Thermodynamics
Entropy
Entropy (S) is a measure of the disorder or randomness of a system. The second law of thermodynamics states that the total entropy of an isolated system can only increase over time or remain constant in ideal cases where the system is in a steady state or undergoing a reversible process. A system’s entropy increases when it becomes more disordered (e.g., a gas expanding into a vacuum). The change in entropy (ΔS) for a process is given by:
$$ \Delta S = \frac{q_{rev}}{T} $$
where:
- ΔS = change in entropy
- qrev = heat transferred reversibly
- T = absolute Temperature