Thermodynamic entropy: The spreading and sharing of energy

A new approach to thermodynamic entropy is proposed to supplement traditional coverage at the junior-senior level. It entails a model for which: (i) energy spreads throughout macroscopic matter and is shared among microscopic storage modes; (ii) the amount and/or nature of energy spreading and sharing changes in a thermodynamic process; and (iii) the degree of energy spreading and sharing is maximal at thermodynamic equilibrium. A function S that represents the degree of energy spreading and sharing is defined through a set of reasonable properties. These imply that S is identical with Clausius' thermodynamic entropy, and the principle of entropy increase is interpreted as nature's tendency toward maximal spreading and sharing of energy. Microscopic considerations help clarify these ideas and, reciprocally, these ideas shed light on statistical entropy. (C) 1996 American Association of Physics Teachers.