**** Info via Environment Canada
Why do snowflakes have six sides?
Snow is fascinating. From a distance, snow that accumulates on the ground and on trees creates splendid scenery. But when we look at the snowflakes that fall on our coats up close, they get even more interesting. Aren’t they beautiful? But how do they form?
First, let’s define the following terms:
- Snow is an accumulation of snowflakes;
- A snowflake is a cluster of crystals frozen together; and
- A snow crystal is a configuration of water molecules in a solid state.
A snowflake made of snow crystals.
Why do ice crystals have six branches or six sides?
It’s because of the shape of water molecules (H2O). The two hydrogen atoms connected to the oxygen atom are arranged in such a way that the molecule looks like a Mickey Mouse head. The hydrogen atoms (the ears) have a positive charge, while the oxygen atom bears the negative charge. At low temperatures, the atoms move more slowly and get closer together. The most efficient way for an ice crystal to form is for connections to be made between the molecules at a 120º angle. When there are six such connections, we end up with a mini molecular hexagon.
This large network of molecules grows as water vapour is deposited on the crystal. When snow crystals grow, the water vapour molecules are deposited wherever it’s easiest.
Melting snow crystals.
When there is a lot of water vapour in the air, it is more likely to latch onto the tips, which is why flakes can grow into dendrites or plates. When water vapour is scarcer, it is easier for a water molecule to attach itself to the top of the structure, so the original plate will tend to thicken into a column. Some columns are so thin that they look like needles. Other columns move around within the cloud and begin to grow plates at both ends like caps. And sometimes, a very short column can connect two dendrites offset by 30° from each other, which creates the illusion of a 12-branched snow crystal.
A few types of snow crystals. Source: Ken Libbrecht.
Did you know that the Order of Canada, the highest civilian distinction, uses a stylized snowflake as a symbol of our country’s northern heritage and diversity?
Medals of the Order of Canada. Source: Governor General of Canada.
