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Materials: • One 17 oz bottle, ideally a plastic one • 1 balloon • 1 envelope of bread yeast (Saccharomyces cerevisiae) • 2 tablespoons of sugar • Warm water • 1 pitcher (or similar) • 1 spoon (15 mL) • Tape

In the pitcher, pour 1 ½ cup of warm water and add the yeast (1 envelope). Mix everything together. Then, add 2 tablespoons of sugar. Stir until having a homogeneous mixture and pour the content into the bottle.

At the same time, blow up the balloon to make it more elastic. Then, deflate it and put it in the mouth of the bottle. Fix it with tape. Finally, place the bottle with the balloon on a flat surface.

Incubate during some hours and observe and register the processes that happen with the balloon and the yeast dissolved inside the bottle.