Science Buddies: "Ask an Expert"

Hi! I'm Hannah, and I had a question about the Yeast Busters project. I have completed the first stage or so, the trial on the yeast without any antifungal agents applied to it. The layer of foam was very visible, but there were so few bubbles and so little water displaced that I had to take it off the side of the bucket and tilt it up to under the black bottom. Should I repeat the trial on the control group, or is this the normal result?
Thank you for your time!
Have a blessed day,
~Hannah

Hi Hannah,

There are several possibilities why you did not see much CO2 in the cylinder:

1. The plastic tube was not completely sealed into the bottle cap.

2. The yeast was no good (unlikely if you bought it fresh from the grocery store)

3. You forgot to add sugar to the yeast or you added too much

4. The temperature was too low. Yeast grow best at 43-45C (110-112F)

5. The temperature was too high. If it was above 50C (122F) the yeast could have been killed.

6. You did not let the yeast work long enough. How long did you collect gas?


This is all I can think of. Maybe other experts know of another possibility for why you did not collect much gas. Since you got foam in the bottles the yeast must be ok, so I am guessing that there was a leak at the tubing and the gas came out before getting to the cylinder. How cold was the room where you did the experiment? If the bottles containing the yeast were chilled then the gas would contract and might not be expelled into the cylinder.

Let us know what you think might have been the problem and we'll try to help you get it right. You should do the experiment without the antifungal agent again so that you can be sure it is working before you proceed.

Good luck!

Sybee

Hi Sybee!

I think the two main reasons that it didn't work was the tube probably had a leak or the seal wasn't completely cured, and the room was really cold (I had the window up). I will set the sealant again tonight and repeat the trial again in a warmer room. I let it work for 30 minutes, and though the foam changed drastically, there were only about four bubbles. I'll leave it for 60 minutes. That really helped me! Thank you so much for your help.

Have a blessed night,

-~Hannah