What does ΔH stand for in ΔG = ΔH - TΔS?

• A. Gibbs free energy change
• B. Enthalpy
• C. Entropy
• D. Temperature

Answer: (B)

ΔH represents enthalpy, the heat content of a system. Enthalpy H is defined as U + pV, combining internal energy with the pressure–volume work part of the energy. In the Gibbs free energy expression ΔG = ΔH − TΔS, the enthalpy change captures the energy associated with heat exchanged at constant pressure (the heat content change during the process). The term TΔS reflects how the system’s disorder contributes to the energy balance at a given temperature. Together, they determine ΔG: when ΔG is negative, the process is thermodynamically favorable. So ΔH stands for enthalpy, not Gibbs energy change, entropy, or temperature.