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| Standard enthalpy of | Exothermic or Endothermic | Definition |
| Formation | Exothermic | The formation of 1 mole of substance from constitute elements under Standard Condition |
| Combustion | Exothermic | The complete combustion of 1 mole of substance from constitute elements under Standard Condition |
| Atomization | Endothermic | The formation of 1 mole of gaseous atoms from an element in its normal state under Standard Condition |
| Neutralization | Exothermic | The formation of 1 mole of water when an acid is neutralized by an alkaline under Standard Condition |
| Solution | Both | The dissolving of 1 mole of solute in sufficient solution so that no further enthalpy change occurs on adding |
| Fusion (or melting) | Endothermic | The melting of 1 mole of substance under Standard Condition |
| Vaporization | Endothermic | The vaporization of 1 mole of a liquid substance under Standard Condition |
| Hydrogenation | Both | The complete hydrogenation of 1 mole of substance under Standard Condition |