Which term best fits the definition: a molecule entering or starting a chemical reaction?

• A. Product
• B. Catalyst
• C. Reactant
• D. Inhibitor

Answer: (C)

In a chemical reaction, the substances that enter the reaction and undergo change are the reactants. They are the starting materials that are transformed into new substances as the reaction proceeds. The term for what you get after the reaction is the product. A catalyst is something that speeds up the reaction without being consumed itself, helping the process proceed but not becoming part of the final outcome. An inhibitor slows down or blocks the reaction by hindering the steps involved. For example, in the formation of water from hydrogen and oxygen, hydrogen and oxygen are the reactants, and water is the product.