Final answer:
A catalyst is a substance that increases the rate of a chemical reaction without being consumed, by lowering the activation energy needed for the reaction to proceed, allowing the reaction to reach equilibrium faster.
Step-by-step explanation:
The best definition of a catalyst is option C) A catalyst is a material that speeds up the rate of a chemical reaction without being consumed during the reaction. While both A and B are partially correct, they omit the important detail that a catalyst is not consumed during the reaction.
In chemistry, a catalyst is a substance that increases the rate of a chemical reaction by lowering the activation energy and providing a new reaction pathway. It essentially reduces the energy barrier that reactants must overcome, thereby increasing the number of successful collisions per unit time. However, it is important to note that a catalyst does not change the overall balance or position of a reaction at equilibrium; it simply helps the reaction reach equilibrium faster. Furthermore, because the catalyst is not consumed in the reaction, it can be recovered unchanged at the end and reused.