Often my students ask why learning a particular concept is important. What they want is real-life examples of the concept in action. A simple way to demonstrate one common scientific concept is to have students apply it and look for real-life applications. One example is the concept of heat transfer. We see the applications of isolative properties of matter around us. For our students to see them, we have to wrap a discovery around the concept.
In presenting this to my students, I would discuss what keeps them warm and why that particular item keeps them warm. We would discuss what properties that the item has and why those properties work in the way they do. We would talk about how other things in their lives have to be kept warm and what is used to insulate those products. To explore this concept, I experimented with different products to keep a cup of water warm for thirty minutes.
For my experiment, I chose to use various materials to keep water warm in an ordinary coffee cup. I had chosen four identical cups and positioned them on the counter out of drafts. I will fill each with ¾ cup of water at 200° Fahrenheit. I will cover them with various materials to test their isolative properties. The materials I choose to cover the cups were a towel, a plastic bag of foam peanuts, doubled cardboard sleeve with cap, and a cake plate cover. I labeled them Cup A (towel), Cup B (foam peanuts), Cup C (doubled cardboard), Cup D (metal cake plate cover). I believe that the bag of Styrofoam peanuts will have the best isolative properties. Being that refrigerators and ice chests are encased Styrofoam, their primary function is to insulate.
I attached temperature strip thermometers to the same position in each cup instead of the thermometer included in the materials from the course. The thermometer would not be accurate from cup to cup because recalibration time for the thermometer to cool between each cup would affect the data collection time and temperatures of the remaining cups. I poured the 200° water into the cups. The materials are placed over the cups and left undisturbed for a period of 30 minutes.
After 30 minutes, I checked the temperature strips in each cup. Cup A (towel) had dropped in temperature to 127°. Cup B (foam peanuts) had dropped to 113° Fahrenheit. Cup C (doubled cardboard) had dropped in temperature to 146° Fahrenheit. Cup D (cake plate) had dropped to 88° Fahrenheit, which, was still above the room temperature of 69° Fahrenheit. After recording my data, I poured out the water, rinsed the cups with cold water to reset the thermometers and repeated the experiment two more times. The results were close to the same with only a + 3° Fahrenheit temperature difference which is not enough to skew the data to another conclusion.
I was wrong about my assessment of the Styrofoam peanuts being the most effective insulator. I did not account for the spaces between the peanuts being a heat loss factor. The towel was very effective. I believe that the air spaces in the fabric were large enough to trap air but not so large to cause as great a heat loss as the large spaces amongst the peanuts. The cake plate cover was a dismal failure. The large space under the cover was not isolative enough to retain any heat. Being metal it actually served as a heat conductor.
It was surprising to find that the doubled cardboard did the best job at keeping the liquid in the cups hot. It was not until my son walked in to the kitchen and said, “Mom, doesn’t Starbucks use cardboard sleeves?” that I realized that this concept had been explored quite extensively by engineers of a leading corporation (Sorensen 1995). It was one of those fore-head slapping moments. I had not realized that the chambers in the cardboard make excellent heat insulators. The cardboard being a wood product that has isolative properties added to its success in keeping the liquid hot. It was also slightly waxed. Sometimes the obvious just is not quite so observable. I suppose that an old dog can be taught new tricks after all.
References
Sorensen, J. (1995-06-20). International Patent No. A47G23/02; B65D25/28;B65D3/28; B65D81/38;(IPC1-7): B65D3/22. Washington , DC U.S.A.
No comments:
Post a Comment