Yeast Beasts in Action

WARNING! Our test was conducted without yeast in two tubes, so the outcome of the experiment might be different than expected.

Hypothesis: If we test the acid, neutral and basic substances, the acid substance's pressure will rise the fastest.

Results: We poured 3mL of hydrogen peroxide into each test tube, and used yeast for the first beaker. It was tested for 120 seconds. It was sealed with an airtight cap. We recorded the pressure (kPa) of all the tubes. It rose considerably fast (much faster than the other two). In just two short minutes, it went from 97.31 to 109 kPa, the most dynamic change of all three. Next, we poured 3mL of skim milk into another test tube, and sealed it with the cap. We tested the pressure- there was almost no change. There was only a VERY slight increase in pressure- it started at 97.32, and ended at 97.65 kPa. Our final test (tube) involved acids. We used 3mL of diet soda. It didn't rise very much, although it rose faster and higher than the skim milk. It started at 97.32, and ended at 98.88 kPa. My hypothesis was incorrect, although the pressure rose faster than the skim milk.

1. In what mixture was the activity greatest?

The activity was greatest in the tube we put yeast in. The yeast seemed to play a large role in manipulating the amount of pressure.

2. In what mixture was the activity least?

There was almost no activity in our neutral experiment (with skim milk). It had almost no change over a 2 minute period. However, had yeast been used, this could have yielded different results.

3. What can you conclude from your experiment results?

Our results were (likely) very different from others, however, as we had an absence of yeast in the last two test tubes. When there was no yeast, there were no great changes in pressure (increase, decrease). The yeast most likely affected this experiment, and we had a very different outcome.