#111
Factors affecting rate (collision theory)
Paper 2 · Higher combined
Key steps (method)
Use collision theory to explain rate changes:
- Temperature ↑ → particles move faster → more collisions + more have Ea.
- Concentration/pressure ↑ → more particles per volume → more collisions.
- Surface area ↑ → more exposed particles → more collisions.
- Catalyst → lower activation energy → more successful collisions.
Common mistakes
- Saying catalysts make collisions “more energetic” (they change Ea).
- Forgetting pressure only affects gases.
- Not linking surface area to collision frequency.
Exam-style questions (quick)
- Explain why increasing temperature increases rate (collision theory).
- Explain why powdered marble reacts faster than chips.
- Explain the effect of concentration on reaction time.