Science Common Sense

1524 - How does the contact surface area of a substance affect the rate of a reaction?

The contact surface area of a substance can greatly affect the rate of a reaction. Imagine breaking a cookie into smaller pieces.

• The smaller pieces have more surface area touching the air, which makes them get stale faster.
• Similarly, when a substance has more surface area exposed, there are more particles interacting with other substances, making the reaction happen faster.

For example, if you had a big rock of limestone and you wanted to react it with acid (like vinegar), it would react very slowly. But if you broke the rock into small pieces or even powder, it would react much faster because more of the rock's particles are exposed to the acid. This is why increasing the contact surface area can increase the rate of a reaction.