining energy to the next level.

Ecological Succession •

It includes a series of changes that a biotic community undergoes in maturation towards a stable or climax condition.

Types of Succession (1) Primary succession : If an area is colonized by organisms for the first time, the succession is called primary succession. Eg. - Newly exposed rock ; modified desert. (2) Secondary succession : If succession starts on the area previously colonized, but has been cleared off by some environmental force (fire, flood, lightening), it is called secondary succession. Eg. - forest devastated by fire. (3) Hydrarch : Succession which begins in water bodies like ponds. (4) Xerarch : Successions initiated on bare rocks, sand dunes, rocky slopes etc. where there is extreme scarcity of water, are termed as xerarch.

Biodiversity The sum total of all the species including plants, animals and micro-organisms on the earth. The 3 richest region of biodiversity in India are : (a) Western Ghats (b) North East (c) Kashmir. Levels of Biodiversity (1) Genetic Diversity : It refers to variations of genes within species. (2) Species Diversity : It refers to variety of species per unit area. (3) Community and ecosystem diversity : It has three perspectives (a) Alpha diversity : Diversity of organisms sharing the same community (intra community diversity). (b) Beta diversity : Diversity among the members of different communities. (inter community diversity).

Ecology and Environment Awareness (c) Gamma diversity : Diversity over the total landscape or geographical area. •

Biodiversity increases, as we move from high to low lattitude as (i.e., from poles to equator).

Causes of Loss of Biodiversity (i)

Natural extinction: Some species disappear and are replaced by other species when environmental conditions change. (ii) Mass extinction: Disappearance of large number of species because of some catastrophe. (iii) Anthropogenic extinction : Disappearance or extinction of species due to human activity. Conservation of Biodiversity

• There are 2 basic methods of biodiversity conservation: (i) In situ (on site) (ii) Ex situ (off site) In situ conservation • Example of protected areas are National Park, wild life sancturies and biosphere reserve. Ex situ conservation • Ex situ conservation includes botanical gardens, zoos, pollen seed, seedling, tissue culture and DNA banks. • Cryopreservation is an in vitro conservation technique by which vegetatively propagated crops like potato are preserved in liquid nitrogen at a temperature of –196°C. • IUCN and WWF are leading International Organisations concerned with biodiversity conservation. Sanctuaries and National Parks : A sanctuary or a National park may be defined as an area declared by state, for the purpose of protecting, propagating or developing wild life therein, or it’s natural environment for their scientific, educational & recreational value. Biosphere Reserves : Launched in 1975 as a part of UNESCO’s “Man & Biosphere” programme. They are special category of protected area wherein people are an integral component of the system. • It consists of 3 zones Transitional zone (Area of people settlement, cropping, etc.) Buffer zone (Human activity like research and educational activities allowed) Core zone (Undisturbed by human activity)

Pollution : It is an undersirable change in physical, chemical or biological characteristics of environment which adversely affects the biological species including Man. Waste products are of 2 categories (1) Biodegradable waste : These are such waste substances which are acted upon by microorganisms and broken into simpler components. E.g. - Most of the organic waste. (2) Non - biodegradable waste : These are such waste substances which are not acted upon by micro-organisms and remain in the same form for a long period of time. E.g. - Polythene, glass, DDT, etc.

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Air Pollution Imporrtant Air Pollutants and their Impact (1) SO2, H2S : Lichens are most sensitive to SO2. Eye irritation, destroys bronchial cilia. Causes acid rain thus decreasing the pH of soil. (2) Carbon Monoxide : Reduces O2 carrying capacity of blood by forming carboxy haemoglobin. (3) Nitrogen oxides : Collapse of leaves. Nitrogen oxides reacts with hydrocarbons like methane, ethane, toluene, etc. to form peroxyacetyl nitrate or PAN (C2H3O5N). Photochemical smog : The mixture of PAN with ozone and various organic radicals. (4) Ozone : NO2 ® NO + O, O2 + O ® O3. • Causes premature senescence in plants. • Damage pulmonary organ in animals. (5) Cadmium • Causes cancer of liver and lungs. • itai - itai (ouch ouch) disease (painful joints)

Water Pollution • •

•

The term water pollution refers to any type of aquatic contamination between the following 2 extremes A highly enriched, over productive biotic community, such as river or lake with nutrients from sewage or fertilizer (cultural eutrophication) or, A body of water poisoned by toxic chemicals which eliminate living organisms or even exclude all forms of life.

