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Kinetic theory: WJEC A‑Level Physics questions

Every WJEC A-Level Physics exam question on 3.3 Kinetic theory, 2016–2025, with its mark scheme and examiner’s report.

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1,173 questions

  1. Q1(b)(i)

    Summer 2025 · Unit 3

    4 marks3.3 Kinetic theory
    The whole paper ↗
    Summer 2025 Unit 3, question 1(b)(i): Sinead claims that the expansion AB takes place at a constant temperature of approximately 500 K. Evaluate this claim. [4]

  2. Q2(a)(i)

    Summer 2025 · Unit 3

    3 marks3.3 Kinetic theory
    The whole paper ↗
    Summer 2025 Unit 3, question 2(a)(i): Show that the balloon contains approximately 6 mol of helium. [3]

  3. Q2(a)(ii)

    Summer 2025 · Unit 3

    3 marks3.3 Kinetic theory
    The whole paper ↗
    Summer 2025 Unit 3, question 2(a)(ii): Calculate the rms speed of the helium molecules in the balloon. [3]

  4. Q2(a)(iii)

    Summer 2025 · Unit 3

    3 marks3.3 Kinetic theory
    The whole paper ↗
    Summer 2025 Unit 3, question 2(a)(iii): A sample of five helium molecules have speeds 950, 1200, 1325, 1500 and 1625 m s–1. Explain whether the rms speed of this sample is consistent with your answer

  5. Q2(b)(iii)

    Summer 2025 · Unit 3

    4 marks3.3 Kinetic theory
    The whole paper ↗
    Summer 2025 Unit 3, question 2(b)(iii): At an altitude of 10 km, the pressure in the balloon reaches 28 kPa whilst the surrounding atmosphere is at a pressure of 25 kPa. Natalie states, ‘The rms speed

  6. Q7(b)

    Summer 2025 · Unit 3

    3 marks3.3 Kinetic theory
    The whole paper ↗
    Summer 2025 Unit 3, question 7(b): Read through the following article carefully. Paragraph Are Cepheid variables giant stars or giant musical instruments? Stars called Cepheid variables vary in b

  7. Q7(a)

    Summer 2024 · Unit 3

    3 marks3.3 Kinetic theory
    The whole paper ↗
    Summer 2024 Unit 3, question 7(a): State three assumptions of the kinetic theory of ideal gases. [3]

  8. Q7(b)(i)

    Summer 2024 · Unit 3

    2 marks3.3 Kinetic theory
    The whole paper ↗
    Summer 2024 Unit 3, question 7(b)(i): Determine the rms speed of these five molecules. [2]

  9. Q7(b)(ii)

    Summer 2024 · Unit 3

    3 marks3.3 Kinetic theory
    The whole paper ↗
    Summer 2024 Unit 3, question 7(b)(ii): Determine the temperature of a sample of oxygen gas whose molecules have this rms speed. (Relative molecular mass of oxygen = 32.) [3]

  10. Q7(c)

    Summer 2024 · Unit 3

    4 marks3.3 Kinetic theory
    The whole paper ↗
    Summer 2024 Unit 3, question 7(c): Gareth states that when the temperature of the gas is doubled both the rms speed of the molecules and the pressure are doubled. Determine whether or not Gareth

  11. Q8(f)(ii)

    Summer 2024 · Unit 3

    4 marks3.3 Kinetic theory
    The whole paper ↗
    Summer 2024 Unit 3, question 8(f)(ii): Paragraph 8 Read through the following article carefully. Some Interesting Aspects of Quantum Physics The whole idea of quantum physics usually starts with the

  12. Q5(b)(i)

    Summer 2023 · Unit 3

    1 mark3.3 Kinetic theory
    The whole paper ↗
    Summer 2023 Unit 3, question 5(b)(i): State what is meant by the Avogadro constant. [1]

  13. Q2(a)(i)

    Summer 2022 · Unit 3

    2 marks3.3 Kinetic theory
    The whole paper ↗
    Summer 2022 Unit 3, question 2(a)(i): the number of molecules in the balloon; [2]

