to show how fermentation produces carbon dioxide. As gas accumulates, the balloon expands, providing an easy visual indication that a reaction is taking place.
Could It Be Making Alcohol?
Possibly—but you can’t determine that from the photograph alone.
If yeast ferments the sugars in fruit juice, alcohol can be produced as a byproduct along with carbon dioxide. That’s why similar balloon-on-bottle arrangements are sometimes used in homemade alcoholic fermentation.
But the presence of a balloon doesn’t prove that alcohol is being made.
A very similar setup can be used simply
