Factors that Affect the Rate of Reaction (AQA GCSE Chemistry)

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Factors that Affect the Rate of Reaction

  • There are several factors that can affect the rate of a reaction. These are:
    • Concentration of the reactants in solution or the pressure of reacting gases
    • Temperature at which the reaction is carried out
    • Surface area of solid reactants
    • The use of a catalyst

  • Changes in these factors directly influence the rate of a reaction
  • It is of economic interest to have a higher rate of reaction as this implies a higher rate of production and hence a more efficient and sustainable process

The Effect of Increased Concentration or Pressure

Concentration of solution, IGCSE & GCSE Chemistry revision notes

Graph showing the effect of the concentration of a solution or gas pressure on the rate of reaction

Explanation:

  • Compared to a reaction with a reactant at a low concentration, the graph line for the same reaction but at a higher concentration/pressure has a steeper gradient at the start and becomes horizontal sooner
  • This shows that with increased concentration of a solution, the rate of reaction will increase 

Effect of Increasing Temperature

temperature-diagram-igcse-and-gcse-chemistry-revision-notes

Graph showing the effect of temperature on the rate of reaction

Explanation:

  • Compared to a reaction at a low temperature, the graph line for the same reaction but at a higher temperature has a steeper gradient at the start and becomes horizontal sooner
  • This shows that with increased temperature, the rate of reaction will increase

Surface Area

surface-area-graph-igcse-and-gcse-chemistry-revision-notes

Graph showing the effect of increased surface area on the rate of reaction

Explanation:

  • Compared to a reaction with lumps of reactant, the graph line for the same reaction but with powdered reactant has a steeper gradient at the start and becomes horizontal sooner
  • This shows that with increased surface area of the solid, the rate of reaction will increase

Surface Area and Particle Size

Surface Area of a Solid Reactant, IGCSE & GCSE Chemistry revision notes

Diagram showing that surface area increase as particle size decreases. A 2 cmcube has a surface area of 24 cmand the same cube cut up into 8 cubes has a surface area of 48 cm2

Effect of a Catalyst

 

effect-of-catalyst-on-rate-of-reaction

Graph showing the effect of using a catalyst on the rate of reaction

Explanation:

  • Compared to a reaction without a catalyst, the graph line for the same reaction but with a catalyst has a steeper gradient at the start and becomes horizontal sooner
  • This shows that with a catalyst, the rate of reaction will increase

Exam Tip

You should be able to recall how changing the concentration, pressure, temperature, surface area and catalysts affect the rate of reactions

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Stewart

Author: Stewart

Stewart has been an enthusiastic GCSE, IGCSE, A Level and IB teacher for more than 30 years in the UK as well as overseas, and has also been an examiner for IB and A Level. As a long-standing Head of Science, Stewart brings a wealth of experience to creating Topic Questions and revision materials for Save My Exams. Stewart specialises in Chemistry, but has also taught Physics and Environmental Systems and Societies.