Systems prefer to lose energy.
Therefore, systems prefer to undergo exothermic processes. This is a driving force for all chemical processes and can serve as a reason for a chemical process to take place. When a process is exothermic, it will have a change in enthalpy that is negative. Gibbs Free Energy is a mathematical expression that combines the two driving forces into a single expression. Frequently, the driving forces do not work together to produce a reaction, or inhibit a reaction.