You will need the following items to complete your yeast experiment:
- Yeast
- Balloon
- Water
- Sugar
- Measuring spoon
- Measuring cup
- Sandwich bag
- Funnel
- Tape measure
- Notebook
- Pencil
Follow the instructions below to have the yeast blow up your balloon:
- Decide if you want each student to have their own balloon or if you want to put them into pairs to conduct the experiment.
- Have the students stretch out the balloons to make them easier to work with.
- Have a volunteer combine 1 Tablespoon of active dry yeast with 1 teaspoon of sugar in a sandwich bag.
- Have another student stick the funnel into the opening of the balloon and pour in the sugar-yeast mixture.
- Tell another student to fill the measuring cup with lukewarm water and then tie the balloon shut. Students may need assistance from an adult to do this step.
- Have the students get their notebooks and pencils. Have them record the procedure.
- Have a student measure the length and width of the balloon. Write the measurements on the board and have the children record them into their notebook.
- Every fifteen to twenty minutes, have a student measure the length and width of the balloon and write the figures onto the board. All of the children should copy this information into their notebooks.
- Finally, the balloon will have expanded to it's fullest size. Discuss with the children how this happened. Allow the children time to tell you what they think happened before you explain the truth. Even if a child is wrong, be sure to encourage him or her about making an educated guess.
- Finish the day by telling children that the yeast is a living organism. It was feeding on the sugar and warm water. As it was growing it was expending carbon dioxide, much like we do when we breathe. Since carbon dioxide is a gas, it was filling up inside the balloon. It didn't have any way to escape, since the balloon was tied shut.
This science activity must be preceded by a lesson on how to read a measurement tool, like a measuring tape or ruler.