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Safety Issues

This investigation uses latex balloons. Be aware of any allergy issues. Also to prevent choking, keep the balloons away from young children. Wash hands after any experiment using yeast. 

Material Availability

Readily available or easily purchased from the grocery store 

Approximate Time Required to Complete the Project

One hour to complete the investigation and collect the data; one day to prepare the science fair display. 


To investigate yeast fermentation and its results 

Materials and Equipment

  • 2 empty plastic 16-ounce water bottles
  • Water
  • 2 packages of active dry yeast
  • 2 latex balloons
  • 2 tablespoons of sugar
  • Masking tape
  • Pen
  • Measuring spoons 

Background Information

Yeast is an ingredient used to make baked goods rise. Yeast is a live microorganism. When yeast feeds on sugars, such as in bread, it ferments. Fermentation produces carbon dioxide. Carbon dioxide is a gas that expands. 

In this experiment the carbon dioxide that is released when the yeast and sugar combine inflates the balloon. 

Terms, Concepts, and Questions to Start Background Research


fermentation: the chemical reaction of yeast and sugar to carbon dioxide  

microorganism: an organism that is too small to be seen by the eye alone   


Fermentation is the process that happens when sugar is added to yeast. Fermentation produces carbon dioxide.  

Research Questions
  • How does yeast make bread rise?
  • What happens when sugar is added to yeast? 

Experimental Procedure

  1. Gather the necessary materials.
  2. Using the masking tape, label one bottle “Yeast and Sugar” and the other bottle “Yeast Alone.”
  3. Pour 1 cup of warm water into bottle.
  4. Add on package of yeast to each bottle.
  5. In the bottle labeled “Yeast and Sugar,” add two tablespoons of sugar.
  6. Gently shake both bottles until the yeast has dissolved.
  7. Place a balloon over the opening of each bottle and tape the balloons in place.
  8. Observe the bottles for 30 minutes. Record any changes.  



“Yeast” at 

“Explaining Yeast to Kids” by Frederick Foodie at

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Warning is hereby given that not all Project Ideas are appropriate for all individuals or in all circumstances. Implementation of any Science Project Idea should be undertaken only in appropriate settings and with appropriate parental or other supervision. Reading and following the safety precautions of all materials used in a project is the sole responsibility of each individual. For further information, consult your state's handbook of Science Safety.

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