Exothermic and Endothermic Reactions

IGCSE Edexcel Chemistry
3.1 Exothermic and endothermic reactions
Key Concept: Exothermic reactions release heat; endothermic reactions absorb heat.

Section A: Identifying Reactions

1. Define exothermic and endothermic reactions. [2]
2. A reaction causes the temperature of the solution to rise from 20 C to 35 C. Is it exothermic or endothermic? [1]
3. Give one example of an exothermic reaction and one example of an endothermic reaction. [2]

Section B: Energy Profiles

4. On an energy profile diagram, which is higher: reactants or products for an exothermic reaction? [1]
5. Explain what activation energy means. [2]

Total marks: 8

Mark Scheme

1. Exothermic releases heat to surroundings; endothermic absorbs heat from surroundings [2]
2. Exothermic [1]
3. Examples: combustion/neutralisation (exo); thermal decomposition/dissolving ammonium nitrate (endo) [2]
4. Reactants higher than products [1]
5. Minimum energy needed for particles to react [2]