Jr. scientist A often asks why we add different ingredients when we cook and one of the common ingredients we use (since we make a lot of pizzas) is yeast. I decided a while back to try to give a better answer than my standard, "yeast makes dough get bigger" response. I knew that there was carbon dioxide being released that formed little pockets in the dough, thus expanding it, so I thought we could do an experiment where we use yeast to blow up a balloon. Originally I put some yeast and water in a bottle and covered the mouth with a balloon. We checked on our experiment the next morning to find a still deflated balloon. I tabled the experiment for a while and was poking around online and found I was missing a key ingredient - sugar. We re-did the experiment with two bottles. The smaller bottle had yeast and water and the bigger one had yeast, water, and sugar. By the next morning the bottle with sugar had a nicely bulbous balloon sitting on top of it. Thanks to some laziness, we discovered that the bottle without sugar did eventually make enough carbon dioxide to partially inflate the balloon, but it took a few days to happen.
