Answer:
Step-by-step explanation:
First Question:
Melting is a physical process that involves the phase transition of a substance from its solid to its liquid state. Burning, on the other hand, is a chemical process that involves a substance being broken down and changed into different substances. It's still the same substance, though: water.
Second Question:
Mass is therefore never conserved because a little of it turns into energy (or a little energy turns into mass) in every reaction. But mass+energy is always conserved. Energy cannot be created out of anything.