Which term defines a substance that increases the rate of a chemical reaction?

Which term defines a substance that increases the rate of a chemical reaction?

• A. A substance that reduces temperature
• B. A substance used to color diamonds
• C. A substance that increases the rate of a chemical reaction
• D. A substance that changes shape of crystal

Answer: (C)

A catalyst is a substance that increases the rate of a chemical reaction by providing an alternative pathway with lower activation energy. It speeds up how quickly reactants are converted to products and is not consumed in the overall reaction, so it can continue to work in repeated cycles. Catalysts can operate in the same phase as the reactants (homogeneous) or on a different phase (heterogeneous). This definition directly matches the idea of speeding up reactions, which is what the term describes. Other options describe effects that don’t change reaction speed: lowering temperature tends to slow reactions, substances used to color diamonds don’t affect how fast a reaction occurs, and changing the shape of a crystal relates to structure rather than reaction kinetics.

A catalyst is a substance that increases the rate of a chemical reaction by providing an alternative pathway with lower activation energy. It speeds up how quickly reactants are converted to products and is not consumed in the overall reaction, so it can continue to work in repeated cycles. Catalysts can operate in the same phase as the reactants (homogeneous) or on a different phase (heterogeneous).

This definition directly matches the idea of speeding up reactions, which is what the term describes. Other options describe effects that don’t change reaction speed: lowering temperature tends to slow reactions, substances used to color diamonds don’t affect how fast a reaction occurs, and changing the shape of a crystal relates to structure rather than reaction kinetics.