Question

A heap of wet wood is burnt. It produces lot of smoke and leaves a residue. What do you call that residue and what is its use?

Answer 1

I t's coal which lefts while burning wet wood.

Answer 2

A heap of wet wood is burnt. It produces lot of smoke and leaves a residue which is known as coal.

its uses
1) It can be used to obtain lots of heat energy by burning it.
2) coal is used electricity production
3) it can be used in cement factory.