The Heat is On - Heat Transfer

During the Heat is On experiment, all three methods of heat transfer were present. The hot water heated the air within the cup by radiation. The air at the surface of the water was heated by emitted heat from the water so radiation took place. The rest of the air within the cup was heated by convection. Hot air that was heated by contact with the water rose inside the cup (hot air is less dense than cold air and, thus, rises). When the hot air rose, the colder, denser cold air sunk inside the cup to be heated through conduction by the hot water. This cycle continues, heating all of the air inside the cup (Tillery, Enger, and Ross, 2008). When the hot air rises in the cup it comes in direct contact with the cover material and transfers heat to the material through conduction. The heat then passes through the material to the surrounding outside air through radiation.

When I conducted this experiment, I used wax paper(13 degree change), aluminum foil (15 degree change), plastic wrap (11 degree change), and no covering (24 degree change). If I were to do this experiment again, I would try using fabric and glass as a cover to see if their insulating properties are different than the insulators that I originally chose. I think that the glass would prove to be the best insulator because it would not allow any steam to escape from the cup as fabric might. Glass, like air, however, has a very low specific heat which would indicate that it will change temperature very easily and would transfer heat more readily (Tillery, Enger, and Ross, 2008). This would indicate to me that, after air, glass would transfer the heat from the cup fastest; faster even than the aluminum which has a higher specific heat.

I would like to try this experiment again with an object wrapped in the different materials so that the air pocket inside the cup could be removed from the experiment. I think a hotdog would be a good material to use because hotdogs are uniform in shape, they are easy to heat, and also easy to wrap in the experimental materials. I think that the hotdogs would cool faster than the water because water has a very high specific heat which requires a great deal of energy to change its temperature (Tillery, Enger, and Ross, 2008).

I think that this exact experiment could be used in my classroom. A wide variety of materials could be available for students to test out as potential insulators and conductors. To make this experiment more interesting for my students, I would present them with a scenario in which I had guests over to my house and I was trying to keep our dinner warm while everyone finished up their appetizers. I couldn’t find an appropriate covering for the food, everything got cold very quickly, and dinner was ruined (other scenarios could be used). I will ask my students for their advice on the matter and then invite them to try out their ideas. Once students had experience with this activity, I think a good extension of the lab would be to have students design their own thermos in which they have to sustain a specific water temperature for a given amount of time. Students would have to use their knowledge of heat transfer (all forms) to eliminate any possible loss of energy.

I would like students to learn about the three different methods of heat transfer, the different types of conductors and insulators and their properties, and I would like them to gain some experimental design experience. I achieved all of these goals while I was engaged in this activity.

Tillery, B. W., Enger, E. D., & Ross, F. C. (2008). Integrated science (4th ed.). New York: McGraw-Hill.