Answer: Enthalpy
Step-by-step explanation:
Activation energy is the extra energy that must be supplied to reactants in order to cross the energy barrier and thus convert to products. It is the difference between the energy of activated complex and energy of reactants.
Ionization energy is the energy required to remove an electron from the valence shell of an isolated gaseous atom of an element.
Enthalpy is the difference between the potential energy of products and the potential energy of reactants.
Heat of vaporization is the amount of heat required to evaporate 1 mole of liquid to 1 mole of gaseous state.