Exothermic and endothermic reactions

• Exothermic reaction


  A reaction that gives out heat
• Endothermic reaction


  A reaction that takes in heat
• Energy changes in chemical reactions

  1. Reactants store energy

  2. If products store more energy than reactants, energy is released (exothermic)

  3. If products store less energy than reactants, energy is absorbed (endothermic)

  4. Total energy is conserved - it can only be moved around, not created or destroyed
• Exothermic reactions


  • Combustion reactions
  • Reaction of sodium with water
• Endothermic reactions


  • Decomposition of calcium carbonate
  • Heating cold packs
• Exothermic reactions have many everyday uses, like heating hot chocolate and coffee
• Endothermic reactions are less common than exothermic reactions
• When an acid is mixed with water

  The temperature increases
• The question is asking whether the reaction between the acid and water is exothermic or endothermic