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
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.