16. Why can grinding a solid into a fine powder increase the rate of reaction?

The process of grinding or breaking a substance tends to increase the surface area of the substance. When the surface area increases, there is a better chance for reactants to react and form product. Hence, the more the surface area, the more will be the reaction rate.

The increase in surface area causes the substance to collide with more force with the other reactant and as a result, the reaction rate increases.