State of matter:
Melting and Freezing
What happens when materials are heated or cooled?
The Materials will undergo changes.
Example:
Paper burns to form ash
when it is heated.
Water turns into ice
when it is cooled.
What are permanent and temporary changes?
 Permanent changes:
Materials that has undergone changes cannot return to its original form. But it forms a new substance.
Example:
Wood when it is burnt, it turns into ash. It cannot be changed
back to the original wood.
The new substance that is formed is ash.

Temporary changes:
Materials that has undergone changes can return to its original form. And no new substance is formed.
Example:
Ice when it is heated turns into water. Water can be
changed back into ice when we freeze it.
What happens when solids and liquids are heated or cooled?
 There are 3 states of matters: solid, liquid and gas.
 The state of matter can be changed when it is heated or cooled.
 A solid can change into liquid when it is heated.
Example:

A liquid can change into solid when it is cooled.
Example:
What is melting?
 Melting is the process of changing solid into liquid.
 It takes place when the solid gains heat.
 Melting point is the temperature at which a solid melts.
 The melting point of ice is 0 °C
What is freezing?
 Freezing is the process of changing a liquid into a solid.
 It takes place when the liquid loses heat.
 Freezing point is the temperature at which a liquid freezes.
 The freezing point of ice is 0 °C