Which factor increases the likelihood of productive collisions by exposing more surface area?

• A. Increased concentration
• B. State of matter
• C. Increased surface area
• D. Inert atmosphere

Answer: (C)

Productive collisions depend on how often reacting particles meet and can orient properly to overcome activation energy. Exposing more surface area increases the number of reactive sites available at interfaces, so collisions that lead to a reaction become more likely. Grinding a solid into a powder creates many more surface sites for interactions, boosting the reaction rate. The other factors change collisions in different ways—higher concentration increases how many particles are present and collide, and a change in state affects mobility—while an inert atmosphere alters the environment but does not by itself increase the surface area exposed to reactants.