Effect of Surface Area on Rate

Surface area is another key factor that affects the rate of a chemical reaction. This lesson focuses on how breaking a solid reactant into smaller pieces increases the rate, and why this is explained by collision theory. You will also look at real-world examples, experimental evidence, and how to interpret surface area experiments on graphs. This topic is part of the Edexcel GCSE Chemistry (1CH0) specification.

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Why Does Surface Area Affect Rate?

When a solid reactant is broken into smaller pieces, the total surface area exposed to the other reactant increases. This means:

1. More of the solid is exposed and available to collide with particles of the other reactant (usually a liquid or gas).
2. There are more frequent collisions between the solid surface and the other reactant.
3. Therefore there are more successful collisions per second.
4. The rate of reaction increases.

The total amount of product formed remains the same (the same mass of solid is used), but the product is formed more quickly.

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Comparing Lumps, Chips and Powder