Fermentation: Yeast & Sugar Balloon — Science Magic!
Feed tiny living things some sugars and watch a balloon blow itself up like magic!
Science Fun for Ages 5–10
What Is This Experiment?
You are going to mix yeast (tiny living things) with warm water and sugars inside a bottle. The yeast will eat the sugars, produce a gas called carbon dioxide (CO₂), and that gas will inflate a balloon sitting on top of the bottle.
The Big Science Word: FERMENTATION
Fermentation (say it: fer-men-TAY-shun) is when yeast eats sugars and turns it into carbon dioxide gas (CO₂) and a little bit of alcohol. The CO₂ gas is what blows up your balloon! Bread rises the same way — yeast makes bread fluffy and bubbly too!
What You Need
- 1 small plastic bottle (500 ml)
- 1 packet of dry yeast (7 g)
- 1 teaspoon of sugars
- Warm water (not hot)
- 1 balloon
- About 30 minutes
Steps
Step 1: Warm Up the Water
Ask a grown-up to help you get warm water — not too hot, not too cold. It should feel like a warm bath! Hot water will kill the yeast, so this step is very important.
Step 2: Add the Yeast
Open your yeast packet and pour it into the bottle. Yeast looks like tiny brown powder — but it is actually millions of tiny living things that are sleeping right now!
Step 3: Add the Sugars
Spoon in one teaspoon of sugars. This is the food for the yeast. When it wakes up, it will start eating the sugars straight away!
Step 4: Add the Warm Water
Pour warm water into the bottle until it is about half full. Give it a gentle swirl. You might already see tiny bubbles starting — that means the yeast is waking up!
Step 5: Attach the Balloon
Carefully stretch the opening of the balloon over the mouth of the bottle. Make sure it is nice and snug so no gas can escape!
Step 6: Wait and Watch
Now put the bottle somewhere warm and wait! In about 10–20 minutes, you will see the balloon slowly start to rise and inflate — powered by yeast burps!
This happens because fermentation has started, and the yeast is producing carbon dioxide (CO₂) gas.
What’s Happening Inside?
During fermentation, yeast uses sugar and warm water to produce carbon dioxide (CO₂) gas. The gas rises and fills the balloon, making it inflate.
Yeast + Sugars + Water CO₂ Gas rises ↑Balloon inflates! = yeast cells eating sugar
Yeast Wakes Up
Warm water activates the yeast and helps it begin feeding. Once the yeast starts eating the sugar, the process of fermentation begins.
Sugar Is Food
The yeast uses the sugar as an energy source.
CO₂ Gas Is Produced
As the yeast breaks down the sugars, it releases carbon dioxide gas.
Balloon Inflates
The gas rises and collects inside the balloon, causing it to expand.
Tips for Success
- Use warm water, not hot water.
- If the water is too cold, the yeast may stay inactive.
- Try different amounts of sugars and compare the results.
- Place the bottle in a warm location to speed up the reaction.
- Record your observations every 5 minutes like a scientist.
Where Do We See This in Real Life?
Bread
Yeast produces carbon dioxide gas that gets trapped in dough, making bread soft and fluffy
Pizza Dough
Yeast helps pizza dough rise and become light and airy.
Fermented Drinks
Fermentation creates carbon dioxide gas, which can produce bubbles in some drinks.
Glossary
Yeast
Tiny living organisms that feed on sugar.
Carbon Dioxide (CO₂)
A gas produced when yeast consumes sugar.
Fermentation
The process in which yeast breaks down sugar and produces carbon dioxide gas.
Reaction
A process in which substances interact and change into something new.
Conclusion
You learned that yeast is alive, that it eats sugar, and that it produces carbon dioxide gas. This gas can inflate a balloon and also helps bread rise.
Next time you eat bread or pizza, remember that yeast helped make it soft and fluffy through fermentation.
Enjoy your experiment and keep exploring science!
