How does decreasing particle size affect the rate of a reaction between a solid and a liquid?

How does decreasing particle size affect the rate of a reaction between a solid and a liquid?

• A. Decreases surface area, slows rate
• B. No effect on rate
• C. Increases surface area, increases rate
• D. Increases surface area, slows rate

Answer: (C)

When a solid reacts with a liquid, the reaction can only occur at the surface of the solid that is in contact with the liquid. The rate therefore depends on how much surface area is exposed. Making the solid into smaller particles increases its total surface area for the same mass, so more surface is available for reaction at once. With more surface contact, more molecules can collide and react per unit time, speeding up the reaction. So decreasing particle size increases surface area and increases the rate.

When a solid reacts with a liquid, the reaction can only occur at the surface of the solid that is in contact with the liquid. The rate therefore depends on how much surface area is exposed. Making the solid into smaller particles increases its total surface area for the same mass, so more surface is available for reaction at once. With more surface contact, more molecules can collide and react per unit time, speeding up the reaction. So decreasing particle size increases surface area and increases the rate.