This video was produced by... This demonstration has safety risks. Because of these risks, we wear closed-toe shoes and safety goggles. This demonstration should only be done by a trained professional and should not be tried at home. Hello, my name is Kevin Karen and I'm coming to you today from the Chemistry and Biochemistry Department here at James Madison University. I've got three identical mugs here in front of me and I'm going to pour water into the first mug. Just regular deionized water, nothing fancy. What I'd like you to do is I'd like you to follow the mug that has the water in it. So you saw me pour water into this mug, so this is where the water is. I want to move these around a little bit. Okay, keep your eye on the water. Follow that water. I can get pretty fancy, so watch out. One last minute. Okay, so where is the water? Is it in mug number one, two or three? Number one? You think it's a number one? Okay, let's try it. Let's see. Look, it doesn't look like the water is in mug number one. Is it? You weren't following very well. So where do you think it is now? It's not number one. Maybe it's a number three? All right. Let's see if it's a number three. Huh. Doesn't look like it's a number three. So if it's not in one, it's not in three, it must be in mug number two. What's going on here? You saw me pour the water in. Well, in fact, you were right the first time. It actually was in mug number one, but I had something else in the bottom of that mug that I didn't tell you about. It's a polymer, a powdered polymer called sodium polyacrylate. And what happened when I poured the water into the sodium polyacrylate, the combination of the water and that polymer formed a gel. And you can see inside this cup, you can see the gel that formed. This is actually the same polymer that's used inside diapers to absorb moisture inside a diaper. And I'm going to show you this demonstration one more time, except this time instead of using mugs. I'm going to use a beaker. So we can see what's going on. Okay, so here I've got a beaker. And this time you can see the sodium polyacrylate at the bottom of the beaker. That's my powdered polymer. I'm going to pour my water in. And as I pour it, you can see within a couple of seconds, the polymer swells and we quickly form a nice stable gel. It does not flow even when I tilt the mug. I can tilt it all the way upside down and it doesn't flow. Even though this is largely water, almost completely water, except for that small amount of polymer that we had in there. So the way this works is that polymer, a polymer is a long chain of atoms. And this particular polymer has negative charges, anionic charges, regularly spaced along this polymer. Each of those anionic charges has a sodium cation associated with it. And when I add the water, the sodium cation and the anionic polymer separate from each other. They ionize. And the negatively charged polymer chains, which are all anionic, they repel each other. And so they swell. This swells the polymer and traps the liquid water in between those polymer chains. So I can do something to reverse this process now. I can add some salt, some sodium chloride. So this is just regular table salt. I'm going to add this on top. Okay, and then I'm going to stir it in just a little bit. And as the salt starts to interact with the polymer here, it's going to soften it up. And it makes it so it is again a free-flowing liquid. So it's no longer a gel. It's again a free-flowing liquid. And the way this works is the sodium cations from that salt end up surrounding the anionic components of the polymer. And so it shields those negative charges. So those negative charges are less apparent and that decreases that that anionic, anionic repulsion that we see between the polymer chains. So the polymer is no longer swell. Then we've essentially reversed the process to get to a free-flowing system again. Well, I hope you've enjoyed that. I certainly have. I hope you have a wonderful day. This is Kevin Karen coming to you from James Madison University.