Lesson 3.6.2.3

3.6.2.3 Molecular kinetic theory model Quiz: AQA Physics, Unit 6

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.6.2.3, Molecular kinetic theory model: 20 multiple choice questions for the AQA Physics (7408), Unit 6: Further mechanics and thermal physics (A-level only), written with Revision Ninja.

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The 20 questions

  1. What causes the random, erratic motion of visible smoke particles in Brownian motion?

    • Unbalanced molecular collisions
    • Electrostatic repulsion
    • Gravitational attraction forces
    • Thermal convection currents

  2. What type of collisions do ideal gas molecules undergo with container walls in kinetic theory?

    • Completely sticky
    • Perfectly elastic
    • Perfectly inelastic
    • Partially inelastic

  3. What molecular property change during wall collisions creates the force that causes gas pressure?

    • Charge
    • Mass
    • Temperature
    • Momentum

  4. The kinetic theory equation for an ideal gas of N molecules of mass m in volume V is:

    • pV = (1/2) N m c_rms
    • pV = 3 N m c_rms^2
    • pV = (1/3) N m c_rms^2
    • pV = N m c_rms

  5. The average kinetic energy of a molecule of an ideal gas is related to temperature by:

    • (3/2) kT
    • 2 kT
    • kT
    • (1/2) kT

  6. For an ideal gas, the internal energy consists entirely of which energy form?

    • Electrostatic energy
    • Gravitational energy
    • Potential energy
    • Kinetic energy

  7. Which assumption is NOT part of the kinetic theory model for an ideal gas?

    • Strong intermolecular attraction
    • Elastic collisions
    • Rapid random motion
    • Negligible molecular volume

  8. Take an ideal gas (N2, molar mass 0.028 kg mol^-1) at 300 K. Estimate its rms speed (R = 8.31 J K^-1 mol^-1).

    • about 1040 m s^-1
    • about 2700 m s^-1
    • about 520 m s^-1
    • about 260 m s^-1

  9. A gas has N = 1.0 x 10^23 molecules, each of mass 4.0 x 10^-26 kg, and rms speed 500 m s^-1. Its volume is 0.050 m^3. What is its pressure?

    • 6.7 x 10^3 Pa
    • 6.7 x 10^4 Pa
    • 3.3 x 10^3 Pa
    • 1.7 x 10^2 Pa

  10. If the absolute temperature of an ideal gas doubles, the mean kinetic energy of its molecules:

    • doubles
    • is unchanged
    • halves
    • quadruples

  11. Find c_rms for a molecule of mass 4.8 x 10^-26 kg at 300 K (k = 1.38 x 10^-23 J K^-1).

    • about 250 m s^-1
    • about 1000 m s^-1
    • about 130 m s^-1
    • about 510 m s^-1

  12. What motion observed in smoke particles in air provides direct experimental evidence for atoms?

    • Constant circular motion
    • Random erratic motion
    • Simple harmonic motion
    • Uniform linear motion

  13. At constant volume and temperature, how does doubling the number of molecules affect gas pressure?

    • Doubles
    • Stays constant
    • Quadruples
    • Halves

  14. A gas has 2.0 x 10^24 molecules at 300 K in a volume of 0.020 m^3 (k = 1.38 x 10^-23 J K^-1). What is its pressure?

    • about 8.3 x 10^3 Pa
    • about 4.1 x 10^5 Pa
    • about 1.0 x 10^5 Pa
    • about 4.1 x 10^3 Pa

  15. The rms speed of gas molecules at a fixed temperature, when the absolute temperature is quadrupled, becomes:

    • unchanged
    • double
    • quadruple
    • halve

  16. At the same temperature, compared with molecules of mass m, molecules of mass m/4 have a mean square speed that is:

    • the same
    • four times greater
    • four times smaller
    • twice as great

  17. Helium-like molecules of mass 6.6 x 10^-27 kg, number 2.0 x 10^23, rms speed 1200 m s^-1, fill 0.010 m^3. Estimate the pressure.

    • about 1.9 x 10^5 Pa
    • about 2.1 x 10^4 Pa
    • about 6.3 x 10^3 Pa
    • about 6.3 x 10^4 Pa

  18. A gas of 3.0 x 10^23 molecules at 300 K has total translational kinetic energy of about:

    • 3.7 kJ
    • 0.62 kJ
    • 620 J
    • 1.9 kJ

  19. How are the gas laws described in contrast to the theoretical kinetic model?

    • Theoretical
    • Empirical
    • Hypothetical
    • Derived

  20. At constant volume, raising temperature increases gas pressure mainly because molecules have greater mean what?

    • Kinetic energy
    • Volume
    • Mass
    • Potential energy

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