The average kinetic energy of gas particles is directly proportional to which temperature scale?

• A. Celsius temperature.
• B. Fahrenheit temperature.
• C. Kelvin temperature.
• D. Rankine temperature.

Answer: (C)

The average kinetic energy of gas particles is directly tied to absolute temperature via the equipartition principle, which says ⟨KE⟩ = (3/2) k_B T. Here T must be an absolute temperature—zero on the scale corresponds to no molecular motion.

Kelvin is the absolute temperature scale used in this relation because it starts at absolute zero and its units directly reflect energy changes. That makes the proportionality between kinetic energy and temperature clean and straightforward. Celsius and Fahrenheit clocks don’t align with zero kinetic energy in a simple way, since their zero points are arbitrary offsets. Rankine is also an absolute scale, but in this standard expression Kelvin is the conventional choice, so it’s the best answer.