Generic plot showing to possible Gibbs free energy changes over time: the lower Gf position indicating a free energy change decrease, the higher Gf position indicating a free energy change increase. |

(add discussion)

Enthalpy and entropy

The expression for Gibbs free energy change, can be expanded, by substitution for the Gibbs function, in terms of initial and final values of enthalpy

or

which states that Gibbs free energy change of a process can be studied in terms of the difference in the measures of the enthalpy and entropy of the system in the final state, Hf and Sf, as contrasted with the values of the enthalpy and entropy in the initial state, Hi and Si.

Further reading

● Anslyn, Eric V. and Dougherty, Dennis A. (2006).