Phenomenological Thermodynamics of Quasi-Equilibrium and Equilibrium States

Abstract

The main objectives of phenomenological thermodynamics are:

• (i) Characterization of thermodynamical quasi-equilibrium states (Gibbs’ fundamental equation of Section 67.2).

• (ii) Characterization of thermodynamical processes (laws of thermodynamics of Section 67.4).

• (iii) Computation of thermodynamical equilibrium states from quasi-equilibrium states (extremal properties of thermodynamical potentials of Section 67.6).

Temperature, energy, and entropy are state variables, i.e., they are independent of the history of the body.

The energy of the universe is constant (first law).

The entropy of the universe tends towards a maximum (second law).

Rudolf Clausius (1865)

In the huge factory of natural processes, entropy plays the role of a president, because it prescribes the way in which the entire course of business takes place. The energy principle plays the role of the book-keeper by balancing debit and credit.

Robert Emden (1938)

Only through the second law a certain direction is given to the course of the world. This is not present in the mechanical world picture.

Arnold Sommerfeld (1954)