Science Buddies: "Ask an Expert"

Hey! I have a question about this science experiment we did a couple of weeks ago. Essentially, we mixed yeast with apple juice in a sealed container and attached a balloon as the lid.

So, the yeast performed cellular respiration with the apple juice, converting the glucose into ATP, and releasing CO2. The CO2 blew up the balloon as a result.

However, we decided to leave the containers out for a couple of weeks, and something interesting happened to one of my classmate's container; the balloon was completely sucked into the container, like a vacuum. Does anyone know why this is the case? Thanks!

Hi mango77,

Thanks for your question -- I did the yeast fermentation experiment for a science fair years ago and so your question caught my interest as well.

I believe the balloon was sucked back into the container due to the solubility of carbon dioxide in rubber/latex. Air and helium are both able to diffuse (rather slowly) through the pores in a balloon -- this is what causes a balloon to deflate over time. I believe carbon dioxide diffuses more rapidly; therefore, the balloon would deflate faster. Also, since the yeast was inactivated by this time, there was no source of carbon dioxide to keep the balloon inflated. It is interesting that only one balloon was sucked back into the container though.

Also, it should be noted that the process you studied in your experiment can also be called alcohol fermentation and ethyl alcohol is also produced as a waste product, aside from the carbon dioxide

--Brandi

Oh wow! I would have never guessed that, but it definitely makes sense. Thank you so much!

My science teacher said this phenomenon I described only happens occasionally.

I still don't quite understand how it would turn into a vacuum though. I see that CO2 would deflate the balloon faster, but do you mean that it deflates so fast that it becomes a vacuum?

I am not sure what caused only one balloon to be sucked back into the container -- perhaps it does have to do with the rate at which the carbon dioxide was able to diffuse out of the balloon. Nonetheless, it is an interesting project and phenomenon

--Brandi