Which statement is true regarding the relationship between temperature and kinetic energy?

• A. It measures average kinetic energy of molecules
• B. It measures average potential energy
• C. It measures molecular velocity
• D. It measures molecular momentum

Answer: (A)

Temperature reflects the average kinetic energy of the molecules in a substance. In kinetic theory, the translational kinetic energy of a molecule is (1/2) m v^2, and the average of this energy across all molecules is proportional to temperature. That means hotter substances have higher average kinetic energy, which is why gas molecules move faster on average as temperature rises. Temperature does not measure potential energy, nor does it directly measure velocity or momentum—the energy content matters, not the exact speed or the product of mass and velocity. (For gases, at the same temperature, different molecules share the same average kinetic energy, while their speeds vary with mass.)