Heat transfer in reactions
Heat transfer in reactions

Nearly every chemical change transfers heat between the reacting system and its surroundings. A temperature change is evidence that energy has moved, but temperature and energy are not the same quantity.
Step-by-step lessons on Edexcel GCSE Chemistry 8.2 Heat energy changes in chemical reactions, covering 8.2.1 Exothermic and endothermic changes, 8.2.2 Bond breaking, bond making and overall energy change, 8.2.3 Calculating energy change from bond energies, and 8.2.4 Activation energy and reaction profiles. 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.