Specification Point 3.9:
Describe experiments to investigate the effects of changes in surface area of a solid, concentration of a solution, temperature and the use of a catalyst on the rate of a reaction
Rate of reaction, Edexcel IGCSE Chemistry

Effect of Surface Area of a Solid on the Rate of Reaction

Downwards displacement, Edexcel IGCSE Chemistry

The process of downwards displacement to investigate the effect of the surface area of a solid on the rate of reaction

Method:

  • Add dilute hydrochloric acid into a conical flask
  • Use a capillary tube to connect this flask to a measuring cylinder upside down in a bucket of water (downwards displacement)
  • Add calcium carbonate chips into the conical flask and close the bung
  • Measure the volume of gas produced in a fixed time using the measuring cylinder
  • Repeat with different sizes of calcium carbonate chips (solid, crushed and powder)

Result:

  • Increase in the surface area of the solid, the rate of reaction will increase.
  • This is because more surface area particles will be exposed to the other reactant so there will be more frequent and successful collisions, increasing the rate of reaction.

Effect of Concentration of a Solution on the Rate of Reaction

Effect of Concentration, Edexcel IGCSE Chemistry

The apparatus needed to investigate the effect of concentration on the rate of reaction

Method:

  • Measure 50 cm3 of Sodium Thiosulfate solution in a flask
  • Measure 5 cm3 of dilute Hydrochloric acid into a measuring cylinder
  • Draw a cross on a piece of paper and put it underneath the flask
  • Add the acid into the flask and immediately start the stopwatch
  • Look down at the cross from above and stop the stopwatch when the cross can no longer be seen
  • Repeat using different concentrations of Sodium Thiosulfate solution (mix different volumes of sodium thiosulfate solution with water to dilute it)

Result:

  • Increase in the concentration of a solution, the rate of reaction will increase
  • This is because there will be more reactant particles in a given volume, allowing more frequent and successful collisions, increasing the rate of reaction

Effect of Temperature on the Rate of Reaction

The apparatus needed to investigate the effect of temperature on the rate of reaction

Method:

  • Dilute Hydrochloric acid is heated to set temperature using a water bath
  • Add the dilute Hydrochloric acid into a conical flask
  • Add a strip of Magnesium and start the stopwatch
  • Stop the time when the Magnesium fully dissolves
  • Repeat at different temperatures and compare results

Result:

  • Increase in the temperature, the rate of reaction will increase
  • This is because the particles will have more kinetic energy than the required activation energy, therefore more frequent and successful collisions will occur, increasing the rate of reaction

Effect of a Catalyst on the Rate of Reaction

Effect of catalyst, Edexcel IGCSE Chemistry

The apparatus needed to investigate the effect of a catalyst on the rate of reaction

Method:

  • Add Hydrogen Peroxide into a conical flask
  • Use a capillary tube to connect this flask to a measuring cylinder upside down in a bucket of water (downwards displacement)
  • Add the catalyst Manganese (iv) Oxide into the conical flask and close the bung
  • Measure the volume of gas produced in a fixed time using the measuring cylinder
  • Repeat experiment without the catalyst of Manganese (iv) Oxide and compare results

Result:

  • Using a catalyst will increase the rate of reaction
  • The catalyst will provide an alternative pathway requiring lower activation energy so more colliding particles will have the necessary activation energy to react
  • This will allow more frequent and successful collisions, increasing the rate of reaction
Specification Point 3.10:
Describe effects of changes in surface area of a solid, concentration of a solution, pressure of a gas, temperature and the use of a catalyst on the rate of a reaction

Effect of Factors on the Rate of Reaction

*Surface area of a solid:

Surface area of a solid, CIE IGCSE Chemistry

The effect of the surface area of a solid 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.

*Concentration of a solution:

Concentration of a solution, CIE IGCSE Chemistry

The effect of the concentration of a solution 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 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.

*Pressure of a gas:

The effect of the pressure of a gas on the rate of reaction

Explanation:

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

*Temperature:

Temperature, CIE IGCSE Chemistry

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.

*Use of a catalyst:

The effect of the use of a catalyst on the rate of 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, allowing more successful and frequent collisions.
  • This shows that when a catalyst is used, the rate of reaction will increase.
Specification Point 3.11:
Explain the effects of changes in surface area of a solid, concentration of a solution, pressure of a gas and temperature on the rate of a reaction in terms of particle collision theory

Particle collision theory: For particles to react, they need to collide with one another

Effect of Factors on the Rate of Reaction

*Surface area of a solid:

Surface area of a solid, CIE IGCSE Chemistry

Surface area to volume ratio of various sized cubes

Explanation:

  • Increase in the surface area of the solid, the rate of reaction will increase
  • This is because more surface area particles will be exposed to the other reactant so there will be more frequent and successful collisions per second, increasing the rate of reaction

*Concentration of a solution:

Concentration of a solution ii, CIE IGCSE Chemistry

Increase in concentration of solution

Explanation:

  • Increase in the concentration of a solution, the rate of reaction will increase
  • This is because there will be more reactant particles in a given volume, allowing more frequent and successful collisions per second, increasing the rate of reaction

*Pressure of a gas:

Pressure of a gas ii, Edexcel IGCSE Chemistry

Increase in pressure of a gas

Explanation:

  • Increase in the pressure of a gas, the rate of reaction will increase
  • This is because there will be more reactant particles in a given volume, allowing more frequent and successful collisions per second, increasing the rate of reaction

*Temperature:

Temperature ii, CIE IGCSE Chemistry

The effect of temperature on particles

Explanation:

  • Increase in the temperature, the rate of reaction will increase
  • This is because the particles will have more kinetic energy than the required activation energy, therefore there will be more frequent and successful collisions per second, increasing the rate of reaction

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Author: Jamie

Jamie got a First class degree in Chemistry from Oxford University before going on to teach chemistry full time as a professional tutor. He’s put together these handy revision notes to match the Edexcel IGCSE Chemistry specification so you can learn exactly what you need to know for your exams.