The standard enthalpy change for the fusion reaction of solid sodium at its melting point to liquid sodium at its freezing point is known as the enthalpy of fusion. For sodium, the enthalpy of fusion is approximately 2.60 kJ/mol. This value represents the amount of energy required to convert 1 mole of solid sodium to liquid sodium at its melting/freezing point, which is around 97.8C 370.9 K .