in chemistry we have available to us a fairly diverse collection of materials that we can use to make super saturated Solutions uh and super saturated Solutions are really kind of interesting most of the super saturated solutions that we get to work with are pretty unstable and you can make them and cross your fingers that they'll last a little while uh there is one super saturated solution that's easy to make in a laboratory with inexpensive materials that is real stable and can be used over and over again and that is uh sodium acetate and that's what we're going to take a look at today real quick I have up here a flask and if you look at it just to begin with you'll notice that the solution inside here is kind of a yellowish color that's because this particular solution is is now almost 3 years old and it's been used over and over again in the process of heating it and cooling it and heating it and recycling it it's lost a little bit of its color or a little bit of its Lack of Color I guess is a better way to say it and it's picked up a little bit of yellowish to it but um I have talked to people that have kept a super saturated solution of sodium acetate for years and years uh and they'll use use it over and over and over and I personally had a 2 L flask that I had with sodium acetate in it that was probably 20 years old that I'd made way back of when I first started teaching so I mean they do last they're pretty stable and they can be used over and over and recycled so what we want to get across is how do you get a how do you make first of all a super saturated solution generally it's done by heating uh a quantity solid with liquid you drive a temperature up above the point where all of the solid will dissolve so you don't have a super saturated solution then as it cools back off at the point where it reach sat reaches saturation instead of crystallizing out it continues to cool back down and so now what you have in here is actually more material dissolved then the handbook says can be dissolved consequently the term super saturated now to get it back out of solution there are a number of ways it can it can be done you can shake the solution sodium acetate is kind of nice in the sense that it's pretty stable shaking won't ordinarily cause it to fall out sometimes just a piece of dust falling into it will cause the solution to fall out and solidify again sodium acetate is pretty stable that normally won't happen about the only way you can get sodium acetate to recrystallize out and go back uh to a saturated solution or in this case it'll go almost to a solid when we take a look at it is to give it a couple of crystals drop a couple crystals in there and it's almost like the rest of the sodium acetate and the beaker sees these crystals falling down inside and says oh that's how we're supposed to line up let's all gang up around the outside of it and you'll see when the crystals fall in here that it just kind of like hey guys here's the way we're supposed to line up that's the crystal structure quick let's all get together and you'll observe what's going on the other thing that's kind of interesting about this one is that the reaction is pretty exothermic so I'm going to take a wood splint now and just get a few crystals of sodium acetate and pull the stopper out and shake them in and you can see almost instantly all those other sodium acetate ions that were in there are now getting together and solidifying uh they found the crystal structure and in a very very short period of time it's gone in now can't tell this on camera but the bottom of this is quite warm not so warm I can't hold on to it but it's heated up is there practical use for this indeed there is they sell these heat packs you may have seen them it's uh it says the heat it actually says the heat of solution pack but they'll sell these in camping stores Etc that you can put into a glove or your pants pocket or whatever you want uh they're recyclable you can warm it up uh and it'll go back but it's got a little thing down here I don't know if you can see that piece of metal that's in there this thing when it's bent and I'm going to just reach in here and give it a bend and then move it out whoops I'm going to give it a bigger Bend maybe a huge Bend maybe a gigantic Bend maybe a bend in a different direction hey there we go all right again you can see that crystallization starting to take place and this once again gets quite warm you can recycle this put it in some boiling water put it in some hot water let it go until it all goes back to a clear solution it's ready to go again do the same thing with this flask that I used before stick it on a hot plate heat it for a little while it'll go back into it put the stopper on it set on the Shelf leave it there until next year when I need to use it it that in itself is really kind of neat um something that's a little different but the same situation another example of a sodium acetate super saturated solution I suppose you could use this in earth science if you want wanted to demonstrate the formation of stalagtites stalagmites in this case it would be a stalagmite because we're going to see it Grow from the bottom up in a lot of ways it is the same process that does produce stalagtites and stalagmites because that is a precipitation of a crystal out of solution it's not a super saturated solution but it is a solution and the and it stuff crystallizes out when drops of liquid hit the surface so again sodium acetate super saturated solution inside the buet I'm going to open the stop coock now a couple of tricks with this that make it work cuz you might be looking at this going this looks like it might be kind of tough to deal with uh first of all if you've closed the top which is always a good idea take that off the top because it doesn't run out very well if the top is sealed there's no air pressure pushing down or very little air pressure pushing down from the top and that kind of messes up the process the other thing is that when you put this in the trick is I always have a little distilled water in the bottom around the stopcock so I'll put in enough distilled water to fill up this part and just above the stopcock because if I put that super saturated solution down that far and when I turn the stopcock sometimes that's enough twist just like that little tab was in there to cause crystallization to start taking place I mean it's neat to watch it go up inside the buet that's fun but it's it's a booger to clean out so it's just you know something you want to probably avoid uh and then after I filled it I'll put maybe again a half a milliliter distill water on top so that I don't get any evaporation to the top that causes crystals to form that shoots it down now if I'm lucky here and I'm good with the buet I'll get some drips here the first few shouldn't do anything because they're just distilled water after they fall out then hopefully that super saturated solution is going to come through when it hits the crystals on the platform here I'm hoping that it'll start to solidify and if I'm really doing a good job with it and as the drops fall down I'll start to build a stalagmite up from the uh base here and so we'll take a look at it and see how it works and we'll cross our fingers that in fact it's going to start building up and yes it is stalagmite formation there it is millions of years happening before your eyes this is Mammoth Cave cut down into a 20 second process are you counting the drops that's another Co process we can do reaction rates here let's get off yep well we can start another one earthquakes occasionally occur or vandalism in the cave and millions of years go by and here we are again when I was a graduate school on the weekends I used to do a lot of caving here she comes again it's just a little bit different way to do super saturated solution of sodium acetate if you notice when it goes a little slower the column's a little bit more uniform and I was just about to say it's less likely to fall over but I can see this one starting to tilt