Abstract

A new way of understanding entropy as a macroscopic property is presented. This is based on the fact that heat flows from a hot body to a cold one even when the hot one is smaller and has less energy. A quantity that determines the direction of flow is shown to be the increment of heat gained divided by the absolute temperature. The same quantity is shown to determine the direction of other processes taking place in isolated systems provided that q is determined by the state of the system. Entropy emerges as the potent energy of a system [Σ], the potency being determined by 1/T. This is shown to tie in with the statistical mechanical interpretation of entropy. The treatment is shorter than the traditional one based on heat engines.