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4.5 Energy changes

3 dot points across 3 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How do we calculate the overall energy change of a reaction from bond energies?

Bond energy calculations; energy in to break bonds and out to make bonds; calculating the overall energy change; and linking the sign to exothermic or endothermic.
A focused answer to AQA GCSE Chemistry 4.5.1, covering how breaking bonds takes in energy and making bonds releases energy, calculating the overall energy change from bond energies, and linking the result to exothermic and endothermic reactions.
9 min answer →

What is the difference between exothermic and endothermic reactions?

Exothermic and endothermic reactions; energy transfer to and from the surroundings; everyday examples; and the required practical on temperature changes.
A focused answer to AQA GCSE Chemistry 4.5.1, covering exothermic and endothermic reactions, how energy is transferred to or from the surroundings, everyday examples such as hand warmers and sports packs, and the required practical on temperature changes.
8 min answer →

How do reaction profiles show energy changes and activation energy?

Reaction profiles for exothermic and endothermic reactions; activation energy; and how a catalyst lowers the activation energy.
A focused answer to AQA GCSE Chemistry 4.5.1, covering reaction profiles for exothermic and endothermic reactions, reading the overall energy change and activation energy from them, and how a catalyst lowers the activation energy.
8 min answer →