What's the Matter with My Snow? Background Information

Note: Prior to the first snowfall, ask students to bring in empty 12-ounce orange juice concentrate containers. Six to eight will be needed each time the class conducts this investigation.

Related Topics: matter, density, measurement, fractions, decimals, water, water cycle, phase change

Ohio Academic Standards Alignment: Click here to view content standards alignment to Science for Ohio by grade level.

Classroom Time Required: 45 minutes (lesson), 45 minutes (extension and/or assessment)

Background Information:

• What is snow? Snow crystals are the result of water vapor depositing on a speck of ice or some minute particulate, often a piece of mineral dust. Snow is not frozen raindrops. The deposition of water vapor into the solid form results in a crystal, the characteristics of which depend very much on the temperature and water vapor content within the cloud. Their shapes can be in the form of plates, needles, feathery dendrites, or capped columns. It is possible to predict the general characteristics of ice crystals formed in clouds if you have enough information about the temperature and moisture conditions. Snowflakes are actually aggregates of many individual ice crystals. (Source: The Handy Weather Answer Book) For more information on snow, check out the National Snow and Ice Data Center's Snow Information Page which includes information, photos of crystals, and links to many sites.
• What is density? The mathematical formula for density is Density = grams / milliliters. The density scale is based on the density of water. One gram (g) of water has a volume of one milliliter (ml), so the density of water is 1 g/ml. Matter having a greater density than water (i.e., rocks, liquid soap, etc.) will have a higher weight number than volume number which will result in a density of greater than 1 g/ml. Matter having a lesser density than water (i.e., snow, oil, air, etc.) will have a lower weight number than volume number which will result in a density of less than 1 g/ml.
• Is snow melting a physical change or a chemical change? The melting of snow is a physical change because the water in the form of snow has changed form through melting rather than through a chemical reaction. Under the right conditions, the melted water can be returned to snow again. On the other hand, a chemical change such as the burning of wood involves a chemical reaction (the release of energy and carbon) which makes it difficult to return the matter left after burning into wood again.
• What is phase change? Phase change refers to the changing of some form of matter (in this case, snow) from one state to another. Snow phase changes from solid to liquid when it melts (the reverse when it freezes). Water phase changes from liquid to gas when it boils (the reverse when it condenses).
• How are the water cycle and snow connected? The water cycle has four main processes: precipitation, collection, evaporation, and condensation. Snow is a form of precipitation which collects on the ground. Once melted, the water from this snow continues in the water cycle by evaporating into the air, condensing into clouds, percolating in the soil, traveling to waterways via a watershed, etc. For more information on the water cycle, see Related Resources.
• Cautions. Set clear expectations for behavior before taking students out to sample snow. This will prevent most management issues for this fun activity.
• Misconception(s).  Misconception: Snow is frozen rain. Fact: Sleet (or ice pellets) is frozen rain.
• Expected Results.   Students should discover:
  • Snow has a density between 0.1 and 0.9 g/ml.
  • Snow phase changes from solid to liquid as it melts.
  • Snow melting is a physical (not chemical) change.
  • Snow is a part of the water cycle.