Learning objective
(HT only) Calculate the overall energy change as energy needed to break bonds minus energy released when bonds form.
Read the explanation, check the common trap, then practise with flashcards and questions.
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Topic
Exothermic and endothermic reactions
Subtopic
The energy change of reactions (HT only)
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(HT only) Calculate the overall energy change as energy needed to break bonds minus energy released when bonds form
- This point belongs to Exothermic and endothermic reactions, especially The energy change of reactions (HT only).
- You need to be able to (HT only) Calculate the overall energy change as energy needed to break bonds minus energy released when bonds form.
- The key ideas to know are HT only, energy released, and overall energy change.
- Use the linked flashcards and practice questions to check recall, then practise applying the idea in an exam-style answer.
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This objective helps connect The energy change of reactions (HT only) to exam-style questions, flashcards, and revision notes for Exothermic and endothermic reactions.
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What should you know about (HT only) Calculate the overall energy change as energy needed to break bonds minus energy released when bonds form?
Direct answer
In Chemistry, this page helps you answer questions about (HT only) Calculate the overall energy change as energy needed to break bonds minus energy released when bonds form within Exothermic and endothermic reactions. Focus on the key process, correct scientific terms, and how the idea links to exam-style questions. Key terms to check are overall energy change and bond energy.
Key terms
- overall energy change: The difference between the energy needed to break bonds in reactants and the energy released when bonds form in products.
- bond energy: The amount of energy required to break one mole of a specific bond in a molecule. In The energy change of reactions (HT only), this term is used specifically to support the learning objective: (HT only) Calculate the overall energy change as energy needed to break bonds minus energy released when bonds form.
Common trap
Mis‑applying the sign convention: Remember the formula: ΔE = ΣE(bonds broken) – ΣE(bonds formed). For an exothermic reaction the second term is larger, so ΔE is negative, indicating energy is released.
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Revision notestopic notes
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Open revision notesRelated learning objectives
- State that energy is conserved in chemical reactions.
Energy transfer during exothermic and endothermic reactions
- Explain that a reaction transferring energy to the surroundings leaves products with less energy than the reactants by the amount transferred.
Energy transfer during exothermic and endothermic reactions
- Define an exothermic reaction as one that transfers energy to the surroundings.
Energy transfer during exothermic and endothermic reactions
- Explain that the temperature of the surroundings increases during an exothermic reaction.
Energy transfer during exothermic and endothermic reactions
- Identify combustion, many oxidation reactions and neutralisation as examples of exothermic reactions.
Energy transfer during exothermic and endothermic reactions