ΔG, or the change in Gibbs free energy, is a measure of the spontaneity and overall energy change of a chemical reaction. It indicates whether a reaction is exergonic (favorable, ΔG < 0) or endergonic (unfavorable, ΔG > 0).
The minimum amount of energy required for a chemical reaction to occur.
A reaction that releases energy to its surroundings.
A reaction that absorbs energy from its surroundings.