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Absorption and Radiation of Energy: Land and Water Objective: 4.2 – Students know and understand the general characteristics of the atmosphere and fundamental processes of weather. o 4.2.3 – Describing how energy transfer within the atmosphere influences weather (for example, the role of conduction, radiation, convection, and heat of condensation in clouds, precipitation, winds, storms) o 4.2.3a – Describe the transfer of heat energy within and between the oceans, continents and atmosphere. o 4.2.3b – Analyze a diagram to explain the relationship between differential solar heating and wind patterns. Purpose: To see whether land and water differ in the absorption and radiation of heat energy. Problem Statement: When land and water are heated and allowed to cool for the same amount of time, which will heat up faster and which will cool off faster? Background: The continents and islands of the Earth make up about one fourth of its surface. The other three-fourths is water. If these two materials – land and water – absorbed and retained the heat energy from the Sun differently, this would help to explain the great differences between the weather and climate of coastal regions and regions in continental interiors. In this investigation, you will compare the temperature changes that occur on a small “land” surface and a small water surface, first as they are warmed by the radiation from an incandescent bulb (the “Sun”), and then as they cool off after the Sun “sets”. Materials: Small beakers or deep dishes or bowls; desk lamp or clip-on lamp; incandescent bulb (at least 100 watt); thermometers; ring stands and clamps; sand or soil; water. Procedure: 1. Write down the title and problem statement. 2. Write a hypothesis that addresses the problem statement. (Remember to use the “If… then …” format.) 3. Summarize the background information using your own words. 4. Set up the equipment as demonstrated by your teacher. 5. Half fill one container with water at room temperature. 6. Half fill the second container with sand or soil. 7. Put the two containers close together, but not touching. Place the electric light (OFF) directly over the center point between the two containers, about one foot above the water and soil surfaces. 8. Place one thermometer in the soil with its bulb just below the surface. 9. Place the second thermometer at exactly the same level in the water. 10. When both thermometers show the same reading – which should be just about room temperature – record the reading in the data table. 11. Turn ON the bulb. 12. Take and record the readings on both thermometers every two minutes for 20 minutes. 13. At the end of 20 minutes, turn OFF the light. 14. Continue to record the thermometer reading every two minutes for 20 more minutes. 15. Plot the readings on one piece of graph paper. Be sure to create a key – designate which line is for water and which line is for land. 16. Complete ALL three of the question sections. 17. Write a conclusion that discusses the difference between the heating and cooling of land versus water. Data Table: LIGHT ON Time 0 2 4 6 8 10 12 14 16 18 20 (min.) Water Land LIGHT OFF Time 22 24 26 28 30 32 34 36 38 40 (min.) Water Land Questions: Absorption of Heat Energy 1. Did the two materials warm up at the same rate? (HINT: Look at the graph lines.) 2. If not, which warmed up faster? 3. How many other lab groups have results that agree with yours? (HINT: You need to check with every other lab group and find out what their results showed.) 4. How many differ? 5. On the basis of these results, what can you say about the relative ability of land and water to absorb radiant energy? (HINT: Which absorbed energy faster, land or water?) Radiation of Heat Energy 1. Did the land and water cool off at the same rate? (HINT: How many degrees did each lose in the 20 minute cool down period?) 2. If not, which cooled off faster? (HINT: Which lost more temperature in the 20 minutes?) 3. How many other lab groups have results that agree with yours? (HINT: Please check with each group again.) 4. On the basis of these results, what can you say about the rate at which land and water lose heat? 5. What reasons can you give for the different rates at which land and water absorb and lose heat? Application to the Earth 1. What effect will the different rates of heating and cooling of land and water have on the summer weather of inland places as compared with coastal places? 2. What effect will there be on their winter weather?
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