What word describes a substance that speeds up a chemical reaction without being consumed?

• A. Base
• B. Inhibitor
• C. Acid
• D. Catalyst

Answer: (D)

A catalyst is a substance that speeds up a chemical reaction without being consumed in the process. It provides a faster reaction pathway with lower activation energy, so more molecules have enough energy to react in the same amount of time. Because it isn’t used up, the catalyst can continue to work through many cycles, and it doesn’t change the final amounts of products and reactants, just how quickly equilibrium is reached. Enzymes are a common example of catalysts in biology. In contrast, acids and bases describe proton-transfer properties and don’t inherently mean a substance speeds up reactions without being consumed, and inhibitors slow down or stop reactions. So the term that fits is catalyst.