What does Gibbs free energy represent in a chemical system?

Gibbs free energy represents the energy available to perform work in a chemical reaction. In thermodynamics, Gibbs free energy is a crucial concept that combines the system's enthalpy and entropy to predict whether a reaction can occur spontaneously at constant temperature and pressure.

When the change in Gibbs free energy (ΔG) is negative, it indicates that the reaction can proceed spontaneously, meaning there is energy available to do work during that process. This is essential for understanding many chemical and biological systems since it helps predict reaction feasibility and direction.

In contrast, the total energy of a system relates to a broader scope that includes all forms of energy, while enthalpy change focuses solely on heat content without considering the directionality of the reaction or the work aspect. Energy lost as heat during a reaction might occur, but it does not directly correlate to the Gibbs free energy, as Gibbs addresses both entropy and usable energy. Thus, Gibbs free energy is specifically about the portion of a system's energy that can be harnessed for work in a given reaction context.