What is smoke?

A fire is fed by fuel such as wood and coal. When the dancing flames blaze away, the wood and coal gradually disappear. The smoke which coils up from the blaze in sooty clouds explains part of this mystery. In the heat of the fire, the wood and coal turn into other things   and orgy of these things is smoke.

Wood and coal are made from tiny particles and the heat of the fire breaks these particles to pieces. They are now different particles. Same become gases and float off to mix with the other invisible gases in the air. Some become fragments of carbon, small enough to float in the air. It is these carbon particles which make the clouds of sooty smoke.