AQA GCSE Chemistry

Revision Notes

6.1.5 Factors that Affect the Rate of Reaction

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 & 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 & GCSE Chemistry revision notes

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

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 using catalyst, IGCSE & GCSE Chemistry revision notes

Graph showing the effect of using a catalyst on the activation energy of a reaction

Explanation:

  • The diagram shows that when a catalyst is used, the activation energy is reduced as it creates an alternative pathway requiring lower activation energy
  • Lowering the activation energy means more particles will have enough energy to react when they come together
  • This shows that when a catalyst is used, 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

Author: Francesca

Fran has taught A level Chemistry in the UK for over 10 years. As head of science, she used her passion for education to drive improvement for staff and students, supporting them to achieve their full potential. Fran has also co-written science textbooks and worked as an examiner for UK exam boards.
Close

Join Save My Exams

Download all our Revision Notes as PDFs

Try a Free Sample of our revision notes as a printable PDF.

Join Now
Already a member?
Go to Top