Science Buddies: "Ask an Expert"

I am doing the experiment "An Aerobic Exercise: Yeast Metabolism with and without Aeration" (https://www.sciencebuddies.org/science- ... y&from=TSW). It involves reacting yeast with sugar water both with and without oxygen; then recording the amount of CO2 produced.I have the apparatus set up, and when I react the yeast with the sugar water, nothing happens. No CO2 goes into the collection apparatus. I've done experiments similar to this one before and I'm pretty sure that the apparatus is right, so what is wrong? Is a lot of CO2 supposed to appear? Am I doing something wrong? The instructions have been followed to the letter but it is not working. I also had no clue what to expect with the experiment. A little direction would be greatly appreciated.


Thanks,
jmewin

Hi jmewin,

You have a great project, and I'm sorry to hear that you are having trouble getting results.

It's hard to comment for sure what might be wrong without seeing your setup in person , but if you are not getting any CO2 for either of your experimental conditions, you may have a leak in your system. The key step here is "Seal the tube to the cap with epoxy or silicone sealant so that it is air-tight. Allow the epoxy or silicone to cure fully before conducting your experiment." Note that silicone sealant can take some time to cure fully, and epoxy can be prone to cracking.

I would start by double- and triple-checking that your apparatus is airtight. If you solve this problem and are still having trouble, please write again.

Good luck!

Heather

How old is the yeast you are using? I remember my mother having trouble baking sometimes because the yeast she had hadn't kept well. When you mix the sugar and the yeast, are you getting bubbles at all? If not, you probably need new yeast from the store.