1. Fill the bottle half way with water. Water will come out of the hole.
2. If you put your finger over the hole, you can stop the water from squirting out. What do you think will happen if you put your finger over the hole in the top of the bottle?
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Try it. Make sure to press your finger down tightly.
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Why is this happening? What has it got to do with air pressure?
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3. What do you think will happen to the water if you increase the air pressure in the bottle?
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Try it. Increase the air pressure by blowing into the top hole. What happens?
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