Why should the solid be crushed before a reaction?

• A. It reduces the mass of the solid.
• B. It increases the surface area for a faster rate of reaction.
• C. It makes the solid easier to weigh.
• D. It changes the chemical identity of the solid.

Answer: (B)

Increasing the surface area of a solid exposes more of its particles to the other reactant. When a solid reacts, only the particles at the surface can interact at a given moment. By crushing, you create many more surface sites, so there are more opportunities for collisions to occur. This raises the frequency of effective collisions and makes the reaction happen faster. Crushing doesn't change what the substance is or how much there is; it just increases contact with the other reactant.