Effect of solid particle size (surface area) - higher tier

The rate of a chemical reaction can be increased by using smaller solid particles which increases the surface area of a solid reactant. This is done by cutting the substance into small pieces, or by grinding it into a powder. If the surface area of a reactant is increased:

  • more particles are exposed to the other reactant
  • there are more successful collisions per unit time
  • the rate of reaction increases
Reaction rate graph – surface area

Compared to a reaction with lumps of reactant, the graph line for the same reaction but with powdered reactant:

  • has a steeper gradient at the start
  • becomes horizontal sooner

This shows that the rate of reaction is greater when the surface area is increased.