Ever wondered why some showers are really weak and
some really powerful? It’s all to do with pressure.
Do you know where the water is stored in your house?
Usually it is up in the loft, let’s look at why.
Make a Water Tower
You will need
•
•
•
•
a plastic drinks bottle
a knitting kneedle
sticky tape
lots of water
Try this…
Use the knitting needle to make four
holes in the plastic bottle at different
heights.
Cover the holes with sticky tape.
Fill the bottle with water.
Put the bottle in a sink or a bowl.
Remove the sticky tape.
Look at the jets of water coming out
of the holes. Are they different?
Why?
What’s happening?
There is more pressure on the lower jets due
to the weight of the water pushing down.
The higher the water can be stored the
greater the pressure. This is why water towers
are usually as high as possible and the water
in your house is stored as high as possible.
Make a ketchup packet sink on
command!
You will need
• 1 ketchup packet (available in most restaurants)
• a plastic bottle
• some water
Try this…
Place the ketchup packet in a
bowl or cup of water to check if
it will float. Keep trying until you
find one that does.
Put the ketchup packet in to the
bottle. Completely fill the bottle
with water and close the lid
tightly.
Now squeeze the bottle hard and
you can make the ketchup packet
sink!
What’s happening?
There is a small air bubble trapped inside the ketchup
packet. When you squeeze the bottle, the pressure inside
increases. It is very hard to squeeze water, so all the
pressure squeezes the air bubble inside the packet. The
density of the ketchup packet is increased as it is squashed.
When the air is squashed enough the packet will become
denser than the water in the bottle, and the packet will
sink. When you let go of the bottle, the pressure inside the
bottle decreases again so the air in the packet will expand.
This causes the packet to rise back to the top.
Supported by:
The Oakdale Trust
The Mr & Mrs J T Morgan Foundation