Which statement best describes a catalyst?

Which statement best describes a catalyst?

• A. Substances that decrease activation energy
• B. Substances that increase activation energy
• C. Substances that are consumed in the reaction
• D. Substances that speed up a reaction by changing the products

Answer: (A)

Catalysts speed up reactions by providing an alternate pathway with lower activation energy. By lowering the energy barrier that reactants must overcome, more molecules can react at the same temperature, so the reaction goes faster without adding heat. Catalysts aren’t consumed in the reaction and don’t change the final products or overall equilibrium—they just make the process happen more quickly. That’s why describing catalysts as substances that decrease activation energy is the best fit. The other ideas don’t fit because increasing activation energy would slow the reaction, being consumed would mean it’s a reactant, and changing the products would mean it alters the outcome rather than the rate.

Catalysts speed up reactions by providing an alternate pathway with lower activation energy. By lowering the energy barrier that reactants must overcome, more molecules can react at the same temperature, so the reaction goes faster without adding heat. Catalysts aren’t consumed in the reaction and don’t change the final products or overall equilibrium—they just make the process happen more quickly. That’s why describing catalysts as substances that decrease activation energy is the best fit.

The other ideas don’t fit because increasing activation energy would slow the reaction, being consumed would mean it’s a reactant, and changing the products would mean it alters the outcome rather than the rate.