Which action would likely increase the rate of a chemical reaction?

Reducing particle size is a correct action to increase the rate of a chemical reaction. When the particle size of reactants is decreased—such as by grinding a solid into a finer powder—there is an increase in the surface area available for collisions between reactant particles. This higher surface area allows more frequent collisions to occur, therefore providing more opportunities for effective reactions to take place. The rate of reaction is directly proportional to the number of collisions; hence, a reduction in particle size leads to an accelerated reaction.

In contrast, decreasing concentration would reduce the number of reactant particles in a given volume, leading to fewer collisions per unit time and a slower reaction rate. Lowering the temperature typically decreases the kinetic energy of the particles, resulting in fewer effective collisions between them; hence, the reaction slows down. Adding an inhibitor serves to slow down a reaction by interfering with the reactants or the catalytic process, effectively decreasing the rate of the reaction.