Getting myself in hot water!

This week’s experiment was one I had never performed with a class before, so my conclusions were less foregone than other experiments I’ve done for this course. I did have a lot of background knowledge about insulation, just from everyday use and research I have done as a homeowner. I selected newspaper, aluminum foil, a china saucer and a down vest to act as insulators in my experiment. I used the first two because they are materials I have commonly seen people use to wrap things they want to keep hot. The saucer idea came because I’ve seen people put their saucers on top of their cups to keep their drinks hot when they had to leave them for a bit. Finally, I used the down vest because I know down is a good insulator for geese and humans, so I figured it would work well for hot water too. Both the newspaper and aluminum foil were folded into 8 layers. My hypothesis was that the down vest would keep the water the hottest after 30 minutes.

My results showed that after 30 minutes, my water which was initially 155º F (using my digital probe thermometer, which has a built in timer) were as follows:
Newspaper:    116º F
China saucer:  117º F
Aluminum foil: 118º F
Down vest:      121º F
So my hypothesis was supported. The range of difference in the other three tested materials was quite small, but I have confidence in the accuracy of the temperature measurement due to the use of the digital probe.

If I were to do this experiment again, it would be interesting to use some materials commonly used as household insulation. I would like to try a “lid” made of Styrofoam, some insulating expandable foam sprayed onto a cardboard circle cut to fit the top of the mugs, and some Fiberglass insulation, provided I could find a way to contain it so that I could avoid glass slivers. With these, I could do a direct comparison of the R value of each material before using it. I believe that the Fiberglass would do the best job of insulating, for the same reason that down was the best insulator: it traps air in small spaces.
The insulating expandable foam might also do quite well, I have less experience with it but it would be an interesting product to test. It could certainly be useful for “tightening” air leaks in the home, so if it performed well as an insulator in this experiment, it would be well worth considering for household use.

To address the question of whether hot dogs or spaghetti would stay hot longer or cool faster than the hot water, I believe that they would cool faster. I was having a discussion today with my seventh grade class about the effect of large bodies of water on weather, and we noted that meteorologists have observed that it takes water a long time to warm up, but it is much slower to cool off than land is. (This explains why coastal areas tend to have milder winters in general than inland regions.) I think that the same would apply to water and other solids, including hot dogs.

These experiments would not be easy to perform in my classroom due to lack of access to hot water and some reluctance to use hot plates to heat water (or hot dogs). I do believe with modifications, such as exchanging the mugs for paper carry out cups and adjusting the length of time for measurement, students would find this activity engaging, and would be able to see immediate applications to their lives.