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"Yeast Beast" alive and well at Leawood

Contributed by: Liz Keating on 3/17/2008

The annual Science Fair at Leawood Elementary School in Littleton is a big deal! Last week students presented their science experiments which were judged on creativity, scientific thought, thoroughness, skill and clarity. Fourth graders third place winners Moira Laughlin and Bailey Martinez teamed to enter their project titled "The Yeast Beast." See their story below.

The Yeast Beast Experiment
by Moira Laughlin and Bailey Martinez

The first experiment we did was to test yeast with a cut banana. We made three different baggies-one without yeast, one with dry yeast, and one with yeast activated in some warm water. Then we observed for several days what happened. The banana without yeast just turned drier and browner as the days went by. The banana with dry yeast didn't do anything the first day or much the second or third day. It did produce some gas (carbon dioxide) and blew up the baggie a little bit. Also, there was a little foam and bubbles on the banana. The banana with the yeast and water had the most reaction. It made the most carbon dioxide gas and blew up the bag the most. Also, the banana looked foamy and had lots of bubbles. This started the first day and continued to have more each of the other days. We didn't think anything would happen with the banana without yeast. We did think the banana with dry yeast would produce a lot of gas and bubbles but it didn't make much. We thought the banana with water and yeast would be like the banana with just dry yeast but it made a lot more gas and was foamier.

The second experiment we did was putting yeast in water, coke cola, sprite and apple juice. We also tested coke and sprite without yeast. We placed balloons on top of the open bottles to test whether there was gas produced. When we put yeast in water it did nothing because the yeast had nothing to eat. When we put yeast in coke the balloon puffed up some. It also puffed up some in the coke bottle without yeast, but not as much. When we put yeast in the sprite, it made a lot of gas and the balloon got really big. The sprite without yeast also made the balloon puff up but not as much. All of these happened as soon as we added the yeast or opened the bottle. The apple juice with the yeast took some time before the balloon puffed up. This lesson taught us that yeast needs something to eat like sugar that is in sprite, coke, and apple juice. It didn't have anything to eat in water so it didn't make any gas. Also, the apple juice doesn't have carbon dioxide gas in it so the yeast actually had to produce the carbon dioxide gas to get the balloon to puff. The surprising thing is that the coke and sprite without yeast also puffed the balloons up but then we realized that soda has carbon dioxide gas in it so the bottles were releasing that gas

The third experiment we did was yeast and water to activate the yeast and 5 different ingredients. You need 2 1/4 tsp of dry yeast plus 1 cup of 90 degree F water. Then we put 5 different cups out with the water and yeast and put 1 tbsp of corn syrup in one. In another, we put 1 tbsp of corn starch and in one we put 1 tbsp of sugar. In the next one, we put 1/4 tsp of salt and the last one we put 1 tbsp of flour. The first cup that had the corn syrup in bubbled up pretty quickly and got foamy. The cornstarch one took a while before much happened but then it bubbled and became foamy. The sugar quickly had small bubbles and some foam. The salt never did anything even with a long time to see if the yeast worked on it. The flour also took a long time but then did have big air bubbles and was foamy. We thought that the sugar and corn syrup world work but weren't sure about the cornstarch and flour. We didn't think the salt would work and it didn't . The cornstarch and flour did work because they are starch and starch can break down to sugar so that is why they did work but it took longer.
The last experiment we did was to make bread with yeast and bread without yeast. First we put the ingredients in from experiment and put them in a bowl with milk and eggs then we stirred it. After awhile the bread got super hard and it was tough to stir. Then we let it sit for an hour. In that time we started on the bread without yeast. First we put milk, eggs, flour, sugar, corn starch and corn syrup. Then we stirred it. The bread without yeast also got hard. Also, we let it sit for an hour. When time was up, the bread with yeast almost went over the top of the pan. Then bread without yeast didn't get any bigger. Then, we felt it. The bread with yeast was sticky. The one without yeast was not really sticky, just made our hands greasy. After that, we put them both in a pan and baked them for half an hour. Then we took them out. The bread with yeast was over the top of the pan. The bread without yeast was the same as when we started. Then we weighted them and the two loaves of bread weight the same. No more, now less. (1 pound). That told us that yeast makes things rise but doesn't make them heavy. Because it adds air to the bread by eating the sugar corn syrup and flour. It also puts a little taste to them.


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CONTRIBUTOR INFORMATION

Liz Keating

Denver , CO

Liz Keating has posted 132 stories and 0 comments since joining on 9/17/2006. Liz Keating 's average story rating is 4.96.
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