How does increasing the concentration of reactants affect reaction rates?

Increasing the concentration of reactants directly impacts the reaction rate by increasing the frequency of collisions between reactant molecules. When the concentration of reactants is higher, there are more molecules available in a given volume. This higher density means that the likelihood of molecules coming into contact with each other, and thus colliding, is increased. Since reactions occur when reactant molecules collide with enough energy to overcome the activation energy barrier, more frequent collisions lead to a greater number of successful reactions, thereby increasing the overall reaction rate.

In essence, higher concentration means more reactant particles are present, which enhances the probability of effective collisions required for the reaction to take place.