Freezing water expands. What if you don't let it?

when water freezes it expands that's why ice floats and why cans and jars

bulge or explode in the freezer on the other hand when water is compressed

it melts you need a lot of pressure that Ice Cube that's 4 degrees

Celsius below freezing can withstand around 500

times atmospheric pressure before it'll melt but it will melt so

if when you freeze water it expands

and when you compress it it melts what happens if you try to freeze

it while it's compressed

like what if you cool water below zero degrees Celsius inside a super strong

pressure vessel that can't bulge or stretch if the water is liquid it's not

under pressure so below zero Celsius it should freeze but if it's frozen it

expands creating pressure and so it should melt which means it should freeze which

means it should melt you

see the problem the

pressure that causes melting is being generated by expansion that requires being frozen it

seems we've arrived at a paradox if

by Paradox you mean phase diagram you

know those pictures that tell you the phase of matter for a substance whether

it's a solid liquid or gas for different combinations of temperature and pressure on

the phase diagram for water you can see here that at normal atmospheric

pressure when you cool water down it goes from a liquid to a solid

as you'd expect and

at minus 4 degrees Celsius and atmospheric pressure water is frozen solid but if

you increase the pressure the solid water goes back to a liquid so

what if you don't let the water expand when it freezes well

when water is below zero degrees Celsius it

wants to freeze but only some of it can because any bits that freeze

expand which pressurizes the container and eventually the pressure builds up enough to keep

any more liquid water from freezing at that temperature on the phase diagram we

followed the line between liquid and solid in the direction of Colder temperature and

higher pressure If you cool the container even more then slightly more bits of

water will be able to freeze and expand until the pressure again builds up

enough to keep any more liquid water from freezing and

so on the colder you make the container the higher the percentage of ice

and the higher the pressure in the container this

graph shows the percentage of ice versus liquid when you cool a fixed volume

of water to different temperatures and

I've labeled the pressures that are generated at each temperature too as

for whether the container ever completely turns to ice while

looking at the phase diagram again we see that once the temperature is low

enough and the pressure high enough the remaining liquid water can freeze into a

different phase of ice called ice 3.

and Ice 3 contracts

and becomes denser when it freezes creating more space and allowing the entire container

to freeze solid though some will still be our normal ice called ice1h

and some will be ice 3.

so there is no Paradox the

phase of water it turns out can be non-binary

wait water what are you doing don't click away I

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