# How does hot ice exist?

## Main Question or Discussion Point

So I've heard that increasing pressure in water would make the molecules more compact and then eventually become a solid. So it's possible to have hot ice.

But isn't it also true that as pressure increases, the temperature increases as well. For example, if I increase the force per volume, the average kinetic energy should increase because the force increased. So in hot ice, the kinetic energy should be higher, so how would it be in a solid form? Perhaps there is something I'm not understanding. Would it just be a vibrating solid?

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If you compress something it gets hotter, but heat can radiate away.
You then have the compressed something in a denser state, but at it's original temperature

CWatters
CWatters
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So I've heard that increasing pressure in water would make the molecules more compact and then eventually become a solid. So it's possible to have hot ice.
Unlike most liquids water expands when it forms conventional ice but other forms of ice with different structures can exist that are smaller than water.

You can control the pressure and temperature of something independently. What happens is described in a phase diagram (graph of pressure vs temperature)..

You can learn about things like this by looking at a phase diagram for a substance.

That red horizontal line is what water normally does. If the temperature goes down (move left on the line), water will eventually freeze. Freezing is at 0o C under 1atm of pressure (or 101.3 kPa). Duh.

What happens if you take liquid water and squish it instead? Will it turn solid? Just follow the liquid region up to higher pressures and the answer is yes (assuming while compressing it you're also keeping it at a steady temperature which might be difficult). How much pressure are we talking about? Well, look at the lines... looks like you need at least 200-400 MPa, or a few thousand times atmospheric pressure to do this!

You'll notice that water compressed to its 'freezing point' turns into either Ice VI or Ice VII. Most people don't realize that water ice has at least 15 phases! These phases are distinguished because the crystalline structure of the ice will be different in each phase. Pretty cool stuff!

instead of comparing it to ice, imagine it as instead going from water to gelatin to a solid form of gelatin. thats the best I can do to explain it without giving you a headache. you are correct with the fact that as it gets more compressed it would get warmer but the heat would radiate away eventually. leaving you with "hot" ice.