Naked Science Forum

Non Life Sciences => Chemistry => Topic started by: thedoc on 30/09/2016 12:23:01

Title: What happens if you cool water in a space where it has no room to expand?
Post by: thedoc on 30/09/2016 12:23:01

Tim asked the Naked Scientists:
    If I filled a very big watertight safe with water and cooled it to minus 200,  ie so the water had no room to expand, what would happen to it?
What do you think?

Title: Re: What happens if you cool water in a space where it has no room to expand?
Post by: chiralSPO on 30/09/2016 13:22:59

It would freeze. Here is a link to a page that has a phase diagram of water that extends over a very wide temperature and pressure range: http://www.k9spud.com/freeze-drying

You can see that for any pressure on the chart, water is a solid at –200°C. This temperature happens to lie on the boundary between two types of solid ice for most pressures, but it will certainly be solid.

Title: Re: What happens if you cool water in a space where it has no room to expand?
Post by: evan_au on 30/09/2016 23:53:17

I think the interesting behavior will happen between about 4C and -4C. An absolutely rigid and watertight safe could reach very high pressures.

Looking at the phase diagram, an increase from atmospheric pressure of 100kPa to around 100MPa will depress the freezing point below -4C, and it will form (some variant of) ice.

The question is whether a safe could withstand 1000 atmospheres of pressure without bowing, exploding, or springing a leak?

Title: Re: What happens if you cool water in a space where it has no room to expand?
Post by: Bored chemist on 01/10/2016 00:29:18

By  the time it reached -200 the water (as ice) would shrink again.
The idea has been used for a simple way of generating high pressures.
Fundamentally, there's a problem. How do you stop the  stuff expanding?
Even a thick metal container has some "give"- or a finite Young's modulus if you prefer that terminology.