The Yellowknife clip turns a splash of hot water into a bright cloud against a cold outdoor background. The effect is visually striking, but describing every drop as instantly evaporating is too simple.
Why hot water produces a white cloud
Breaking water into small droplets increases its contact with cold air. Evaporation, condensation and freezing can all contribute to what is seen; the white cloud is not a direct view of invisible water vapour.
The Celsius and Fahrenheit readings differ
There are two temperature scales in the account, and they describe different conditions. The video title gives minus thirty Celsius; the accompanying text converts minus thirty Fahrenheit. Neither is a weather measurement independently established by the image. This is also hot water, even in freezing surroundings: a portion that falls back as liquid can still burn someone nearby.
Explore more: the white fog around dry ice; freezing bubbles without a hot-water throw.
Video: Evaporating Water in -30C in Yellowknife, NWT (published by samantha683).
A visible plume does not mean all the water evaporated
Look at the outline of the splash and the cloud around it as separate parts of the scene. The camera records light scattered by suspended droplets or ice particles, while water vapour itself remains invisible. A bright plume therefore cannot tell us that all the liquid has become gas. That is the interesting part of this short demonstration: one familiar substance can produce several visible effects during a very quick change.
Two temperatures, converted consistently
For a like-for-like comparison, minus thirty degrees Celsius equals minus twenty-two Fahrenheit. Minus thirty Fahrenheit, meanwhile, is approximately minus thirty-four Celsius. The eight-degree Fahrenheit difference between the two quoted temperatures disappears if they are casually described as just “minus thirty”. Keeping the unit beside the number makes reports from Yellowknife and other cold places much easier to compare.
Sources, photography and further reading
Original feature and image attributions:
- Spectacular Photos of Bubbles Frozen in Frigid Temperatures
- Embrace Christmas Spirit in Beautiful Quebec City, Canada
- Firefighters Turn Massive Warehouse Blaze Into Ice!
- Frozen Air Bubbles in Abraham Lake, Alberta Canada
- Ice Castle at Silverthorne, Colorado
- the white fog around dry ice
- freezing bubbles without a hot-water throw
- Evaporating Water in -30C in Yellowknife, NWT
Sublimation is the conversion between the solid and the gaseous phases of matter, with no intermediate liquid stage. For those of us interested in the water cycle, sublimation is most often used to describe the process of snow and ice changing into water vapor in the air without first melting into water. The opposite of sublimation is "deposition", where water vapor changes directly into ice—such a snowflakes and frost.
ReplyDelete-30c is -22f.
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