Energy changes in bonds
Energy changes in bonds

During a reaction, bonds in the reactants are broken and bonds in the products are formed. These processes occur as the reaction takes place rather than as strictly separate stages. Bond breaking always requires energy, so it is endothermic, while bond making always releases energy, so it is exothermic.
Step-by-step lessons on Edexcel GCSE Chemistry 8.2.2 Bond breaking, bond making and overall energy change. Each one builds up to exam-style questions. Nail the core quantitative topics — moles, balancing equations and calculations — early on, since they underpin higher-tier questions across every paper and topic.