Thermal Mass Lab Teacher Sheet

Thermal Mass Lab Teacher Sheet By Fred Bauder [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0), via Wikimedia Commons


In this investigation, students will determine the best material to be used as a thermal mass in a passive solar home design. 


  • 12 small boxes. Empty tissue boxes work well. Small shoe boxes could work.
  • Several small plastic bottles and clear plastic containers with lids that fit inside the boxes
  • Plastic wrap
  • 12 thermometers
  • 12 heat lamps
  • 2 samples of butter or margarine in plastic containers: 250 grams in each
  • 2 rocks: 250 grams each
  • 2 samples of water in plastic containers: 250 grams in each
  • 2 pieces of wood: 250 grams each
  • 2 pieces of plastic: 250 grams each
  • Black and white construction paper
  • Stop watch or clock
  • Tape

Set up
Organize the class into groups of two or three. You can have as few as six or as many as 12 groups.

There are 12 thermal masses to be tested. Each (with the exception of air) should have the same mass (between 250 and 500 grams depending on the size of your boxes). The actual masses are not important so long as you control for the mass by having each of your samples the same. You will need each of the following:

  1. Air (empty box as a control)
  2. Water (in bottle)
  3. A dark-colored rock
  4. A light-colored rock
  5. Oil that melts at a low temperature like butter or margarine or lard (in plastic container)
  6. Wood painted black
  7. Wood painted white
  8. Black plastic
  9. White plastic
  10. Brick
  11. Dark tile
  12. Light tile

Feel free to add additional materials to make that list longer. 

The idea behind using the oil is that latent heat will be absorbed and released during melting and freezing. The material is not as important as the idea that heat can be stored and released during the phase change. Stress to the students that obviously no one would build their home with a huge butter tub in the living room to absorb heat, but there are materials that melt at the correct temperature range that can be used in home design. They are not used in this lab due to availability and cost.

Have each group test one of the materials and record the data in a class data table. There is a sample class data table file called Thermal Mass Lab Class Data Spreadsheet included in the resources for this lesson that will allow students to input data and have the graphs automatically generated. Either display the graph using a projector or print a copy for each group to aid in answering questions.

When you have students put the boxes in the light source, there are several things to consider. If it is a bright, hot day, you can do this using the natural sunlight. If not, having several heat lamps will be necessary. High wattage bulbs will generate the most heat. Having the lamps close to the boxes will also generate more heat. You may have to put more than one box under one heat lamp, which can lead to groups having to work in close proximity. Just be aware of possible off-task behavior that can result. You also want to have the students keep the boxes under the heat lamps when taking temperature readings. They should be able to read the thermometer through the plastic on the front of the box.

This teacher sheet is a part of the Mitigating Climate Change through Passive Solar Design lesson.

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