Balloon and bottle fountain
How to assemble a simple fountain!
Warning! Only under adult supervision.
- plastic bottle;
- any sealant;
- tinted water;
Make a hole in the base of a plastic bottle. Insert a balloon into the bottle as shown, fastening it over the bottleneck. Bore a hole in the bottle cap and thread a straw through it, and seal it with any sealant. Inflate the balloon and plug the hole in the base of the bottle with your finger, pour in tinted water, and close the bottle with the modified cap. Remove your finger from the hole and the fountain begins!
The bottle is filled with air, and when we put the balloon on the bottle, we create a closed system in which the pressure is equal to atmospheric. Our lungs wouldn't be able to inflate the balloon if we hadn't bored the hole in the base to let out excess air. After inflating the balloon, you need to plug the hole with your finger so that the balloon doesn't deflate. In fact, the balloon deflates slightly when you close the hole. This causes the air pressure in the bottle to decrease, and the resulting difference between the atmospheric pressure inside the balloon and the reduced pressure in the bottle keeps the balloon inflated. You may not even notice this deflation; such a slight change in the bottle's free space is necessary to keep the balloon inflated. When we let the air in, the pressure in the bottle is compared with atmospheric and the balloon is blown away by the force of elasticity and thereby pushes the water out, forming a fountain. A small amount of water will remain inside the balloon – be careful during cleanup!