Explain why increasing the temperature of a reaction increases the rate of reaction.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A student notices that a chemical reaction happens much faster when heated. The student says: 'The particles must be moving faster.'
Model answer (5 marks)
Increasing temperature raises the kinetic energy of the reacting particles.
Higher kinetic energy means particles move faster and collide more often – there are more collisions per unit time.
Because the energy distribution widens, a larger proportion of the particles possess energy equal to or greater than the activation energy.
Thus more collisions are successful, giving a higher number of successful collisions per unit time.
Consequently the overall rate of the reaction increases.
Higher kinetic energy means particles move faster and collide more often – there are more collisions per unit time.
Because the energy distribution widens, a larger proportion of the particles possess energy equal to or greater than the activation energy.
Thus more collisions are successful, giving a higher number of successful collisions per unit time.
Consequently the overall rate of the reaction increases.
Examiner tips
- Use the sequence: kinetic energy → collision frequency → activation energy → successful collisions → rate.
- Show the logical flow and link each point to the next.
- Mention the energy distribution (Maxwell–Boltzmann).
Common mistakes
- Confusing collision frequency with activation energy; writing them as the same thing.
- Failing to explain that only collisions with sufficient energy are successful.
- Using vague phrases like "more energy" without linking to activation energy.
Mark scheme (5 marks)
- Increasing temperature increases the kinetic energy of the particles
- Particles collide more frequently / there are more collisions per unit time
- A greater proportion of particles have energy greater than or equal to the activation energy
- So there are more successful collisions per unit time
- Therefore the rate of reaction increases
Key terms in this question
Related
- All AQA A-Level Chemistry (7405) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →