BRAINCAKEEffect of Surface Area
When one reactant is a solid, the reaction can only happen at its surface, because only the particles on the surface can collide with particles of the other reactant.
Breaking a solid into smaller pieces, or grinding it into a powder, increases its surface area for the same mass. More particles are exposed, so there are more collisions per unit time and more successful collisions per unit time, and the rate increases.
For example, calcium carbonate powder reacts much faster with dilute hydrochloric acid than the same mass of marble chips:
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More in Reaction Rates
- Activation Energy
- Steric Hindrance
- Effect of Concentration
- Effect of Pressure
- Maxwell-Boltzmann Distribution Curve
- Effect of Temperature
- Collisions in Solution
- Effect of Catalysts
All 12 lessons in Reaction Rates · All Edexcel AS-level Chemistry topics