The relation between Gibbs energy (G) and entropy (S) is described by the Gibbs free energy equation, which is a fundamental concept in thermodynamics. The equation is as follows:
ΔG = ΔH - TΔS
where ΔG is the change in Gibbs energy, ΔH is the change in enthalpy (heat content) of the system, T is the temperature in Kelvin, and ΔS is the change in entropy.
The Gibbs free energy (G) is a measure of the energy available to do useful work in a system at constant temperature and pressure. It incorporates both the enthalpy change (ΔH) and the entropy change (ΔS) of the system. The equation expresses how the change in Gibbs energy of a system is related to changes in enthalpy and entropy.
Entropy (S) is a measure of the disorder or randomness in a system. It quantifies the number of microstates or possible arrangements that a system can have. An increase in entropy corresponds to an increase in disorder or randomness.
The equation ΔG = ΔH - TΔS tells us that for a spontaneous process to occur at constant temperature and pressure (where ΔG is negative), there are two factors at play:
Enthalpy (ΔH): A process may be driven by a decrease in enthalpy, such as when heat is released or when bonds are formed that are energetically favorable.
Entropy (ΔS): A process may be driven by an increase in entropy, which corresponds to an increase in disorder or randomness.
The temperature factor (TΔS) in the equation emphasizes that the change in entropy is temperature-dependent. At higher temperatures, the contribution of entropy to the spontaneity of a process becomes more significant.
In summary, the Gibbs free energy equation relates the changes in Gibbs energy, enthalpy, and entropy of a system, providing insights into the spontaneity and direction of thermodynamic processes. It indicates that processes tend to be spontaneous if they involve a decrease in enthalpy or an increase in entropy or both.