Heat Transfer

This week our challenge was to determine the best insulator.  I chose cling wrap, aluminum foil, a wool hat, and newspaper to test this question.  I hypothesized that the wool hat would be the best insulator while the cling wrap would be the worst.  Having tested materials with my students, I knew that wool should be the best insulator due to its many air pockets, while something with more compacted molecules would transfer heat faster.  (Tillery, Enger, & Ross, 2008)  I thought that the cling wrap would be the worst because it had been in my previous experiments, and newspaper is an insulator used by homeless people. 

Based on Tillery, Enger, and Ross (2008), the materials encouraged and discouraged different types of heat transfer.  All of the materials inhibited radiation to some extent, as radiation is the transfer of heat energy across space.  The materials covered the top of the water that is exposed to the air; therefore, some heat energy is trapped as it does not have an unobstructed path.  All of the mugs exhibited conduction as well as convection seeing as the water transferred heat energy to the mug through touch and fluid.

If I were to conduct this experiment again, there are several other materials I would like to test.  Paper towels, dish towels, or even ceramic covers would be interesting to use.  I think that the ceramic cover would probably lose the most heat energy due to the compact nature of the molecules.  The dish towel would most likely retain the most heat energy because of the air pockets and spaces in the material, thus making it more difficult for the energy to transfer throughout the towel.

Testing other materials could be interesting.  I think that hot dogs and spaghetti would probably cool faster depending on where you take the temperature reading.  The middle of the material will be able to retain the heat energy the longest, but they are both solid materials.  Because they are solids, the closeness of the molecules would allow heat energy to transfer much more easily than through a fluid or a gas.

Earlier this year, my students took part in a heat transfer unit where they had to test the insulating abilities of a variety of materials in order to determine which to use for their penguin igloo.  The goal of the inquiry exercise was to keep their ice cube penguin from melting.  The students loved it, and because it was a 5E lesson, we were able to teach the methods of heat transfer in a way that connected it to life.  We talked about why the upper levels of a house are always warmer and how to tell if your house is adequately insulated.  The students loved it and were eager to put their new knowledge into practice.

Tillery B.W, Enger E.D., & Ross F.C. (2008). Integrated Science 4th edition. United States of America: The McGraw-Hill Companies.