In this experiment my young laboratory assistant, Rylie, and I investigated heat transfer and insulators. Heat can be transferred three ways. Conduction is the passing of heat energy from molecule to molecule (Tillery, Engel, and Ross, 2008). Convection is the movement of heat from one area to another by the movement of molecules. Radiation is the movement of energy through space (Tillery, et al, 2008). An insulator is a material that slows the transfer of heat energy. Materials whose molecules are farther apart make better insulators than those whose molecules are closer together (Tillery, et al, 2008). The materials we chose for our insulators were heavy duty aluminum foil, a latex glove, cotton cloth, and paper towel. We thought the best insulator would be the foil because it is used to keep food warm. To test our hypothesis we filled each of four identical mugs with one cup of hot tap water. We let the tap open for several minutes to make sure the water was as hot as it could be. We quickly covered each mug and secured the material with a rubber band. We let the mugs spaced evenly apart on the quartz countertop and set a timer for 30 minutes. When the timer rang, we uncovered each of the mugs and placed the thermometer in mug #1. It took quite a few seconds for the thermometer to stop rising. Meanwhile the other three mugs sat uncovered waiting to be measured. The temperature of the water in each mug was measured and recorded:
Mug # | 1 | 2 | 3 | 4 |
Material | Aluminum foil | Latex glove | Cotton cloth | Paper towel |
Temperature (*C) | 42 | 38 | 39 | 41 |
Our hypothesis was correct; the foil was the best insulator. Aluminum molecules are far apart and take longer to heat up (Tillery, et al, 2008). We were surprised that the paper towel came in second, followed by the cotton cloth. The paper towel was thicker and had more air spaces to slow heat transfer. The latex glove was the least effective insulator. We thought it would make a better insulator than the thin cotton cloth because latex is rubbery. However, the glove is waterproof which means the molecules must be very close together. We decided stuffing our shirts with napkins would keep us warm if we got too cold at Rylie’s soccer game this weekend. It would be a good idea to keep foil in an emergency kit in the car in winter. It could be used to reflect radiant body heat and keep us warm if we got stranded in the cold. We also noticed the countertop under the mugs was warm to the touch, indicating that heat was conducted through the bottom of the mugs and into the stone.
One challenge we experienced was efficiently measuring the temperature with only one thermometer. Error could have been introduced because the experiment was not well controlled. Not only was the covering material varied; but, time became a variable as well. Ensuring an accurate thermometer reading caused an increased time for the remaining three mugs. Additional cooling may have happened while the mugs were waiting to be measured. Having four thermometers would allow us to control the experiment and eliminate the error. Thermo-meters should be in place when the mugs are filled so accurate readings can be taken at exactly 30 minutes. All four mugs should be filled and thermometers must be read at exactly the same time, making lab assistants necessary, also. Recording temperature readings every five minutes would be best because the data could be graphed to show the rate of heat loss. Another challenge we experienced was due to a malfunction of the thermometer. The glass tube was not fixed to the calibrated strip so it moved freely in the brackets. We had to tape it fast, but we were not sure we had it at the correct location. We figured it would work as long it stayed at the same spot for all four measurements.
