OBSERVING & PRESERVING SNOWFLAKES
Overview
Students capture falling snowflakes, observe with hand lenses/cell phone microscopes, draw/describe snowflake types and hexagonal symmetry, and preserve snowflakes by casting in superglue. Ideally, this activity will be done when it is snowing out. If that is not possible, observations can be based on snow on the ground, if the latest snow is relatively recent and if it has not been significantly changed by melting, rain on snow, strong winds, or other conditions that would destroy the snow crystal structure.
Background/Reference
Ken Libbrecht – Snowflake Science: A Snowflake Primer – http://www.snowcrystals.com/science/science.html
Ken Libbrecht – Types of Snowflakes chart – http://www.snowcrystals.com/guide/snowtypes4.jpg
Ken Libbrecht – The Snow Crystal Morphology diagram (explanation of the Nakaya Diagram): http://www.snowcrystals.com/morphology/morphology.html
Materials
● Black velvet snow catcher sheets
● magnifying glasses
● cell phone microscopes
● Nakaya diagram handouts – laminated
● Snow crystal types charts – laminated
● Small paintbrushes
● Superglue (thin, liquid type – not gel)
● Microscope slides and cover slips
Procedures
1. Activity set-up
At least 30 minutes prior to beginning the activity, place snow catcher sheets, paintbrushes, and slides and cover slips outside. This will allow them to cool down so that snowflakes don’t melt upon contact with them.
2. Introduction: What are snowflakes?
Definition of precipitation
What types of precipitation have you experienced or heard about?
What types of frozen precipitation – forms (snow, sleet, freezing rain, graupel, hail)
Snow is special in that it is formed from water vapor that freezes in the clouds without first passing through its liquid phase
In order for this to happen, there must be a tiny speck of dust, bacteria, or some other type of tiny particle in the cloud. Water that is in its vapor form in the clouds starts to freeze onto the particle. (The particle around which a snow crystal forms is called a condensation nucleus.) The water vapor freezes in a special, orderly pattern, called a crystal. Once a snow crystal forms, it continues to grow as it moves around in the cloud, eventually falling from the sky and landing on the ground.
Watch Ken Libbrecht falling/growing snow crystal animations. http://www.snowcrystals.com/videos/videos.html
When we see these crystals falling from the sky, we usually call them snowflakes. Snowflakes can be individual snow crystals, or they can be clumps of snow crystals stuck together.
Snow crystals can be different shapes and sizes, but they all have six sides or arms. (Sometimes when we find them they are broken, so we can’t see all of the arms.)
Look at snow crystal types chart. http://www.snowcrystals.com/guide/snowtypes4.jpg
Transition
We are going outside now to observe snowflakes. We’ll do this by catching them on velvet and looking at them through magnifying glasses and cell phone microscopes so we can see all the details.
When you are looking at the snowflakes that you catch, pay special attention to these things:
● Is it a single snow crystal or a clump of crystals stuck together?
● If it’s a crystal, what shape is it? How would you describe it/what does it remind you of? Which of the snow crystal types on the chart does it look most like?
● Can you see/count 6 sides or 6 arms, depending on the shape of the crystal?
3. Outdoor Session – catching and observing snowflakes
Pass out velvet snow-catcher cards and magnifying glasses (cell phone microscopes optional)
Place snow crystal types cards in accessible location
4. Explain procedures for making snowflake “fossils”
Refer to Ken Libbrecht activity sheet/web page: http://www.snowcrystals.com/preserve/preserve.html
5. Snow crystal stories: Messages from the sky
Snow crystals aren’t just beautiful, but they provide information about the conditions under which they formed in the clouds. Certain types of snow crystals form under different conditions.
What types of snow crystals did you observe during our observation session? Refer to snow crystal types chart: http://www.snowcrystals.com/guide/snowtypes4.jpg
Ukichiro Nakaya was a Japanese scientist who lived during the 1900s. He studied how different temperature and humidity (moisture) conditions in the clouds influence the types of snow crystals that form. He created a diagram to explain this relationship, and it is referred to by scientists today as the “Nakaya Diagram” in his honor.
Pass out copies or display on overhead the Nakaya Diagram from Ken Libbrecht: http://www.snowcrystals.com/morphology/SnowflakeMorphology2med.jpg
Provide an orientation to diagram axes (temperature and humidity) and explain what it shows. (Note temperature scale is given in both Celsius and Fahrenheit.) Read an explanation here: http://www.snowcrystals.com/morphology/morphology.html.
Ask students to find the snow crystal on the diagram that best matches the type they observed. Coach them through the process of determining what the temperature and humidity conditions were like in the cloud where and when this snow crystal formed.