What is the difference between melting and burning a substance? Is mass conserved in either process?

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.

Explanation:

water is used to store them because it would keep the radiation from getting out in the open and causing harm to the workers

idk what the question is about