Catalyst vs intermediate

[Crystal Escobar 1F]

How do we know the difference between a catalyst and an intermediate used in a reaction?

[504646485]

A catalyst only speed up the reaction so the amount of the catalyst won't change after the reaction. However, an intermediate can only be seen during the reaction.

[Christopher Lew 1L]

A catalyst lowers the activation energy of a reaction and pretty much never undergoes a chemical change as a result of the reaction. It provides a new pathway for the reaction which requires less energy. However, an intermediate is the substance that is formed briefly before reacting again to form another product. When there are two steps a reactant becomes a product and then this product reacts again to make another new product. It is easy to confuse the two, but the difference is that there should be catalyst left after the reaction. When you are combining steps you cancel the catalyst even though it is at the start and at the end.