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Thread: question about liquid nitrogen

  1. #1 question about liquid nitrogen 
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    if i pour it into water , will it cool the things around it.
    eg. help fight global warming


    or will it quickly evapourate and have no effect

    also, pretend there is no emmission produced in me making the liquid nitrogen


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  3. #2  
    Forum Isotope Bunbury's Avatar
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    What is the point of pretending something that is the opposite of what we know to be true? You cannot liquefy nitrogen without expending energy. If you were planning to use solar energy to liquefy nitrogen and then use the liquid nitrogen in some secondary way, it will unavoidably be less efficient than just using the solar power to produce electricity.


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    Forum Sophomore oceanwave's Avatar
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    couldnt agree more...AND u'd most probably kill the millions of sea creatures living in the sea by doing so...and freeze the thousands directly under the flood of liquid N2
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    Instant freeze.... dip your finger in a small bowl, then tap that finger on the table.. you'll get a shattered-like-glass finger.
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  6. #5  
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    The main problem is that you would release heat when you made the liquid nitrogen, so there wouldn't be any net reduction in the earth's heat when you used it to cool something down.
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    Forum Sophomore oceanwave's Avatar
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    Adding on to Scifor's post, global warming is the result of more of the sun's rays/heat energy being trapped in/into our system and on earth, i believe that the energy/heat is being cycled around (reduce heat in one place equals to an increase in heat in another) and until we find an efficient way of releasing heat back into the atmosphere (maybe by bringing excess CO2 to mars, etc) then will we see a drop in temperatures arising from less heat being retained and more being reflected into space.
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  8. #7  
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    Quote Originally Posted by CoolEJ
    Instant freeze.... dip your finger in a small bowl, then tap that finger on the table.. you'll get a shattered-like-glass finger.
    You'd need to hold it in there for a fair while to freeze right through. The stuff sure is cold but the Hollywood take on liquid nitrogen is rather exaggerated.
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  9. #8  
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    You'd need to hold it in there for a fair while to freeze right through. The stuff sure is cold but the Hollywood take on liquid nitrogen is rather exaggerated.
    hmm...from what i saw from a science show a few years ago, the guy took a banana and dipped it into liquid nitrogen. after like 5 secs he removed the banana and used it to knock a nail into hard wood....lol..
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  10. #9  
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    Quote Originally Posted by oceanwave
    You'd need to hold it in there for a fair while to freeze right through. The stuff sure is cold but the Hollywood take on liquid nitrogen is rather exaggerated.
    hmm...from what i saw from a science show a few years ago, the guy took a banana and dipped it into liquid nitrogen. after like 5 secs he removed the banana and used it to knock a nail into hard wood....lol..
    I've never tried putting a banana into liquid nitrogen so I don't know about that. A finger should take a little longer though. Not that I've tried that either. Just basing this on my observations of how quickly the stuff freezes cells.
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    Forum Sophomore oceanwave's Avatar
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    hmm...at what temperature did u based your observations on? liquid nitrogen really is very cold...much colder than the Arctic, Antarctic and even the average freezer...so the time it takes and even the slow process of freezing cells may not apply in this sense..and oh, it will also depend on how fat the finger is or the banana...
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  12. #11  
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    Quote Originally Posted by oceanwave
    hmm...at what temperature did u based your observations on? liquid nitrogen really is very cold...much colder than the Arctic, Antarctic and even the average freezer...
    What temperature? The stuff only stays liquid below -196 degrees C... Since it's just in a double walled container rather than being actively cooled I'd say it's probably at that temperature or a little above. The average freezer is a -20C, and the better low temp ones we have at my lab only manage -80C so I'm fully aware that liquid N2 is really damn cold The Arctic doesn't compete and I think even the surface of Mars only compares to the -80C freezer.

    Quote Originally Posted by oceanwave
    ...so the time it takes and even the slow process of freezing cells may not apply in this sense..and oh, it will also depend on how fat the finger is or the banana...
    Yep! A finger will be slower I think because of adipose tissue (fat) and of course circulation. Both will stave off the freezing a bit more. I've actually "burnt" my (very skinny) finger on liquid nitrogen more than once and ended up without even a blister- not that I'd recommend any to actually try it for themselves. The stuff will mess you right up with sustained contact!

