Which statement describes a catalyst? Catalysts appear as reactants in a chemical equation.
Catalysts are completely consumed by the reaction.
Catalysts provide a lower energy pathway for the reaction.
Catalysts speed up chemical reactions by increasing surface area.

Aphysical change is one that you can put in and remove like a ham sandwich. the stuff you put in there can be changem its not permanet. a chemical change is on that can't be change thats permanet. like when you make a cake and bake it. you can't get those ingredients back.