For 10 points, name this thermochemical quantity, a thermodynamic potential named for a German physicist.
The differential of this quantity, which is given in general by minus Boltzmann's constant times the thermodynamic temperature times the natural logarithm of the partition function, is non-positive for isothermal, isometric processes, so it is minimized for equilibria in constant-temperature, constant-volume systems. It gives the available useful energy from a closed system, so it is usually symbolized A from the German for "work." The p-V Legendre transform of a similar quantity named for Gibbs, it is given by the internal energy minus the absolute temperature times the entropy. For 10 points, name this thermochemical quantity, a thermodynamic potential named for a German physicist.
The differential of this quantity, which is given in general by minus Boltzmann's constant times the thermodynamic temperature times the natural logarithm of the partition function, is non-positive for isothermal, isometric processes, so it is minimized for equilibria in constant-temperature, constant-volume systems.
{Helmholtz} free {energy} [or {Helmholtz function}; prompt on {free energy} or {Helmholtz} or {A}]