Differential Heating of Materials
Lab Report in Geography
The heating of materials varies considerable depending on material composition and atmospheric conditions. A considerable amount of the sun's energy can be reflected back into the atmosphere, in a process called albedo (Lutgens & Tarbuck, 1998, p. 36). The average albedo rates for sand, mud, asphalt, and water are approximately 20-30%, 10%, 5-10%, and 3-80%, respectively, depending on the position of the sun relative to the surface of water (p. 40).
The process of heating materials will vary as well. For example, asphalt and dry sand would primarily use conduction for thermal transfer, while bodies of water or air would use convection (p. 30). On the other hand, thermal transfer for wet soil or mud has the added complexity of latent heating (p. 76). Latent heating or evaporation has a strong cooling effect on the liquid moisture remaining, a loss of 600 calories for every gram of water turned into vapor. Based on the above information, the materials that would heat the quickest when exposed to a heat source would be asphalt > sand > water > mud. This hypothesis assumes that the air is not saturated with water vapor.
Procedure
Containers filled with sand, water, asphalt, and wet garden soil (mud) were placed at the front fo the...
35). Initial temperatures were recorded at 0 minutes, representing the ambient temperature. The heat lamps were then turned on and a countdown timer set for 30 minutes. Once the 30 minute period had ended the heat lamps were turned off. Air, surface, and internal temperatures were taken every 10 minutes for a total period of 50 minutes.
Results
The surface temperature of asphalt (Fig. 1) increased the greatest of the four materials analyzed. When exposed to the heat source the temperature increased from 30° to 65° C. within 50 minutes, but the internal temperature of the asphalt remained relatively stable and increased by only 8° C. The surface of sand (Fig. 2) and water (Fig. 3) increased at near equivalent rates, reaching a final temperature of 30° and 31° C, respectively, within the same time frame. Sand appears to have started at a lower temperature compared to water, but based on subsequent readings, sand and water probably started at almost the same temperature. The overall increase of the surface of sand and water during the 50 minute period of heating was about 6-7° C, while the internal temperature increased by 4° C. For both materials. The air temperature reading for sand at 20 minutes appears to be erroneous and therefore an outlier. By comparison,…
