Keeping Up the Heat: Insulators

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Author: Janice VanCleave

The process of heating and cooling a building is expensive and requires a great deal of energy. The expense plus the need to save energy have focused the attention of scientists on studying how to restrict heat flow by using insulating materials.

In this project, you will compare the insulating ability of different materials. The conductivity of materials and the reflective nature of solar energy will be determined. You will also look at the methods of energy transfer.

Getting Started

Purpose: To determine whether sand has insulating properties.


  • cardboard box at least 2 inches (5 cm) taller and wider than one of the jars
  • sand
  • 2 l-quart (1-liter) jars with lids
  • l-cup (250 ml) measuring cup
  • water
  • 2 thermometers


  1. Cover the bottom of the box with 1 inch (2.5 cm) of sand.
  2. Set one jar in the box.
  3. Fill the box with sand up to the top of the jar.
  4. Use the measuring cup to add 2 cups (500 ml) of hot water to each jar.
  5. Stand one thermometer in each jar of hot tap water for one minute (see Figure 30.1).
  6. Read and record the temperature of the water in each jar.
  7. Remove the thermometer and seal the jars with their lids.
  8. Quickly cover the jar in the box with a I-inch (2.5-cm) layer of sand.
  9. Insulators Resistors to Heat Flow

  10. Close the lid on the box.
  11. Allow the jars to remain undisturbed for ten minutes.
  12. Uncover the jars and stand one thermometer in each jar.
  13. Allow the thermometers to stand for one minute.
  14. Read and record the temperature of the water in each jar.


The water in the jar that is placed in the box surrounded by sand stays warmer longer than the water in the uncovered jar does.


Heat energy moves from a warm area to a cooler area. The water inside the jars is warmer than the sand and the air outside the jars. As heat flows from the warm water to the materials outside the jars, water in the jars cools. The water in the jar that is placed in the box surrounded by sand stays warmer longer because the heat is slowly conducted out of the water into the sand. The heat leaves the water in the uncovered jar more quickly as it flows to the cooler air outside.

The rate of heat flow from a material depends on what surrounds it An insulator is something that restricts or retards heat flow. A good insulator, such as the sand, slows the energy flow. Thus, the water surrounded by sand is kept warmer for a longer period of time.

Try New Approaches

  1. Compare the insulating properties of other materials. Repeat the experiment replacing the sand with other materials such as cotton balls, feathers, polystyrene beads, and crumpled balls of paper. Loosely pack the materials in the box. Science Fair Hint: Display samples of the testing materials in order from the one with the greatest to the one with the least insulating property.
  2. A vacuum is the best insulation, but next best is motionless air. Do the insulating properties of the previously used materials depend on the amount of trapped pockets of dead air they have? Repeat the previous experiment tightly packing each material in the box to squeeze out as much air as possible.
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