cold liquid question

[JayUK]

Hi,

 

excellent forum you have here!

 

So, my question is one that has been on my mind for ages and I was hoping that someone could please put me out of my misery.....

 

 

Is there such a liquid that stays cold even if it is heated? For example, say the liquid was contained in a beer can, completely sealed and then put in a hot atmosphere like an oven, is there a liquid that you know of that will stay cool?

 

 

Thanks in advance and I look forward to your replies

[YT2095]

no, not if it were left sealed and not allowed to evaporate, the pressure would just increase inside the vessel, and providing it didn`t rupture, it would assume the same temperature as it`s surroundings.

[JayUK]

Thanks YT2095 for your reply, much appreciated.

 

So, if the container wasn't sealed and the liquid was allowed to evaporate, what liquid (preferably safe) could be used?

[YT2095]

there`s all sorts to choose from, liquid nitrogen to use an extreme example, it`s still very cold even in a warm room, because it`s allowed to boil.

 

now an example that you May have seen yourself, ever filled up a cig lighter with Butane gas?

 

the tin can clearly has a liquid inside and it`s also under pressure, and yet it`s at room temp, when you let the pressure drop by filling the lighter it cools almost instantly, occasionaly if you`re really messy and get some liquid on you or the lighter, you can see it boil and it feels cold and you can see Frost form.

[Klaynos]

A liquid nitrogen example:

 

For my MPhys project we have a CCD cooled with Liquid nitrogen, in a temp controled room, the room is around 19deg C 24/7.

 

The LNi dewer for the camera holds about a litre, it's really rather insulated, but is activily heated by the CCD, which is on most of the time. It takes 3 days for the temperature of the CCD to rise from a base of around 120K to 140K the LNi is liquid even after this point, there's just alot less of it.

[someguy]

if you heat a liquid then the liquid must get hotter. you can make a protective casing for the liquid to protect it from the heat.. but you can't make it perfect. as for letting it boil.. a liquid when going into gas form is using up all of the energy of heat to turn it from liquid to gas that's why liquid nitrogen will stay at the same temperature while it evaporates. the temperature of evaporation is determined by the liquid but also the atmosphere because at higher pressure, in order for the gas to lift out into the higher pressure it needs more energy because higher pressure causes more resistance to the gas that wants to rise. so in higher pressure water can be brought to a higher temperature before boiling, and that's why we have pressure cookers so that you can cook stuff faster in water at higher temperature. Up in the mountains your water will boil at a lower temperature so you would need to cook stuff for longer, the water won't go a higher temperature than its boiling point. so if your oven was a perfect vacuum you could achieve the same thing that liquid nitrogen does at our regular atmosphere with a larger variety of liquids i guess, i'm not sure at what temperature water would boil in a perfect vacuum but i think quite alot less then 100C. so i guess it depends what temperature you'd want your liquid to stay at also.

[Klaynos]

Well it'd stop being a perfect vacuum with water in it to boil.... If you look at the phase diagram for water you can see that for 0.0...1Pa then it cannot be anything other than gas.