Inside-out Balloon in a Bottle

(Physics for ages 5+)

Balloons are almost always fun, and they also make a great tool to learn a bit about science! In the video above, they do a simple activity to turn a balloon inside-out inside a glass container simply using hot water. Ready to try it for yourself? Here’s how it’s done:



Narrow-necked glass bottle or flask (like an Erlenmeyer flask used in the video)
Adult supervision



  1. Start by boiling some water (Adult supervision required here please). This can be done several ways: using a microwave, using a tea kettle on the stove top, or using a hot plate as seen in the video above. The water can be heated in your glass bottle or flask, or it can be heated in a different container and transferred to your bottle.
  2. Your water should be boiling hot, so be very careful! If you heated the water in your bottle or flask, remove it from the heat and set it on your counter or table.
  3. Take the balloon and stretch it over the mouth of the bottle or flask. Again, be very careful because there will be hot steam coming out of the bottle and it can burn you. This task might be best completed by an adult.
  4. Now just sit back and watch the magic happen!



When water is boiling hot and creating steam, the molecules are moving around very quickly and excitedly. This is why you can see steam leaving the bottle. Placing the balloon over the mouth of the bottle traps all of those molecules and keeps them inside which creates an equal amount of pressure inside and outside of the glass.

As the water cools down and becomes liquid again, the molecules slow down and need less room than when they were in the gaseous form (steam). This change leads to a higher pressure outside the bottle than inside, which forces the balloon to suck into the bottle until the pressures are all the same again.