Materials that contain many small air spaces are generally good insulators because the air spaces are poor conductors since the molecules of air are far apart compared to that of a solid (Tillery, Enger, & Ross, 2008). We were tasked with testing different materials to find the best insulator. We were to use identical mugs, fill them with hot water and cover them with various materials to find the best insulator. The materials I chose to test were aluminum foil, paper towel, newspaper, and Saran wrap. Even though the experiment only called for four items I also used a piece of cardboard and a scarf. The scarf is made of acrylic. As a control I had a mug that was uncovered. I thought that the aluminum foil would be the best insulator.
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| All my mugs in a row |
To start of I figured out how much liquid the mugs could hold to be 12 oz, since I did not want to fill them to the top I decided I would fill them with 8 oz of water. In order to be able to heat enough water to fill all of the glasses I put some water in a pot and heated it on the stove. I then quickly measured the water and poured it into the containers and covered them with their corresponding materials. The major complication in this experiment was the thermometer. The thermometer that was in our kit only went up to 120ºF and the water was at a higher temperature than this. I ended up using my meat thermometer which went up to 220ºF. The increments were 2ºF so I sometimes estimated when it was in between two of the lines. It was also hard to read at times. The starting temperature of the water was 138ºF I waited 30 minutes and took my first reading. With all but the mug with the scarf and the one with no covering having the same temperature I decided to continue. When I took the temperature I lifted the covering just enough to allow the thermometer in so what heat was being trapped did not escape. I ended up taking four readings every half hour for a total of a two hour time frame. At the end of two hours I found that the Saran wrap (84ºF) insulated the best, followed by the cardboard (83ºF) and then aluminum foil, paper towel, and newspaper (82
ºF) all tied. Had the scarf (86ºF) been under the same conditions it probably would have done the best since it did retain more heat than the Saran wrap.
These results are not what I would have expected at all. First off when I placed the materials on top of the mugs I could feel heat coming through the paper towel, newspaper and the scarf some, but not through the aluminum foil, Saran wrap and cardboard. With this observation I would have thought that there would have been a bigger difference between the aluminum foil and the paper towel and newspaper. Some of my thoughts on the Saran wrap is since it is plastic, the water condensed on the top providing another protective layer. Also by keeping the water in the container it held onto heat since water does have a high specific heat. I think in the case of the newspaper and paper towel some of the water could have been evaporating through the materials since they were both moist to the touch. I did expect the scarf to do well since we use them to insulate ourselves. Some else to consider and the results is the material of the mugs I used. I used my Corelle Stoneware mugs, which even without any covering (78ºF) held the heat fairly well. I think the material of the mug used is also a huge factor. I would not expect to get the same results as someone that might have used paper or Styrofoam cups. It would be interesting to first test different materials to hold the liquid and find the best insulator without covering and then find the best insulator cover to support it.
The main challenge I had was measuring the temperature. I wish I had a regular alcohol thermometer that might have been more reliable and given me better data. Or even having a digital thermometer might have been the most accurate. I feel like any errors that may have occurred were due to the use of the thermometer.
I would like to repeat this experiment using more reliable equipment. I would also like to try it using paper coffee cups instead and see how much of a difference that makes. I would think using the paper coffee cups would result in a higher degree of heat loss. The Stoneware mugs proved to be too good of insulators themselves. It would also be interesting to see what a difference covering the entire mug in each material would make. Again I think this would be better seen using the paper cups. After working with the various materials it would also be interesting to combine the various materials to make the best insulator possible. I would have the students design a container to keep something like a bowl of soup warmest the longest.
Overall I did learn more about heat and the use of insulators through this lesson. I learned how important it is to have equipment that is reliable to get more accurate results. I would like to repeat this experiment again using a better thermometer and different containers to keep the water in and see how the results compare. I think it would be fun to challenge the students to design a container to keep something hot longer. This would also bring engineering into the lesson.
