Through a teacher demonstration using water, heat and food coloring, students see how convection moves the energy of the Sun from its core outwards. Students learn about the three different modes of heat transfer (convection, conduction, radiation) and how they are related to the Sun and life on our planet.
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- Colorado: Math
- Colorado: Science
- Common Core State Standards for Mathematics: Math
- 3. Draw a scaled picture graph and a scaled bar graph to represent a data set with several categories. Solve one- and two-step "how many more" and "how many less" problems using information presented in scaled bar graphs. For example, draw a bar graph in which each square in the bar graph might represent 5 pets. (Grade 3)  ...show
- International Technology and Engineering Educators Association: Technology
- Next Generation Science Standards: Science
- Make observations to provide evidence that energy can be transferred from place to place by sound, light, heat, and electric currents. (Grade 4)  ...show
- Define the three different modes of heat transfer.
- Explain how heat gets from the Sun to Earth.
- Give one example of why engineers need to understand heat transfer.
To share with the entire class (teacher demonstration):
- clear baking dish (ideal: 8x8 inch [20x20 cm] PyrexTM baking dish)
- 6 or more dictionaries or thick text books
- portable heat source, such as a small burner, can of SternoTM, propane or small warming candle in a fireproof holder
- fireproof surface
- food coloring (orange works well)
- digital thermometer
- Heat Transfer Worksheet, one per person
|conduction:||The transfer of heat from a region of higher temperature to a region of lower temperature by increased kinetic energy moving from molecule to molecule.|
|convection:||Transfer of heat in a fluid (liquid or gas) when higher-temperature fluid expands and moves, creating heat transfer.|
|density:||The compactness of matter described by a ratio of mass (or weight) per unit volume.|
|radiation:||The transfer of heat from a region of higher temperature to a region of lower temperature by greater emission of radiant energy from the region of higher temperature.|
Before the Activity
- Gather materials for the teacher demonstration.
- Make copies of the Heat Transfer Worksheet.
With the Students
- Explain to students the three different modes of heat transfer (radiation, conduction and convection). Refer to examples in Table 1.
- Have students write their heat transfer definitions on the worksheet, with an example of each that they have experienced or seen in their own lives.
- Tell students that they will be recording observations and data on their worksheets to use in making a bar graph at the end of the demonstration.
- Make sure all students can see the demonstration and that, for safety, no student is too close to the flame.
- Place the baking dish on two piles of dictionaries that are high enough and far enough apart to place a fireproof plate and sternoTM can (or warming candle) under the baking dish (see Figure 1).
- Pour cool water into the baking dish.
- Make sure the table is very still so that the water does not move. Take the temperature of the water in Celsius or Fahrenheit. Have students record the temperature. Repeat the temperature several times so all students have time to record the temperature on their worksheets (a volunteer may want to keep track on the board).
- Carefully light the heat source. Drop a few drops of food coloring and some glitter into the water. It works best to drop the glitter and food coloring into the water directly above the heat source.
- Take the temperature of the water in Celsius or Fahrenheit at two-minute intervals. Be sure to take the temperature in roughly the same location in the dish every time. What is happening to the glitter as the water gets hotter? Have students record the temperatures.
- The heat source should slowly heat the water in the middle of the baking dish. The food coloring helps students observe the movement of the water.
- The glitter flows from the high heat in the center to the outsides where it is cooler. Convection transfers heat (energy) by currents of gas or liquid. (It may help to have students get up and walk past the demonstration so that they can get a closer look.)
- Have students record their observations on the worksheet.
- Explain to students that their evaluation will be graded on how thoroughly and accurately they record the demonstration.
- Have students make a bar graph of the temperature. What do they notice about the temperature? (The water temperature should show an increase.)
- Conclude by reviewing the learning objectives. Clarify any questions and conduct the post-activity assessment in the Assessment section. Review the ways that heat moves.
- Conduction = by direct contact of two materials
- Convection = by the interaction of fluid molecules (such as air or water)
- Radiation = by the movement of heat waves.
- Have the students stand back a safe distance from the heating element.
Activity Embedded Assessment
- When you heat a container of water, does the water move or stay still?
- Name one of the three types of heat transfer methods. (Answer: Conduction, convection, radiation.)
- Heat moves from the Sun to the Earth through conduction. (Answer: False, conduction only occurs when there is matter in which to travel.)
- Heat cannot move. (Answer: False, it moves all the time.)
- A liquid or gas that is moving because of heat is called convection. (Answer: True)
- Why do engineers need to understand the methods of heat transfer? (Possible answers: Engineers must understand heat transfer so they can design products and devices that work well and are safe. Think of things in your house or school that get hot or get cold, or keep something from getting hot or cold. For example, stoves, ovens, refrigerators, heaters, air conditioners, cookware, cooking utensils, curling irons, fans, light bulbs, music players, engines, insulation, pools, water heaters, sunscreen, airplanes, satellites, spacecraft, etc.)
- For younger students, create the bar graph as a class activity on the classroom board.
- For older students, have them convert their data to a different temperature scale, or use two thermometers to record data from both scales.
Kagen, Spencer. Cooperative Learning. San Juan Capistrano, CA: Kagan Cooperative Learning, 1994. (Source for Numbered Heads assessment)
Wilson, Jim (editor). NASA. Last updated January 12, 2007. National Aeronautics and Space Administration. Accessed January 15, 2007. http://www.nasa.gov/
Jessica Todd, Geoffrey Hill, Jessica Butterfield, Denise W. Carlson
© 2006 by Regents of the University of Colorado.
Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder
Last modified: September 4, 2015