Page 98 - Science Class 6 Times Publication

Melting
When solid substances are heated, molecules absorb heat. Due to

this, intermolecular force decreases but the intermolecular space
increases. Thus, solid changes into liquid. This process is called
melting.
Activity 9.4

To show melting process
Materials required: A beaker, ice cubes, etc.

Procedure

1. Take some ice cubes in a
beaker.
2. Heat the beaker by using gas
burner or spirit lamp. What
happens?

Observation: The ice melts into liquid water.
Freezing

When a liquid substance is cooled, intermolecular space decreases

but the intermolecular force increases. Due to this, liquid substance
changes into solid state. This process is called freezing. This process
is also called solidi cation.
Activity 9.5

Take a candle and burn it. What do you nd after some time?
The candle melts. Most of the melted wax is used for burning.
A small part of wax ows down. When the wax  owing

downward cools, it freezes to solid. Here, freezing into solid
is due to cooling.
Evaporation

When liquid substance is heated, intermolecular space increases but
the intermolecular force decreases. Due to this, molecules are free to
move and liquid converts into gas. This process is called evaporation.

Times' Crucial Science and Environment 94 Book 6