CBSE Class 9 Chemistry Matter In Our Surrounding Worksheet

Question. Which of the following has highest kinetic energy?
(a) Particles of ice at o ·c
(b) Particles of water at 0 ·c
(c) Particles of water at 100 ·c
(d) Particles of steam at 100 ·c

Exam Questions NCERT Class 9 Science Chapter 1 Matter in Our Surroundings

Question State the effect of pressure on boiling point.
Answer : Boiling point increases with increase in pressure.

Question. Name any two substances which sublime.
Answer : Camphor and naphthalene.

Question Define condensation.
Answer : The change of solid state from liquid state on cooling

Question Which is the slow process, evaporation or boiling?
Answer : Evaporation.

Question. What is the effect of surface area on rate of evaporation?
Answer : If the surface area is increased, the rate of evaporation increases.

Question A karate expert can easily move his hand through a solid block of wood but we cannot. Why?
Answer : In a solid block of wood, the inter-particle forces are very strong and hence, it is not easy to separate the particles. Therefore, it is not easy to move our hand through a solid block of wood, only a karate expert can do it as he has expertise in this.

Question What is latent heat of fusion?
Answer : The heat required to change 1 kg of a solid substance into liquid state at the melting point of the substance.
For example : Amount of heat required to melt ice at 0°C into water, at 0°C will be known as the latent heat of fusion of ice.

Question. Express the boiling point of water in Celsius as well as Kelvin scale.
Ans : 100°C and 373 K.

Question. What do you mean by latent heat of vaporization?
Ans : The latent heat of vaporization of a liquid is the quantity of heat in joules required to convert 1 kilogram of the liquid to vapour or gas at its boiling point, without any change in temperature.

Question. What property of gas is used when natural gas is supplied for vehicles?
Ans : A gas is highly compressible and a large quantity of it can be compressed to a small, manageable volume. Thus, natural gas is compressed and is supplied for use by vehicles in the name of CNG (compressed natural gas).

Question. How is pressure developed in a container full of a gas?
Ans : The gaseous particles are free to move in the container. These move at high speed and collide with other particles of the container. The bombardment of the particles on the walls of the container produces a steady force that depends on the temperature. This force per unit area is called as pressure of the gas.

Question. Why evaporation is called surface phenomenon?
Ans : Evaporation is called surface phenomenon as evaporation occur on the surface of liquid.

Question Name two processes from which it may be concluded that the particles of a gas move continuously.
Ans : Compressibility and Brownian movement.

Question Is it not proper to regard the gaseous state of ammonia as vapours? Explain.
Ans :The gaseous state of a substance can be regarded as vapours only in case it is a liquid at room temperature.
Since ammonia is a gas at room temperature, its gaseous state cannot be regarded as vapours. Naphthalene is volatile solid and has a tendency to sublime. So, it changes into vapours completely, thus disappear into the air and no solid is left.

Question. State characteristics of matter demonstrated by :
(i) Diffusion.
(ii) Brownian motion.
Ans : (i) Diffusion involves movement of different particles so that they become intermixed uniformly.
(ii) Brownian motion : It is the zig-zag movement of the small particles suspended in a liquid or a gas.

Question Write the SI unit of temperature?
Ans : Kelvin.

Question. Why is Kelvin scale of temperature regarded as better scale than Celsius?
Ans : As it has wide range of measurement and Kelvin scale of temperature has always positive sign, hence regarded as better scale than Celsius. Kelvin is an absolute thermodynamics scale, which uses its null point as the temperature at which all thermal motion ceases to exist.

Question. What is compressibility? How it is negligible in solids?
Ans : Compressibility is the ability of a substance to be reduced to its volume under pressure. Solids are incompressible as their particles are held together. So, we can tell that compressibility is negligible in solids.

Question. Two cubes of ice are pressed hard between two palms and after releasing the pressure, the cubes join  together. Why?
Ans : Pressure is directly proportional to temperature when we apply pressure, temperature increases then the ice in contact melts and it turns into water. When pressure is removed, the temperature decreases again and melted ice again freezes. Hence, cubes join together.
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Question Convert 10°C into Kelvin scale.
Ans : 273 + 10 = 283 K

Question. Does solid ice and liquid water co-exist together? If yes, then at what temperature?
Ans : At 0°C, the three phases of water co-exist called triple point.

