What happens to the chemical elements that make up the molecules of living things as they pass through a food web?

What happens to the chemical elements that make up the molecules of living things as they pass through a food web is that some of their energy is stored in newly-made structures.
When molecules circulate freely like that, they become energy at some point. Especially if they are eaten by organisms - then the energy they become is stored in those organisms and used for everyday functions such as moving, eating, and generally living.

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.