Thermodynamics: past paper questions
Real questions on thermodynamics
The newest 20 of 86 written questions, plus 1 multiple-choice. Open one to see it on the real paper.
- 9702/41 · October/November 2025 · Q2a[2]
State two ways in which the first law of thermodynamics describes that the internal energy of a system may be changed.
See it on the paper → - 9702/41 · October/November 2025 · Q2b(i)[3]
Use the first law of thermodynamics to explain why a bicycle pump gets hot when it is used to pump up a tyre quickly.
See it on the paper → - 9702/41 · October/November 2025 · Q2b(ii)[3]
With reference to molecular energies, explain why the temperature of water remains at 100 °C when it vaporises in a kettle, even though it is being heated.
See it on the paper → - 9702/42 · October/November 2025 · Q4a[2]
State the first law of thermodynamics.
See it on the paper → - 9702/42 · October/November 2025 · Q4b(i)[1]
Use Fig. 4.1 and Fig. 4.2 to determine the general expression for the internal energy U of the gas when it has pressure p and volume V. U =
See it on the paper → - 9702/42 · October/November 2025 · Q4b(ii)[2]
An ideal gas at thermodynamic temperature T contains N molecules. Use your answer in (b)(i) and the equation of state for an ideal gas to deduce an expression for U in terms of N and T. Identify any other symbols you use. U =
See it on the paper → - 9702/42 · October/November 2025 · Q4c(i)[1]
change AB W =
See it on the paper → - 9702/42 · October/November 2025 · Q4c(ii)[1]
change CD. W =
See it on the paper → - 9702/42 · October/November 2025 · Q4d[3]
Use your answers in (c) and the first law of thermodynamics to determine an expression, in terms of X and Y, for the net thermal energy Q supplied to the gas during one full cycle ABCDA. Explain your reasoning. Q =
See it on the paper → - 9702/43 · October/November 2025 · Q2a[2]
State two ways in which the first law of thermodynamics describes that the internal energy of a system may be changed.
See it on the paper → - 9702/43 · October/November 2025 · Q2b(i)[3]
Use the first law of thermodynamics to explain why a bicycle pump gets hot when it is used to pump up a tyre quickly.
See it on the paper → - 9702/43 · October/November 2025 · Q2b(ii)[3]
With reference to molecular energies, explain why the temperature of water remains at 100 °C when it vaporises in a kettle, even though it is being heated.
See it on the paper → - 9702/41 · May/June 2025 · Q4a(i)[2]
State what is meant by the internal energy of a system.
See it on the paper → - 9702/41 · May/June 2025 · Q4a(ii)[2]
Explain why the internal energy of an ideal gas is directly proportional to the thermodynamic temperature of the gas.
See it on the paper → - 9702/41 · May/June 2025 · Q4b[4]
A sample of an ideal gas at thermodynamic temperature T has internal energy U. The gas is compressed so that its temperature increases to 3T. During this compression, work W is done on the gas. The gas is then cooled at constant volume so that its temperature decreases to 2T. Complete Table 4.1 to show, in terms of som...
See it on the paper → - 9702/43 · May/June 2025 · Q4a(i)[2]
State what is meant by the internal energy of a system.
See it on the paper → - 9702/43 · May/June 2025 · Q4a(ii)[2]
Explain why the internal energy of an ideal gas is directly proportional to the thermodynamic temperature of the gas.
See it on the paper → - 9702/43 · May/June 2025 · Q4b[4]
A sample of an ideal gas at thermodynamic temperature T has internal energy U. The gas is compressed so that its temperature increases to 3T. During this compression, work W is done on the gas. The gas is then cooled at constant volume so that its temperature decreases to 2T. Complete Table 4.1 to show, in terms of som...
See it on the paper → - 9702/42 · February/March 2025 · Q3b(i)[3]
The temperature of the nitrogen gas is increased from 0 °C to 210 °C. Determine the work done on the gas. work done = J
See it on the paper → - 9702/41 · May/June 2024 · Q3c[2]
The volume V of the gas in (b) is now varied, keeping its pressure constant. On Fig. 3.1, sketch the variation with V of the internal energy U of the gas. U 0 0 V Fig. 3.1
See it on the paper →
What examiners said
Many candidates correctly used the equation for work done on a gas when changing volume at constant temperature. However, only the strongest candidates realised that, because the gas is expanding, the work done on the gas must be negative.
— Examiner report, February/March 2025, 9702/42 Q3(b)(i) (Cambridge)
There was much confusion between the definition of internal energy and the first law of thermodynamics (which deals with ways in which internal energy can be changed).
— Examiner report, October/November 2023, 9702/42 Q3(a) (Cambridge)
In both parts of this question, there was a widespread misunderstanding of the terms involved in the first law of thermodynamics. Many candidates seemed to think that all three of internal energy, thermal energy and work are quantities that are possessed by the system. Awareness was rare that it is internal energy that is possessed by the system, and that the transfer of thermal energy and the doi...
— Examiner report, October/November 2023, 9702/42 Q3(b) (Cambridge)
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