Question What is the reason that “Ice has lower density than water”?
Ans : The mass per unit volume of a substance is called density (density = mass/volume). The density of substance decreases as the volume of a substance increases. Space between particles increases when water changes into ice. These spaces are larger as compared to the spaces present between the particles of water. Thus, the volume of ice become greater
as compared to the water. Hence, the density of ice ecome lower than that of water. And, a substance with lower density than water can float on water. Thus, ice floats on water.

Question. Why does the temperature remain constant during the change of state, for any substance?
Ans : On increasing the temperature of solids, the kinetic energy of the particles increases which is used up in changing the state as it overcome the forces of attraction between the particles, therefore, the temperature remains constant during the change of state.

Question What is common among the three states of matter?
Ans : They all contain molecules.

Question. Which property of gas is used in supplying oxygen cylinders to hospitals?
Ans : Compressibility.

Question. Both the process of evaporation and boiling involves he change of state from liquid to gas but still they are different from each other. Justify.
Ans : Evaporation is different from boiling as evaporation is a natural phenomenon, occurs on the surface of the water and also it is a slow process, whereas boiling is an artificial phenomenon, it occurs in the bulk of the liquid and is a fast process.

Question. How can you show that evaporation causes cooling?
Ans : When we put some acetone on our hand, after some time we will feel coolness on our hand because the acetone absorbs kinetic energy from our hand and evaporates and evaporation causes cooling.

Question A substance x is highly compressible and could easilybe liquefied. It can also take the shape of the container.
Guess the nature of the substance.
Ans : Gas.

Question What is plasma?
Ans : Plasma is a state of matter consisting of super excited particles of very high energy level.

Question. Camphor disapperars without leaving any residue. Explain? 
Answer : Camphor disappears without leaving any residue because of sublimation, as it changes its state directly fromsolid to gas without changing to liquid.

Question. Why do we feel cool when we touch a piece of ice?
Answer : We feel cool because the temperature of ice is 0 deg C and our body's temp is higher than 0 deg C.

Question. Convert the following:

a) 573 K
Answer : 573-273= 300 deg

b) 36 deg C
Answer : 273+36 = 309 K

c) 373 deg C
Answer : 373+273= 646 K

Question. Both the process of evaporation and boiling involves the change of state fromliquid to gas but still they are different from each other. Justify.
Answer : Evaporation is different fromboiling as evaporation is a natural phenomenon, occurs on the surface of the water and also it is a slow process whereas boiling is an artificial phenomenon , it occurs in the bulk of liquid and is a fast process

Question. Why is Kelvin considered as the best scale for measuring the temperature?
Answer : Kelvin is the best scale for measuring the temperature because it has no max temp. and it can measure temperature to any extent.

Question. How can you show that evaporation causes cooling?
Answer : When we put some acetone on our hand , after sometime we will feel coolness on our hand because the action absorbs kinetic energy fromour hand & evaporates and evaporation causes cooling.

Question. What is the significance of boiling point & melting point of a substance?
Answer : The significance of boiling point and melting point is that it shows the purity of the substance.

Question. When we put CuSO₄ in water, after sometime we find the soln. turns blue.Why? Also, on heating it what change will occur?
Answer : The solution turns blue because of diffusion. On heating the solution nothing will happen.

Question. How can you justify that table is a solid?
Answer : When we apply force on the table it doesn't change its shape because its intermolecules are tightly packed , this shows that table is solid.

Question. Arrange the following in decreasing order of force of attraction:Water, Salt, Oxygen, Also, state the reason.
Answer : Salt,Water, Oxygen Salt has themaximum force of attraction as it is a solid, followed by water as it is a liquid. Oxygen is a gas so its force of attraction is the least. 

Question. State characteristics of matter demonstrated by :
a) diffusion
b) Brownian motion
Answer : a. Diffusion involves movement of different particles so that they become intermixed uniformly .
b. It is the zig-zagmovements of the small particles suspended in a liquid in a liquid or a gas.

Question. When an incense stick (agarbatti) is lighted in one corner of a room, its fragrance spreads in the whole room quickly .Which characteristic of the particles of matter is illustrated by this observation?
Answer : Particles of matter are constantlymoving.

Question. The boiling point of alcohol isn 78 deg C.What is this temperature on Kelvin scale?
Answer : K= Deg C + 273 = 78 + 273 = 351 K

Question. The Kelvin scale temperature is 0 K.What is the corresponding Celsius scale temperature?
Answer : -273 degree Celsius.

