Balloon Magic Trick

Want to know how to inflate a balloon without even blowing into it? Well then have I got the science experiment for you! This experiment came from 100 Science Experiments, a book we love and reference all the time. This one takes a little bit of patience, so I suggest you start it and then do another short science experiment or eat lunch while you watch the balloon inflate.

Total Time: About 10 minutes to set up, then about an hour until completion
Difficulty: So easy even a four-year-old can do it

Materials You Need:
2 Tbsp dried yeast
1 Tbsp sugar
2 Tbsp lukewarm water
Glass bottle
Bowl half-full of lukewarm water
Some kind of cup in which to mix our ingredients


  • Mix together the yeast, sugar, and water in your cup. You may add more water if it’s not runny enough to pour into your glass bottle. (Just be sure it’s lukewarm, too!)
  • Pour this mixture into your bottle.
  • Quickly stretch the balloon over the mouth of the bottle.
  • Set your bottle/balloon in the bowl of warm water and wait!
Our bubbly yeast mixture. That’s how you know it’s working!

You should see your mixture start to bubble within the first few minutes. These bubbles are the result of the chemical reaction we are interested in here. Yeast is a microbe that “eats” sugar when it is wet and warm. As it “eats” it gives off carbon dioxide, which are the bubble you see. This carbon dioxide gets trapped in the balloon over the top of the bottle, which makes it inflate. As the minutes tick by you should also start to see the mixture bubble up and grow higher and higher in the bottle. After about an hour it is done reacting (we call this equilibrium) and the mixture recedes back to the bottom of the bottle. However, the balloon stays inflated as long as the seal is in tact with the bottle.

This is the exact same reaction that happens whenever someone makes bread, rolls, breadsticks, pizza crust, or cinnamon rolls. As the dough rises (AKA as this yeast reaction occurs) it produces carbon dioxide bubbles, but they get trapped inside the dough. This makes the dough expand, so when you bake it, you have a fluffy, soft texture to bite into. YUM!

Print These Instructions

The beginning of our reaction. Not much going on.
After about 10 minutes the balloon was inflated enough to stand up on its own!
After about 30 minutes. The balloon is bigger and the mixture is bubbling up higher.
This is our experiment at equilibrium. You can see how high the mixture is in the bottle! Shortly after this it receded down, but the balloon stayed this inflated until we took it off the bottle.

Let me know if you give this a try and how it works!

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