Hello!
The answer is Evaporation!
When you add enough heat to a liquid, it boils turning into a gas. This is called Evaporation
Answer:
Coal is formed under the ground when pressure is high and there is a lot of heat also to make coal you need dead and composed organisms put together all of this makes a lump of dark coal.
Explanation:
Convection is when cool air sinks and warm air rises. i am not 100% sure though