• At the temperature at which a change of state occurs, the two states are in equilibrium with one another.
  • For an ice-water system, equilibrium takes place at 0°C, so  is equal to 0 at that temperature.
  • The heat of fusion of water is known to be equal to 6.01 kJ/mol, and so the Gibbs free energy equation can be solved for the entropy change that occurs during the melting of ice.
  • The entropy change is positive as the solid state changes into the liquid state.
  • Condensation from vapor to liquid would give a negative value for .
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