Define standard enthalpy of fusion or molar enthaply of fusion `(Delta_(fus) H^("ϴ"))`.

Explanation

The standard enthalpy of fusion may be defined as the enthalpy change that accompanies the melting of one mole of a solid substance in standard state. Melting of solid is endothermic, so enthalpies of fusion are positive. For examle,
`H_(2) O(L)to H_(2) (g), Delta_(vap) H^("ϴ") = + 40.79 kj mol^(-1)`.