Air Pressure Demonstration - Drinks Dispenser

This easy activity is a super simple, fun 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!

For this air pressure experiment 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 half way up the bottle and push the straw through the bottle leaving ⅓ to ½ on the outside.

Fill the bottle about three quarters full with 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 put a glass under the straw.

When you’re ready remove the peg and watch as the water shoots out of the straw into your glass!

Be careful as it might shoot out further than you expect.

Why does this happen?

This works because air presses down equally on the water in the bottle and in the straw when there is no balloon 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.