Snow science: What is a snowflake?

What we call snowflakes are actually snow crystals. Learn more about their shape and formation.

Snow science: What is a snowflake?

For most of Michigan, the first (or perhaps second, third, fourth…) snowfall of the season has changed the scenery of late fall into a glistening landscape waiting to be explored. As this change in the season happens, a new world of outdoor observation and exploration opens up for youth to ask questions and discover answers about their world.

This series from Michigan State University Extension and 4-H Youth Development program will explore winter science questions and activities regarding snow. The first two articles in the series describe the physical and acoustic properties of snow. This article will explore the shape of snowflakes in more detail.

When we think of snowflakes, we often think of the perfect, beautiful, six-sided shape we commonly see as decoration during winter. This hexagonal figure is actually termed a snow crystal. A snowflake is a more general term to describe many different types of precipitation that fall during the winter. It would be like calling a Holstein just a general cow or a German Shephard just a dog—the breed name gives us a more specificity than stating just the animal type.

A snow crystal is a special type of snowflake that occurs when water vapor directly freezes and does not go through a liquid phase. If the vapor turns to liquid first, it will become sleet or freezing rain.

A true snow crystal will be six-sided. Why six? That’s easy—chemistry! Snow crystals are made of water, chemically described as H2O—two hydrogen molecules bonded to one oxygen molecule. The detailed chemistry of water and exactly how the molecules bond is more than we can get into here, but this webpage explains all about water chemistry (click on Chem218 in the left sidebar and scroll down to Water to access content).

Simply put, snow crystals have six sides because that is the most efficient way for the hydrogen and oxygen molecules to be arranged. Many factors will influence the final shape of snow crystals, including humidity, the path the crystal travels to the ground, and temperature.

Scientists have been studying snow crystals for years and have found many different ways to describe and classify them. One way is to break them down into four broad categories: plates, columns, needles and dendrites. Another scientist goes into more detail and uses eight categories: column crystals, plane crystals, combination of column and plane crystals, aggregation, rimmed snow crystals, germ of ice crystals, irregular particles, and other solid precipitation. Yet another uses 35 different, distinct crystal shapes to describe snow crystals. All of these methods are correct and are used to study snow crystals by scientists around the world.

Something else we commonly hear about snow crystals is that no two are alike. This is a true statement because no two crystals follow the exact same path from the clouds to the earth’s surface. Scientists have been able to create identical-twin snowflakes in a laboratory with specially designed equipment. These artificially grown snowflakes look identical, just like identical human twins, but do vary beyond what the eye can see.

The identical-twin snowflakes are indeed real snowflakes that come about after the production of designer snowflakes, which start as a small bit of ice grown from water vapor and then are shaped by temperature and humidity to create elaborate designs. These crystals are still bound by the chemical properties of water, so there are limitations to what can be grown.

Snow crystals: something so small and so abundant this time of year. I bet you’ll never look at one the same again!

For more information about snow crystal science, visit the following webpages:

MSU Extension and the Michigan 4-H Youth Development program help to create a community excited about STEM (Science, Technology, Engineering, and Mathematics). 4-H STEM programming seeks to increase science literacy, introducing youth to the experiential learning process that helps them to build problem-solving, critical-thinking and decision-making skills. Youth who participate in 4-H STEM are better equipped with critical life skills necessary for future success.

To learn more about the positive impact of Michigan 4-H youth in STEM literacy programs and animal science programs, read our 2016 Impact Report: “Building Science Literacy and Future STEM Professionals.”

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