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McREL Standards Activity

What Causes the Wind?

Purpose:As a result of this activity, students will understand how the Sun causes winds.
Related Standard & Benchmarks:
 Standard 1.Understands atmospheric processes and the water cycle
   Level III [Grade 6-8]
   Benchmark 3. Knows that the Sun is the principle energy source for phenomena on the Earth’s surface (e.g., winds, ocean currents, the water cycle, plant growth)
 Standard 12.Understands the nature of scientific inquiry
   Level III [Grade 6-8]
   Benchmark 1. Knows that there is no fixed procedure called "the scientific method," but that investigations involve systematic observations, carefully collected, relevant evidence, logical reasoning, and some imagination in developing hypotheses and explanations
Student Product:Written predictions, description of experimental results, and conclusions
Material & Resources:
  • Table lamp with incandescent bulb (no lamp shade)
  • Talcum powder, or similar
  • Construction paper
  • Scissors
  • String
  • Bead (optional)
Teacher's Note:
  • You may wish to draw a spiral on a piece of paper and provide each student with a photocopy of it to cut out, although the spirals do not have to be "perfect" to work.
  • Please note that this activity only models one phenomenon powered by the Sun (i.e., winds); other phenomena are touched upon in the discussion but should be extended with other activities.
Explain to students what they will be doing in this activity and that it is designed to demonstrate the cause of winds.  Review what they’ve learned about winds, including that warm air rises.  Guide the students in using this knowledge to develop predictions for the behavior of the powder and the spiral when they are held over the hot lamp.  You could have them develop predictions independently, or you may want to do it as a class.  Students should write their predictions on a blank sheet of paper (which will be turned in at the end of the activity).

  1. Turn on the lamp and let it heat up.  While you wait, cut out a moderately wide spiral from a piece of construction paper (i.e., in the form of a snail shell).  Carefully poke a small hole through the inner end and thread a piece of string through it.  Tie the string around the paper (loosely, so as not to rip the spiral), or tie it off on a bead, so that the spiral can be held up by the string.  

  2. When the lamp is hot, sprinkle a little talcum powder just above the bulb.  On your sheet of paper, describe what happened to the powder; compare its behavior to your prediction.  Did it do what you expected it to?  If not, why do you think it behaved the way it did?  If necessary, modify your prediction for the spiral.

  3. Lift the spiral up by the string and hold it just above the warm bulb; observe for several seconds.  On your sheet of paper, describe what happened to the spiral; compare its behavior to your prediction.

  4. Students should write a short paragraph discussing their results; they should address their predictions and provide scientific explanations for their results.  Then they should write a second paragraph relating this to winds.

Follow with a discussion that addresses any discrepancies between predictions and results; have students share ideas regarding the behavior of the powder and the spiral and how that relates to the cause of winds.  Compare this to ocean currents, and touch on other phenomena that are also powered by the Sun (e.g., the water cycle, plant growth).

Student written products and class discussion should evidence a basic understanding of the following:
The heat from the light bulb warms the air around it.  As this warmed air rises, it takes the talcum powder with it.  The spiral spins for the same reason:  the bulb heats the air around it, so the air rises through the spiral causing it to spin.  In nature, the sun heats the ground, which warms the air just above the ground.  This hot air rises because it expands and becomes less dense as it warms up; when it rises, cold air moves in to take its place.  This movement of air is wind.