In honor of Blizzard Nemo, today's post will talk about the science and chemistry of snowflakes! It is said that no two snowflakes are alike, but how could this be possible? How do these intricate ice crystals come to form and what controls the various shapes they make.
Courtesy of blog.needsupply.com
Before we delve deeper, it's important to briefly review the various states of matter and how they interchange. There are four basic types of matter observable in everyday life: solid, liquid, gas, and supercritical fluid. The distinction between these types of matter is mainly based on their qualitative properties. At low temperatures, individual molecules don't have a lot of energy, and as such, they tend to stick together due to intermolcular forces. The molecules pack together in an order arrangement giving the material a high density and rigid shape, making them very difficult to compress. As the molecules warm up, they eventually gain enough energy to break some of the intermolecular bond which hold them in place. The molecules then begin to diffuse into their container, leading to an increase in disorder of the system. This is the liquid state. The particles are still close to one another but now have the ability to move freely. When the temperature gets high enough, the molecules gain enough energy to escape from their intermolecular forces and entirely seperate from one another. In this state, the gaseous state, particles have complete freedom of motion and individual molecules are very spread apart and moving very fast. Because they are mostly space, gases completely fill their containers and can be easily compressed. The fourth state of matter is supercritical fluid, a state with both gas and liquid properties. This state arises at high temperatures and pressures when molecules have too much energy to be compressed into a liquid at any pressure.
Courtesy of chem.ufl.edu
High up in the clouds, when the temperature drops below 32° F (0°C) water droplets (liquid) begin to freeze around dust particles. It is from these small crystals that snowflakes then form! While snowflake formation is a highly dynamic process that depends on temperature, humidity, air currents, etc. there are several general guidelines regarding what types of crystals form at different heights and temperatures. Generally, in high clouds, six-sided hexagonal crystals form, while at mid range heights flat six-sided crystals dominate. At colder temperatures, sharper tipped snowflakes with more intricate branching patterns also tend to form. The short video below gives a great overview of the whole process.
Who knew that fluffy white stuff could be so amazing!
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