Answer:
A: It is used for the phase change.
Explanation:
During a phase change, the heat added or realeased, the temperature remains constant and is used to be stored as potential energy.
Side Note: I hope this helps, feel free to let me know if you have any other questions :)
I don't think so. No way that I know anyway. It it could be done then the need for more coal to be mined would have stopped hundreds of years ago. Once coal is burned, it forms water and carbon dioxide (essentially) with some sulfur oxides.
How do you put that back together again. It's a little like humpty dumpty.