Wednesday, March 23, 2011

Yeast Pressure Investigation

Today we investigated yeast activity and air pressure in Yeast Beasts in Action. We wanted to know how yeast activity varied in acidic, neutral, and basic mixtures. In order to perform the investigation you need 1 teaspoon of yeast, 50mL of water, 2 beakers, 1 gas sensor, black rubber stopper, 3 test tubes, 1 test tube rack, soda, milk, antacids, Vernier software, laptop, LabQuest Mini, graduated cylinder, 3% hydrogen peroxide, and an eye dropper.

First we set up the Vernier software and connected all the sensors with the LabQuest Mini. Then we placed the three test tubes on the rack and labeled them A, N, and B. Then we measured out 3mL of hydrogen peroxide and poured it into each tube. Then we made our yeast solution by filling up one of the beakers with 50mL of water and 1 teaspoon of yeast and stirring. We used the eye dropper to add 2 drops of the yeast solution to Test Tube A. Then we added 3mL of the soda and put the rubber stopper on top. We then collected the data and recorded the highest pressure of Test Tube A. We waited after the 2 minute mark until the pressure started going down so that we could get a more accurate pressure amount. We repeated these steps for the next two tests, but we used milk and antacids for the mixtures.

My hypothesis was: If yeast breaks down and releases the gas of compounds, then the acidic mixture will have the highest pressure because the other two mixtures will have lower kPa.
The reason I thought that the neutral and basic would have low pressure was because the neutral mixture (milk) would be cold which (as concluded from a previous lab) causes a lower pressure and the antacids neutralize acidity, so I did not think that they would cause a high pressure.

My hypothesis was close, but was not exactly supported by the data. The chart below shows the results of the tests:

Basically, the Basic mixture ended up having the highest pressure at 128.3 kPa. The Acidic mixture was close with 122.13 kPa. Last was the Neutral mixture with 117.19 kPa.
Below are charts containing the pressure info for each mixture:
(The Acidic Mixture)
(The Basic Mixture)
(The Neutral Mixture)

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