Yeast Beast in Action Investigation

Our first test of the gas pressure was on our acid, the 3 mm of Diet Coke and hydrogen peroxide. Once we added the hydrogen peroxide to the soda all carbonation dissipated. When the yeast was added, the fizzing began again, but not before subsiding into an extremely thin layer of foam at the top of the liquid. We added the rubber stopper to begin testing the pressure. After two minutes with the yeast reaction taking place, the pressure had risen from 96.88 kPa to 104.7 kPa.

In the milk/hydrogen peroxide (neutral) test, there was also a bubbly, foaming reaction when the yeast was added. This time the foam was taller than in the soda test. Our neutral test boasted significantly slower and lower reactions than in the acid. In two minutes the pressure increased from 96.88 kPa to only 99.77 kPa.

For our final test of antacid and hydrogen peroxide (base), another foam layer was created on top. This one was the largest of the three tests. With the yeast added, the pressure increased from 96.88 kPa to 101.79 kPa, the second highest recording in our experiment.

Here are our results:


My group's hypothesis was that the acidic mixture would produce the greatest pressure, followed by the neutral mixture and the basic mixture.

The greatest yeast activity was in the acid, judging by its production of the most gas pressure. This may be due to several reasons, such as the corrosive nature of the acids broke down the yeast or hydrogen peroxide faster. Also, the diet coke we used contained gases to begin with, so CO2 was being released along with oxygen from the hydrogen peroxide. This addition may have added to the results.

The lowest yeast activity was found in the neutral mixture. This may have been simply because the substance was neutral and didn't really have any effect.

Some sections of our hypothesis were supported by this experiment. We predicted that the acid would have the greatest effect on the yeast because of its corrosive properties. We mixed up the neutral and basic mixtures however, saying that the base would cause less of a reaction than the neutral compound. When we actually tested the experiment, this was switched, because the neutral mix remained, well, neutral and didn't have much affect at all. The hydrogen peroxide was used in all of the mixtures in this experiment because of it chemical reaction to yeast. Without the hydrogen peroxide there may not have been much increase in pressure, due to lack of gas release. Another interesting aspect of this experiment was the fact that our starting pressure was a consistent 96.88 for all of the tests. The beginning kPa is often varied in these tests. From this experiment, we learned how different PH levels can affect the gas pressure in an enclosed area.