Yeast Metabolism With and Without Air: I am not getting any change in the volume of CO2

[deleted-801544]

I have been working on this project for a long time now and every time there is no decrease in the amount of water in the graduated cylinder. I have a few things I am confused about that could be the cause. 1. Do you have a specific spot in the graduated cylinder to put the end of the tube, for example, do you push the tubing to the top of the full graduated cylinder? 2. Other projects have included silicone sealant and this project does not, so should I be using silicone sealant or does it not matter? 3. Does the graduated cylinder need to be push all the way to the bottom of the plastic tub and does it need to be standing straight up in the tub? 4. Do you have to go immediately from setting up the apparatus into sticking the end of the tube into the graduated cylinder? My graduated cylinder starts bubbling before the yeast solution is even connected to it. I would appreciate any help that can be offered if none of these questions will help fix the problem.

[pharrast]

I cannot see a reason that it would matter where in the cylinder your tube is, nor the depth or angle of the cylinder as long as it is submerged and you can get an accurate reading of the gas change (that's why they recommend straight up). It shouldn't require a specific sealant, but it is critical that there is no leak at the site where the tubing attaches to the plastic bottle tip, so whatever works. As the project instructions say, everything should be in place before you add the yeast in each condition. Is it possible you forgot to boil the water? Here's the SB project page if you want to check over the method details again.
https://www.sciencebuddies.org/science- ... #procedure