• Bond-forming releases energy and bond-breaking requires energy.

• Average bond enthalpy is the energy needed to break one mol of a bond in a gaseous molecule averaged over similar compounds.

• Calculation of the enthalpy changes from known bond enthalpy values and comparison of these to experimentally measured values.

• Sketching and evaluation of potential energy profiles in determining whether reactants or products are more stable and if the reaction is exothermic or endothermic.

• Discussion of the bond strength in ozone relative to oxygen in its importance to the atmosphere.

• Bond enthalpy values are given in the data booklet in section 11.

• Average bond enthalpies are only valid for gases and calculations involving bond enthalpies may be inaccurate because they do not take into account intermolecular forces.