If you don't have the mass, but you've got avagadros and the mr then why do you divide by avagadros instead of multiplying because mass is moles times the mr

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.