Final answer:
A reaction with a negative ∆G results in increased disorder and is spontaneous. It is termed an exergonic reaction, demonstrating that energy is released and entropy increases.
Step-by-step explanation:
If a reaction results in a negative change in the free energy of the molecule, -∆G, then the reaction increases disorder and is therefore spontaneous.
A negative change in free energy, indicated as a negative ∆G, suggests that the reaction is exergonic, meaning that energy is released and the products of the reaction have less free energy than the reactants. Since exergonic reactions are spontaneous, they tend to increase entropy, which is a measure of disorder within a system. Contrary to our everyday understanding of 'spontaneous,' in thermodynamics, it implies that the reaction is favorable and can proceed on its own over time, but not necessarily that it will occur quickly. The rusting of iron is a classic example of a spontaneous process that happens gradually.
Additionally, all reactions require some energy to overcome the initial barrier to reaction, known as the activation energy. In spontaneous reactions, after surpassing the activation energy, the system releases free energy, and the overall entropy of the universe increases.