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Ice clouds

Tom Kuntzleman's picture
Mon, 12/16/2013 - 08:33 -- Tom Kuntzleman

I get excited when I see the outside temperature drop below 0°F (-18°C). This is not because I enjoy cold weather. It is because when the outside temperature gets this cold, I can conduct a particular experiment that I think is quite beautiful. The experiment is easy to carry out: boil some water and throw the hot water into the frigid air. Check it out below:

Isn’t that cool? Throwing very hot water into very cold air results in the rapid formation of a cloud.

This simple experiment brings several questions to my mind. First, what is going on here? I’ve thought about this experiment a bit, and I’m still not completely sure what is happening. My guess is that the hot water has a very high vapor pressure, which causes a lot of the hot liquid molecules to vaporize into the cold air. The vaporized water molecules quickly condense, then freeze (or do they just sublime?) into tiny particles of ice to form an ice cloud. I’d be interested to hear your thoughts on what you think might be happening.

I’ve also wondered about the factors involved in cloud formation. I’ve conducted this experiment at outside temperatures ranging from 5°F (-15°C) to -4°F (-20°C). While I haven’t performed in-depth experiments, the cloud formation seems to work better at colder air temperatures. I think an analysis of cloud formation at various outside air temperatures would be a great winter project for students. The temperature rarely drops below 0°F (-18°C) where I live so unfortunately I haven’t had my students look at this.

A second set of experiments involves looking at the temperature of the water thrown into the air. As seen in the video, water close to its boiling temperature forms a nice cloud. However, I have tried using hot water from the tap (about 104°F or 40°C), but water at this temperature does not form a cloud. Is there a threshold temperature above which the water must be to form a visible cloud? And does this threshold temperature change with the temperature of the outside air?

I’ve conducted this experiment as a demonstration for my chemistry classes when the weather cooperates. (Be sure to do a trial run before demonstrating this to your classes! I once tried this experiment in front of my class when the outside temperature was too warm for cloud formation. I am sure my students wondered why their professor decided to take them outside on a cold day so he could throw hot water into the air for no reason at all). If you happen to try this demonstration for your classes or if you try any of the suggested experiments above, let me know how things work out. I would love to hear from you.

Comments

Jon Holmes's picture
Submitted by Jon Holmes on

Your experiment reminds me of contrails, those cloud trails seen behind airplanes, and smokestack clouds. Of course the altitude of a jet plane is different and jet engines and smokestacks are 'throwing' water vapor and not boiling water into the air, but the products are both interesting and beautiful. Contrails have undergone significant study in order to understand their impact on the atmosphere and to debunk the conspiracy theory of "chemtrails". The Journal of Chemical Education published a tech report on a physical chemistry exercise (1) about contrails. Another article about fog machines (2) refers to similar experiments/demonstrations and may provide some answers to your questions. Relating your demonstration/experiment to contrails and smokestack clouds might provide some connections for students.

References

  1. Chen, Franklin. "Contrail. A Module from the Physical Chemistry On-Line Project", Journal of Chemical Education 2007 84 (4), 735.
  2. Vitz, Ed and Lyle, Kenneth S. "Fog Machines, Vapors, and Phase Diagrams", Journal of Chemical Education 2008 85 (10), 1385.

Jon Holmes

Tom Kuntzleman's picture
Submitted by Tom Kuntzleman on

Yes!  It does appear as though many condensation trails form during the ice cloud experiment.  I will look into the reference on contrails you provided.  Thanks for the input!

Tom Kuntzleman

Submitted by Kathy Hockman on

Remembering your entry about ice clouds made a -22F morning a much more fun experience...or experiment. We were able to do this ice cloud experiment until noon today and the kids loved it!! I have read about it in the past but not usually when the weather was cooperating. Thanks for a great end of the semester fun activity. And we can start a new semester with new students in January!! It's a two-fer!!

Kathy Hockman

Tom Kuntzleman's picture
Submitted by Tom Kuntzleman on

Hi Kathy, I'll bet you guys had a blast.  -22F is REALLY cold!  What did the clouds look like and how did they behave at -22F?  Were the clouds similar in structure and behavior to the clouds you see in the my video?  Thanks for letting me know you gave this experiment a try.

Tom Kuntzleman

Submitted by Kathy Hockman on

Hi Tom,

The clouds we made looked like yours except I rationed the water among the students in their styrofoam cups so we made little ones. I did notice that by the third class (when the temps had warmed up to -3F) there was more liquid water that hit the ground, but we still had clouds. =)

 

Kathy Hockman

Tom Kuntzleman's picture
Submitted by Tom Kuntzleman on

Thanks, Kathy

Tom Kuntzleman

Submitted by John Bennett on

Hi Tom,

In a related weather vein (vane..pun intended) i did an experiment to capture a snowflake using Super Glue.  I read it years ago in Poplular Science.  The idea was to collect a snowflake on a microscope slide, add a few drops superglue before it melts, then a slide cover to "freeze" it in time.  So for weeks I kept Super Glue, slides, and slide covers outside on my front porch waiting for snow.  When it finally came I capture several full snowflakes, then brought them with me to class.  My students then used a microscope to see the elaborate crystal structure of the snowflakes.

Thanks for your video.  If I can find my snowflake slides I will use my new document camera and a microscope to add some pictures.

John

Tom Kuntzleman's picture
Submitted by Tom Kuntzleman on

John, that is a fantastic idea - I hope you find the pictures!  If you do find the pictures, could I talk you into potentially guest-blogging about how to carry out the experiment? 

Tom Kuntzleman

Submitted by Eugenio Jelacic on

Nice experiment. There are a few phenomena going on here as I see it. Hot water obviously evaporates and the rate of evaporation depends not only on temperature of water but also on atmospheric pressure, hence lower the pressure – higher the rate of evaporation. Water vapor itself is invisible. What we see are droplets of liquid water or tiny ice crystals in this case. First case is condensation and second either freezing or inverse sublimation. Now the rate of condensation depends on the relative humidity of the air. The higher the humidity, the less additional water vapor can the air receive and the stronger the condensation. I suggest you carry out before the experiment two measurements of atmospheric conditions: barometric pressure and relative humidity. These two factors, besides atmospheric temperature, will determine the cloud effect. Best wishes!

Tom Kuntzleman's picture
Submitted by Tom Kuntzleman on

Hi Eugenio:

I wish the weather around my home cooperated more often so that I  could systematically study the ice cloud under various atmospheric conditions.  However, the temperature where I live rarely drops below 10 Fahrenheit.  Nevertheless, I appreciate your comments and insights and will start measuring the barometric pressure and relative humidity whenever I have the opportunity to conduct this experiment.

Tom Kuntzleman