Chemistry C2 GCSE AQA - Unit 4

Follow up to units 1, 2 and 3

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How Fast?

  • Rate= amount of reactant used / time
  • OR
  • Amound of product formed / time
  • This equals the RATE OF REACTION
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Collision Theory

  • States reactions only happen if particles COLLIDE
  • The particles must collide with enough ENERGY to change into NEW SUBSTANCES
  • Minimum energy needed is called the ACTIVATION ENERGY
  • Factors that increase this are
    • TEMPERATURE
    • CONCENTRATION / PRESSURE
    • SURFACE AREA of solids
    • Use of a CATALYST
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Effect of Temperature

(http://i48.tinypic.com/2u5tipy.png)

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Effect of Concentration

(http://i45.tinypic.com/33e55k6.png)

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Effect of a Catalyst

  • Catalysts change the rates of chemical reactions
  • Most used to SPEED UP reactions
  • Catalyst is left at the end of the reaction so it can be REUSED
  • Work by LOWERING the ACTIVATION ENERGY
    • Means MORE collisions in a reaction
  • Most expensive, but ECONOMICAL - they do not need replacing often
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Comments

Nuha

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this is good :)

Jemima

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thanks :D 

OneTooManyAnOpinion

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Jemima wrote:

thanks :D 

No problem :)

OneTooManyAnOpinion

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Nuha wrote:

this is good :)

 Thank you! :)

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