Atmospheric Processes — Radiation

As you've discussed in class, practically all of the energy that reaches the earth comes from the sun. A small part is directly absorbed by the atmosphere, and some is reflected back to space by clouds, but most of the radiation is absorbed by the earth's surface. The energy that is absorbed is extremely important in determining the global and local climate. In this activity, you will investigate how different surfaces absorb heat and apply that experience to interpret real-world situations.

Materials (per group)

• Three pie pans
  
  
• Dark potting soil
  
  
• Light-colored sand or perlite
  
  
• Water
  
  
• Three thermometers
  
  
• Reflector lamp with a 200-watt bulb
  
  
• Graph paper
  
  
• Watch with a second hand
  
  

Procedure

1. Form groups according to your teacher's instructions.
   
   
2. Create tables to help you carefully record time and temperature data in this investigation. You may copy the examples below, or make your own. It is important that they be well organized and easy to use and understand.
   
   

   Heating Cycle
   Surface material	Start time	Start temp.	Temperature each minute
   			1	2	3	4	5	6	7	8	9	10

   
   

   Cooling Cycle
   Surface material	Start time	Start temp.	Temperature each minute
   			1	2	3	4	5	6	7	8	9	10

   
   
   
3. Gather the materials listed above. Fill the pie pans to the same level, one with dark soil, one with light sand, and one with water.
   
   
4. Place the pie pans on a table or desk and position the lamp about 12 inches above them. DO NOT TURN THE LAMP ON, YET.
   
   
5. Place a thermometer into each pie pan, securing it so it measures the temperature just under the surface of the substance in the pan.
   
   
   
   
6. Record the starting temperatures for each pan on the data table.
   
   
7. Turn on the lamp and record the temperature of each substance every minute for ten minutes.
   
   
8. At the end of ten minutes, turn the lamp off.
   
   
9. Continue to record temperatures for each pan every minute for ten minutes.

Note: If available, you may wish to do this experiment using other materials in the pans. Examples would be: different colored soils, dry and wet soils, grass, green or dry leaves, or different types of coverings such as plastic or aluminum foil.

Observations and Questions

Answer these questions in your notebooks or on a separate sheet of paper.

1. Using the data tables, graph the heating and cooling cycles to compare the rates at which the various substances heated and cooled.
   
   
2. Which material absorbed more heat in the first ten minutes?
   
   
3. Which material lost the most heat in the last ten minutes?
   
   
4. Imagine that it's summer and that the sun is shining on the ocean and on a stretch of land. Which will heat up more during the day? Which will cool more slowly at night? Explain.
   
   
5. Imagine three cities in the desert, all at about the same altitude and latitude.
   
   
• One city (A) is surrounded by a dark-colored rocky surface.
  
  
• Another city (B) is surrounded by a light-colored sandy surface.
  
  
• The third city (C) is built on the edge of a large man-made desert lake.
  
  
Which city would likely have the highest average summer air temperature and why?


6. The earth's surface tends to lose heat in winter. Which of the above cities would have the warmest average winter temperature? Why?
   
   
7. Since the sun is approximately 93 million miles from the earth and space has no temperature, how do we get heat from the sun?
   

When you're finished with the activity, click on Back to Teacher Guide at the top of the page.