GCSE Combined Science (AQA)

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Exothermic Reactions

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Energy changes Exothermic and endothermic reactions

Exothermic Reactions

4:28 Types of Chemical Reaction
Spec 4.5.1.1
Previous Conservation of Energy Next Endothermic Reactions
  • Exothermic reactions transfer energy to the surroundings.
  • Exothermic means heat moving outwards, derived from "exo" (outside) and "thermic" (heat).
  • Energy transfer during exothermic reactions increases the temperature of the surroundings.
  • Measuring temperature before and after a reaction shows an increase due to energy release.
  • Combustion reactions are examples of exothermic reactions, such as methane burning in oxygen.
  • The word equation for methane combustion: methane + oxygen ��� carbon dioxide + water.
  • Combustion requires an initial energy input but releases a lot of energy as a flame.
  • Neutralization reactions (acid + alkali ��� salt + water) are exothermic, releasing energy.
  • Oxidation reactions (metal + oxygen ��� metal oxide) are exothermic, e.g., sodium burning in oxygen.
  • Everyday uses of exothermic reactions include self-heating cans and hand warmers.
  • Hand warmers use exothermic reactions to release heat, often triggered by a start disc.
  • Self-heating cans contain chemicals that react exothermically to heat the drink inside.
  • Familiarity with these examples is important for exams, including evaluating their use.

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