What is a substance that increases the rate of a reaction but itself remains chemically unchanged?

• A. Catalyst
• B. Enzyme
• C. Substrate
• D. Product

Answer: (A)

A catalyst is a substance that speeds up a chemical reaction by providing an alternate pathway with a lower activation energy, and it is not consumed in the process. Because it’s not used up, the catalyst ends the reaction in the same chemical form it started with and can catalyze more reactions. That’s why it’s the best fit here.

Enzymes are a specific kind of catalyst found in living organisms, so they also speed up reactions without being permanently consumed. Substrates are the reactants, and products are what you get after the reaction, so neither of those changes the rate in the way a catalyst does.