Energy Definitions

It should be noted that many of the energy definitions can be considered in the reverse direction with a corresponding change of sign for the energy. Bond formation = exothermic ΔH negative, bond cleavage = endothermic ΔH positive

Enthalpy of vaporisation

The energy required to vaporise one mole of a liquid

Enthalpy of atomisation

The energy required to produce one mole of gaseous atoms from an element in its standard state

Bond dissociation enthalpy

The energy change when one mole of a specific bond is broken or created

Bond enthalpy

The average energy change when one mole of a specific type of bond is broken or created.

Enthalpy of Combustion

The energy released when one mole of a compound is burned in excess oxygen

Enthalpy of formation

The energy change when one mole of a compound is formed from its constituent elements in their standard states

Enthalpy of solution

The energy change when one mole of a substance is dissolved in an infinite amount of water

Hydration enthalpy

The energy change when a particle is taken from infinite separation in the gaseous state to its position in an aqueous lattice

1st Ionisation energy

The energy required to produce one mole of gaseous ions from one mole of gaseous atoms by removal of one mole of electrons

Lattice enthalpy

The energy change when one mole of an ionic substance is broken into its constituent atoms at infinite separation.