Making Water Safe

Why it matters

The water in a river looks brown and full of mud. Before it reaches your tap, it goes on an amazing cleaning journey to become safe to drink.

Predict first

What is the very FIRST thing done to clean muddy river water?

First the water is left to stand so the heavy mud settles to the bottom. This is called sedimentation. Only later is chlorine added to kill germs.

• Add chlorine to kill the germs straight away
• Let it stand so the heavy mud settles to the bottom — correct
• Boil it until it is steaming
• Pour it straight into the tap

What you do

Put the water-cleaning steps in the correct order, from first to last.

Check yourself

At the water works, what is chlorine added to the water for?

Chlorination means adding a small amount of chlorine to the water. It kills harmful germs so the water is safe to drink.

At home, what is the simplest way to make water safe to drink?

Boiling water kills the germs in it, so boiling is a simple and reliable way to make water safe to drink at home.

Which kind of water is the purest, yet tastes flat and dull?

Distilled water is the purest water because everything dissolved has been removed. With no minerals left, it tastes flat and dull.

• To kill germs and make the water safe to drink — correct
• To make the mud settle faster
• To give the water a nice colour
• To make the water taste sweet
• Boil the water, which kills the germs — correct
• Add sugar to the water
• Leave the water in sunlight for a minute
• Freeze the water into ice
• Distilled water, because it has no dissolved minerals — correct
• Sea water, because it is salty
• Muddy river water
• Rain water during a storm