Yeast Balloon Experiment: How to blow up a balloon with yeast and sugar?

In this fun experiment containing yeast, balloon, and sugar, we will learn
– How to activate the yeast?
– What happens when fungus eats sugar?

Materials Required (What Do I Need?)

  • 1 packet of dry yeast
  • 2 Teaspoon of sugar
  • 1 small (1-liter) clean and clear plastic or glass bottle
  • 1 large rubber balloon (Try to blow the balloon at least 3-4 times to stretch it)
  • 1 cup of warm water

Do You Know?

“A packet of dry yeast contains about 18 billion yeast cells per gram”

Procedure (What to do?)

  1. Fill the bottle with warm water
  2. Add the packet of dry yeast in the bottle and gently stir the bottle for a few seconds
  3. Add sugar into it and again stir it for some time.
  4. Now attach the balloon to the mouth of the bottle.
  5. Keep the bottle in a warm place for around 20 minutes and observe.
  6. You will notice that the balloon will inflate in some time and will get bigger and bigger on the top of the bottle.

Science Behind This Experiment (What’s Going On?)

  • Initially, the yeast in the packet is in inactive mode but as the yeast dissolves in warm water, it becomes active which means it comes to life.
  • As we mix sugar into the bottle, the yeast starts to eat the sugar and releases carbon dioxide gas due to fermentation.
  • Now, this carbon dioxide gas occupies the empty space available in the bottle. As more gas is produced it tries to escape the bottle through the mouth.
  • This escaping gas from the mouth of the bottle now starts to fill the balloon and eventually the balloon gets inflated.


  • Yeasts need to be warm and moist in order to be active.
  • Yeasts are a microscopic fungus that converts sugar into alcohol using fermentation and produces carbon dioxide. Therefore, carbon dioxide gas is released when yeast eats sugar. This fermentation process is used in food processing such as bread.

Professor Atom

View posts by Professor Atom
Professor Atom is a science enthusiast and alumni of IIT Bombay. According to him, every question can be solved with curiosity and mind mapping. ( Curiosity = Asking Questions = Learning )

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