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GCSE Chemistry · key term
The difference between the energy taken in to break bonds and the energy released when new bonds form during a reaction.
Used by AQA, Edexcel and OCR
Specification 4.5.1.2, 4.5.1.3 · Paper 1
The difference between the energy levels of the products and the reactants.
Revise: Reaction ProfilesThe overall energy change is the difference between the energy level of the reactants and the energy level of the products. It is shown by a vertical arrow connecting those two levels.
The energy needed to break the reactant bonds minus the energy released when the product bonds form.
Paper 2
The difference between the energy absorbed in breaking reactant bonds and the energy released when product bonds form.
Revise: Mathematical ApplicationsThe overall energy change depends on the balance between them.
Specification CM3.2ii, C3.2b, C3.2d · Paper 1 (Foundation), Paper 3 (Higher)
The difference between the energy levels of the products and reactants in a chemical reaction.
The energy transferred overall when a chemical reaction takes place; in a bond-energy calculation, it is the energy needed to break bonds minus the energy released when new bonds form.
Paper 1 (Foundation), Paper 2 (Foundation), Paper 3 (Higher), Paper 4 (Higher)
The difference between the energy levels of the products and the reactants; it is negative for an exothermic reaction and positive for an endothermic reaction.
Revise: Reaction profilesThe overall energy change is the difference between the reactant and product levels. For an exothermic reaction it is negative because the products are at lower energy than the reactants. If this change is included, draw its arrow between the two energy levels; do not confuse it with the larger arrow from the reactants to the peak.
The difference between the energy associated with the products and the energy associated with the reactants.
The energy taken in to break bonds minus the energy released when new bonds form, for the amounts specified by a chemical equation.
The difference between the energy transferred in breaking reactant bonds and the energy transferred out when product bonds form.
Keep the activation energy and overall energy change distinct: one reaches the peak, while the other compares reactants with products.
Keep the sign of the overall energy change and give the unit.
Show the overall energy change between the reactants’ and products’ energy levels.
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