What Gives Snowflakes Their Shape?
Ice-crystals come in millions and millions of shapes and patterns. The shapes of snowflakes depend on how high up in the clouds they are formed. Every single tiny variation in the air where the snowflake forms affects its final shape, so no two snowflakes are exactly alike.
Every snowflake is a hexagon, meaning it has six sides. This is because water molecules each contain two hydrogen atoms and one oxygen atom. (This is why water is called H2O). The most efficient way for the molecules to attach together is in a hexagon shape.
The patterns that these frozen crystals make depends on the temperature of the clouds that they fall through as well as the amount of water in the air. An ice-crystal needs a temperature of -15°C to keep growing. The colder the temperature the sharper the ice-crystal tips.
Very complicated snowflakes are called dendrite snowflakes. They look as though they have branches, like those on a tree. This type of snowflake forms high up in very cold clouds. In warmer temperatures, the ice-crystals grow more slowly and are smoother. This means the crystals are plainer to look at. Snowflake which are formed when there is not enough moisture in the air to form ‘branches’ are called thin plate snowflakes.
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