I have 10g of magnesium oxide that I heat to make 6g of magnesium and oxygen. how much oxygen is made? What kind of change is this, physical or chemical? why did you pick your answer? Explain in 2 sentences

Answer 1

The study of chemistry is called "Gateway" where you live? That's a new one on me!

Answer 2

I can tell you that you do not make oxygen by heating MgO. You make MgO by heating Mg and O2. However, in the spirit of the question, I will answer as written. This is the Law of Conservation of Mass. You started with 10 g so you must end up with 10 g.
.....MgO ==> Mg + O2
.....10......6.....? so ? must be 4. I did NOT check to see if the chemistry is right since I don't have my calculator with me.