phase changes.svg What is `Delta U` when `2.0` mole of liquid water vaporises at `100^(@)C`? The heat of vaporisation `(Delta H_("vap".))` of water at `100^(@)C` is `40.66 KJmol^( 1)`. What is Enthalpy Change delta h Definition Standard enthalpy of vaporization (vapH) for water at 100C is 40.66 kJ.. Law of Equipartition of Energy Energy is equally distributed among all degrees of freedom Each degree contributes kT per molecule Translational, rotational,