Propane (C3H8) reacts with oxygen (O2) during a combustion reaction, producing carbon dioxide (CO2) and water (H2O).
Which equation demonstrates the law of conservation of matter for this reaction?

The molecules contain like 54 of water 

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.