Students develop their understanding of air convection currents and temperature inversions by constructing and observing simple models.
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- Colorado: Science
- a. Develop and communicate an evidence-based scientific explanation for changes in weather conditions (Grade 5)  ...show
- d. Use data collection tools and measuring devices to gather, organize, and analyze data such as temperature, air pressure, wind, and humidity in relation to daily weather conditions (Grade 5)  ...show
- International Technology and Engineering Educators Association: Technology
- C. The use of technology affects the environment in good and bad ways. (Grades 3 - 5)  ...show
- Next Generation Science Standards: Science
- Develop a model using an example to describe ways the geosphere, biosphere, hydrosphere, and/or atmosphere interact. (Grade 5)  ...show
- Understand and explain convection currents.
- Build simple models to investigate convection currents and temperature inversions.
- Understand how engineers study temperature inversions and convection currents to know why pollution levels may be higher in some areas than in others
Demo 1: Warm Air is Less Dense than Cool Air
- 1 empty, two-liter plastic bottle
- 1 balloon
- 1 large bowl
- Hot water
Student Activity: Spinning Snakes
- Spinning Snake Worksheet, 1 per student
- Scissors, 1 per student
- Colored pencils, crayons, markers, etc.
Demo 2: Convection Current Model
- 2 aquariums (or very large glass jars/beakers)
- 2 small plastic bags with strong seals\
- Dark-colored food coloring
- Bowl (to mix water, ice and food coloring)
- 1 long straight pin
- 1 long-handled spoon or ladle
- Ice cubes
- Hot plate/microwave/stove (optional; required only if tap water is not hot enough)
- Pan or cooking container (optional; to heat water on hot plate/microwave/stove)
Why do Engineers Care?
|Convection current:||The movement of air due to temperature differences.|
|Temperature inversion:||When an upper thick layer of warm air traps a lower layer of cold air close to the Earth, causing the temperature to be warmer at higher elevations.|
Before the Activity
- Gather materials and make copies of the Spinning Snake Worksheet.
With the Students
- Fit the mouth of the balloon over the mouth of the empty, two-liter bottle (see Figure 3).
- Stand the bottle in the center of the bowl. Fill the bowl with hot water, around the outside of the two-liter bottle (see Figure 3).
- After a few minutes, notice the balloon start to inflate.
- Carefully pour the water out of the bowl and fill the bowl with ice (see Figure 3). What happens?
- Ask students why the balloon inflated and deflated in response to the hot and cold water. Explanation: When air is warmed, it expands and needs more space, so it stretches out the balloon. When air is cooled, it contracts and needs less space, so the balloon deflates. In this closed system, the mass of air in the bottle remains constant, so this shows that the warm air requires more space (and thus is less dense, based on the fact that density = mass/volume) than the cool air. Warm air rises because it is less dense than cold air.
- Distribute a Spinning Snake Worksheet to each student.
- Have the students color their snakes.
- Ask the students to cut the snake along the spiral lines.
- Attach a thread to the head of the snake.
- Hang the snake near the radiator or other heat source (or, at different places around the room, for comparison purposes).
- Observe the snakes carefully.
- Which direction does it turn? Can you explain why it turns different directions in different places?
- To create a model of typical atmospheric conditions (normal convection currents), heat a pan of water on a hot plate and add a few drops of food coloring to the water. Fill one of the aquariums about 3/4 full of cold water and add several ice cubes to it.
- Fill one of the plastic bags half full with warm water heated on the hot plate. Seal the plastic bag so there is no air in the bag.
- Remove the ice cubes from the aquarium. Lower the bag with the warm, colored water (representing air pollution) into the cold, colorless water of the aquarium.
- Without disturbing the water in the aquarium, poke a hole in the bag with the pin and observe the interaction of the warm water with the cold water. What happens when the warm water enters the cold water?
- To simulate a temperature inversion, add several ice cubes and several drops of food coloring to a bowl of water.
- In another container, heat several quarts of water with which to fill the second aquarium about 3/4 full.
- Fill the second plastic bag about half full with the cold, colored water, and seal it so there is no air in the bag.
- Lower the bag with the cold, colored water (representing air pollution) into the warm, colorless water of the aquarium.
- Without disturbing the water in the aquarium, poke a hole in the bag with the pin and observe the interaction of the cold water with the warm water. What happens when the cold water enters the warm water?
- Students should be mindful when handling scissors and glass containers.
- Students should be careful not to slip on wet floors and make sure to clean up any spills as soon as they happen.
- What is a temperature inversion?
Activity Embedded Assessment
- These demos and student activity are also appropriate for lower grades.
Amy Kolenbrander, Daria Kotys-Schwartz, Janet Yowell, Natalie Mach, Malinda Schaefer Zarske, Denise Carlson
© 2004 by Regents of the University of Colorado.
Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder
Last modified: March 27, 2015