  14. Q2(a)(ii)

    Summer 2022 · Unit 3

    2 marks3.3 Kinetic theory
    The whole paper ↗
    Summer 2022 Unit 3, question 2(a)(ii): the rms speed of the molecules. [2]

  15. Q2(b)(i)

    Summer 2022 · Unit 3

    4 marks3.3 Kinetic theory
    The whole paper ↗
    Summer 2022 Unit 3, question 2(b)(i): Show that the mean kinetic energy of a gas molecule is kT where k is the 2 Boltzmann constant. [4]

  16. Q2(b)(ii)

    Summer 2022 · Unit 3

    1 mark3.3 Kinetic theory
    The whole paper ↗
    Summer 2022 Unit 3, question 2(b)(ii): Calculate the mean kinetic energy of a molecule in the gas. [1]

  17. Q1(a)

    Summer 2019 · Unit 3

    2 marks3.3 Kinetic theory
    The whole paper ↗
    Summer 2019 Unit 3, question 1(a): Justify the number of significant figures used to record the length, l. [2]

  18. Q1(b)(i)

    Summer 2019 · Unit 3

    2 marks3.3 Kinetic theory
    The whole paper ↗
    Summer 2019 Unit 3, question 1(b)(i): Calculate the volume of the gas at 0.0 °C. [2]

  19. Q1(b)(ii)

    Summer 2019 · Unit 3

    3 marks3.3 Kinetic theory
    The whole paper ↗
    Summer 2019 Unit 3, question 1(b)(ii): Show that the percentage uncertainty in this volume, V, is approximately 15%. [3]

