Things are Heating Up
OverviewEnergy is transferred through three different methods: convection, conduction and radiation. These three methods impact the earth’s temperature and also how weather patterns affect us.
The student will be able to define the three different methods of heat transfer (convection, conduction and radiation). The students will also be able to describe why dark colors capture more heat than light materials. Finally the students will be able to outline the relationship between energy transfer and weather patterns.
1. Assign students to get a dictionary or science book. Computers and the internet may also be used. Have them define the following terms:
2. Go over the definitions
Convection- Movement of molecules in fluids and gases where heat increases the movement of molecules. Generally warmer molecules tend to rise and cooler molecules tend to sink. This movement of molecules in both fluids and gases often results in a circular motion. This circular movement is responsible for weather patterns and overall climate in an ecosystem. Convection ovens also use this principle to cook food as the hot air circulates around the inside of the oven to evenly cook foods.
Conduction- The process of transferring energy between two objects of different temperature by physical contact. The better the conductor, the more energy (heat) will be transferred. For instance metal is a better conductor than wood or rubber.
Radiation- The transfer of heat through electromagnetic waves. Heat from the sun is known as radiation. Radiation can come in different wave lengths, such as gamma rays, x-rays, ultra violet (UV) waves and infra-red (IR) waves.
Albedo - the fraction of solar energy reflected from the Earth back into space. It is a measure of the reflectivity of the earth's surface. White surfaces have a greater albedo (or reflection of heat) affect.
Weather - the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy.
Climate - defined as the weather averaged over a long period. The standard averaging period is 30 years, but other periods may be used depending on the purpose. Climate also includes statistics other than the average, such as the magnitudes of day-to-day or year-to-year variations. "The difference between climate and weather is usefully summarized by the popular phrase "Climate is what you expect, weather is what you get."
3. Explain the three types of heat to students by using the example of cooking a pot of water on a stove. The stove heats the pot through conduction. The stove is transferring its energy directly to the pot, and then from the pot into the water through physical contact. You can feel the heat from a hot burner without touching it because of radiation. Once heat is transferred through conduction inside the pot, convection is used to heat all the water. The hot water at the bottom rises and heats the remainder of the liquid through convection
- Six pie pans
- Dark soil
- Light colored sand or perlite
- Six thermometers
- 1-2 Reflector or heat lamps (depending on # of experiments running)
- Graph paper (enclosed with lesson, see link below)
- Watch with a second hand
- A small fan
Explain to students that today they are going to be measuring how different objects hold heat from radiation. They will explore how this energy transfer affects both weather and climate. An increase in the Earth's temperatures is playing a large role in climate change.
Print off and hand out the heating and cooling cycle temperature charts so that each group has one set for each pie pan. Fill the pie pans to the same level, two with dark soil, two with light sand, and two with water. (One set of the pans will be used for the light-only treatment and one set will be used for the fan-and-light-together treatment.)
In order to assure that each pan is treated to the same conditions, you should test the pans individually unless you have 3 lamps with the same light bulbs. Position the lamp(s) 12 inches above the pans. (Note: In order to get reliable results, the amount of heat/light should be the same for each pan.)
Next (or if you have enough materials) place the fan close to the second set of the sets of pie pans. These pans will be exposed to both the fan (simulating wind) and the light. Again, if you have only one fan, you can test one pan at a time in order to get reliable results.
Place a thermometer into each pie pan, securing it so it measures the temperature just under the surface of the substance in the pan. Record the starting temperatures on the data tables enclosed with this lesson (see Materials).
Turn on the lamp and record the temperature of each substance every minute for ten minutes.
At the end of ten minutes, turn the lamp off. Continue to record temperatures for each substance every minute for ten minutes.
The experiment should take around 30-40 minutes to set up and run. Discuss the results with students once the experiment has been completed. Use the following questions as a starting guide for discussion:
- What substance absorbed the most heat? Emphasize the fact that dark colored materials absorb more heat. This is also true of open water in the Arctic. Scientists estimate that water can hold up to 5 times the heat energy that land does. If there is more open water around the Seward Peninsula then what will likely happen to the temperature on land?
- What substance lost the most heat? Let the students know that light colored materials reflect more heat (the Albedo Effect).
- If the sun shines on the land and the sea during the day, which will heat up more? Which will lose more heat during the night? Think back to the experiment and list the surface that lost heat the quickest. The soil surfaces should have absorbed the most heat, but should have also cooled off the quickest. Water has a high heat capacity which means it changes temperature more slowly than many substances. In this way it acts as a temperature regulator in coastal environments.
- How did the wind impact the heating process? Did the wind have an effect on how the materials heated up or cooled down? Was your soil or soil wet or dry when you began? How would this affect your results? What would be some other substances that we could have tried in the experiment? Would different kinds of rocks or soil with plants trap heat any differently? How do you think different materials trap heat? How does heat transfer affect the weather patterns?
- The Seward Peninsula does not receive the same amount or intensity of sun as other parts of the Earth do. What is going to affect the temperature of the land more, heat trapped by the land or heat trapped by the sea?
Have the students review the three types of energy transfer. Discuss how heat transfer can affect the weather. List some climate change threats that can affect heat transfer and weather on the Seward Peninsula.
As an extension, have students graph the change in temperature versus time. Put time on the X axis and Temperature on the Y axis. Use Draw all three graphs (water, dark soil, and light soil) on one graph using different colors for each.
Share the Christian Science Monitor article about Alaskan Climate change with the students. Highlight the fact that melting ice sheets could raise ocean levels by 5-7 meters. Tell the students that 5-7 meters could be anywhere from 15-22 feet. That means anything close to the shore lower than 15-22 feet could be submerged under water. Have the students answer the following questions:
- How will rising ocean temperatures affect the Earth's temperature? Reflect back on your experiment. More ocean surface will probably mean what for the overall global temperature?
- What impact will this have on the Seward Peninsula?
- What industries and pastimes could be affected?
- Snow reflects up to 95% of the solar radiation that hits it. This fact illustrates snow's high Albedo effect. Read more about it here. What do you think the temperature of snow would be like under the lamp? How long would it stay before melting?
Christian Science Monitor: http://www.csmonitor.com/Environment/Global-Warming/2008/0828/alaska-climate-change-frontier
Albedo Change About to Alter Alaska: http://www2.gi.alaska.edu/ScienceForum/ASF19/1978.html