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Snow Science
Snow Melting
Testing how well different things melt snow
Learning Goals:
At the completion of this unit, students should be able to demonstrate their understanding of data collection, measurement and analysis by:
- Participating in the data collection activity
- Completing the Data Measurement handout
- Explaining their conclusions from the Data Analysis handout (grades 2-4)
- Writing their conclusions in a short research paper (grades 5-6)
Background:
Snow is a wonderfully beautiful thing, but it can also be a dangerous thing. Snow on the roads creates a dangerous travel situation that has caused many, many traffic accidents, including many deaths. Snow on a runway of an airport or on the wings of a plane can be a serious threat to airplane safety. Maybe the most common danger comes from snow on our sidewalks and other walkways. It is difficult to walk, drive or fly in snow because it makes everything slippery.
If we want to continue to travel on our roads and use our walkways in winter as easily as we do in summer, there are only two choices: remove the snow or melt it . Both methods are used extensively all over the world. While removing snow might be a good PE activity, this unit focuses on the chemical methods used for melting snow.
In this unit, students will play the role of scientists to discover which chemicals are best at melting snow. The activities provide students an opportunity to include the snow in their study of scientific methods. They can also learn about chemistry and snow. The teacher may want to preview the quiz as a guide to the lectures.
Freezing:
Water is made up of many molecules. A single water molecule contains one oxygen atom and two hydrogen atoms. All these molecules are moving around in water. When the water gets cold, the movement slows down and the molecules eventually come to rest in a hexagon-shaped grid with many identical layers (a crystal). At each intersection of the hexagon grid, there is a water molecule. The empty space in the middle of a hexagon explains why ice takes up more volume than water. This is also why ice floats, because it is less dense than water. When a liquid, the water molecules are actually closer together, bumping into each other and moving around. The hexagon formation also explains why snow flakes tend to have a six-sided shape. Snow flakes are formed high in the clouds as single crystals and often clump together as they fall to earth.
Chemical Melting
Imagine that all the water molecules in snow are members of a marching band. Each musician stands in a straight line, equally spaced from the others. Now imagine the day is very hot and a large ice cream truck leaves the road and drives into the center of the marching field. Soon, the musicians leave their assigned positions and surround the ice cream truck. This is similar to what happens when a water-soluable substance, such as salt, is placed on snow or ice. The large salt atoms, potassium and chloride, split off from each other (dissolve) when they come in contact with the water molecules and the water molecules leave their grids to surround these larger, charged atoms. When the molecules leave the grid, this is melting.
Learning Activities
Introductory Discussion:
Ask the students what is the purpose of science? Discuss how scientific study is a process for solving problems. (Write hypothesis, design a test, do an experiment, record data, write conclusion.) Next, ask the students what problems are caused by snow and how scientists have tried to solve these problems. Discuss the use of chemicals to melt snow. With your students, preview the activity and experiment that follows.
Preparation Activity:
Over a few days, you can build anticipation for the experiment by gathering chemicals and other potential snow-melting substances in a specific spot in your classroom. All substances should be the same temperature at the time of the experiment. Note that some chemicals are harmful to vegetation. Some of the substances you might want to gather include:
- Rock Salt (Halite, a common snow melter)
- Potassium Chloride or potash (KCl, another common snow melter)
- Calcium magnesium acetate (CMA, one of the best snow melters)
- Ammonium sulphate (A Fertilizer)
- Alcohol or Ethylene glycol (a liquid deicer)
- Soda pop, fruit juice, peanut butter, salt, pepper, sugar, etc.
- Whatever The Kids Want
Field Trip:
Using snowshoes, take the class into the deep snow. Choose a location that will not be damaged the substances you have collected for snow melting. The snow should be at least 2 ft. deep. Mark each test spot. Place the potential snow melter on the snow. Cover a 12 inch circle as completely as possible, but do not pile more than a half inch of the snow melter on top of the snow. Mark the time that each substance was placed on the snow. After about 15 minutes, use a yardstick to measure the depth of the snow melt for each substance. You may want to allow more or less time depending on conditions. Try to make every test identical except for the melter being tested (Data based on a single variable is easiest to record and use).
Using Handouts:
Where possible, ask the children to fill out the Data Measurement Handout during the experiment. Some conditions might require them to take notes on a small pad and transfer the notes to the handout later, inside the school.
Reporting Conclusions:
The Data Analysis Handout has been provided to help guide the children through the reporting phase. Depending on the grade level of your children, you may wish to have them write the report themselves.
Learning Assessment:
A Snow Melting Quiz has been provided as a possible learning assessment method. Use the quiz as best fits your student's needs.
Handouts:
Variation:
Another measurement you could test would be temperature above and below the snow. Seal two thermometers inside a quart jar at room temperature. Bury one jar under at least 3 ft. of snow. Leave the other jar in the surface of the snow. Allow the two jars to stay in the cold for a half hour. Take readings on both and compare the difference. Wait times may vary depending on conditions. Discuss how it is warmer under the snow because there is no movement of the air to move heat away from the jar that is buried.
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