00:01
Let's start by drawing a phase diagram for most substances.
00:06
In the vast majority cases, your phase diagram is going to look something like this, where we have a solid over here, we have a liquid over here, we have a gas over here, we're going to have some supercritical region over here, and this line is just going to keep going on to infinity.
00:30
And we'll just go ahead and label these axes.
00:33
We've got pressure over here, and we've got temperature over here.
00:36
Water has one very key difference that you're going to notice.
00:40
It's kind of difficult to tell because it's very subtle, but it's that this line here, which i've exaggerated for the purposes of this diagram, is going to be a very partially negative slope.
00:53
This boundary between solid and liquid is, in fact, negative, whereas almost every other substance is going to have a positive slope.
01:01
And the reason for this is because water is less dense when it's in a liquid form, when it's in solid form than when it's in liquid form.
01:12
This is why if you just have a glass full of water and you plop ice cubes in it, those ice cubes are going to float right on the surface...