  20. Q1(c)(i)

    Summer 2019 · Unit 3

    2 marks3.3 Kinetic theory
    The whole paper ↗
    Summer 2019 Unit 3, question 1(c)(i): Use the graph to estimate the temperature of absolute zero in °C, together with its absolute uncertainty. [2]
All 39 questions on Kinetic theory, as a list
  1. Summer 2025, Unit 3, Q1(b)(i) (4 marks): Sinead claims that the expansion AB takes place at a constant temperature of approximately 500 K. Evaluate this claim. [4]
  2. Summer 2025, Unit 3, Q2(a)(i) (3 marks): Show that the balloon contains approximately 6 mol of helium. [3]
  3. Summer 2025, Unit 3, Q2(a)(ii) (3 marks): Calculate the rms speed of the helium molecules in the balloon. [3]
  4. Summer 2025, Unit 3, Q2(a)(iii) (3 marks): A sample of five helium molecules have speeds 950, 1200, 1325, 1500 and 1625 m s–1. Explain whether the rms speed of this sample is consistent with your answer
  5. Summer 2025, Unit 3, Q2(b)(iii) (4 marks): At an altitude of 10 km, the pressure in the balloon reaches 28 kPa whilst the surrounding atmosphere is at a pressure of 25 kPa. Natalie states, ‘The rms speed
  6. Summer 2025, Unit 3, Q7(b) (3 marks): Read through the following article carefully. Paragraph Are Cepheid variables giant stars or giant musical instruments? Stars called Cepheid variables vary in b
  7. Summer 2024, Unit 3, Q7(a) (3 marks): State three assumptions of the kinetic theory of ideal gases. [3]
  8. Summer 2024, Unit 3, Q7(b)(i) (2 marks): Determine the rms speed of these five molecules. [2]
  9. Summer 2024, Unit 3, Q7(b)(ii) (3 marks): Determine the temperature of a sample of oxygen gas whose molecules have this rms speed. (Relative molecular mass of oxygen = 32.) [3]
  10. Summer 2024, Unit 3, Q7(c) (4 marks): Gareth states that when the temperature of the gas is doubled both the rms speed of the molecules and the pressure are doubled. Determine whether or not Gareth
  11. Summer 2024, Unit 3, Q8(f)(ii) (4 marks): Paragraph 8 Read through the following article carefully. Some Interesting Aspects of Quantum Physics The whole idea of quantum physics usually starts with the
  12. Summer 2023, Unit 3, Q5(b)(i) (1 mark): State what is meant by the Avogadro constant. [1]
  13. Summer 2022, Unit 3, Q2(a)(i) (2 marks): the number of molecules in the balloon; [2]
  14. Summer 2022, Unit 3, Q2(a)(ii) (2 marks): the rms speed of the molecules. [2]
  15. Summer 2022, Unit 3, Q2(b)(i) (4 marks): Show that the mean kinetic energy of a gas molecule is kT where k is the 2 Boltzmann constant. [4]
  16. Summer 2022, Unit 3, Q2(b)(ii) (1 mark): Calculate the mean kinetic energy of a molecule in the gas. [1]
  17. Summer 2019, Unit 3, Q1(a) (2 marks): Justify the number of significant figures used to record the length, l. [2]
  18. Summer 2019, Unit 3, Q1(b)(i) (2 marks): Calculate the volume of the gas at 0.0 °C. [2]
  19. Summer 2019, Unit 3, Q1(b)(ii) (3 marks): Show that the percentage uncertainty in this volume, V, is approximately 15%. [3]
  20. Summer 2019, Unit 3, Q1(c)(i) (2 marks): Use the graph to estimate the temperature of absolute zero in °C, together with its absolute uncertainty. [2]
  21. Summer 2019, Unit 3, Q1(c)(ii) (4 marks): Justify the statement that the results are consistent with the ideal gas equation. [4]
  22. Summer 2019, Unit 3, Q1(e) (2 marks): The scale resolution of the ruler affects the final uncertainty in the value of absolute zero. Identify two other factors that could affect the accuracy. [2]
  23. Summer 2019, Unit 3, Q5(a)(i) (2 marks): the number of moles of oxygen gas in the container; [2]
  24. Summer 2019, Unit 3, Q5(a)(ii) (1 mark): the number of molecules in the container; [1]
  25. Summer 2019, Unit 3, Q5(a)(iii) (3 marks): the rms speed of the molecules; [3]
  26. Summer 2019, Unit 3, Q5(a)(iv) (1 mark): the force exerted by the gas on the piston. [1]
  27. Summer 2019, Unit 3, Q5(b)(i) (2 marks): Calculate the final pressure of the gas. [2]
  28. Summer 2019, Unit 3, Q7(a) (2 marks): Calculate the maximum force required to separate two Magdeburg hemispheres of radius 10 cm (atmospheric pressure = 1.01 × 105 Pa, see paragraph 2). [2]
  29. Summer 2019, Unit 3, Q7(b) (2 marks): Suggest why lightning discharge travels further at low pressures (see paragraphs 4 & 5). [2]
  30. Summer 2018, Unit 3, Q2(a)(i) (2 marks): State the meaning of the terms: [2]
  31. Summer 2018, Unit 3, Q2(a)(ii): Kinetic theory for an ideal gas gives an expression that can be written as: 1 pV = nNAmc2 3 c2 (ii)
  32. Summer 2018, Unit 3, Q2(b) (3 marks): Defining both symbols, explain what quantity is given by nNA . [3]
  33. Summer 2018, Unit 3, Q2(c) (4 marks): The product of pressure and volume for an ideal gas may also be expressed as pV = nRT. Show in clear steps that the total translational kinetic energy of one mo
  34. Summer 2018, Unit 4, Q2(b)(i) (4 marks): The temperature of the surface of the Sun is 5 780 K. Use a kinetic theory equation to show that the rms speed of a free electron on the surface of the Sun is a
  35. Summer 2017, Unit 3, Q3(c)(i) (3 marks): Show that the temperature is constant along the new path from C to A. [3]
  36. Summer 2017, Unit 3, Q4(a) (6 marks): Heat is supplied to an ideal gas in a sealed container of fixed volume. Explain carefully the physical processes that cause an increase in the temperature and p
  37. Summer 2017, Unit 3, Q4(b)(i) (2 marks): Five oxygen molecules have speeds 400, 425, 450, 550 and 625 m s–1. Determine their rms speed. [2]
  38. Summer 2017, Unit 3, Q4(b)(ii) (3 marks): Using an appropriate calculation, determine whether or not the rms speed calculated in part (b)(i) is consistent with the expected rms speed of the molecules of
  39. Summer 2017, Unit 3, Q4(b)(iii) (2 marks): If the gas in the container is heated and the pressure of the gas increases by 20% of its initial value, determine the rms speed of the molecules of the gas. [2

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