In Hot Water

We have been asked to conduct an experiment comparing the insulating abilities of four different materials. I went with materials that keep people warm in these cold and blustery months. I chose wool, traditionally used for centuries to make clothing. I selected a synthetic felt which is not woven but tightly matted acrylic and polyester. Being thick, I thought it would hold in the heat well. The next material I chose was fleece. We have use fleece to make throw blankets to snuggle on the couch with. The last material I selected was not a fabric but a foil, aluminum foil. I wanted to branch away from textiles and use an insulator commonly used to keep wood warm.

I selected four mugs identical in size, shape, and composition.  Into each mug, I poured one cup of boiling water; measured and recorded the temperature; cover the cup’s opening with one of the selected insulators; and then secured it with a rubber band. After waiting the designated 30 minutes, I uncovered each container; measured and recorded the temperature; then recovered the each mug. I calculated the drop in temperature for each of the four cups as I waited an additional 30 minutes before taking the temperatures again.

I found the water temperature in both the wool and the felt covered mugs dropped 91° total, within two, 30 minute testing periods. The aluminum foil covered mug dropped 94°, while the fleece covered mug lost 96° in the one hour period. I thought the wool and felt would come out on top, but was surprised the foil held in more heat than the fleece.

 I do not believe the data I collected to be reliable enough to draw an accurate conclusion. I would want to perform the experiment several times over to gather more data. My experiment did however, seemed to show wool and felt being the best insulators. They were able to trap more of the radiant heat inside the mug. Less heat energy could escape than in the other two mugs resulting in a smaller change in temperature.

I think if I were to conduct this experiment again, I would choose different insulating materials to test. I would consider using a hot pad/oven mitt. We use oven mitts to protect our hands for being burned when removing hot objects from the oven. They must make good insulators. I would also use a sheet of Styrofoam. We use Styrofoam often for containing hot drinks because the material prevents our hands from burning. It retards the conduction of heat energy. The heat of the contents does not transfer to the cup and then to our hands, easily.  I would also try cardboard like the sleeves put on coffee cups in fancy coffee joints. Surely, coffee companies tested different materials to find the most efficient choice for protecting the hands or their customers.

I could use this experiment to help my students understand diffusion, the movement of particles from an area of high concentration to an area of lower concentration. Diffusion can be a difficult concept to grasp so using a variety of examples is beneficial. Additionally, understanding the movement of heat energy from high concentration to low will better prepare my students for physical science next year.

All in all, I would say this experiment was a success for me. 

Who's the Biggest Swinger?

Which will come to rest more quickly, a heavy pendulum or a lighter one? I attempted to answer this question despite my lack of background knowledge. After several trial and error efforts, I still feel that I came up short. I went through a series of failed attempts before coming up with a procedure that seemed to work. I tied two strings, one with the smallest washer and the other with the heaviest. I hung them on a yardstick, which I laid atop the back of two chairs.  In the beginning, the strings were too long so the pendulum knocked into the chairs and tangled together. I tried timing the swings but that took too long, and I soon realized was not necessary. I assumed the flat surface of the yardstick contributed to the wild swinging, so I tied shorter strings and the washers to a dowel. I struggled being able to tell when the pendulum actually stopped. They both continued to sway a tiny bit but the smaller one seemed to stop first but it was close.

                The inconclusive data forced me to try other options. Changing only one variable at a time, I tried using spoons, various string lengths, even taping the string to the dowel instead of tying it. Nothing gave me the definitive answer I was hoping for. I figured I was doing something wrong. At this point I began to seek out help. I returned to the Pendulum Ship from the Newton’s Amusement Land, theme park found in the Walden resource page. It talked about the length of the hanging device being more critical than the mass of the swinging object. I decided to try another approach by attacking my hypothesis from a different angle. I took two identical pair of scissors, and tied them to the dowel using a short string and a longer string. When I pulled the scissors back and released them, the scissors on the shorted string stopped earlier than the other pair. At last I could actually see a result.

                                Help…. found

                I was still unsure of my conclusion and found no information in the text that helped me. I did find using the PhET’s Interactive Simulation website posted by the University of Colorado helpful. I set up a simulation that mirrored my original experiment. I set both pendulums to have an equal length from the top, and used two differently weighted objects. The pair, despite their difference in mass, stopped at the same time. Finally I found a definitive answer to the original question. To satisfy my compulsion to be right, I googled the question to see what I could find. The most helpful information came from Mrsstrasbaughsblogspot.com. She is apparently a teacher earning her master’s degree and took a class last spring similar to ours. Her work was well done and helpful.

                I could never use an activity like this without better closure. Sometimes inquiry is done for the sake of inquiry. This will never work without follow up to assure the students master the concepts.

                                A Scenario…. The Flying Dutchman

                To make this activity more interesting for my students I would propose a scenario as follows. A group of friends go to White Water’s American Adventure Park. They are in line to ride the Flying Dutchman (a pendulum boat ride). Two of the kids start to argue. One of the pair believes that the ride will last longer if there are fewer people on the boat. He said that if there were fewer people, the lower mass would result in the ride stopping slower, thus lasting longer. The other friend said the ride would actually last longer with more people on it. The more mass, the more momentum; therefore, the longer the boat swings back and forth. I would then challenge the students to create an experiment to discover which of the friends was right.  I would then follow up to make sure the concept I wanted them to uncover was understood by them all.

                                What should they learn?

                I have no idea what they should learn from this experiment. I never figured it out on my own. I can only share what I learned from Mrs. Strasbaugh??????

                                To wrap this up….

                It was good for me to experience the frustration of not knowing what I was trying to discover, I guess. It let me see how my students might feel. However, they work in groups and have team mates to bounce ideas off and me as an instructor to provide guidance.