Causes of Water Pollution (1) Sewage (2) Industrial waste (3) Agrochemicals • Methaemoglobinuria or Blue baby syndrome : The surface run off water from agricultural fields contain high percentage of nitrates. When it enters the body of foetus, it reacts with the haemoglobin and forms methaemoglobin which has a highly reduced oxygen carrying capacity. • Excess of fluoride - causes skeletal fluorosis (teeth and skeletal deformity) • Arsenic - Black foot disease • Mercury - Minimata disease (numbness of limbs, lips and tongue) (4) Thermal pollution or Calefaction : • The source is the heat from thermal & nuclear power plants. • Gives thermal shocks which affect the aquatic life. Biological Magnification (Amplification) : It is the increase in the effect of any non degradable chemical as it passes on in the food chain. E.g. - Polychlorinated biophenyl, DDT. Biological (Biochemical) Oxygen Demand (BOD) : It is the measure of oxygen required by aerobic decomposers for biochemical degradation of organic materials (biodegradable) in water. This demand of oxygen is directly proportional to increasing input of organic wastes in water.

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GENERAL SCIENCE

Noise Pollution

Global Warming

•

Noise is an undesired sound. Sound pollution starts from 80 decibel. A constant exposure to noise level of 80 db causes : Mental irritation, Hypertension, Temporary deafness.

Organic farming • Integrated approach, a cyclical, zero waste procedure, where waste products from one process are cycled in as nutrients for other processes. This allows maximum utilization of resource and increases efficiency of production.

Ozone Depletion •

Radioactive wastes

•

This waste is generated as a result of generation of electricity from nuclear energy in nuclear reactors. Radiation emitted out by waste is lethal at high doses and cause mutation and genetic disorder at high doses which can be transmitted generation after generation.

•

Greenhouse gases such as CO2, CH4, N2 O and CFC’s present in atmosphere radiate part of radiowave radiations emitted by earth back to the earth. This downflux is called greenhouse flux which keeps the earth warm and phenomenon is called greenhouse effect.

Effect of Greenhouse Effect • Temperature of earth has increased by 0.6°C in last 3 decades. This increase in temperature is leading to deleterious change in environment and resulting in climatic changes (El Nino Effect), leading to increased melting of polar ice caps as well as of other places like Himalayas snow caps. • CO2 fertilization effect – Increase in the growth rate of plants in response to elevated concentrations of CO2 is known as carbondioxide fertilisation effect. Kyotoprotocol (1997) was signed to reduce the emission of green house gases. Under the protocol, industrialized countries as a whole will cut their overall CO2 emission by at least 5.2% below 1990 level.

Dobson unit is the unit for measurement of O3 level in stratosphere. – 1 DV = 0.1 mm of compressed O3 at NTP. – Normal O3 level should be greater than 400 DV.

Major O3 depleting substances

Greenhouse Effect and Global Warming •

The mean annual global temperature is 14oC. Any significant rise in this temperature is regarded as global warming. Major green house gases are CO2, Methane, Chlorofluorocarbons (refrigerators, sprays), Nitrous oxide (NO2).

• • •

Chlor ofluorocarbon (C 1 componen t destr oys O 3 ), Chloroform, CCl4, Methane, N2O (Nitrous oxide). – O3 layer protects life from harmful U.V. radiations. – 3 forms of U.V. radiations : (a) U.V. C - 100 nm to 280 nm – Completely absorbed by O3. (b) U.V. B - 280 nm to 315 nm – O3 layer transforms it into infrared. – Thinning of O3 layer leads to more penetration of U.V. B. Harmful impact of U.V. B : * Cataract * Skin Cancer (Melanoma) (c) U.V. A - 315 nm to 400 nm. – Reaches the surface of earth – harmless. Montreal protocol (1987) ® Stop use of ozone depleting substances. London protocol (1990) Chernobyl tragedy - Radioactive pollution - Russia.

