Year 10 - Energy Changes in Chemical Reactions

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Exothermic and Endothermic Reactions:

  • When chemical reactions occur, energy is transferred to or from the surroundings
  • An exothermic reaction is one that transfers energy to the surroundings
    • E.g Combustion and Neutralisation
    • Uses include hand-warmers and self-heating cans
  • An endothermic reaction is one that takes energy from the surroundings
    • E.g Thermal Decomposition
    • Uses include sports injury packs
  • If a reversible reaction is exothermic in one direction, it is endothermic in the other direction

Calculating and Explaining Energy Changes:

  • The relative amounts of energy released when substances burn can be measured by simple calorimetry 
    • e.g by heating water in a glass or metal container
    • Q = m c ΔT
  • Energy is normally measured in J (Joules) 
    • For comparison purposes, energy values could…

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