What do you call a substance that speeds up a chemical reaction?

A substance that speeds up a chemical reaction is known as a catalyst. Catalysts work by lowering the activation energy required for a reaction to occur, thereby increasing the rate at which the reaction proceeds. They are not consumed in the reaction, meaning they can be used repeatedly in multiple reactions, facilitating the transformation of reactants into products more efficiently. This ability to enhance reaction rates without being altered themselves is a critical characteristic that distinguishes catalysts from other substances involved in chemical reactions.

In contrast, reactants are the starting materials in a chemical reaction, and products are the substances formed as a result of that reaction. An inhibitor, on the other hand, is a substance that slows down or prevents a chemical reaction. Thus, the definition and role of a catalyst is pivotal in chemistry, especially in industrial applications and biochemical processes.