Snow crystalsappear when water vapor condenses directly into ice.
A snowflake describes asingle snow crystal or a group of snow crystals. The foundation of a snowflakebegins with a water droplet. Water droplets in clouds are unique in that theydo not freeze immediately when the temperature decreases below zero degreesCelsius. Alternatively, they stay in their liquid form in a supercooled state.At negative forty degrees Celsius pure water droplets will freeze. Waterdroplets with dust, on the other hand, start freezing at a much highertemperature of negative six degrees Celsius because the dust allows for a solidsurface to begin the freezing process. Individual frozen droplets will grow asthe water vapor condenses onto the surface, solidifying into a crystal-latticestructure. When the snow crystal accumulates enough weight, gravity will pullit down.
There is truthwhen people say that no two snowflakes look alike. Each snowflake has a uniqueshape and pattern. To start, the angles between atoms in a water moleculecreate a hexagon shaped ice lattice, causing six-fold symmetry.
Shapes ofsnowflakes can range from thin hexagonal columns to slender hexagonal plates.One example of a particular shape of snowflake is bullet rosettes, named forits bullet shaped columns. Star-shaped or stellar snow crystals are anothershape. These snow crystals have six primary branches which are embellished withridges or patterns. These could have additional side branches that would be separatedby multiples of sixty degrees and run parallel to their adjacent rows of branches.One special shape of snowflakes is called capped columns.
These are created whena snow crystal begins to form as a column and changes to forming into a plate growth.The shape of a snowflake emerges with time as water vapor condenses to the crystalsurface. The lattice structure helps to explain the six-fold symmetry, but failsto explain the complex shapes of snowflakes. The crystal shape formed is dependenton the temperature and humidity of the surroundings. At negative two degrees Celsiusthin plate-like crystals appear. At negative five degrees Celsius slender needlesform.
At negative fifteen degrees Celsius large, thin plate-like crystals develop.At negative twenty-five degrees Celsius and below the crystals grew as short columns.
