Target Concepts: Snow has many unique characteristics. There are six major types of snowflakes and these change when they undergo different processes of metamorphism. The density and temperature of snow varies depending on the depth and conditions. Snow is a good insulator.
Teacher Background: Students will observe, collect, and cast snowflakes. They will identify specific attributes found in the six major types of snow crystals. They will record and analyze temperature, water content, density, depth of layers and profiles of snow by digging snow pits in four specific habitats at Creamer's Refuge (muskeg, forest, meadow, and pond).
HOW SNOWFLAKES ARE FORMED: Snowflakes begin as water vapor which freezes around tiny, solid particles in the air, such as dust or salt, forming a crystal. As a snow crystal falls, it encounters a variety of air temperatures, air currents, and humidity levels. The determining factors that affect what kind of flakes are formed are: temperature, amount of water vapor in the air, time it takes a flake to fall, and wind. Slight changes in any one of these factors can dramatically alter snowflake patterns. Water molecules are attracted to each other and grow naturally in six directions.
There are two major categories of snow: snow that falls from the sky (precipitated snow) and snow that is changed by a variety of forces and conditions (metamorphosed snow). All snow crystals start as precipitation, but many snowflakes go through a process of metamorphism as they fall or after they reach the ground. For detailed explanations, of these processes, see Field Guide to Snow Crystals by E.R. LaChapelle, Pages 3-23.
SNOW CRYSTAL CLASSIFICATION: Snowflakes, as we commonly refer to them, are actually snow crystals. Crystals are ice particles with a molecular arrangement of repeated symmetrical and three-dimensional patterns. The Snowflake Classification Sheet included in this unit shows the seven main categories of snow crystals: columns, capped columns, needles, spatial dendrites, stellar crystals, hexagonal plates, and irregular crystals.
There are two other types of crystals that, technically speaking, are not snow at all. They are rime and hoarfrost.
METAMORPHISM: Metamorphism means a change in structure. After snow falls, the sun, wind, changes in temperature, and pressure from new snow causes snow to change. Every snowflake changes as it ages. For a detailed explanation of metamorphism, see Field Guide to Snow Crystals. pages 15-22.
Vocabulary:
Materials: (included in the kit)
(not included in kit)
Procedure:
Gear Up: Bring a dishpan of snow into the classroom. Gather everyone around it, and ask them what they know about snow. Record observations on a piece of butcher paper. (Refer to these comments later in the unit to compare what students have learned.) Ask questions like:
What is snow?
How is it formed?
Are there different kinds of snow?
Do you know any names for different kinds of snow?
Does snow change throughout the winter?
Could snow help you stay warm?
Read Chapter One-"The Language of Snow" from the book The Secret Language of Snow (in the kit). Discuss the chapter, and refer to the chart of Inuit Snow Words. Why do the Inuits use so many diffent words for snow? What do you think of Dr. Pruitt's idea of a universal snow language?
Explore: This activity can be done any time snow is falling. It would be ideal if students could collect and observe snow crystals in a variety of conditions. After this lesson is introduced and experienced once, students will be familiar with the procedures and can be ready to collect or just observe snowflakes at any time during the winter. Taking the felt boards and hand lenses out for 10 minutes during a snowfall can be a great learning experience. Jotting down the temperature, conditions, and types of snow crystals observed would be a great data collection project that wouldn't take too much time.
"PERMANENT SNOWFLAKES". To be prepared for this activity, you need to keep felt boards, nail polish, bamboo skewers, microscope slides, and Krylon in the freezer.
Ask students if they think it is true no two snowflakes are alike. This may be true, but by scamining snowflakes, we can put them into groups. Display the overhead transparency of snowflake classifications. Students should follow along on their handouts. Read the descriptions of snowflakes, discuss various attributes (special features) such as branches, cylinders, and plates of each type and the weather conditions in which each crystal is formed.
Divide students into small cooperative groups. Give each group an envelope of snowflakes to classify into the major groups. (After students classified these snowflakes, read Chapter 3, "Annui-Falling Snow" in The Secret Language of Snow.
On a day when it is snowing, go outside to collect and preserve snowflakes. Each student should have a felt board and hand lens. Take the microscope slides, bamboo skewers, and Krylon outside with you. Students should catch snoflakes on their felt boards and examine them with hand lenses. Follow the directions in "Permanent Snowflakes" to cast and preserve snowflakes.
Generalize: Have students complete the data sheets. Discuss what they discovered. Ask what types of snowflakes were found. What were the weather conditions: temperature, cloud cover, humidity, etc.
Apply: Are your discoveries and observations beneficial to humans, plants, or animals? Why or why not?
Evaluation: Data sheets and participation.
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