Water covers 70% of the earth’s surface.
	H2 + O2 = H2O
	A water molecule is made up of one oxygen atom joined to two hydrogen atoms.
	Water is a compound because it is made up of the hydrogen and oxygen combined chemically.
	Water dissolves many compounds: Solids, liquids and gases.
	Water is a good solvent.

--------------------------------	Oxygen	Nitrogen
Air dissolved in water	34%	66%
Air in the atmosphere	21%	78%

 

Fish breathe the oxygen dissolved in water. It gets dissolved in water when it splashes on rocks when raining.

Def: Surface tension is the force that holds the surface of water together.

 

Def: Capillarity causes water to rise up narrow tubes.

 

Water must be treated to remove solids, debris, bacteria that could cause sickness. They must also remove anything that adds colour or taste to the water.

 

Screening

Coarse screens remove large floating and suspended debris. It is then filtered through sands to remove other suspended materials.

 

Sedimentation\Settling

Aluminium sulphate is added to get tiny suspended clumps to form bigger clumps. The material falls to the bottom clearing the water of any brown colour.

 

Filtration

The water is filtered by fine sand.

 

Chlorination

A small amount of chlorine is added to the water to remove bacteria.

 

Fluoridation

Fluorine is added to help prevent tooth decay.