If you were in charge of making the decision to clean up the city’s polluted water, would you make laws to reduce the use of chemicals, schedule cleanups, or stop all use of chemicals?

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.