If the density of the gas is 1.2 g/L at 745. torr and 20 C, what is its molecular mass?

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.