The category into which a chemical reaction can be classified can be understood with the help of the corresponding enthalpy name. For example, the enthalpy of combustion is closely related to combustion reactions, which are highly exothermic in nature. The standard enthalpy of combustion for a chemical reaction can be defined as the change in enthalpy for each mole of substance that undergoes combustion, assuming that all products and reactants are in their standard states.
Another similar example can be observed in the enthalpy of atomization, which is the change in enthalpy when a molecular bond is broken to afford two atoms. The standard enthalpy of atomization for a reaction can be defined as the change in enthalpy that accompanies the breakage of one mole of chemical bonds. The enthalpy of atomization for the breakage of 1 mole of H2 molecules to afford individual hydrogen atoms is 435 kilojoules per mole.