A LevelPhysicsCambridge (CIE)Exam Questions16. ThermodynamicsInternal Energy

Internal Energy (Cambridge (CIE) A Level Physics): Exam Questions

Exam code: 9702

55 mins6 questions
Easy
Medium
1a
1 mark

Define internal energy.

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1b
1 mark

Describe the change in internal energy if a system's temperature decreases.

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1c
2 marks

Complete the sentence, using words from the options below:

For an ideal gas, temperature is .................... proportional to ................... kinetic energy. 

inversely

never

an atom's

total

directly

average

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1d
2 marks

Explain why the following statement made by a student is only true for an ideal gas:

'internal energy is the sum of the kinetic energies of all the particles'.

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2a
3 marks

For an ideal gas, internal energy is directly proportional to temperature in kelvin.

A sample of ideal gas is in a perfectly insulated box of fixed volume.

The temperature of the sample rises from 400 K to 600 K. Its internal energy was initially 2800 J.

Calculate its new internal energy.

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2b
2 marks

Calculate the increase in total kinetic energy of the particles in the ideal gas.

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2c
1 mark

The sample contains 3 moles of ideal gas.

Calculate the number of atoms in the sample.

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2d
2 marks

Calculate the average kinetic energy of a particle in the sample of ideal gas after it has been heated.

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3a
3 marks

Draw three lines on Fig 1.1 between the corresponding effects on internal energy and changes to the system.

3a

Fig 1.1

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3b
1 mark

The internal energy of an ideal gas increases. 

Describe the change in average particle motion.

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3c
2 marks

Name two ways the internal energy of the system may be increased.

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3d
2 marks

The volume of a container filled with an ideal gas is reduced. In this process, 3.5 kJ of work is done on the system.

At the same time, 1.2 kJ of thermal energy is transferred from the system to its surroundings. 

Calculate the change in internal energy.

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1a
1 mark

Define internal energy.

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1b
6 marks

State and explain, in molecular terms, whether the internal energy of the following increases, decreases or does not change.  

(i) A lump of copper as it is cooled.

[3]

(ii) Some water as it evaporates at a constant temperature.

[3]

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2a
2 marks

A monatomic gas, contained within a balloon, increases in temperature from 260 K to 310 K.

Calculate the factor by which the internal energy changes, stating whether this is an increase or decrease.

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2b
5 marks

The initial internal energy was 2.3 kJ. The gas in the balloon is perfectly insulated.

(i) Describe the heat transferred between the gas and its surroundings. 

Explain your answer.

[2]

(ii) Calculate the work done on the gas.

[3]

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2c
3 marks

State whether the balloon increases or decreases in size.

Explain your answer.

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2d
2 marks

Describe and explain the change in average kinetic energy of the particles in this process.

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3a
3 marks

A container of fixed volume holds 15.0 moles of a monatomic ideal gas. This is 9.03 × 1024 atoms in total.

Each atom has a mass of 6.64 × 10−27 kg. 

The gas is held at a temperature such that the root-mean-square speed is 1680 m s−1.

Calculate this temperature.

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3b
2 marks

The gas undergoes a process and now has a pressure of 150 kPa. The container has a fixed volume of 0.300 m3.

Calculate the new temperature of the gas.

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3c
7 marks

For the process outlined in part (b):

(i) Describe the change in internal energy. Explain your answer.

[3]

(ii) Describe the process which caused this change in internal energy. Explain your answer.

[4]

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3d
2 marks

The boiling point of this gas is 350 K. Explain why the potential energy of this ideal gas does not change. 

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