Osm Physics by Ashish

Clausius–Clapeyron Equation | Physics Notes Derivation and physical significance of the phase-equilibrium relation The phase-equilibrium curve shown in a pressure–temperature (P–T) diagram can be described mathematically by a differential equation known as the Clausius–Clapeyron equation . It gives the relationship between pressure and temperature during a phase transition, such as melting, vaporisation or sublimation. 1. Derivation of the Clausius–Clapeyron Equation Consider two points B and C lying very close to each other on a phase-equilibrium curve. At point B, the temperature and pressure are T and p , respectively. At point C, the temperature and pressure are T + dT and p + dp , respectively. Since the two phases are in thermodynamic equilibrium at point B, their Gibbs free energies per molecule are equal: g 1 (T, p) = g 2 (T, p) (1) Similarly, at point C: g 1 (T + dT, p + dp) = g 2 (T + dT, p + dp) For small changes in temperature and ...