Rising Hot and Sinking Cold
A tactile experience that teaches opposites.
Objectives:
Predicting reasonable outcomes from the application of known facts. Measurement of temperature.
Prior Experience:
Ice is cold, a light bulb is hot.
NOTE: Students may see talc fall with their own hands only when the electrical wall plug area is successfully and completely barricaded.
Materials:
1) Two identical and dependable thermometers (any size).
2) A lamp with an incandescent light bulb. Turn it on at least a half hour before beginning the lesson because it needs to be at full temperature to work well.
3) A plastic bucket of a few pounds of ice (light plastic lidded container or a Tupperware container with a lid) .
4) Talcum powder.
Focus:
Quickly tell the students that they can make predictions if they use what they do know to guess about what they don't.
Procedure and monitoring (prediction setup):
1 Sprinkle some talcum powder in the palm of each student.
2 Ask them to hold up their hand and describe what they see when they rub your fingers and the powder falls to the table. Does the powder fall straight down?
3 Now gather the class as close as you can around the lamp. Darken the room. Use a sheet of paper to block the glare from the bulb.
4 Rub a tiny bit of talcum powder about six inches above the bulb. The powder moves around but it doesn't fall because of the current of hot air coming up. My kids described a big difference right away between seeing the talc fall straight at their desk and what occurred over the bulb. Tell them that the difference is from the hot air rising from the light bulb. You may catch a glimpse of some particles being carried upward.
5. Turn the ceiling lights back on and show the two thermometers. Ask several students to verify to the rest of the class that both read almost exactly the same temperature.
6 Now present the lidded bucket ( light plastic or Tupperware container with lid) of ice.
7 Put the bucket on top of one of the thermometers. Put the second thermometer on top of the bucket.
8 While the thermometers are adjusting the students should write short predictions into their journals:
The thermometer under the bucket will read _______ than the thermometer on top.
Choose: hotter colder
9 Present a premise and some questions: Cold air is the opposite of hot air. If hot air goes up, where does cold air go? What do you think is going to happen to the two thermometers? Students may revise their predictions until the truth is revealed.
10 Have several students come forward to verify and confirm that the thermometer under the bucket is colder than 40 degrees but the one on top has barely changed at all.
Close:
In my class they cannot revise a prediction after the proof has been revealed. However, my students always really enjoy adding a written description of the result regardless of whether or not their prediction was correct. I allow them to touch the ice and powder after the lesson in centers time if they wish.
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To find a lesson about weather and the water cycle. For another lesson plan about contrasting hot and cold liquids link to dissolve.
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