Entropy
#Physics
Thermodynamics
$\displaystyle \Delta S=\frac{Q_{\text{reversible}}}{T}$
- $\displaystyle \Delta S$ is the change in entropy of the system
- $\displaystyle Q_{\text{reversible}}$ is the heat gained or loss by the system in a reversible process
- $\displaystyle T$ is the temperature of the system
$\displaystyle \Delta S_{\text{universe}}=\Delta S_{\text{system}}+\Delta S_{\text{surroundings}}$
$\displaystyle \Delta S=nR\ln\left( \frac{V_{f}}{V_{0}} \right)$
- Entropy change in free expansion going from volume $\displaystyle V_{0}$ to $\displaystyle V_{f}$
- Derivable by Sackur–Tetrode Equation
Statistical Mechanics
Topics
$\displaystyle S=k_{B}\ln \Omega$
- The statistical mechanics definition of entropy
- $\displaystyle k_{B}$ is the [Boltzmann Constant]
- $\displaystyle \Omega$ is multiplicity of the system
- Sackur–Tetrode Equation