revision booklet of thermal physics
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REVISION BOOKLET OF THERMAL PHYSICS
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KINETIC THEORY
1 Name the three states of matter. (3)
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2 The statements below refer to the molecules in the three states of matter. One refers to the molecules in a solid,
one to the molecules in a liquid and one to the molecules in a gas. Say which one refers to which state of matter by
writing SOLID, LIQUID or GAS as your answer to each part.
a) Close packed, moving to and fro about fixed positions.
b) Widely separated, moving freely and randomly.
c) Closely packed, jostling & changing positions with nearby molecules. (3)
3 In terms of molecules, explain why each of the statements below would be true:
a) Solids have a definite shape. (2)
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b) Liquids can flow. (2)
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c) Gases have no regular shape. (2)
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4 A gas is contained in a thick walled container.
a) Explain, in terms of the molecules, why a gas exerts a pressure. (3)
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b) If left in the sun, the pressure of the gas increases. (4)
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5 In the Brownian motion experiment,:
a) Why is light shone into the container? (1)
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b) Describe what you would see when you look through the microscope. (2)
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c) Explain what you have described in part b). (3)
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6 a) Name the process by which laundry dries when left in the sun. (1)
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b) Explain this in terms of the molecules and their energies. (5)
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c) Name 4 ways in which the rate of drying could be increased. (4)
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7 a) Explain, in terms of molecular theory, why the pressure of a gas should increase with decreasing volume
(for a fixed mass of gas at a constant temperature). (3)
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b) State a relationship between the pressure and volume of a gas under these conditions. (2)
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c) What is the pressure of a gas, originally at 20Pa with a volume of 5cm3
, when the volume is increased to
10cm3
? (3)
8 For a gas of fixed mass and volume, what would be the new pressure if its original pressure were 30Pa at a
temperature of 20C, if its temperature were raised to 50C?
(4)
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9 a) State the relationship between volume and temperature for a fixed mass of gas at a constant pressure.
(2)
b) Calculate the volume a gas will expand to if its new temperature is 57 0
C and its original temperature and
volume were 17 0C and 0.5m3
. (4)
10. What happens at 0
K? (zero degrees Kelvin)? What temperature is this on the centigrade scale?
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SPECIFIC HEAT CAPACITY AND LATENT HEAT
1. Define specific heat capacity.
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2. Define latent heat.
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3. An electrical immersion heater supplies heat at a steady rate to 2.5 kg of water at 20°C in a
container of thermal capacity 1500 J/K and it is noticed that in 8.0 minutes the temperature of
the water rose to 100°C.
After another hour, the water was just boiled away.
(a) Calculate the rate at which energy is supplied by the heater.
(Specific heat capacity of water = 4200 J/kg K)
(4 marks)
(b) What value does this experiment give for the specific latent heat of vaporisation of water?
(2 marks)
(c) The quoted value for the specific latent heat of vaporisation of water is 2.3 x 106 J/kg.
Explain why the experimental result value differs from this.
(2 marks)
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4. An electric kettle of thermal capacity 820 J/K contains 0.90 kg of water.
If it takes 9.0 min to raise the temperature of the kettle and its contents from 19°C to 100°C,
how much longer should it take to boil away half the water?
(Specific heat capacity of water = 4200 J/kg K Latent heat of vaporisation of water = 2.3 x 106 J/kg)
(5 marks)