*intro music*
Hi everyone, Cody here. And welcome to my freezer.
Let's turn on a light here, so you see a little bit better.
Okay. Now in here, I've got a bottle of purified water,
which has been sitting here for an hour, and it's not frozen.
Which means it is supercooled down to below its freezing point.
I've got a thermal camera, so we can see how the temperature changes as the water is solidified.
To get it to solidify,
I either need a starting crystal for the water molecules to link up with or enough agitation, and it will start the process.
So I'm just gonna whack it with a spoon here.
There it goes. See the water crystallizing?
And in a thermal camera,
you can see it lit up.
The yellow indicates that the temperature had risen.
Yeah, that's right. As this water froze, it got warmer.
Isn't that wild?
What happened here is what sometimes happens to gold as it solidifies.
If you have a droplet of liquid gold and it's cooling off, cooling off, at some point it lights up.
And what happens is the temperature goes down, down, down, and then jumps up back to the freezing point.
Then it goes down slowly again.
In the case of liquid gold, it jumps up and produces visible light.
In the case of water, I had to use the infrared camera to see it.
But same thing, it lit up as it froze as well.
If you happen to live someplace where it snows, you might have noticed that it actually gets warm during the snowstorm.
And that is because as the water freezes and crystallizes, it releases a lot of energy.
It takes a lot of heat to cause water to undergo a phase change.
That's between melting or freezing.
But it doesn't actually take a lot of heat to cause it to cool down below the freezing point.
It's still a liquid, you haven't caused those bonds to happen.
So I might be able to explain this a little bit better with magnets, just like my gas model.
This probably won't work itself, but...
Take some magnets here and imagine these are your water molecules.
They're moving around in liquid fast enough that they don't slam together.
Like maybe they'll come together, but they've got enough kinetic energy to come back apart.
Now of course they've got much less kinetic energy then a gas does, so they never really get very far, so they're almost like in orbits.
It's terrible analogy, but...
As you cool them down, they lose their kinetic energy,
and they reach a point where they do have a low enough kinetic energy that they could stick.
and that is the freezing point.
Then they don't stick and become a rigid structure like a crystal lattice.
But if they're oriented wrong.
And [if] they don't have anything to [stick to].
Like a pattern to stick to, then they'll kind of just bounce off of each other and they won't
stick until you give them a little bit of a nudge to flip one...
Get it to come together.
And then others will follow suit.
And it'll create the crystal.
What I think is kind of interesting, is that the total thermal energy of the bottle remains the same,
before and after I initiate the freezing.
Essentially what happens, is when the water molecules link up and form an ice crystal,
the momentum of the ice crystal (or, you know, that the pairs that have bonded), is now less than they had originally.
So some energy got released and that energy goes into the surrounding molecules and actually causes them to speed up a little bit.
Of course it can't heat it up more than the melting point, because then it would cause some of the ice crystals to come apart.
Now this of course means that the water did not freeze solid, it's kind of slushy.
So only a small fraction of it actually crystallized.
The gold solidifies much faster than the water because well,
it's a lot smaller than the bottle of water and it's thermal conductivity is a lot higher.
Anyway, hope you enjoyed.
I'll see you next time.
*music* *real-time infrared outro of supercooled water crystallization resulting in heat released*
*laser heat gun showing 23F (-5C) before and 36F (2.2C) after freezing*