Glossary
Thermodynamic Equilibrium
A thermodynamic system is said to be in thermodynamic equilibrium when it is in thermal equilibrium, mechanical equilibrium, and chemical equilibrium. The local state of a system at thermodynamic equilibrium is determined by the values of its intensive parameters, e.g., temperature and pressure.
Thermodynamic equilibrium is characterized by the minimum of a thermodynamic potential, such as the Helmholtz energy (for systems at constant temperature and volume):
F = U - T·S
Or as the Gibbs energy (for systems at constant pressure and volume):
G = H - T·S
A system that is in equilibrium experiences no changes when it is isolated from its surroundings.