heat transfer physical change law of conservation of mass law of conservation of energy
I gave my students this multiple choice question: A substance with a mass of 10 g is heated to produce two new substances. The mass of the first new substance is 9.3 g and the mass of the second new substance is 0.7 g. Which of the following is best demonstrated by this example?

Only one answer is correct among these 4 choices:
- heat transfer
- physical change
- law of conservation of mass
- law of conservation of energy

Could you tell me which one is correct?

law of conservation of mass