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Author Topic: Why does dry ice ‘smoke’ in water?  (Read 7704 times)

Offline John Chapman

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Why does dry ice ‘smoke’ in water?
« on: 15/03/2009 19:13:33 »
Every schoolboy knows that dry ice is solid (ie frozen) carbon dioxide. He may also knows that carbon dioxide turns from solid to gas without bothering to inconvenience itself with a liquid phase. A process which I believe is known as sublimation. But my question is this:

Since gaseous CO2 is colourless, and to all intents and purposes invisible, why does melting dry ice in water produce a thick fog? Dry ice and water provide the mechanism by which theatrical fog machines work.

I'm sorry guys. I don't know if this is a physics or chemistry question.


 

Offline lightarrow

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Why does dry ice ‘smoke’ in water?
« Reply #1 on: 15/03/2009 21:59:28 »
Every schoolboy knows that dry ice is solid (ie frozen) carbon dioxide. He may also knows that carbon dioxide turns from solid to gas without bothering to inconvenience itself with a liquid phase. A process which I believe is known as sublimation. But my question is this:

Since gaseous CO2 is colourless, and to all intents and purposes invisible, why does melting dry ice in water produce a thick fog? Dry ice and water provide the mechanism by which theatrical fog machines work.

I'm sorry guys. I don't know if this is a physics or chemistry question.
It's an interesting question (and you are right about having difficulty defining it as a chemistry or physics question, infact it's "physical chemistry"  :)) because the answer seems obvious but it's not, at least for me. I'm almost sure that water has the main purpose to heat solid CO2 quickly: water is at room temperature and being a liquid, it enters in contact with the solid piece through a great area.
What is the fog/smoke, is less obvious; it is presumably made of solid CO2 particles quickly detached from the vaporization process, but there could be others mechanisms, or be made also of solid water vapor freezed by the cold CO2. I'm almost sure it can't be carbonic acid because it shouldn't exist pure or in high concentrations.
« Last Edit: 15/03/2009 22:01:58 by lightarrow »
 

Offline RD

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Why does dry ice ‘smoke’ in water?
« Reply #2 on: 16/03/2009 00:54:47 »
I suspect the CO2 fog is actually the water in air (~2% @ 20 oC) condensing into visible droplets in the very cold CO2 gas.
« Last Edit: 16/03/2009 00:58:45 by RD »
 

Offline Chemistry4me

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Why does dry ice ‘smoke’ in water?
« Reply #3 on: 16/03/2009 04:17:05 »
I agree with RD.

Quote
When you place dry ice into some warm or hot water, clouds of white fog are created. This white fog is not the CO2 gas, but rather it is condensed water vapor, mixed in with the invisible CO2.

http://www.west.net/~science/co2.htm

Quote
As dry ice sublimes, the very-cold-but-now-gaseous CO2 vapor is invisible, but is plenty cold enough to condense water in the air. It is the condensed water vapor which is visible above a block of dry ice as "fog."

http://ocw.mit.edu/NR/rdonlyres/Music-and-Theater-Arts/21M-735Spring2004/10F93278-4C1B-44AA-BCE2-71AD21D7C13F/0/mpd_tn8.pdf
 

Offline Raghavendra

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Why does dry ice ‘smoke’ in water?
« Reply #4 on: 16/03/2009 09:04:58 »
good question dude, i think RD is right
 

Offline lightarrow

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Why does dry ice ‘smoke’ in water?
« Reply #5 on: 16/03/2009 17:14:03 »
I agree with RD.

Quote
When you place dry ice into some warm or hot water, clouds of white fog are created. This white fog is not the CO2 gas, but rather it is condensed water vapor, mixed in with the invisible CO2.

http://www.west.net/~science/co2.htm

Quote
As dry ice sublimes, the very-cold-but-now-gaseous CO2 vapor is invisible, but is plenty cold enough to condense water in the air. It is the condensed water vapor which is visible above a block of dry ice as "fog."

http://ocw.mit.edu/NR/rdonlyres/Music-and-Theater-Arts/21M-735Spring2004/10F93278-4C1B-44AA-BCE2-71AD21D7C13F/0/mpd_tn8.pdf
Very interesting. Thank you.
 

Offline dentstudent

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Why does dry ice ‘smoke’ in water?
« Reply #6 on: 16/03/2009 18:03:37 »
When reading this thread title, who else in their head went "ne ne ne, ne ne ne-ne, ne ne ne, ne ne"



(They all came down to Montreux...)
 

Offline Bored chemist

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Why does dry ice ‘smoke’ in water?
« Reply #7 on: 16/03/2009 20:45:47 »
I certainly thought of
 

Offline yor_on

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Why does dry ice ‘smoke’ in water?
« Reply #8 on: 17/03/2009 21:53:03 »
Nice one Dentstudent


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And a great recording too BC :)
« Last Edit: 17/03/2009 21:56:36 by yor_on »
 

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Why does dry ice ‘smoke’ in water?
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