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Today was hockey day. Two games at Four Seasons Arena in Kassson, MN. Name of that arena should be Winter Arena, it’s the coldest arena. My son played first game against Sartel forward, second game against goalie. Unfortunately they lost both games. After each game was shootout. All team including parents had evening Pizza party at Gorilla’s, team sponsor.

I was trying accomplish with my son several tasks, so morning  we created plan, and I set for each task timer. Later during the day I found that my son has also timer, which was beeping approximately in the same time like that mine. He set time on his Nintendo DS, and probably for the first time used it for time scheduling. Very good. And on Nintendo web I see there is also PersonalTrainerMath.com. Hmm.

We had fun to throw several times boiling water into freezing air in front of our house.  Yesterday and today was really low temperature, less than -22F/-30C. So it was an opportunity do experiment with boiling water thrown into the air. It morphs immediately into white vapor cloud, and almost no liquid water hits the ground.

But why?

Let’s say we have cup of boiling water. As soon as we throw that water in the air, it will disperse into many smaller or bigger droplets, which fly through  air. Cold air is very dry, is has low relative humidity, and very low absolute humidity. Flying droplet is warming boundary layer of the air. Warmer air is able to absorb much more  water, and vapor from droplet surface is evaporating quickly into very dry air. Only big drops don’t evaporate completely, and hit the ground. Soon after air cools off and water vapor condense into little droplets and ice crystals. And we see it as a white cloud.

Links: Phase diagram of water, Psychrometrics diagram, Psychrometrics, Relative humidity.