- Dust is always present in the air and smoke is produced by the burning of fuel.
- Smoke contains some gases and fine dust particles which are harmful.
- Burning of fuel produces smoke, smoke also enters air from vehicles and burning of coal in factories.
Activity to show the presence of dust particle in the air:
- In a sunny room, close all the doors and windows, pull down all the curtain to make the room dark.
- Allow sunlight to pass through slit.
- Now look carefully through the slit.
- We will see tiny shining particles moving in the sunlight.
- These are dust particles.