Gibbs free energy is a thermodynamic quantity that helps predict whether a process or chemical reaction will occur spontaneously under conditions of constant pressure and temperature. It combines the system’s internal energy and entropy (disorder) to give a single value.
If the change in Gibbs free energy (ΔG) during a process is negative, the process can happen on its own without any external input — it is spontaneous. If ΔG is positive, the process requires energy to proceed and is non-spontaneous. When ΔG is zero, the system is in equilibrium.
This concept is fundamental in chemistry and biology, helping explain why some reactions occur naturally (like water freezing) while others need energy (like photosynthesis). It also guides engineers in designing energy-efficient systems.