Explain why increasing the temperature of a reaction mixture increases the rate of a chemical reaction.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A student notices that hydrogen peroxide solution decomposes much more quickly when it is warmed than when it is kept in a cool cupboard.
Model answer (4 marks)
Increasing the temperature gives the reacting particles more kinetic energy, so they move faster.
As a result, collisions between the particles become more frequent.
With a higher kinetic energy, a larger proportion of the collisions have energy equal to or greater than the activation energy.
Consequently, more collisions lead to product formation, so the rate of reaction increases.
As a result, collisions between the particles become more frequent.
With a higher kinetic energy, a larger proportion of the collisions have energy equal to or greater than the activation energy.
Consequently, more collisions lead to product formation, so the rate of reaction increases.
Examiner tips
- Use the word "explain" to show cause and effect, not just state facts.
- Mention kinetic energy, collision frequency and activation energy in the correct order.
- Show the logical chain from temperature to rate increase.
Common mistakes
- Failing to link temperature to kinetic energy and then to collision frequency.
- Omitting the activation energy step.
- Using vague phrases like "more energy" without specifying kinetic energy or collisions.
Mark scheme (4 marks)
- Particles move faster / have more kinetic energy at higher temperature
- Particles collide more frequently / there are more collisions per unit time
- A greater proportion of collisions have energy equal to or greater than the activation energy
- Therefore more product is formed per unit time / the rate of reaction increases
Related
- All Cambridge International IGCSE Chemistry (0620) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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