Standard enthalpy change of formationIn chemistry, the standard enthalpy change of formation is the enthalpy change (i.e. heat absorbed) when some amount of a compound is formed from its elements in their standard states under standard conditions. If heat is released in the process of formation (for example burning carbon in oxygen to form carbon dioxide), then the sign will be negative. It is typically given the symbol ΔHf
Due to conservation of energy, enthalpies of formation can be used to calculate the heat absorbed or released in any chemical reaction.
Notational note: In the above definition the plimsol sign