Page 210 - Primary Five Science

Heating

 If ice (solid) is heated, it changes to water (liquid). This

change is called melting.

 Water (liquid) can change to water vapour (gas). This is

called evaporation.

 If water (liquid) is heated until it boils, it

changes to water vapour (gas) very

quickly. Water boils at 100°C

 Heat can change solids into

liquids or gases.

 Most solids melt into liquid

when they are heated.

 A liquid evaporates into a gas when it is heated.

Cooling

 If water vapour (gas) is cooled, it changes to water (liquid).

This change is called condensing.

 If water (liquid) is cooled, it changes to ice (solid). This

change is called freezing. Water freezes at 0°C

When we cool something we take heat away from it. Cooling

changes a gas into a liquid, and a liquid into a solid.

A gas condenses into a liquid when it is cooled.
A liquid freezes into a solid when it is cooled.

Melting points

Different solids melt at different temperatures. Ice melts at 0

degrees Celcius (0°C). Chocolate melts at about 35°C.