Lesson 9.2.1

9.2.1 Internal energy and absolute zero Quiz: Pearson Edexcel Physics, Unit 9

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 9.2.1, Internal energy and absolute zero: 20 multiple choice questions for the Pearson Edexcel Physics (9PH0), Unit 9: Thermodynamics, written with Revision Ninja.

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The 20 questions

  1. Internal energy of a system is best described as

    • the gravitational potential energy of the substance due to its height
    • the energy stored only in the chemical bonds of the substance
    • the total kinetic energy of the molecules moving in one common direction
    • the sum of the random kinetic and potential energies of its molecules

  2. What is the lowest possible temperature on the kelvin scale?

    • 273 K
    • 0 C
    • -100 K
    • 0 K

  3. Which is the best statement about absolute zero?

    • It is the temperature at which the internal energy of a substance doubles.
    • It is the temperature at which all molecules stop moving and collide with each other.
    • It is the temperature at which the average kinetic energy of molecules is theoretically zero.
    • It is the temperature at which water freezes at standard atmospheric pressure.

  4. The mean translational kinetic energy per molecule of an ideal gas is

    • (3/2) k T^2
    • (2/3) k T
    • (3/2) k T
    • (1/2) k T

  5. The Boltzmann constant k has the approximate value

    • 1.38 x 10^-23 J K^-1
    • 6.02 x 10^23 mol^-1
    • 8.31 J mol^-1 K^-1
    • 6.63 x 10^-34 J s

  6. A gas has mean molecular kinetic energy 6.21 x 10^-21 J. Using k = 1.38 x 10^-23 J K^-1, what is its absolute temperature?

    • 600 K
    • 450 K
    • 300 K
    • 200 K

  7. A gas is cooled from 127 C to -73 C. What is the ratio of its initial to its final absolute temperature?

    • 2.0
    • 0.5
    • 1.5
    • 4.0

  8. The mean kinetic energy of gas molecules at 600 K, compared with 300 K, is

    • four times as large
    • half as large
    • twice as large
    • the same

  9. Convert 25 C to absolute temperature.

    • 25 K
    • 273 K
    • 248 K
    • 298 K

  10. Two different ideal gases are at the same temperature. Which statement about mean kinetic energy per molecule is correct?

    • The heavier gas is greater, since its molecules carry more mass.
    • The lighter gas is greater, since its molecules move faster.
    • The gas with more molecules is greater, since it has more total energy.
    • They are the same, since mean kinetic energy depends only on temperature.

  11. Why does a body at 0 C still have internal energy?

    • Absolute zero is reached only at 0 C, so internal energy is always positive there.
    • Internal energy is defined from the body's height above the ground, not its temperature.
    • Its molecules still have random kinetic and potential energy, so it is not zero.
    • Ice has no internal energy, so the body must be above 0 C to hold any internal energy.

  12. Gas A has twice as many molecules as gas B. Both are ideal gases at the same temperature. Which has greater internal energy?

    • Gas A, since its total energy sums over twice as many molecules.
    • They are equal, since internal energy depends only on temperature, not on molecule count.
    • Gas B, because its molecules move faster than those of gas A at the same temperature.
    • Gas B, because it has the higher pressure, so its internal energy must be greater.

  13. 2.0 mol of an ideal monatomic gas is at 300 K, where the mean kinetic energy per molecule is 6.21 x 10^-21 J. What is the total translational kinetic energy? Use N_A = 6.02 x 10^23 mol^-1.

    • 7.5 kJ
    • 3.7 kJ
    • 15 kJ
    • 0.37 kJ

  14. Which statement correctly links average kinetic energy to absolute temperature?

    • Temperature is the speed of the fastest molecule in the gas, measured at its surface.
    • Temperature is the total energy of all molecules divided by their total mass in the gas.
    • Temperature measures only the potential energy stored between molecules, not their motion.
    • Temperature is proportional to the mean translational kinetic energy of molecules.

  15. Which assumption about an ideal gas applies to its internal energy?

    • Intermolecular potential energy is the dominant part of the internal energy of the gas.
    • Intermolecular potential energy is negligible, so internal energy is mostly kinetic.
    • Internal energy is independent of temperature for all ideal gases in every state.
    • Molecules are fixed in position, so their kinetic energy is zero at every instant.

  16. The mean kinetic energy per molecule of an ideal gas rises from 4.14 x 10^-21 J to 8.28 x 10^-21 J. Between which temperatures does the gas change?

    • from 300 K to 400 K
    • from 200 K to 400 K
    • from 100 K to 200 K
    • from 200 K to 800 K

  17. Which change reduces the internal energy of a fixed amount of ideal gas?

    • Raising its pressure at constant temperature.
    • Expanding it at constant temperature.
    • Compressing it at constant temperature.
    • Cooling it, since the average kinetic energy of its molecules falls.

  18. A gas contains 1 mol of a monatomic ideal gas at 300 K. Using the given result that its internal energy is (3/2)RT per mole, with R = 8.31 J mol^-1 K^-1, what is the internal energy?

    • 7.5 kJ
    • 0.37 kJ
    • 2.5 kJ
    • 3.7 kJ

  19. Which statement about internal energy and temperature is most accurate?

    • Internal energy is independent of molecular motion and depends only on the mass of the container.
    • Temperature tracks mean kinetic energy per molecule, but internal energy also depends on molecule number.
    • Internal energy and temperature are the same quantity, simply measured in different units of energy per kelvin.
    • Temperature depends on the total number of molecules in the sample, while internal energy depends only on their speed.

  20. The mean kinetic energy per molecule of a gas at 273 K is 5.65 x 10^-21 J. At what temperature is it 1.13 x 10^-20 J?

    • 819 K
    • 546 K
    • 1092 K
    • 273 K

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