    I love to play with it
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    it is off topic but: Can you freeze liquid nitrogen so that it becomes solid? how do you do that?
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    Quote Originally Posted by CoolEJ
    it is off topic but: Can you freeze liquid nitrogen so that it becomes solid? how do you do that?
    Yes- cool it to -210C. I think you should be able to do that with liquid helium which is at about -270C or so. Or just depressurise it a whole lot with some sort of vacuum container.
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    so Helium has even lower freezing temp. How do we freeze helium? or how do we acheive lowest possible temperature?
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    Yep! A finger will be slower I think because of adipose tissue (fat) and of course circulation. Both will stave off the freezing a bit more. I've actually "burnt" my (very skinny) finger on liquid nitrogen more than once and ended up without even a blister- not that I'd recommend any to actually try it for themselves. The stuff will mess you right up with sustained contact!
    Gibberish.

    The reason your finger doesn't freeze instantly is because relativistically speaking your finger is superhot compared to the LN2. Basically on first contact the LN2 instantly vapourizes around your finger causing a thin layer of gaseous N2 which acts as an insulator but obviously it will be quickly displaced by the remaning LN2 and freeze your finger.
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    so Helium has even lower freezing temp. How do we freeze helium? or how do we acheive lowest possible temperature?
    Compress it.

    It's theorized that the core of Jupiter is solid metallic hydrogen because the pressures are so great.

    With respect to liquid helium it will only freeze/solidify at 25.2 times atmospheric pressure and at 1.1 degrees Kelvin.
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    Or just depressurise it a whole lot with some sort of vacuum container.
    That will initiate boiling. With no pressure on the molecule it will be free to expand freely i.e. change into its gaseous state.
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  19. #18  
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    Quote Originally Posted by Mars
    Yep! A finger will be slower I think because of adipose tissue (fat) and of course circulation. Both will stave off the freezing a bit more. I've actually "burnt" my (very skinny) finger on liquid nitrogen more than once and ended up without even a blister- not that I'd recommend any to actually try it for themselves. The stuff will mess you right up with sustained contact!
    Gibberish.

    The reason your finger doesn't freeze instantly is because relativistically speaking your finger is superhot compared to the LN2. Basically on first contact the LN2 instantly vapourizes around your finger causing a thin layer of gaseous N2 which acts as an insulator but obviously it will be quickly displaced by the remaning LN2 and freeze your finger.
    Gibberish? I'll certainly accept that the insulating effect of vaporising N2 will be very important, but the rest is certainly not gibberish. My finger is super hot relative to the LN2 because of heat derived both from its surroundings and from its metabolism. Heat that is circulated by by blood and insulated by my fat. Gibberish indeed. There's no need to be so dismissive.

    Quote Originally Posted by Mars
    That will initiate boiling. With no pressure on the molecule it will be free to expand freely i.e. change into its gaseous state.
    Well that certainly makes more sense. The vacuum thing I read somewhere and assumed that meant depressurisation rather than compression.
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    Using Charle' Law, P and T are directly proportional. Thus we need to depressurize to get lower T.
    Right?


    Wow, and to get stronger vacuum you'll need very strong air suction.
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  21. #20  
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    water freezes at 0 degrees, liquid nitrogen is at -203

    dumping 100 litres of N2 into the sea would freeze vast quantities of water, killing thousands of sea creatures and would lower the temperature for miles to frostbite degree the area would take weeks to recover


    and finally you have energy conservation which states you cannot create or destroy energy only manipulate and move it, therefore to lower nitrogen to liquid nitrogen you must take 200 something degrees out of it, which goes straight into the atmosphere, so to make 10 litres of liquid nitrogen you would have to pour 10 litres or 220 degrees of heat into the atmosphere which will superheat most surrounding gasses




    so you have a man made catastrophy there, boiling the atmosphere and freezing the oceans
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    [size=12]I think Charles' Law is for an ideal gas where n and V are held constant. So if you heat up a closed box of gas, the moecules will go faster (because you input kinetic energy), so they will hit the wall harder, and the pressure will increase.

    In this case you are compressing N2(g), so the volume is not constant. If you raise the pressure enough you force N2(g) through a phase change (condensation) to N2(l) because N2(l) is much more dense than N2(g).

    When you compress the gas, and when you make the phase change to liquid nitrogen you would be putting off heat. I'm guessing that you have to have some sort of heat sink to dissipate all of the energy. Is that true?
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    I just looked around a little bit, and it looks like liquid nitrogen is not made by simply compressing it too a liquid (I haven't seen a phase diagram, but perhaps this requires to much pressure?). It's made by compressing it, and then expanding adiabatically several times. The Joule Thomson effect explains why the nitrogen cools upon expansion (it's a property of nonideal gases). Wikipedia is probably best for an intro. to the Joule Thomson effect.
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