As with pressure, let us take a moment to develop our concrete sense of temperature in the context of the ideal gas. The temperature of an ideal gas measures the average translational kinetic energy of its particles as they move and collide. For a real substance, temperature is a bit more complicated. The energy measured by temperature occurs not only as the translational motion of a particle but also as internal energy corresponding to molecular vibration or the excitation of electrons, for example. Temperature predicts the direction of spontaneous heat flows.