Question. What is Latent Heat of Fusion?
Answer : The latent heat of fusion (or melting) of a solid is the q uanity of heat in joules required to convert 1 kilogram of the solid (at its melting point ) to liquid, without any change in temperature.

Question. Define latent heat of Vaporisation?
Answer : The latent heat of vaporisation of a liquid is the quantity of heat in joules required to convert 1 kilogram of the liquid (at its boiling point ) to vapour or gas, without any change in temperature.

Exam Questions NCERT Class 9 Science Chapter 1 Matter in Our Surroundings

Question. Give state of a matter if this substance has neither a fixed shape nor a fixed volume.
Answer : Gas.

Question. Why cannot you smell its perfume at a short distance when incense stick is not lighted?
Answer : The particles of the perfume (matter) do not have sufficient energy to drift through the air. Thus, we cannot smell it at a few steps away from incense stick.

Question. Why a rubber band is considered as a solid?
Answer : We can regard rubber band as a solid, because it regains its shape when the stretching force is removed from it.

Question. Predict the physical state of melting point of a substance is below the room temperature.
Answer : Ice.

Question. What do you mean by vapour?
Answer : A substance that is found in gaseous state only at room temperature is called vapour.

Question. Why is the smell of the perfume of incense stick filled the whole room in few minutes, when lighted?
Answer : When the incense stick is lighted, the heat energy makes the particles of the perfume to move rapidly.
Thus, they easily drift through the air in the room and hence, we can smell it anywhere in the room.

Question. What do you observe when force is applied and then removed on the plunger of the syringe containing air? Give a reason for your answer.
Answer : The plunger moves downward on the application of force to a considerable length. The plunger move backward and takes its original position when the force is removed.
The gases have large intermolecular spaces. So, they easily get compressed on the application of force.
The compressed gases are under high pressure. When the force is removed, this high pressure forces the plunger back to its original position.

Question The Kelvin scale temperature is 0 K. What is the corresponding Celsius scale temperature?
Ans : –273°C

Question. How is the high compressibility property of gas useful to us?
Ans : The gases have high compressibility. This property is used in the following situation :
(i) LPG (Liquefied Petroleum Gas) is a fuel which is made up of petroleum gas. On compressing this petroleum gas it forms liquid.
(ii) Oxygen cylinders in the hospitals have compressed gas filled in it.
(iii) CNG (Compressed Natural Gas) is a natural gas i.e. methane, which is compressed and used as a fuel in vehicles and at home.

Question With the help of an example, explain how diffusion of gases in water is essential?
Ans : The gases from the atmosphere diffuse and dissolve in water. Diffused gases like oxygen and carbon dioxide in water are essential for the survival of aquatic
animals and plants. Animals breathe in this oxygen dissolved in water for their survival and plants can use carbon dioxide dissolved in water for photosynthesis.

Question Is it true to say that fluorescent tube contains plasma? Explain
Ans : It is right to say that fluorescent tube contains plasma. As fluorescent tube has helium or some other rare gas. The particles of the gas get ionized in the presence of high voltage applied. These charged particles are called plasma which glows.

Question A rubber band is a solid, but it can change its shape. Why?
Ans : A rubber band changes shape under force and regains the shape when the force is removed, this is due to less intermolecular force of attraction between the particles.

Question. We can get the smell of perfume sitting several metres away, why?
Ans : This is because perfumes diffuse very fast and can reach to people sitting several metres away.

Question When salt or sugar is poured into different kinds of vessels, why do they take the shape of vessel as they are solid?
Ans : Salt or sugar takes the shape of containing vessel, but does not change its individual shape. For example : Sugar crystal is cubical and they remain cubical in any vessel.

Question. What is dry ice?
Ans : Solid carbon dioxide obtained by cooling and applying pressure on carbon dioxide gas. It does not melt so it is called dry ice.

Question What happens to the rate of diffusion if the temperature is increased?
Ans : With increased temperature, the rate of diffusion also increases as the particles gain energy and vibrate more.

Question Liquids and gases can be compressed but it is difficult  to compress solids. Why?
Ans : Liquids and gases have intermolecular space; on applying pressure externally on them the molecules can come closer thereby minimizing the space between them. But in case of solids, there is no intermolecular space to do so.

