Altering Factors - Particle Size

AQA-style Exam Question

A student reacts hydrochloric acid with magnesium.

Explain why the rate of this reaction is different when magnesium is used as a fine powder compared to large ribbon strips. Refer to collision theory in your answer.

[3 marks]

*Explain = tell us HOW and WHY it is different

• In terms of particles, what makes the reaction occur?

  Reactions happen with particles of the two substances have a successful collision.

• How do particles in magnesium ribbon compare to powder? (1 mark)

  In a ribbon, there is less exposed surface area. In a powder, there is more exposed surface area.

• How frequent are particle collisions when magnesium is a ribbon vs powder? (1 mark)

  When magnesium is a fine powder, the

• So how does that affect RATE of reaction? (1 mark)

  More frequent collisions (more collisions per second) lead to higher probability of successful collisions, therefore speeding up the rate of reaction.

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