Insulative Properties Experiment

Insulation of Covers and Heat Loss

This week I worked on an experiment involving boiling water, a set of identical ceramic cups, and different materials to use as a lid.  The idea of the experiment was to predict what type of cover would better insulate the liquid in the cup, using temperature measurement as a result.  The assumption would be that the better insulator we had the better heat would be retained in the liquid.  Heat transfer can happen in one of three ways, conduction, convection, and radiation (Tillery, Enger, & Ross, 2008).  I believe that the major way that cooling will occur in this test will be through conduction.  This is where energy is transferred from molecule to molecule (Tillery et al., 2008).  I believe that the ceramic cup will block most of the heat radiation as well as the effects of convection that will occur in the test. 

One of my hypotheses is that most of the heat will be lost to the atmosphere through the top of the cup where the conduction of the heat will flow from water, to the air in the cup, to the lid, to the atmosphere.  Given this as a starting point for the experiment, I will then postulate that if heat is going to transfer through conduction.  The better insulator the lid is, the slower the energy will dissipate to the atmosphere.  I selected a few different types of materials for this; a book, plastic bag, ceramic plate, and aluminum foil.  With this I added a control with no cover.  Looking at my hypothesis I will predict that after one hour the water will be hottest in the cup with the ceramic, then the book, the plastic, the aluminum, and finally the control.  I believe that this will be the case because of the mass of the objects in the book and ceramic.  Mass is an integral part of the calculation of specific heat (Tillery et al., 2008) and the higher the mass the more resistant it is to temperature change.  The aluminum is a little different case, I know that the other materials I chose are of mostly organic origin and do not contain a conduction band.  The aluminum (being a metal) has a conduction band so it follows that it is a poor insulator while the plastic should be better.

In the appendix I have recorded my results.  The results of each of the materials were very similar, with there only being one degree separation between the different lid types.  I was a little surprised by my results so I ran the test again and achieved similar results.  It is interesting that these results go against what I saw as something that I knew the results of before I ran the test.  I am reminded that this is what students must feel like every time we have them make a prediction on an experiment before they really know what is going to happen, it can be a little embarrassing to be wrong.  This strengthens my belief that it is essential for teachers to establish an environment that is safe and comfortable to students (Laureate Education, 2010).  I believe that the test could be better improved by further insulating the ceramic cups to eliminate heat loss through the sides.  It would also be a better test of insulative properties if we were able to have cups constructed of the same material as the lids. 

I can explain my results in several ways, the first being that the cups that I used were not completely filled with water and there was a large air gap between the cup lid and the water surface.  This would override the insulative properties of the lid since air is a great insulator.  This is demonstrated with the aluminum cover where it is well established that aluminum is not a great insulator but did well in this test as a cover.  I believe that this test will show that any cover would perform similarly.  Before I assigned this as a laboratory in my classroom I would need to perform this test a few more times to ensure that I understand why I achieved the results I did.  I would also modify the test to achieve more differentiation between the insulators.  An example of this would be to change the material the cup is made of to be the same as the cover.  

References

Laureate Education, Inc. (Producer). (2010). Virtual Field Experience™: Managing the Differentiated Classroom [Video webcast]. In Teacher as professional. Retrieved from http://www.courseurl.com

Tillery, B. W., Enger, E. D., & Ross, F. C. (2008). Integrated science (4th ed.). New York, NY: McGraw-Hill.