Question A balloon when kept in Sun, bursts after some time. Why?
Ans : The balloon has air filled in it. The balloon when kept in Sun gets heated and the air inside it also gets heated. The molecules of air get energy, and vibrate faster thereby exerting large force on the walls of the balloon. Due to this expansion of gases the balloon bursts.

Question Define melting point.
Ans : The temperature at which a solid melts to become liquid at the atmospheric pressure is called its melting point.

Question. Define matter.
Ans : Anything that occupies space and has mass and is felt by senses is called matter.

Question Why do people perspire a lot on a hot humid day?
Ans : On a hot humid day, due to the heat our body starts sweating and gives cooling effect by evaporation. But the air cannot hold any more water on a humid day and therefore, the sweat or perspiration is seen.

Question Why is it advisable to use pressure cooker at higher altitudes?
Ans : At higher altitudes, the atmosphere pressure is low and the water boils very fast and evaporates at faster rate, therefore, the pressure is required to increase the cooking process and this is done by using pressure cooker which increases the pressure inside the container and cooks food faster.

Question What happens if you put copper sulphate crystals in water?
Ans : Copper sulphate crystals mixed between the spaces of molecules of water and disappear.

Matter in Our Surroundings

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1. Which state of matter is characterized by the following properties :
(0 A substance with a fixed arrangement of particles.
(I'O A substance that has large distances between the particles.

2. Why the states of matter differ?

3. Define melting point.

4. Inspite of being solid a sponge is compressible. Comment.

5. What produces more severe burns, boiling water or steam?

6. Arrange the following substances in increasing order of force of attraction between the particles - water, sugar, and oxygen.

7. Suggest a method to liquify atmospheric gases.

8. Arrange the particles of the three states of matter in order of increasing randomness.

9.What is the name of the process due to which dry ice changes into carbon dioxide gas ?

10. Name the process which describes the mixing of copper sulphate crystals and water kept in a beaker on its own ?

11. Even two-three crystals of potassium permanganate can impart colour to a large volume of water. Which characteristic property of particles of matter is illustrated by this observation ? 1

12. Why do we call sponge a solid when it is easily compressible ?

13. Define latent heat of vaporization ?

14. On blowing air into a balloon, it inflates. Explain why ?

15. Define evaporation.

16. Give one example of diffusion of gases in a liquid
(A) A - iv, B - i, C - ii, D - iii
(B) A - i, B - ii, C - iii, D - iv
(C) A - ii, B - iii, C - iv, D - i
(D) A - iv, B - i, C - iii, D - ii

17. Explain how the general property/characterstics of the matter changes in accordance with it's different states.(Write any 5 properties).

18. (a) What do you mean by liquefaction ?
Discuss different ways by which liquefaction be achieved ?
(b) How will you demonstrate that particles of matter are constantly moving ? Give two examples.

19. Choose the false statement:
(A) Liquids have definite volume but no definite shape
(B) Gases are more compressible than liquids
(C) Rate of diffusion is highest in liquids
(D) Increase in pressure changes liquids to solids

20. Name the chemical present in nail polish remover that evaporates quickly to give cooling effect.

21. Which of the following does not affect evaporation?
(A) Surface area
(B) Humidity
(C) Pressure
(D) Temperature

22. What is dry ice ? How is it prepared ?

23. Name two gases which are supplied in compressed form in names and hospitals

24. Why does our palm feel cold when some ice is put on it ?

25. Name the process by which a drop of ink spreads in a beaker of water?

26. What happens to kinetic energy of molecules on heating?

27. A diver is able to cut through water in a swimming pool. Which property of matter does this observation show?

28. The mass per unit volume of substance is called density. Arrange in order of increasing density. exhaust from chimneys,Air ,cotton,Iron, water , honey , chalk.

29. What is the physical state of water at?
(a) 25oc
(b) 100oc

30. Write the full form of L.P.G. & C.N.G.

31. When sugar is dissolved in water, there is no increase in the volume.Which characteristic of matter is illustrated by this observation

32. Which of following statement is true?
(A) Energy of particles in steam at 373 K > Energy of particles in water at 373K
(B) Energy of particles in steam at 373 K < Energy of particles in water at 373 K
(C) Energy of particles in steam at 373 K = Energy of particles in water at 373 K
(D) None of these

33. Define humidity.

34. A liquid is different from a solid in that it has
(A) A definite shape.
(B) A definite volume.
(C) No definite shape.
(D) No definite volume.

