Facts about snowflakes

_Elsa_

‘Why do we associate snowflakes with star shapes?

They may be tiny but there is complicated science happening within each and every flake. That’s all down to what happens when water freezes. Every single time this happens, the flake’s molecules arrange themselves into a distinctive six-sided honeycomb-type structure. 

This six-sided shape is because of the way the hydrogen and oxygen atoms inside the molecules behave when they encounter other water molecules. They link up in a strict pattern known as six-fold symmetry (that’s why we tend to associate snowflakes with hexagons or six-pointed stars) which gives us the basic snowflake template. That shape changes even further as they fall through the air. Snowflakes beneath the microscope show how different each one is.

Is each one actually unique?

As each snowflake falls, it encounters water vapour in the atmosphere. This has a big effect on its shape.

• If humidity is low, there isn’t as much water vapour in the atmosphere so the snowflakes form something called 'plates', the flat hexagonal shapes you see if you look at them under a microscope.

• If humidity is high, with more water vapour in the atmosphere, something called branching happens. Here the molecules form straight lines (dendrites) which branch out in different directions, creating the star-like patterns we tend to see on Christmas decorations. High humidity also creates bigger flakes, as there’s more vapour for the flakes to fall through.

Because a snowflake’s shape evolves as it journeys through the air, no two will ever be the same. Even two flakes floating side by side will each be blown through different levels of humidity and vapour to create a shape that is truly unique. ‘ (Source) 

Let’s continue – Look for different types of snow to build a snowman

Start at the beginning – Let It snow! Let it snow! Let it snow!