The temperature of a gas is related to what aspect of its molecules?

• A. Temperature is proportional to the total energy of all molecules.
• B. Temperature is related to the average potential energy of molecules.
• C. Temperature is related to the average kinetic energy of molecules.
• D. Temperature is unrelated to molecular motion.

Answer: (C)

In gases, temperature reflects how fast the molecules move on average. According to kinetic theory, it is proportional to the average translational kinetic energy, which is the energy of motion given by (1/2) m v^2. As temperature rises, the molecules move faster, so their average kinetic energy increases. For an ideal gas, the link is direct: the average kinetic energy per molecule scales with temperature (for a monatomic gas, it’s (3/2)kT). The total energy of all molecules would depend on how many molecules you have, not just the temperature. Intermolecular potential energy is negligible in an ideal gas, so it doesn’t set the temperature. Therefore, temperature is tied to the average kinetic energy of the molecules.