The term 'catalyst' means what in science?

• A. A substance that speeds up a chemical reaction
• B. A substance that slows down a reaction
• C. A substance that is produced as a result
• D. A substance that alters the color of a reaction

Answer: (A)

A catalyst speeds up a chemical reaction by providing an alternative pathway with lower activation energy, so more particles can react at the same temperature. It isn’t consumed in the reaction, and it doesn’t change the overall energy change of the reaction—it just makes the process happen faster. A common example is enzymes in biology, which accelerate essential reactions without being used up. The idea of something that slows a reaction describes an inhibitor, not a catalyst. A substance produced as a result is a product, not a catalyst, and a color change might come from another component like an indicator, not catalysis.