Prior Knowledge:
*Explain why you can toast marshmallows over a fire even if the flames do not touch the marshmallow. (Heat from the fire is radiated through the air to the marshmallow causing the temperature to rise)
*How is the
radiation from the sun related to heating of the earth? (The sun's
heat energy reaches the earth by infrared radiation)
Definition of Radiation:
Transfer of thermal energy that does not require matter, transfer of thermal energy of electromagnetic waves; energy released from atoms and molecules as they undergo internal nuclear change. Heat is transferred from the sun to earth by means of radiation. The heat energy travels in the form of invisible light called infrared radiation.
Activity
Materials: 2 containers; water; sand; light source (one for each container); 2 Celsius thermometers
1. Allow the water and sand to stand out overnight so they are the same temperature as the air.
2. Fill one container with 1" of water
3. Fill one container with 1" of sand
4. Place a thermometer in each of the containers.
5. Place each container directly under a light source.
6. Read and record the temperature on a graph or table once each minute for ten minutes
7. Turn off the lights
8. Read and record the temperature on a graph or table once each minute for ten minutes
9. Compare the results.
*Which substance radiated more heat, the sand or the water
*What causes the sand at the beach to be warmer than the water?
*What causes the temperature at the beach to be cooler than 2 blocks away?