Ecology and Environment Awareness

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The term 'Ecology' was coined by (a) Haeckel (b) Odum (c) Warming (d) Dudgeon The age of pyramid with broad base indicates (a) high percentage of young individuals (b) low percentage of young individuals (c) high percentage of old individuals (d) low percentage of old individuals Desert regions are characterized by ___ centimeters of rainfall per year. (a) less than 5 (b) less than 15 (c) less than 25 (d) over 50 Resemblance of one organism to another for protection and hiding is (a) Mimicry (b) Predation (c) Adaptation (d) Camouflage Which is not a part of atmosphere ? (a) Light (b) Temperature (c) Edaphic factor (d) Precipitation Human population growth ________. (a) has an S-shaped curve (b) is currently in a logistic phase (c) is currently exponential (d) has reached carrying capacity The term ‘precipitation’ includes (a) Rain (b) Hails (c) Snow (d) All forms of water that fall to the ground Interactions in which the consumer lives within the host and does slow damage to the host are referred to as (a) commensalism (b) parasitism (c) mutualism (d) competition An assocation between two individuals or population where both the benefitted and where neither can survive without the other is (a) Commensalism (b) Amensalism (c) Proto-cooperation (d) Mutualism Which most often limits the primary productivity of the ecosystem ? (a) Solar radiation/light (b) Oxygen (c) Consumers (d) Nitrogen Which of the following is the most stable ecosystem? (a) Mountain (b) Desert (c) Forest (d) Ocean Energy flow in an ecosystem is (a) unidirectional (b) bidirectional (c) multidirectional (d) All of these Which one is nature's cleaner ? (a) Consumers (b) Producers (c) Decomposers and scavengers (d) Symbionts Who is referred to as the farmer’s friend ? (a) Ant (b) Sparrow (c) Earthworm (d) Rabbit

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15. 16.

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How much portion of the PAR is captured by the plants? (a) 5 – 10% (b) 7 – 10% (c) 8 – 10% (d) 2 – 10% The animals which occupy the same trophic level are (a) Lion & Bees (b) Deer & Bees (c) Snakes & Earthworm (d) Crow & Cow In simple ecosystem with grass, deer and tiger in food chain, how much amount of food available to the tiger if the grass production is one tonne ? (a) 100 kg (b) 10 kg (c) 1 kg (d) 100 gm In a food chain herbivores/deer are (a) Primary producers (b) Primary consumers (c) Secondary consumers (d) Decomposers 10% law of flow of energy in ecosystem was proposed by (a) Lindeman (b) Carl Mobius (c) Tansley (d) Darwin More than 70% of world’s freshwater is contained in (a) polar ice (b) glaciers and mountains (c) antarctica (d) greenland Which one of the following animals may occupy more than one trophic levels in the same ecosystem at the same time? (a) Sparrow (b) Lion (c) Goat (d) Frog Which one of the following is not a gaseous biogeochemical cycle in ecosystem ? (a) Sulphur cycle (b) Phosphorus cycle (c) Nitrogen cycle (d) Carbon cycle Which of the following animal has become almost extinct in India ? (a) Wolf (b) Rhinoceros (c) Hippopotamus (d) Cheetah Diversity of habitat over the total landscape is called (a) b diversity (b) g diveristy (gamma) (c) landscape diversity (d) ecosystem diversity Habitat loss and fragmentation, over exploitation, alien species invasion and co-extinction are causes for (a) Population explosion (b) Migration (c) Biodiversity loss (d) Pollution Which Biosphere reserve known as "Valley of Flower" ? (a) Nilgiri (b) Sunderbans (c) Uttarakhand (d) Nokrek Plant genes of endangered species are stored in (a) gene library (b) gene bank (c) herbarium (d) None of these Which National park is the new home of the Indian onehorned rhinoceros ? (a) Dudhwa (b) Jim Corbett (c) Kanha (d) Bandhavgarh 'Project Tiger' in India was started in (a) 1970 (b) 1972 (c) 1981 (d) 1985

