For a gas of volume V in its equilibrium state, if the pressure does change with time then total kinetic energy of gas is constant because:
Correct answer: C. Collisions must be elastic
- A. Collisions between gas molecules occur
- B. Collisions between gas molecules occur linearly
- C. Collisions must be elastic
- D. Collisions must be inelastic
Explanation
The kinetic theory assumes collisions between gas molecules are perfectly elastic, so kinetic energy is conserved in every collision. Individual molecules exchange energy, but the total kinetic energy of the gas stays constant, which is why a gas at equilibrium does not spontaneously cool itself.
This question appeared on the UHS MDCAT 2011 paper, which you can sit online with every answer explained.
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About Thermodynamics
Thermal equilibrium and heat explain how temperature and energy transfer are related, while molar specific heats describe the heat required by a gas at constant volume or constant pressure. The first law connects heat supplied, work done and change in internal energy, with sign conventions kept distinct from temperature changes.
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