What is the effect of increasing surface area on collision frequency?

• A. Collision frequency decreases
• B. Collision frequency increases
• C. Collision frequency stays the same
• D. Collision frequency depends only on temperature

Answer: (B)

Increasing surface area exposes more reactive sites, so more collisions can occur per unit time. When a solid reacts with a gas or liquid, breaking it into smaller pieces or grinding it into powder raises the area in contact with the other reactant. That larger contact area means more opportunities for collisions, which raises the collision frequency and typically speeds up the reaction (assuming there’s enough energy in those collisions for reaction to proceed). Temperature still affects whether those collisions lead to products, but surface area directly increases how often collisions happen.