After this lesson, you should be able to:

• Explain the concept of enthalpy and its relationship to heat of reaction
• Define exothermic and endothermic reactions
• Understand that bond breaking requires energy (endothermic) and bond formation releases energy (exothermic)
• Classify respiration, photosynthesis and fuel combustion as endothermic or exothermic
• Explain a reaction process in terms of energy changes related to bond formation and breaking and to “activation complex”
• Draw graphs of endothermic and exothermic reactions with and without activation energy