TOPICS: Crystal structure and metamorphosis, phase changes, vapor pressure
LEVEL: High school
TIME: One or two class periods
ADVANCE PREPARATION: To save time, you may wish to construct one or more "old snow mounds" for the class (steps A-C) 24 hrs in advance. If so, delete step F before duplicating lab for student use. Students would begin with step D in this case; have several students measure the temperature profile of the old snow mound in steps H-J
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MATERIALS:
Students may observe snow crystals on dark sleeve of classmate or on optional pieces of black cloth (step J)
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PREDICTION:
In class discussion, encourage creative, logical, and critical thinking. We recommend that you introduce the following ideas if they are not suggested by students: Snow crystals in the old snow mound will fuse together, becoming much harder than the fresh mound; the brick should sink deeper in the fresh mound. See answer to question 7 and Snow Teacher Background
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STEP C:
The top of the mound should be leveled slightly so that brick dropped in step G hits squarely
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STEP J:
After data are collected, you may wish to demonstrate the relative hardness of the old and new snow mounds by having a student sit on remains of each.
Questions 5-7 require higher order thinking skills. We recommend that you discuss these questions in class before having students write out their answers
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2-4.
Answers will vary
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5.
Snowpack (and old snow mound) should show greatest temperature variation from snow near warm ground to snow near cold air
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6.
Fresh snow mound should show little temperature variation from top to bottom if snow was well mixed
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7.
When a quinzhee is constructed, warmer snow near the soil is thoroughly mixed with cooler snow near the surface of the snowpack. Water vapor from warmer snow crystals moves to cooler crystals nearby, fusing or sintering the crystals together. The fresh mound of snow becomes hard enough to make a sturdy snow shelter. See Snow Teacher Background.