35. Define matter.

36. Rate of evaporation is highest in
(A) An open vessel of diameter 25 cm.
(B) An open vessel of diameter 30 cm.
(C) An open vessel of diameter 27.5 cm.
(D) An open vessel of radius 25 cm.

37. Write the value of normal atmospheric pressure?

38. Which of the following statements is false?
(A) The states of matter are inter-convertible.
(B) Evaporation is a surface phenomenon.
(C) Kinetic energy of the particles is minimum in case of solids.
(D) The arrangement of particles is most ordered in the case of liquids.

39. Which of the following sublimes on heating?
(A) Ice
(B) Dry ice
(C) Both (1) and (2)
(D) None of these

40. State of matter consists of super energetic and super excited particles in the form of ionized gases?
(A) Solid
(B) Liquid
(C) Plasma
(D) Bose Einstein Condensate

41. On heating temperature of the system does not change
(A) After the melting point is reached, till the entire solid melts.
(B) Before the melting point is reached, till all of the solid melts.
(C) Till solid completely changes into vapour.
(D) When thermometer is faulty.

42. Anne filled 1L of air in jar of capacity 750 ml. What is the Volume of air in jar ?

43. Which of the following will diffuse faster?
(A) A drop of ink in water.
(B) Oxygen in nitrogen.
(C) Milk in water.
(D) Sugar in salt.

44.

What can X represent?
(A)Water
(B) Ice
(C) Oxygen
(D) Steam

45. What type of clothes are comfortable for us in summer?

46. Which is more effective in cooling?
(A) Water at 0°C
(B) Water at 100°C
(C) Ice at 0°C
(D) All of these

47. Melting points of four solids A, B, C & D are 773°C, 826°C, 932K and 1238°C respectively.
Which of these has strongest force of attraction between its particles?

48. A rubber band changes its shape when stretched. Can it be regarded as solid?

49. What are the factors on which evaporation depends?

50. Define diffusion.

51. Evaporation
(A) Makes the surrounding cold.
(B) Makes the surrounding hot.
(C) Does not affect the surroundings.
(D) Makes the surrounding sometimes cold and sometimes hot.

52. What are volatile liquids?

53. Arrange the particles of the three states of matter in order of increasing randomness.

54. A certain substance 'A' cannot be compressed but takes up the shape ofany container in which it is placed. What is the physical state of "A"?

55. Which state of matter is characterized by the following properties :
(0 A substance with a fixed arrangement of particles.
(I'O A substance that has large distances between the particles.

56. Why does our palm feel cold when some ice is put on it ?

57. What is dry ice ? How is it prepared ?

58. Define latent heat of vaporization ?

59. Why do we call sponge a solid when it is easily compressible ?

60. Even two-three crystals of potassium permanganate can impart colour to a large volume of water. Which characteristic property of particles of matter is illustrated by this observation ?

61. Name the process which describes the mixing of copper sulphate crystals and water kept in a beaker on its own ?

62. What is the name of the process due to which dry ice changes into carbon dioxide gas ?

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63. For any substance, why does the temperature remain constant during, the change of state?

64. What are the factors, that determine the state of a substance?

65. Why does our palm feel cold when we put some acetone, petrol or perfume on it?

66. How does evaporation cause cooling?

67. What is the cause of evaporation?

68. Liquids generally have lower density as compared to solids. But ice floats on water. Why?

69. Why do solids generally lack the property of diffusion?

70. How will you demonstrate that air contains water vapours?

71. How are freeze-dried foods prepared ? How do they remain preserved for long periods ?

72. Explain why steam at 100°C is more effective for heating purposes than boiling water at 100°C.

73. How are freeze-dried foods prepared ? How do they remain preserved for long periods ?

74. Why does ice not deposit in the ice chamber of a refrigerator equipped with defrosttechnique ? Explain.

75. How will you demonstrate that water vapours are present in air ?

76. Explain why does not the temperature change during change of state from solid to liquid ?

77. Set up a relation between absolute temperature scale and Fahrenheit temperature scale.

78. Why are we able to sip hot tea or milk faster from a saucer rather than a cup?

79. Explain why steam at 100°C is more effective for heating purposes than boiling water at 100°C.

80. Can matter change its state? State the conditions under which it changes.

81. Why does ice not deposit in the ice chamber of a refrigerator equipped with defrosttechnique ? Explain.

82. How will you demonstrate that water vapours are present in air ?

83. Explain why does not the temperature change during change of state from solid to liquid ?

84. Set up a relation between absolute temperature scale and Fahrenheit temperature scale.

85. Give reasons for -
The smell of hot sizzling food reaches you several meters away, but to get the smell from cold food you have to go close.

