Entropy Change (ΔS)

The change in entropy (ΔS) in a thermodynamic system is calculated as the difference between the final entropy (S_final) and the initial entropy (S_initial) of the system. Entropy, a fundamental concept in the second law of thermodynamics, is a measure of the number of specific ways in which a thermodynamic system may be arranged, commonly understood as a measure of disorder within the system. The units of entropy are joules per kelvin (J/K).

This formula assumes that the initial and final entropies are known and provided as parameters. If the entropy change is positive, it implies an increase in disorderness or the number of accessible microstates in the system. Conversely, a negative entropy change indicates a decrease in disorderness. This concept has practical applications in fields such as chemistry, physics, and engineering, especially in understanding energy transfer processes, the efficiency of heat engines, and the spontaneity of chemical reactions.