Page 99 - Science Class 6 Times Publication

Condensation
When a gas is cooled, intermolecular space decreases but

intermolecular force increases. Due to this, a gas converts into liquid.
This process is called condensation.

Activity 9.6

To show evaporation and condensation

Materials required: Kettle, burner, a plate, ice cubes, etc.

Procedure

1. Take a kettle and put little water
inside it.
2. Heat the kettle with gas burner
or spirit lamp. The water boils

and water vapour comes out from
the spout.
3. Put a plate containing ice just
above the vapour. What happens?

Observation

You will see small droplets of water being formed from water vapour.

Conclusion
Here, at rst, evaporation occurs due to heat then condensation

occurs due to cooling.

Sublimation

Some substances like camphor, ammonium chloride, etc directly
change into vapour when heated. They convert directly, into solid
from the vapour when cooled. This process is called sublimation.

The process of changing of a solid into vapour on heating and vapour
back into solid on cooling is called sublimation.

Times' Crucial Science and Environment 95 Book 6