This equation can be derived by showing that a Carnot engine run between two phases at two close temperatures has the same thermal efficiency.
By the Third Law of Thermodynamics and a magnetic equivalent of this law, the critical magnetic field for a superconductor approaches a constant as temperature approaches absolute zero. This equation can be derived by showing that a Carnot engine run between two phases at two close temperatures has the same thermal efficiency. It can also be derived by finding the infinitesimal change in chemical potential for each of two phases in equilibrium with each other; that form of this equation says that the derivative of vapor pressure with respect to temperature equals the change in entropy over the change in volume. For 10 points, name this doubly-eponymous equation which gives the slope of the coexistence line in a pressure versus temperature plot.
By the Third Law of Thermodynamics and a magnetic equivalent of this law, the critical magnetic field for a superconductor approaches a constant as temperature approaches absolute zero.
Clausius-Clapeyron equation [or Clausius-Clapeyron equation before "vaporization"]