yeast experiment for kindergarten

Inflate a Balloon with Yeast Experiment

Did you know that you can inflate a balloon WITHOUT blowing air into it? It’s true.

In this simple experiment , young scientists use yeast to magically inflate a balloon. How cool is that?!

Check out the simple step-by-step below and then snag our 30 Science Experiments that are kid-approved!

Getting Ready

We headed into the kitchen to grab all of our supplies for this science experiment:

Clear plastic or glass bottle with a narrow neck (a water bottle or soda bottle work great)
2 Tablespoons dry yeast
1 Tablespoon sugar
2-3 Tablespoons lukewarm water
Party balloon
Bowl or mug full of lukewarm water

Inflating a balloon with yeast is a wonderful experiment to do with preschool and kindergarten aged children because all of the materials are nontoxic. It’s nice when the kids can help measure out ingredients without worrying about what they are touching.

My kids helped me measure the yeast, sugar, and warm water into a cup.

They stirred the ingredients and then used a funnel to pour the brown mixture into the bottle. We added a little bit more water to help the yeast mixture get through the neck of the funnel.

We quickly stretched a balloon over the mouth of the bottle.

After placing the bottle into a mug full of warm water, we sat back to observe.

Inflate a Balloon with Yeast

Almost immediately, we observed bubbles in the yeast mixture.

I explained to the kids that yeast is a microscopic fungus that converts sugar into carbon dioxide.

The bubbles they saw were tiny bubbles of carbon dioxide gas that the yeast was producing as it “ate” the sugar.

For yeast to be active, it needs to be warm and moist. That’s why we added lukewarm water and placed the bottle in more warm water.

We set our bottle of yeast on the table and watched it while we ate lunch and read books.

We checked in with our science experiment every 10 minutes or so to observe any changes. Every time we looked, we noticed that the balloon was getting bigger and bigger on top of the bottle! Why?

As the yeast continued to react, it converted more and more sugar into carbon dioxide gas.

This gas was trapped in the balloon, making it inflate as if by magic!

It took about an hour for our balloon to reach its maximum size.

The yeast bubbled up into the bottle quite a bit before it stopped reacting and shrank down again. Simple science at its best.

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Yeast Fermentation Experiment

Fermentation is a fascinating process that kids can easily explore through a simple experiment using yeast and sugar. This hands-on activity teaches students about fermentation and introduces them to the scientific method, data collection, and analysis.

Investigate how different types of sugar (white, brown, and honey) affect the rate of yeast fermentation by measuring the amount of carbon dioxide (CO₂) produced.

Example Hypothesis: If yeast is added to different types of sugar, then the type of sugar will affect the amount of carbon dioxide produced, with white sugar producing more CO₂ than the others.

💡 Learn more about using the scientific method [here] and choosing variables .

Watch the Video:

Active dry yeast
White sugar
Brown sugar
Measuring spoons and measuring cups
Small bottles or test tubes
Rubber bands
Ruler or measuring tape
Notebook and pen for recording data ( grab free journal sheets here )
Printable Experiment Page (see below)

Instructions:

STEP 1. Prepare a yeast solution by dissolving a packet of active dry yeast in warm water according to the package instructions.

STEP 2. Label 3 bottles and add 1 tablespoon of white sugar to the “White Sugar” bottle. Add 1 tablespoon of brown sugar to the “Brown Sugar” bottle. Measure 1 tablespoon of honey and add it to the “Honey” bottle.

STEP 3. Measure and pour an equal amount of the yeast solution into each bottle, ensuring the yeast is well mixed with the sugar.

STEP 4. Quickly stretch a balloon over the mouth of each bottle. Secure the balloons with rubber bands if needed. Ensure the balloons are sealed tightly to prevent CO₂ from escaping.

STEP 5. Place the bottles in a warm, consistent environment to promote fermentation.

STEP 6. Observe and record the size of the balloons at regular intervals (e.g., every 15 minutes) for 1-2 hours. Use a ruler or measuring tape to measure the circumference of each balloon.