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Which one of the following is an example of Ex-situ conservation? (a) Wildlife sanctuary (b) Seed bank (c) Sacred groves (d) National park Which one of the following areas in India, is a hot spot of0 biodiversity ? (a) Eastern Ghats (b) Gangetic Plain (c) Sunderbans (d) Western Ghats Noise pollution is created if noise is in excess to – (a) 70-75 dB (b) 50-60 dB (c) 80-99 dB (d) 40-65 dB Which of the following is most harmful pollutant ? (a) NO2 (b) CO2 (c) SO2 (d) CO Volcano is _____________ source of pollution. (a) artificial (b) natural (c) Both (a) and (b) (d) man-made Ozone layer is formed in which zone of atmosphere (a) Mesosphere (b) Stratosphere (c) Troposphere (d) Ionosphere Today the concentration of green house gases is very high because of (a) use of refrigerator 1 2 3 4 5 6 7 8 9 10

(a) (a) (c) (a) (c) (c) (d) (b) (d) (a)

11 12 13 14 15 16 17 18 19 20

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GENERAL SCIENCE (b) increased combustion of oils and coal (b) deforestation (d) All of the above Green house gases include (a) CO2, CFC, CH4 and NO2 (b) CO2, O2, N2, NO2 and NH3 (c) CH4, N2, CO2 and NH3 (d) CFC, CO2, NH3 and N2 Acid rain is caused due to increase in concentration of (in atmosphere) (a) SO2 and NO2 (b) CO and CO2 (c) CO and SO3 (d) O3 and dust Deforestation causes (a) soil erosion (b) loss of biodiversity (c) disturbance in hydrological cycle (d) All of the above Which constituent of the atmosphere is likely to change if the forest cover is removed ? (a) O2 level is increased (b) CO2 level is increased (c) O2 level is significantly increases (d) CO2 level is significantly decreased

ANSWER KEY (d) 21 (a) 22 (c) 23 (c) 24 (d) 25 (d) 26 (b) 27 (b) 28 (a) 29 (a) 30

(a) (b) (d) (b) (c) (a) (b) (a) (b) (b)

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(d) (c) (c) (b) (b) (d) (a) (a) (d) (b)

HINTS AND SOLUTIONS 3. 5. 6. 8. 11. 19. 20.

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(c) Deserts have less than 25 centimeters of rainfall per year. (c) Because edaphic factors affects through soil and rest are the climatic factors. (c) The exponential growth model virtually describes the population explosion of humans. (b) This is the classic definition of a parasitic interaction. (d) 2/3 parts of each is ocean here, various types of food chains form food webs. This ecosystem is most stable due to buffering action of water. (a) Lindeman proposed the 10% law of flow of energy in ecosystem. According to this law only 10% energy passed from one trophic level to other in a food chain. (a) Three fourth surface of earth is covered by oceans which contain 97.5% of total water. It is marine water with about 3.5% salt content only 2.5% is fresh water which occurs on land. Most of this water (1.97%) occurs as frozen ice caps and glaciers, 0.5% fresh water occurs as ground water. Rivers and lakes contain 0.02%, soil 0.01% while atmosphere possesses 0.001% of water as vapours. (a) It feeds upon grains hence called primary consumer and can also feed on insects hence called secondary consumer at the same time in the same ecosystem.

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(b) Phosphorus is mostly used as phosphate. Its reservoir pool is phosphate rocks while cycling pool is soil for terrestrial ecosystems and water for aquatic ecosystems. (b) Plant genes of endangered species are stored in gene bank which is a collection of cloned DNA fragments representing the entire material of an organism. (b) Ex-situ conservation is the conservation of selected organism in places outside their natural homes. They include off site collection and gene banks. In situ conservation, on the other hand, is the conservation of endangered species in their natural habitat. Biosphere reserves, National parks, Wildlife sanctuaries and sacred groves all are examples of In situ conservation. (d) Hotspots are the geographical area where biodiversity is maximum. Two hot spots in India are Western Ghats and North eastern himlayan region. (a) The main precursors of acid rain are SO2 and NO2 in atmosphere which form H2SO4 (Sulphuric acid) and HNO3 (nitric acid) with H2O and these come down with rain. Such rains are called acid rains.

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References