Chemistry C5

  • Created by: abbiedye
  • Created on: 25-07-18 14:50

What is an Exothermic Reaction?

  • A reaction that transfers energy to the surroundings usually by heating, indicated by a rise in temperature
  • Examples are combustion, neutralisation reactions (acid + alkali) and oxidation reactions (sodium added to water)
    Everyday examples are hand warmers and self-heating cans
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What is an Endothermic Reaction?

  • A reaction that takes in energy from the surroundings, indicated by a fall in temperature
  • Examples are reactions between citric acid and sodium hydrocarbonate, thermal decomposition
  • An everyday example is sports injury packs
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How are bonds formed and broken?

  • Energy must be supplied to break existing bonds in bond breaking (endothermic)
  • Energy is released when new bonds are formed in bond forming (exothermic)
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How do you calculate bond energies?

  • Find the energy required to break the original bonds
  • Find the energy released by forming the new bonds
  • Find the overall energy change for the reaction using the equation:
  • overall energy change = energy required to break bonds - energy released by forming bonds
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