TIP: Note the time it takes for the balloons to start inflating and the differences in balloon size over time for each type of sugar.

STEP 7: Analyze the data by comparing the amount of CO₂ produced (balloon size) for each type of sugar. Create a graph showing the balloon size over time for each sugar type.

STEP 8. Determine which sugar type resulted in the most and least CO₂ production. Discuss possible reasons for the differences, considering what each sugar is made of. Think about whether the results support or disprove the hypothesis. Can you come up with further experiments or variations to explore other factors affecting yeast fermentation?

Free Printable Yeast and Sugar Experiment Project

Grab the free fermentation experiment worksheet here. Join our STEM club for a printable version of the video!

The Science Behind Yeast Fermentation

For Our Younger Scientists: Yeast is a type of fungus that feeds on sugars. When you mix yeast with sugar and water, it starts to eat the sugar and convert it into alcohol and carbon dioxide gas. The gas gets trapped in the balloon, causing it to inflate. This shows that fermentation is happening!

Yeast fermentation is a biological process where yeast converts sugars into alcohol and carbon dioxide (CO₂) in the absence of oxygen. This process is used in baking, brewing, wine making and biofuel production. How much fermentation occurs can vary depending on the type of sugar used.

Yeast contains enzymes that break down sugar molecules through a series of chemical reactions . Here’s how it works:

Enzymes are molecules, usually proteins, that act as catalysts to speed up chemical reactions within living organisms.

First the yeast is mixed with warm water, and it becomes activated. The warm environment “wakes up” the yeast cells, preparing them to consume sugars.

Yeast cells produce enzymes that break down sugar molecules (sucrose, glucose, and fructose) into simpler molecules. This process is called glycolysis. During glycolysis, sugar molecules are converted into pyruvate, releasing a small amount of energy.

In the absence of oxygen (anaerobic conditions), yeast cells convert pyruvate into ethanol (alcohol) and carbon dioxide gas (CO₂). The carbon dioxide produced during fermentation is what inflates the balloons in the experiment.

Different Sugars & Fermentation

Different sugars can affect the rate of fermentation. This is how:

White Sugar (Sucrose): Composed of glucose and fructose and is easily broken down by yeast, leading to efficient CO₂ production.
Brown Sugar: Contains sucrose along with molasses, which includes minerals and additional nutrients. May result in a slightly different fermentation rate due to its composition.
Honey: Contains a mixture of glucose, fructose, and other components. The additional components can influence the fermentation process, potentially leading to different CO₂ production rates compared to pure sucrose.

The amount of CO₂ produced depends on how easily the yeast can break down the sugar molecules and convert them into ethanol and CO₂. Sugars that are more readily broken down by yeast will typically produce more CO₂ faster.

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Helpful Science Resources To Get You Started

Here are a few resources that will help you introduce science more effectively to your kiddos or students and feel confident presenting materials. You’ll find helpful free printables throughout.

Best Science Practices (as it relates to the scientific method)
Science Vocabulary
All About Scientists
Free Science Worksheets
DIY Science Kits
Science Tools for Kids
Scientific Method for Kids
Citizen Science Guide
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Printable Science Projects For Kids

If you’re looking to grab all of our printable science projects in one convenient place plus exclusive worksheets and bonuses like a STEAM Project pack, our Science Project Pack is what you need! Over 300+ Pages!

90+ classic science activities with journal pages, supply lists, set up and process, and science information. NEW! Activity-specific observation pages!
Best science practices posters and our original science method process folders for extra alternatives!
Be a Collector activities pack introduces kids to the world of making collections through the eyes of a scientist. What will they collect first?
Know the Words Science vocabulary pack includes flashcards, crosswords, and word searches that illuminate keywords in the experiments!
My science journal writing prompts explore what it means to be a scientist!!
Bonus STEAM Project Pack: Art meets science with doable projects!
Bonus Quick Grab Packs for Biology, Earth Science, Chemistry, and Physics

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