What you’ll learn7 learning objectivesChoose one objective for a focused lesson, or study the complete topic.5.1.1Chemical reactions are accompanied by enthalpy• Understand: chemical reactions are accompanied by enthalpy changes and these changes can be exothermic (ΔH is negative) or endothermic (ΔH is positive)Syllabus objective5.1.2Construct/interpret a reaction pathway diagram• Construct/interpret: a reaction pathway diagram, in terms of the enthalpy change of the reaction and of the activation energySyllabus objective5.1.3Terms• Define/use:: (a) standard conditions (this syllabus assumes that these are 298 K and 101 kPa) shown by ⦵; (b) enthalpy change with particular reference to: reaction, ΔHr , formation, ΔHf , combustion, ΔHc , neutralisation, ΔHneutSyllabus objective5.1.4Energy transfers occur during chemical• Understand: energy transfers occur during chemical reactions because of the breaking and making of chemical bondsSyllabus objective5.1.5Bond energies and ΔHr• Use bond energies (ΔH positive, i.e. bond breaking) to calculate enthalpy change of reaction, ΔHrSyllabus objective5.1.6Some bond energies are exact and some bond• Understand: some bond energies are exact and some bond energies are averagesSyllabus objective5.1.7Enthalpy changes from appropriate experimental• Calculate enthalpy changes from appropriate experimental results, including the use of the relationships q = mcΔT and ΔH = –mcΔT/nSyllabus objective