The
Gibbs-Helmholtz equation is a
thermodynamic relationship useful for calculating changes in the
energy or
enthalpy (heat content) of a system. Two useful general forms of this equation are:
- <math>\Delta A - \Delta U = T \left( \frac{\delta\left(\Delta A \right)}{\delta T} \right)_V</math>
- <math>\Delta G - \Delta H = T \left( \frac{\delta \left( \Delta G\right)}{\delta T} \right)_P</math>
Where A is the work function, U is the internal energy[?] of the system, T is the absolute temperature[?], V is the volume, P is the pressure, G is the Gibbs free energy and H is the heat content of the system.