CH4 and CO₂ are the chemical formulas for:

CH4 = Methane

CO2 = Carbon dioxide

Hope this Helps:)

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.

Maybe you should get some from your teacher and learn more so you can get your grades up and maybe study a bit more