86. Convert the following temperatures into the Kelvin scale.
(a) 250c
(b) 3730c

87. What is the physical state of water at?
a) 25oc
b) 0oc
c) 100oc

88. What type of clothes should we wear in summer? Why?

89. How does the water kept in an earthen pot (matka) become cool during summer?

90. Why does a desert cooler cool better on a hot dry day?

91. Convert the following temperature to Celsius scale:
(a) 300 k
(b) 573 k.

92. Why is ice at 273k is more effective in cooling than water at same temperature?

93. What is dry ice? Why it is known so?

94. Why do we see water droplets on the outer surface of a glass containing ice-cold water?

95. Give reasons.
a. Naphthalene balls disappear with time without leaving any residue.
b.We can get the smell of perfume sitting several metres away.

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96. How is ammonia gas used for making ice in ice factories ? Explain.

97. Explain the following:
(0 Ice has lower density than water, (ii) We should not wear terylene clothes in summer.
(iii) How does perspiration during heavy exercise cool the body ?

98. Explain the following:
(0 Ice has lower density than water, (ii) We should not wear terylene clothes in summer.
(iii) How does perspiration during heavy exercise cool the body ?

99. Identify each of the following changes of state as evaporation, boiling or evaporation.
Give reason for your answer,
(i) Wet clothes dry when spread on a wire.
(if) After a hot shower, your bath room mirror is covered with water.
(iii) Lava flows into the ocean and steam forms.

100. What is diffusion ? Discuss two applications of diffusion of gases.

101. Give reasons for the following ?
(i) Naphthalene balls kept in stored warm clothes disappear over a period of time.
(a) A gas fills the entire space available.
(iii) It is easier to remove fresh stains of ink from a cloth than stains caused a few days ago.

102. Give two reasons to justify.
a) Water at room temperature is a liquid.
b) An iron almirah is a solid at room temperature.

103. Discuss briefly three properties of particles of matter.

104. What is diffusion ? Discuss two applications of diffusion of gases.

105. Give reasons for the following ?
(i) Naphthalene balls kept in stored warm clothes disappear over a period of time.
(a) A fluorescent tube glows when electricity is passed through it.
(Hi) It is easier to remove fresh stains of ink from a cloth than stains caused a few days ago.

106. Identify each of the following changes of state as evaporation, boiling or evaporation.
Give reason for your answer,
(i) Wet clothes dry when spread on a wire.
(if) After a hot shower, your bath room mirror is covered with water.
(Hi) Lava flows into the ocean and steam forms.

107. Differentiate between evaporation & boiling.

108. What are the characteristics of the particles of matter?

109. Name A, B, C, D, and E & F in the following diagram.

110. Give reason-
(A) A gas fills completely the vessel in which it is kept.
(B) A gas exerts pressure on the walls of the container.
(C) A wooden table should be called a solid.

111. Discuss briefly three properties of particles of matter. >

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112. (a) Define evaporation. How does it differ from boiling ? How does evaporation cause cooling ?
(b) Discuss the various factors which increase the rate of evaporation.

113. a) What is evaporation. Explain the factors with which the rate of evaporation.

114. (a)Write any three differences between evaporation and boiling.
(b) Give reason for the following
(i) clothes dry faster on a windy day.
(ii) it is easy to sip hot cup of tea froma saucer than froma cup

115. (a) Define the following
(i) Latent heat of vaporization
(ii) boiling point
(b) Give reason for the following
(i) Stream produces more saviour burns than water which are at 100° C.
(ii) Temperature remains constant during the change of state of any substance

116. (a) What do you mean by liquefaction ?
Discuss different ways by which liquefaction be achieved ?
(b) How will you demonstrate that particles of matter are constantly moving ? Give two examples.

117. (a) Define evaporation. How does it differ from boiling ? How does evaporation cause cooling ?
(b) Discuss the various factors which increase the rate of evaporation. >

118. (a) What is humidity? Describe an activity to show the presence of humidity in the atmosphere
(b) Ice at 273 k is more effective in cooling than water at the same temperature. Explain

119. Define the following terms.
Fusion, latent heat of fusion, boiling point, latent heat of vaporization, sublimation.