Week 21 · Axis 3, Chapter 3 Life Along the Nile (A) · 3 lessons
3
Filtering water
Discover P2 Term 2: Axis 3, Chapter 3
GoalTest a filter with a grown-up and explain why filtered water can look clean but is still not safe to drink.
New words
filter · something that lets water pass through but holds back bits of dirtclean · without dirtsafe · not likely to hurt us
Explanation
A filter lets water pass through and holds back bits of dirt. Gravel holds back big bits. Sand holds back smaller bits. A piece of cloth or filter paper holds back the smallest bits we can see. After filtering, muddy water looks cleaner. But filtered water can still have tiny germs that we cannot see. So it is not safe to drink. Water stations use more steps to make water safe. We never drink the water from our filter test.
Worked examples
Before filtering the water is muddy. After filtering it looks cleaner. A is before and B is after.
Seif’s water looks clear after filtering. But a germ is too tiny to see. So the water is still not safe to drink.
filter→make safe→pipes
A water station uses many steps. First it filters the water. Then it makes it safe. Only then is the water sent through pipes to homes.
Class activity
Make a filter with a grown-up. A grown-up cuts the bottom off a plastic bottle. Turn the bottle upside down, put cloth in the neck, then add gravel and sand. Mix some soil in water to make muddy water. Pour it slowly through the filter into a clean bowl. Compare the water before and after. Do not drink it. Wash your hands. Water a plant with the filtered water.
Practice
1
What does a filter do?
It lets water pass and holds back bits of dirt.
2
Is the filtered water from our test safe to drink?
No. It may look cleaner, but it can still have germs.
3
Which beaker has the cleanest water? Say the letter.
C.
4
Why should we never drink water straight from the river?
