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How do I measure CO2 output in a Yeast experiment (more details below)


In my bio class right now, we’re doing an experiment where we mix water, yeast and different types of sugar in three different test tubes to see which type of sugar allows the yeast to perform cellular respiration the best.

Our teacher said that the best way to find out which type of sugar performed the best was to find out which type of sugar + yeast released the most CO2. Our group decided to measure this by recording the pH of the water after a couple days, and recording the height of the foam. The test tubes are uncovered. Is this a good approach to find out which test tube released the most CO2?

My first question is which sugars are you looking at (and why do you think that might be an important question)? I would have thought a much better method would have been to weigh it over time in a semi covered vessel to track the loss of CO2, such as in this example:

I do not believe your methods are good ways of measuring CO2 output, especially if they are open to atmosphere. Think about why the pH would be changing. Foam height is problematic for other reasons - in your experience, is foam something that sticks around for long-ish periods?


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