how can you tell when a substance serves as a catalyst?
It makes a reaction run faster and better AND it is not used up by the reaction
The purpose of a catalyst is to provide an alternate pathway for a reaction to proceed, often one with a lower activation energy, such that the reaction will generally proceed faster. The key to catalysts if they they are NOT consumed by the reaction in the end (they may be consumed in an intermediary step, but if so, a subsequent step will recreate the catalyst). In other words, catalysts do not actually participate in the reaction, so they may be reused when the reaction has completed.
