Thermodynamic Potentials and Derivatives

This chapter introduces three important state variables, that is, properties of a system that take a well-defined value in a thermodynamic equilibrium state of the system. They all have the dimensions of energy and, together with the internal energy, are called thermodynamic potentials. These are the Helmholtz free energy, the enthalpy, and the Gibbs free energy (or Gibbs potential). It also talks about the Maxwell relations, which are very useful in the calculation of thermodynamic derivatives. A section in the chapter provides some useful general rules for calculating thermodynamic derivatives.