Hydrogen Peroxide in the Presence of Yeast

A number of different variables, such as the concentration of the hydrogen peroxide solution or the temperature at which the reaction occurs, can affect the rate at which yeast breaks down hydrogen peroxide. To prove this we first tested the solution with 3% concentration of peroxide, the paper that was soaked in yeast rose in 1.7 seconds. After that we changed our concentration to 2.25%, 1.5%, and .75% of hydrogen peroxide to see the effects it had on the amount of time it took the felt to completely drop and rise.

On 2.25% it took 2.8 seconds, 1.5% took 3.2 seconds, and .75% took 3.9 seconds.

Introduction

When yeast and hydrogen peroxide react, the peroxide decomposes into water and oxygen gas causing bubbles to form. These bubbles cause the felt to rise.

Problem

In this experiment we measured how long it took for the piece of felt soaked in a yeast solution to sink and rise in the test tube. The amount of time it takes for the felt to sink and rise indicates how oxygen bubbles are formed, as hydrogen peroxide is broken down.

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Hypothesis

The amount of hydrogen peroxide directly influences the amount of time it takes to break down the yeast resulting in “tiny bubbles”, and the felt to rise to the top of the test tube.

Procedure Supplies:

• Hydrogen Peroxide
• Yeast suspension
• 4 felt disks
• 5 test tubes
• Clock
• Forceps
• 5 paper cups
• Graduated cylinder

Results See Graph on Lab Sheet

Analysis and Conclusion

For this experiment our dependent variable was the paper with yeast on it, and our independent variable was the concentration of Hydrogen Peroxide we put in each solution.

We tested the amount of time it took for the peroxide to break down yeast at 3%, 2.25%, 1.5%, .75% and 0% concentration. The fastest reaction time was 1.7 at 3% concentration. We found out that with no Hydrogen Peroxide the yeast does not float back to the top. So the lower concentration of Hydrogen Peroxide the longer it took to float back to the top.