In this Yeast and Sugar Science Fair Project, we’ll watch yeast feed on sugar to fill a balloon with air. A fun science project for kids that’s with household, everyday materials.
I’ve been baking bread just about every day for the past three weeks (nothing too crazy since it’s all done in the bread maker), but last week my 3.5 year old and I got into a discussion about the properties of yeast.
We like to tinker and experiment — big surprise, I know — and decided to see what would happen if we mixed yeast with warm water.
My preschooler took this job very seriously, poured the water into a bowl, added a couple teaspoons of yeast, and waited a few patient minutes before she said, “it makes a brownish color.” True, and to make it bubble like it does in bread, we needed to activate it with sugar.
What’s so great about an experiment like this is that it’s easy to do with household materials, and it’s ripe for authentic child-generated questions and observations. When I asked what she thought would happen if we added sugar to the yeast she said, “I don’t know! Let’s mix them and find out!.”
Supplies: Yeast and Sugar Science Fair Project
- Sugar, 2 tablespoons
- Active Dry Yeast, 1 packet or 2 1/4 tablespoons
- Warm water (105-115 degrees F, 40.5-46 degrees C)
- Mixing bowl + funnel
- Bottle that you can fit a balloon over
Mix the yeast and sugar into the warm water and stir. I noticed that N was sniffing the concoction and asked her what it smelled like. She said “poop.” I could see what she was saying. Consider yourself warned.
Once it all dissolves, pour the mixture into the bottle and cover the bottle with the balloon.
After a few minutes you’ll be amazed by something like this!
Will it blow off the bottle?
N wanted to feel it as it filled with air. She noticed the balloon was getting bigger and wanted to know how big it would get, wondering out loud, “will it fill up all the way and blow off the bottle?”
My handy-dandy ship captain sister (no joke — that’s her job!) was visiting, and put herself right to work as chief measurer.
Move it to a safe spot
Once the bottle filled up completely, we moved the whole yeast sugar experriment to the sink. The bubbles were slow-moving, and there was nothing to worry ourselves with, but N enjoyed pulling the balloon off and watching the foam slowly pour over the bottle’s top.
Ideas for Extending this Experiment
As we went through the process, I thought of a few fun extensions for older kids or those who want to take this further. You could play around with food coloring/liquid watercolors, have a few bottles going at once and compare the results of different sugar:yeast ratios, or compare the results of different water temperatures.
I found my recipe at The Exploratorium’s Science of Cooking series, where we also learned that as the yeast eats the sugar it makes carbon dioxide, which is essentially the same process that yeast goes through in our bread dough.
Mmmmm. I’m off to eat some whole wheat cranberry walnut oat bread. Toasted. With butter and Maldon salt. How do you like your bread? And have you played around with yeast concoctions?
More Science Experiments for Kids
If you enjoyed this project, you’ll love this article: Science Fair Project Ideas.