Explain why increasing the temperature increases the rate of a chemical reaction.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A student is investigating how changing conditions affects the rate of a reaction between marble chips and hydrochloric acid. She notices that when she heats the acid before adding the marble chips, the reaction appears to be much faster.
Model answer (4 marks)
Increasing temperature gives the reacting particles more kinetic energy, so they move faster.
The higher speed means particles collide with one another more often, increasing the collision frequency.
Because the kinetic energy distribution is broader, a greater proportion of the particles possess energy equal to or greater than the activation energy.
Consequently, more collisions are successful, so the rate of successful collisions – and therefore the reaction rate – increases.
The higher speed means particles collide with one another more often, increasing the collision frequency.
Because the kinetic energy distribution is broader, a greater proportion of the particles possess energy equal to or greater than the activation energy.
Consequently, more collisions are successful, so the rate of successful collisions – and therefore the reaction rate – increases.
Examiner tips
- Use the exact terms: kinetic energy, collision frequency, activation energy, successful collisions.
- Show the causal chain: temperature → kinetic energy → collision frequency & energy distribution → more successful collisions → faster rate.
- Keep each point concise and directly linked to the marks scheme.
Mark scheme (4 marks)
- Increasing temperature gives particles more kinetic energy / particles move faster
- Particles collide more often / collision frequency increases
- A greater proportion of particles have energy equal to or greater than the activation energy
- There are more successful collisions per unit time / rate of successful collisions increases
Related
- All OCR GCSE Chemistry A: Gateway Science (J248) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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