Given, 2Ca + O2 -> 2CaO, what is the 2 located in front of calcium called??

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.

Electrons are emitted