Yeast Fermentation Balloon Race

Project Overview: Yeast may be microscopic, but don't underestimate it; this single-celled organism is alive, hungry, and about to prove it. When yeast eats sugar, it releases carbon dioxide gas as a byproduct, a process called fermentation. It's the same biological reaction that makes bread rise. In this project, you'll race three balloons to find out exactly what yeast loves to eat.

Materials Required: 

1. 3 packets of active dry yeast

2. 3 small empty plastic water bottles

3. Sugar, salt, and baking soda

4. Warm water

5. 3 balloons

6. A funnel or spoon

Instructions: 

1. Label the three bottles "Sugar," "Salt," and "Baking Soda."

2. Add 1 packet of yeast and 2 tablespoons of warm water to each bottle, swirling gently to dissolve.

3. Add 2 tablespoons of sugar to the first bottle, 2 tablespoons of salt to the second, and 2 tablespoons of baking soda to the third.

4. Immediately stretch a balloon over the mouth of each bottle, then set all three bottles side by side.

5. Observe over the next 15 to 20 minutes and record which balloon inflates the most. The sugar bottle should inflate the fastest and most because yeast can ferment sugar for energy, releasing carbon dioxide gas, whereas salt and baking soda don't feed the yeast the same way.

Congratulations, you just watched a living organism produce its own gas in real time.

Fun Fact: The sugar balloon should win every time, because yeast can't survive on salt or baking soda alone; sugar is basically its favorite meal, and carbon dioxide is what it "breathes out" after eating.