Average Kinetic Energy
The mean translational kinetic energy of the particles in a sample, dependent only on absolute temperature.
Formula / equation
KE = (3/2)kT per molecule
Unit
J
In depth
Because the relation involves no reference to molecular identity, all gases at the same temperature have identical average kinetic energy — heavy molecules simply move more slowly. This makes temperature a direct measure of molecular motion and explains why absolute zero corresponds to minimum energy.
Examples in the real world
At 300 K every gas molecule averages about 6.2 × 10⁻²¹ J of translational energy, whether it is helium or xenon.