Question

What happens when wood is burnt in a limited supply of oxygen? Name the residue left behind after the reaction and state two advantages of using this residue as a fuel over wood.

Answer 1

When wood is burnt in a limited supply of oxygen, volatile materials present in it get removed and cooled to get wood tar and wood gas. 

The black residue left behind aftqr the reaction is known as charcoal. Advantages of using charcoal as a fuel over wood are: 

Burning of charcoal does not produce smoke. On the other hand, wood produces a lot of smoke on burning. For a given quantity, charcoal produces ,more heat than wood.