201 Chemistry/2.6

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At Papanui instead of completing Achievement Standard 2.6 we complete Unit Standards 8942: Characterise the nature of chemical systems at equilibrium (2 credits) and 6338: Characterise the behaviour of weak and strong acids and bases (3 credits).


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By the end of this unit you will be able to:
  • Write equilibrium constant expressions for given chemical equations.
  • Predict how the equilibrium position changes as a result of a change in conditions. e.g.
    • Change of temperature
    • Change of concentration
    • Change of pressure
    • Addition / removal of catalyst.

Energy Changes

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By the end of this unit you will be able to:
  • Categorise physical and chemical reactions as exothermic or endothermic
  • Carry out enthalpy change calculations
  • Accurately obtain data from calorimetric investigations

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Key points
Exothermic and endothermic reactions

When you have carried out chemical reactions you will probably have noticed the temperature of the reaction changing. This is due to a transfer of energy. Reactions that give out heat, such as burning and acid plus metal reactions are exothermic and reactions that take in heat such as photosynthesis are endothermic.

Exothermic and endothermic reactions can also be represented using energy level diagrams.


Exothermic Endothermic