[R Uptigrove]

R Uptigrove asked the Naked Scientists:

If you put, let's say a pint, of liquid nitrogen in an unbreakable quart container and let it rise to room temperature, 75F, what will the pressure be?

Will it all become a gas?  If so, then a follow-up question is how cold does the environment have to be where some of the nitrogen remains a liquid?

At that temperature I would assume that the amount of original liquid would not affect the final pressure as long as some liquid was left.

Thanks, whoever you are, wherever you may be.

Bob, old enough where four score and seven years doesn't sound so awfully long as it did when I was your age.

What do you think?

[RD]

If you put, let's say a pint, of liquid nitrogen in an unbreakable quart container and let it rise to room temperature, 75F, what will the pressure be?

The tanks used to contain liquid nitrogen can withstand pressures of 350 psi ...
http://www.apsusa.biz/grams/safetygram7.pdf
[hopefully this includes a large margin of safety]

[Bored chemist]

Don't try the experiment unless you are really sure that the container is unbreakable- otherwise it makes quite a good bomb.
Anyway, the answer is that the nitrogen, as it warmed, would beccome a supercritical fluid.
http://en.wikipedia.org/wiki/Supercritical_fluid
Effectively that's too dense to be a gas, but too hot to be a liquid- so it's neither.

If the ambient temperature were about 200 degrees below freezing (that's below 77K to those who like SI units) the nitrogen wouldn't boil at all. Provided that the temperature is below the critical temperature for nitrogen (-146.9C) you can get a liquid if the pressure is high enough. If the temperature is above that then, no matter how high the pressure, you can't get a liquid.
Interestingly, the critical pressure of nitrogen is quite low (about 33.5 atmospheres) so the "gas" in cylinders of nitrogen, as sold for welding and such, is a supercritical fluid already.

[Madidus_Scientia]

What's the go when science teachers get a little tub of it and dip things into it and then shatter it, why doesn't it explode into gas as soon as they open it up?

[Bored chemist]

Because it's very cold.

[Madidus_Scientia]

So while its under pressure in the cylinder it can't absorb heat? and only begins absorbing it again when you release the pressure on it?

[Bored chemist]

The nitrogen in cylindes is technically a supercritical fluid- but it acts pretty much like a gas under high pressure. Whan you open the valve the gas comes out.
Liquid nitrogen is stored at near atmospheric pressure and very low temperature in Dewar vessels.

[Madidus_Scientia]

I see. How do they cool it so much in the first place, really hardcore freezers?

[Bored chemist]

Pretty close.
http://en.wikipedia.org/wiki/Liquid_air#Principle_of_production

[qazibasit]

while converting from liquid to gas it will make the surrounding cooler and if there is a large volume of liquid nitrogen it may even cause the freezing of its surrounding.