Temperature

Heating the gas raises its temperature, so the molecules gain average kinetic energy and move faster.

Internal energy is therefore an energy store of the whole system, measured in joules (J). It is not the same as temperature: temperature is linked to the particles’ average kinetic energy, whereas internal energy includes both kinetic and potential energy and depends on all the particles present.

Because temperature is related to average particle kinetic energy, the temperature rises.

What happens next depends on the substance's temperature and state. The additional internal energy may raise its temperature, produce a change of state, or contribute to both at different stages of the heating process.