Which term is defined as energy available to do work?

Which term is defined as energy available to do work?

• A. Gibbs Free Energy
• B. Entropy
• C. Internal Energy
• D. Enthalpy

Answer: (A)

Gibbs free energy describes the portion of a system’s energy that can actually do useful work at constant temperature and pressure. It combines enthalpy and entropy into G = H − TS, meaning it accounts for both the energy content and the energy that becomes unavailable as disorder (entropy) increases. Because part of the energy is tied up in maintaining or increasing entropy, Gibbs free energy isolates the energy you could harness to perform work under those conditions. If a process lowers G, it can proceed spontaneously, and at equilibrium G stops changing. In contrast, entropy measures disorder, internal energy is the total energy content, and enthalpy is the heat content at constant pressure. Thus, the term that specifically denotes energy available to do work is Gibbs free energy.

Gibbs free energy describes the portion of a system’s energy that can actually do useful work at constant temperature and pressure. It combines enthalpy and entropy into G = H − TS, meaning it accounts for both the energy content and the energy that becomes unavailable as disorder (entropy) increases. Because part of the energy is tied up in maintaining or increasing entropy, Gibbs free energy isolates the energy you could harness to perform work under those conditions. If a process lowers G, it can proceed spontaneously, and at equilibrium G stops changing. In contrast, entropy measures disorder, internal energy is the total energy content, and enthalpy is the heat content at constant pressure. Thus, the term that specifically denotes energy available to do work is Gibbs free energy.