Collision Theory

IGCSE Edexcel Chemistry
3.11-3.13 Collision theory and catalysts
Key Concept: Successful collisions require sufficient energy and correct orientation. Catalysts lower activation energy.

Section A: Collision Theory

1. State two conditions for a successful collision. [2]
2. Explain why increasing temperature increases rate in terms of collision theory. [3]

Section B: Catalysts

3. What is a catalyst? [2]
4. Explain how a catalyst changes the energy profile of a reaction. [2]

Total marks: 9

Mark Scheme

1. Correct orientation and energy at least equal to activation energy [2]
2. Particles have more kinetic energy; more collisions per second; larger fraction exceed activation energy [3]
3. Substance that increases rate and is not used up/unchanged at end [2]
4. Provides an alternative pathway with lower activation energy [2]