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Dry Ice.

  1. Aug 19, 2009 #1
    Does anyone know why you can see the smoke coming from dry ice? Is it actually CO2? It does not make sense to me, why could I see CO2 evaporating, but I cannot see it normally? Is it the moisture in the air that I can see reacting with the cold CO2?
  2. jcsd
  3. Aug 19, 2009 #2
    What you are seeing is the sublimation point where the solid co2 is converting directly to gas. The smoke as you describe really is nothing more then a dense area of CO2 gas (due to is still low temperature) which quickly expands and dissipates which makes it appear to disappear.
  4. Aug 19, 2009 #3


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    I've never heard of gaseous CO2 being visible anywhere atmospheric pressure, so I severely doubt this. It's far more likely that when you're seeing is water droplets condensed out of the surrounding air due to the low temperature.
  5. Aug 19, 2009 #4
    Good point, and certainly reasonable, though I have seen the same phenomenon in a dry nitrogen / Co2 atmosphere set at normal atmosphere pressure.... maybe there was still some h20 in the system? Anyway good luck with your discoveries.
  6. Aug 19, 2009 #5
    It could be that the temperature drop of the air is causing the relative humidity of the air to reach 100%.
  7. Aug 19, 2009 #6


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    I agree that what you see is condensed atmospheric water. CO2 is invisible. When you use dry ice to make 'smoke', such as for a party, you put it into a tub of water.
  8. Aug 19, 2009 #7

    Vanadium 50

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    The smoke is condensing water vapor - small snowflakes or droplets of water. Capture it on an object and it gets wet.
  9. Aug 19, 2009 #8
    A bit like the condensation on the outside of my glass of cold beer.Cheers.
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