What is the role of a catalyst in a chemical reaction?

A catalyst plays a crucial role in chemical reactions by lowering the activation energy required for the reaction to proceed. Activation energy is the minimum energy that reactant molecules must possess for the reaction to occur. By providing an alternative reaction pathway with a lower activation energy, a catalyst facilitates the reaction, allowing it to happen more easily or at a faster rate without being consumed in the process. This means that while the catalyst participates in the reaction, it is regenerated and can be used repeatedly, which is why it does not alter the final products or the overall energy change of the reaction.

In contrast, increasing the energy of the reactants or altering the final products is not the function of a catalyst. Additionally, whereas a catalyst does indeed participate in the mechanism, it is not consumed, which distinguishes it from reactants. Thus, the correct choice highlights the essential characteristic of catalysts in enhancing reaction efficiency by reducing the activation energy barrier.