As I was driving in to school the snowflakes were perfectly landing on the window so I could see each one's unique shape. It was so cool to see all the different designs. It got me thinking that maybe it's time for a little science behind how snowflakes get their shape. It's a lot more complicated than you think! Actually it's pretty amazing that all these variables came together to form all that white stuff we've had this season.
How do snowflakes form?
Snowflakes start out simply enough, they are just bits of water vapor in the air. High up in the atmosphere where is very cold that water vapor condenses into liquid and you'll get clouds. In snow forming clouds they are cooled below freezing point (about 14 F) and those liquid drops freeze. As time goes by more water vapor condenses on it's surface the snow flake grows. When it reaches a point that it's too heavy it will fall as precipitation. So that's the easy part..now depending on things like temperature, humidity, and atmospheric pressure will determine the shape and complexity.
I could totally nerd out on you because there is a lot of math and molecular/structural engineering if you want to get down to the nitty-gritty of it but I won't and try to keep it simple. If you do want more of that kind information there is a ton of resources out there and people are even obsessed with researching it so! Let me know and I'll point you in the direction.
When water turns to ice those molecules stack to create crystalline lattice (see previous post about ice). Ice has a hexagonal symmetry and this basic shape will determine the overall symmetry of the snowflake and why there is usually 6 arms to a snowflake. The growth of crystals is split between balance of facets and branches. Check out this 2 minute video to watch the stunning growth of snow crystals.
Facets are simple flat surfaces with sharp edges. This is from very slow growth of the crystal and gives you the prisms and plates. Branching makes the more complex structures we tend to think of as a snow flake. Branches start as a small bump of growth that sticks out further on the crystal. Since that is what the vapor will come in contact with first more will grow off of that area quickly. As more grows the flake becomes more complex. If snow crystals are formed below atmospheric pressure there will be less branches, higher pressure means more branches. As snowflake moves it is in differing temperatures and pressures so the growth of arms can be different that other flakes making it unique.
Temperature and humidity will also strongly influence the growth of snowflake between faceting and branching. This means that snow crystals can be very diverse. Have you ever heard that it's too cold to snow? Well really it's about the humidity usually when it is very cold it has already snowed and air is dry. There isn't more water vapor to make new snow. So far this season I've seen the big fluffy flakes, the tiny diamond like grainy ones, wet sloppy, needles, unique branching, and and a white out all these are due to the climate.
Are two snow flakes really alike?
Since there are so many variables that go into play in creating a snowflake statistically it is highly unlikely that two complex snowflake structures are exactly alike... but really who is going to collect and check every snow flake that is ever fallen? Not it! To get a more in depth answer check out this page There also is a wealth of more than you ever wanted to know about snowflakes at that site.
What are some fun activities I can do about snow?
There are lots of cute activities that range from craft to science experiments on the internet. Here are just a few I like that can be adapted to any situation1) snowflake scavenger hunt Printable PDF of the different shapes. Take it outside and see what you can find!
2) 15 great activities that are snow and ice related you can do at home or at school with kids from inspiration laboratories
3) This is one of the those cool kitchen chemistry "magic trick" experiments you can wow kids or adults called hot ice.
4) Go back to basics and enjoy sledding or snowman building
With storm system after storm system I feel like I'm living out part of the Seven Brides for Seven Brothers movie: the June Bride Song sequence...sigh such a great movie.
Don't worry the first day of spring is around the corner....well at least that's what the calendar says!
Here is one more really neat video from BBC about snowflakes sorry I think this is just too cool!
