Temperature actually measures average ___________ of molecules in a substance.

• A. Kinetic energy
• B. Potential energy
• C. Velocity
• D. Momentum

Answer: (B)

Temperature reflects how much energy molecules have in their motion on average. Through equipartition of energy, each degree of freedom that contributes to motion adds an average amount (1/2)kT to a molecule’s energy, so the overall average kinetic energy is proportional to temperature. For a simple gas, the mean translational kinetic energy is (3/2)kT, meaning higher temperature means higher average kinetic energy and, on average, faster molecular motion. This ties temperature to kinetic energy rather than to potential energy stored in bonds or to a specific molecule’s velocity or momentum. Potential energy depends on positions within bonds and intermolecular forces, not on temperature itself, and while higher temperature corresponds to higher speeds on average, temperature is a measure of kinetic energy, not velocity.