Science Buddies: "Ask an Expert"

Ok science buddy experts, its that time of year again. We want to find out if there is a sugar substitute that would activate yeast better than any other. We came across an experiment where you trap co2 in a bucket with a beaker. Any suggestions? This is a 7th grade experiment. Thank you.

Hi patty_r66,

Have you seen:
http://books.google.com/books?id=TfyYMG ... q=&f=false
with the procedure being to test each sugar substitute and seeing which one was the "best."

Is there a way to measure the co2 that is being produced. We like to show numbers as proof. Is there a scale that can be used? Also, what are the benefits of doing this experiment. How can the findings pertain to everyday life?

Hi,

This project has some instructions for how to measure the amount of CO2 produced by yeast under different circumstances: https://www.sciencebuddies.org/science- ... p009.shtml . The answer is yes, it can be measured so you can show numbers as proof.

If you have any questions about this procedure, please let us know.

Does the graduated cylindar have measuring lines on it? Sorry I'm not familiar with how to measure the volume of the co2.

That's okay! Yes, a graduated cylinder is the scientific equivalent of a measuring cup for gases and liquids. Here you can read more:

http://en.wikipedia.org/wiki/Graduated_cylinder

Thank you for all of your input. My daughter won 1st place in the entire school as a seventh grader doing this experiment. She went on to compete at a regional level and received an oustanding award.

Congratulations! You must be very proud. I'm glad we were able to help.

This experiment isnt working for us. We used table sugar, splenda, sweet-n-low, and equal. The results don't prove anything. The yeast was able to produce significant CO2 with sugar and sugar substitutes. What did you find? Help?

Or just make it into bread and make the project how to make bread

Fjlewis1,

Sometimes the results do not come out the way you expect, and that's okay! If the yeast was able to produce CO2 with sugar substitutes in addition to sugar, then your experiment did "prove" something: that the yeast can also ferment with sugar substitutes. That's a very interesting result, and something you can talk about in your discussion.

Heather

Hi, My daughter and I are working through this experiment. Today we did our 3 trials with sugar for the yeast (tomorrow we will experiment with Splenda.) We are collecting the CO2 in a 50 ml graduated cylinder. For each of the 3 trials the yeast fermented very quickly and after about only 10 minutes the graduated cylinder was empty of water, the bottle with the yeast/sugar/water mixture was foamy/bubbly up to the top of the cap, and yeast foam started backing up, through the tube, into the graduated cylinder.

So, is our measurement simply to record that after 10 minutes, 50 ml of H20 was displaced by C02? Should it have happened so quickly?

Thank you.

Hi there,

It sounds like you had a successful experiment! I think your graduated cylinder may be too small for the amount of CO2 your yeast produced. If you noted the time at which 50mL of CO2 was first produced (e.g., 10 minutes) each time, then you have something to compare with your Splenda trials. If you have a larger cylinder or container (like a plastic bottle), you might try using that and doing the sugar trials over again, if you want to know an exact amount.

I hope that helps. Please post again (in this same thread) if you have more questions.

Heather