How Hard Is It To Freeze Flowing Water?

Hello everyone, today we are going to see if it is possible to

freeze

flowing

water

, so I am going to try a few different methods. I'm going to have a pump that pumps

water

and makes it flow and then I also have some water and a magnetic stirrer that stirs it up in a vortex and sees if we can actually

freeze

the water. Now this question has come up a lot in the comments section for me, a lot of people ask if you can really freeze moving water and what is the lowest temperature liquid water can have.

I also received this question from my children. You're outside on a cold winter day and there's ice on the sides of the road. There is snow on the road. Look, everything is frozen, but then, yeah. If you look at a river, it just flows normally, maybe you see some ice on the side of the river, but usually you see the river

flowing

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Now let's go back to our experiment so that we learn from a very young age that water freezes. at zero degrees celsius or 32 degrees fahrenheit however when you say water freezes at zero degrees celsius that doesn't mean it has to freeze it just means it can freeze at that point for example let me show you what I mean I mean if you take some bottles of water and put them in your freezer and then if you measure the temperature after a few hours, you will see that the temperature of the liquid water is actually below freezing.

This is called supercooling, so you've supercooled the water. and the reason it's supercooled is because water can freeze, but to freeze it has to arrange itself in a crystalline pattern and it usually needs a starting point to do that or a nucleation site, so if you don't have a nucleation site nucleation or a way to start forming those crystal patterns, then it won't, so if you take this super cooled water and you pour it over some ice that gives it a nucleation point or a place to start turning into ice, you can see it can instantly form ice with the super cooled water oh amazing it's working look there it goes so we know you can supercool water without giving it a nucleation point but what happens if you actually keep the water moving to that is not stagnant enough to form a crystalline phase is that possible.

Well, let's do some tests to prove it and then we'll talk about how cold you can get supercooled water so you can clearly see the water flowing. Now it's even introducing a little bit of air bubbles. that are coming in here and then you should be able to see it flowing, so let's see if we put liquid nitrogen around the sides here, if we can actually freeze it as it flows, can you freeze the water that flows? Well, here we go. The liquid nitrogen is causing a lot of condensation in the air, so I'll have to keep blowing it out so we can see what's going on here.

I don't think the shovel no longer moves. This is what we are doing. I was left with the pump frozen there, but there is still liquid water, so the pump froze before the water could freeze. Okay, now we're going to try to freeze the water while it's stirred with a magnetic stirrer, so we're going to put liquid nitrogen around it. and then put the water in there and see if it actually freezes, so I've got a little bit of water in the cup here, I'm going to put it in my shaker, I'm going to stir it really quickly and now I'm going to pour in liquid. the nitrogen in this cup increases the agitation, so look how it froze here, it froze, it froze in a rotating pattern with the magnets at the bottom, so it's in its swirl shape and it froze completely, it's a frozen swirl so cool so yes you can freeze yourself moving.

The water is fine, so it finally froze in this cold vortex, but it was very

hard

to see, so now I'm going to pour liquid nitrogen on top and see if we can actually see the shaking stop and form ice so that you can see the magnetic movement. The shaker moves there and I'm going to keep pouring liquid nitrogen on top so we can watch the ice move down and eventually see if it stops completely. Okay, now it's completely solid, so the eye started from the top and as it went lower and lower and lower, it finally reached the spinner that was there, the magnets and as soon as it hit it and hit the first piece of ice, it was already He couldn't move anymore and he couldn't keep turning.

The cool thing about this is that you can see how This ice is white because the air that dissolved in it didn't have time to come out of the solution. Usually when you make ice cubes, they have little air bubbles trapped in them because as water cools it can't hold as much air. dissolves in it and the air usually comes out as little bubbles coming out the top and usually the top has frozen before the bubble can escape so the air bubble is trapped there like a complete air bubble, but in this case it froze. fast that all the little air bubbles didn't have time to merge into big ones, so there are only little air bubbles in all of this that make it look completely white, so you can see in these experiments that moving water doesn't could.

To prevent ice from forming, there are a few reasons for this. One of the reasons is that you will notice that the cold had to come from somewhere, so it had to come from the outer edges of the container, but as happens in fluid dynamics. When you have a liquid moving in a container at the edge of the container where the liquid meets the solid of the container, there is something called the no-slip condition, which means you can model it as if the atoms touching the surface of the container do not. they did. It doesn't move at all, so even though you're spinning the liquid, the atoms touching the side of the container don't move at all, which is why you get this motion profile in a swirl, the edge doesn't move, the middle does, and Also, if you look at the velocity profile of liquid flowing through a pipe, you'll see the same thing at the edges, it's the slowest in the middle, it's the fastest, so this turns out to be a bad thing for the water that It flows, which you're not trying to let it freeze, the cold comes from outside and that's the place where there's the least movement of water, but this doesn't really answer our question we had at the beginning of why the liquid water that we normally see flow in streams really Cold days generally don't freeze well, that's because the water is moving and therefore mixing very well and what that means in a well mixed mass of water to freeze it, all The mass of water has to reach at least zero degrees Celsius.

So if you have a really good mixture, it means you need to remove a lot of heat before the water can freeze, so shaking, mixing or flowing can prevent ice crystals from forming in the water just because you're mixing with a lot of heat. mass of water and so it has to cool everything before the water can form ice, but how cold could this liquid water get before it forms ice crystals? Well, as I showed before, you can supercool water if you don't give it a nucleation point and If you are very careful not to give water a nucleation point and spontaneously form those nucleation points, then you can cool very cold water before it freeze.

The theoretical limit of how cold liquid water can be cooled before it has to form ice is negative. 48 degrees Celsius and the way they got to this temperature is that researchers at the University of Utah actually modeled about 32,000 individual water molecules and looked at how they vibrated and determined what was the minimum temperature that was needed to achieve a point of spontaneous nucleation where it could no longer exist as liquid water, but in practice those temperatures have not been reached at negative 48 degrees Celsius, but at around negative 40 degrees Celsius and negative 42 degrees Celsius. Now remember that is negative 40 degrees Celsius, 40 degrees colder than known freezing. water point and thanks for watching another episode of action lab I hope you enjoyed it if you did don't forget to hit the subscribe button if you haven't subscribed to my channel yet and you can also hit the bell so I can get notified when I posted my latest video and thanks for watching and I'll see you next time.