GCSE Combined Science (AQA)

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Endothermic Reactions

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Energy changes Exothermic and endothermic reactions

Endothermic Reactions

4:59 Types of Chemical Reaction
Spec 4.5.1.1
Previous Exothermic Reactions Next Activation Energy
  • Endothermic reactions absorb energy from surroundings.
  • Energy is taken in from the air and other substances.
  • The prefix "endo" means inside or internal.
  • The suffix "thermic" relates to heat.
  • Endothermic means heat moving inwards.
  • Energy transfer causes the temperature of surroundings to decrease.
  • Surroundings lose thermal energy to the reaction product.
  • Thermometer readings show a temperature decrease after the reaction.
  • Temperature change helps distinguish between exothermic and endothermic reactions.
  • Exothermic reactions increase temperature as energy is released to surroundings.
  • Exam data may include temperature changes to identify reaction types.
  • Reaction A with a temperature rise is exothermic.
  • Reaction B with a temperature drop is endothermic.
  • Example of endothermic reaction: thermal decomposition.
  • Thermal decomposition involves breaking down with heat.
  • Example: heating copper carbonate produces copper oxide and carbon dioxide.
  • Thermal decomposition reactions are endothermic.
  • Another endothermic reaction: citric acid with sodium hydrogen carbonate.
  • Sodium hydrogen carbonate is also known as bicarbonate of soda or baking soda.
  • Endothermic reaction with citric acid shows a temperature drop.
  • Flask feels cold to the touch during the reaction.
  • Practical applications: sports injury packs use endothermic reactions.
  • Cold packs contain water and a chemical pouch.
  • Twisting or squeezing the pack starts an endothermic reaction.
  • Exam questions may involve evaluating endothermic reactions for treating injuries.
  • Choose reactions with appropriate temperature changes to avoid damage.

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