Science Buddies: "Ask an Expert"

We want to use the "Ow, My Tummy Hurts! The Biology and Chemistry of Gas Relief" project (I'll call it Project A). Test the effects of simethicone in dish soap & water. You watch the bubbles form when adding water, when stirring, & then when blowing bubbles with a straw.

One variation (under "Make it Your Own" tab) suggests testing the simethicone in a solution that is more like stomach acid. It gives a link to a different project (I'll call it project B) that tells how to make the artificial stomach acid - with hydrochloric acid and sodium chloride mixed into an almost-full 2-liter bottle of water.

The suggestion seems to be saying to do the same project (A) - with same procedures - but use the artificial stomach acid instead.
It's unclear, though...
Does "acid" replace only the water project A?
To test the effects of the simethicone, do you still add the dish soap to make bubbles in this "acid"?
Do you still use a straw to stir & then to blow through to create bubbles?
Do you still do project A in jars (pouring in some of your 2 liters of acid solution)? ...or do you add the simethicone & create the bubbles in the 2 liter bottles?

Project B (with the acid) is based on pH, so no bubbles are involved. It uses TUMS to test neutralizing the acid. We prefer project A - simulating the gas bubbles & testing simethicone - but we would love to be more "authentic" by using the artificial stomach acid from project B as suggested in the variations. We just want to be clear on the "right", safe way to proceed.

Thanks for the help!!

I read through the projects and I think you can basically replace the water with your "stomach acid" but keep nearly every other aspect of the experiments the same.

You should definitely still pour your "stomach acid" into jars to do your experiment. Ideally you will have multiple trials (as described in Project A), so you won't want to use all of your "stomach acid" in only one trial. You can decide how big each of your jars should be, though. One of the comments to Project A mentions that the average size of an adult human stomach is ~2L, so you could choose to make up more of the acid in the beginning and do multiple trials each with 2L of acid.

I'm not 100% sure whether you will still need to add the dish soap, but my guess is that you won't get bubbles at all without the dish soap because the surface tension will be too high. As part of your experiment you could test it both ways (with and without dish soap), or include a no dish soap control (i.e. do one set of jars with and without simethicone without soap in addition to the multiple trials with soap).

I am a little concerned about using a straw to blow bubbles in your acid though, because you risk splattering some on yourself, and burning yourself with acid. If you do use the straw, please be very careful and make sure there is plenty of space between the surface level of the acid and the person blowing the bubbles through the straw, and that the person blowing bubbles is wearing appropriate protective gear, including eye goggles. Alternatively, you could use other methods to make bubbles, including sealing the jars tightly and shaking them. Project A also suggests using Alka-Seltzer or Pop Rocks to make bubbles, so you could consider one of those options as well.

Additionally, some soap can be somewhat basic (i.e. high pH), so you'll want to make sure that the soap you add is fairly neutral in pH so it doesn't raise the pH of your "stomach acid." I believe soaps labeled "mild" are generally fairly neutral in pH.

I hope this helps. I think this should be a very fun and interesting project.
JMP

Thanks for all of that!!! Those are all the things I had swimming around in my head. I'm helping my son with the project. Even though he's in 7th grade, he has special needs & requires more guidance than some (especially with the background, questions like these, etc.). He did choose this one on his own, though, & is excited about it. He has insisted on doing the version with "real stomach acid" , so I have it on hand, but today we did some trials of the basic project (water & soap) ...hoping he'll be satisfied with that.

As I read your ideas, I had one of my own. Maybe we could put a hole for the straw in the jar lid, even covering further by wrapping a cloth around the place where the straw comes out of the lid. But... I also like the idea of just shaking it. Of course, that should probably involve wrapping fully with a cloth first - to avoid any leaks/drips.

Thanks again for your time & ideas!!