Making an air pressure powered drinks dispenser is easier than it looks, and a fantastic hands-on air pressure demonstration.
What is air pressure?
Air and its particles are crashing into us all the time. What we call air pressure is the force of these particles hitting a surface.
When you suck a straw you reduce the pressure inside the straw, making the pressure outside the straw acting on the liquid greater than the pressure inside the straw. This pushes the liquid up the straw, allowing you to drink it!
Drinks Dispenser Air Pressure Demonstration
You’ll need
Balloon
Peg – optional, but helpful
Plastic bottle – I used a 750ml bottle
Plasticine or putty
Plastic Straw
Water
Small container
How to make an air pressure drinks dispenser
Carefully make a small hole about halfway up the bottle and push the straw through, leaving ⅓ to ½ on the outside.
Fill the bottle about three-quarters full of water.
Blow up the balloon, twist and seal the neck with a peg. Carefully place the end of the balloon on the bottle neck and place a glass under the straw.
When you’re ready, remove the peg and watch as the water shoots out of the straw into the glass!
Be careful, as it might shoot out further than you expect.
Why does this happen?
Air presses down equally on the water in the bottle and in the straw when no balloon is present ( or the balloon is pegged ), but when the peg is removed, air from the balloon increases the air pressure in the bottle, pushing down on the water, forcing it through the straw.
More Air Pressure Experiments
Air pressure is a great concept to explore as it causes lots of fun effects.
Demonstrate the Bernoulli Principle with a very simple demonstration using a plastic bottle and a ball of paper.
Suck a boiled egg into a jar without touching it.
Build and launch a bottle rocket!
Last Updated on May 14, 2025 by Emma Vanstone
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