Winter definitely is here in the Chicago area. As I look out my window, teeny, tiny flakes of snow are falling, or rather briskly blowing. With a temperature of 18 degrees Fahrenheit and a wind chill factor of 3, that puny snowfall doesn’t call us out to play.
The chemical formula for snow is H2O. Snow is simply made up of one or more crystals of frozen water.
Snowflakes require a cycle of nature beginning with the evaporation of water from rivers, lakes and oceans. When temperatures drop to 32 degrees Fahrenheit or below, the moisture forms into tiny ice crystals. As the crystals fall, they connect with other crystals forming snowflakes. The more crystals that join together, the bigger the flake.
Snow may fall in various forms. The English language tends to describe snow with multiple words such as dry and powdery, wet and slushy, or round and icy. The Inuit people of the northern regions of Canada are said to have countless words for snow, perhaps as many as 50. However, this number is likely an exaggeration.
In the past few years, I’ve heard the term, “graupel” often used. Graupel is precipitation that forms when supercooled water droplets are collected and freeze on falling snowflakes and form into balls of crisp, opaque rime. “Graupel” differs from “sleet” in that graupel never re-freezes as sleet does. Sleet is ice pellets resulting from the re-freezing of liquid raindrops or partial melting of a snowflake.
Here are a few other interesting facts about snow.
Snowflakes usually have six sides.
Identical snowflakes are rare but possible.
Most of the volume of a snow layer consists of air.
Nearly every location in the United States has seen snowfall.
We know not to eat yellow snow, but it may not be a good idea to catch even fresh flakes on your tongue. Snowflakes can pick up specks of dust and other pollution along its descent.
Snow and ice usually appear white, because visible light is white.
Snow that looks blue is due to light waves scattered by the ice grains in the snow.
When falling crystals gather foreign substances such as algae and dust, the crystals pick up the color of the substance.
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