How does kinetic energy change with temperature?

• A. It decreases as temperature increases.
• B. It stays the same as temperature changes.
• C. It increases as temperature increases.
• D. It becomes zero at high temperatures.

Answer: (C)

Average kinetic energy of particles rises with temperature. The equipartition theorem says each degree of freedom contributes (1/2) k_B T to the average kinetic energy, so for a simple gas with three translational degrees of freedom the average kinetic energy is (3/2) k_B T, which increases linearly with temperature. The Maxwell–Boltzmann distribution shifts toward higher speeds as temperature increases, reflecting higher average kinetic energy. In solids, higher temperature also means more vigorous atomic vibrations, again increasing kinetic energy with temperature. So, as temperature goes up, kinetic energy increases.