Cambridge IGCSE Chemistry
5.1Exothermic and endothermic reactions
Exothermic and endothermic reactions in Cambridge IGCSE Chemistry: what the syllabus expects you to know, the learning objectives and how to practise.
Subtopic60 practice questions3 lessons
Learning objectives
What the syllabus expects you to be able to do.
- 5.1.1State that an exothermic reaction transfers thermal energy to the surroundings, so the temperature of the surroundings rises.
- 5.1.2State that an endothermic reaction takes in thermal energy from the surroundings, so the temperature of the surroundings falls.
- 5.1.3Interpret reaction pathway diagrams for exothermic and endothermic reactions.
- 5.1.4Supplement: state that the thermal energy transferred in a reaction is its enthalpy change, ΔH, which is negative for exothermic reactions and positive for endothermic reactions.
- 5.1.5Supplement: define activation energy, Ea, as the minimum energy that colliding particles need in order to react.
- 5.1.6Supplement: draw and label reaction pathway diagrams for exothermic and endothermic reactions from given information, showing the reactants, the products, ΔH and Ea.
- 5.1.7Supplement: state that breaking bonds is endothermic and making bonds is exothermic, and use this to explain the enthalpy change of a reaction.
- 5.1.8Supplement: calculate the enthalpy change of a reaction from bond energies.
Lessons
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Enthalpy changes from bond energies
35 min
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Exothermic and endothermic reactions
25 min
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Reaction pathway (energy profile) diagrams
30 min
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Sample question
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