Work out helmholtz free energy instantly with clear inputs, formula shown and shareable results.
The Helmholtz free energy A = U - TS is the portion of internal energy available as work at constant temperature and volume. With U = 5000 J, T = 300 K and S = 12 J/K, the TS term locks away 3600 J, leaving 1400 J extractable. Spontaneous processes at fixed T and V lower A.
Helmholtz free energy
A = U - T S
Spontaneity
dA < 0 at constant T and V
Gibbs uses enthalpy, G = H - TS, and applies at constant pressure. Helmholtz applies at constant volume, which suits sealed vessels and statistical mechanics.
The energy tied up in disorder, unavailable for work. It grows with temperature, which is why hot systems waste more of their energy content.