Its change is minus P Delta V minus S Delta T, or the reversible work, or maximum total work that can be done by the system.
Derived by making the isochoric entropy change in the universe greater than or equal to zero, it can be differentiated with repect to temperature in constant volume to give minus the entropy. Its change is minus P Delta V minus S Delta T, or the reversible work, or maximum total work that can be done by the system. At constant temperature and volume, it is less than zero for spontaneous processes. Equal to U minus TS, FTP name this thermodynamic quantity named for a German physicist, not Josiah Gibbs.
Derived by making the isochoric entropy change in the universe greater than or equal to zero, it can be differentiated with repect to temperature in constant volume to give minus the entropy.
{Helmholtz} (free) energy