Final answer:
A catalyst increases the rate of a chemical reaction by providing an alternative pathway with a lower activation energy, facilitating more effective collisions between reactant molecules.
Step-by-step explanation:
A catalyst may increase the rate of a chemical reaction by lowering the overall activation energy. It does this by providing an alternative pathway for the reaction that requires less energy than the uncatalyzed pathway, enabling a greater number of reactant molecules to have effective collisions and form products. While a catalyst can change the mechanism of a reaction, this doesn't necessarily alter the rate law directly; rather, it allows the reaction to proceed via a method that has a lower activation energy.