EDEXCEL IGCSE CHEMISTRY: DOUBLE SCIENCE 复习笔记:3.1.1 Exothermic & Endothermic

EDEXCEL IGCSE CHEMISTRY: DOUBLE SCIENCE 复习笔记:3.1.1 Exothermic & Endothermic

Exothermic & Endothermic

 

  • The changes in heat content can be determined and measured with a thermometer
  • Note that the overall amount of energy does not change as energy is conserved in reactions
    • This is known as the law of conservation of energy

     

  • This means that it cannot be created or destroyed but it can be transferred
  • So, if energy is transferred to the surroundings during a chemical reaction, then the products formed must have less energy than the reactants by the same amount as that transferred

 

 

Exothermic- reaction, IGCSE & GCSE Chemistry revision notes

 

In exothermic reactions, the temperature of the surroundings increases and the heat content of the system falls

 

 

Endothermic- reaction, IGCSE & GCSE Chemistry revision notes

 

In endothermic reactions, the temperature of the surroundings falls and the heat content of the system increases

 

 

 

  • The following are some examples of heat changes in reactions
    • Neutralisation reactions:
      • These always give energy out

       

    • Displacement reactions:
      • These can either take energy in or give it out

       

    • Combustion reactions:
      • These always give energy out

       

     

 

Exam Tip

Physical processes can also involve heat exchange. Examples include freezing or melting which involve a change in state.

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