Heat Transfer

For the heat transfer activity I chose to use newspaper, aluminum foil, saran wrap and a cotton washcloth for the covers of the four identical mugs. The water was heated to a consistent fifty degrees Celsius and I allowed the four mugs to sit exactly thirty minutes before rechecking the temperature of their contents. My hypothesis was that the washcloth would have the greatest insulating effect due to the many air pockets created by the woven fibers. It was also my guess that the aluminum foil would be the worst because of it being a metal and metals are suppose to be great conductors of heat and electricity so logically it would give up the most heat to the surrounding air. As I finished with this activity I was surprised to find that my hypothesis was the opposite of what I first believed to be true. In reality the aluminum foil was the best insulator only allowing a twelve degree Celsius change in temperature over the thirty minute time period and the cotton washcloth was the worst having a sixteen degree Celsius drop in temperature.

In reflection from the readings this week the text, Integrated Science, (Tillery, Enger, & Ross, 2008) specific heat is the amount of heat required to change the temperature of a certain material one degree Celsius and that aluminum’s specific heat was (0.22 cal/gC°), which means that aluminum is one of those metals that does not heat up easily and also does not transfer heat well. This makes sense when you look at aluminums location on the periodic table, close to the metalloids and non-metals. Aluminum is a good conductor of electricity but not a great conductor of heat probably why you see it used in conjunction with a plastic insulator for things like travel coffee cups.

Setting this up for a classroom, I would get several different types of materials for the students to test. The concept of variables can be easily addressed in that all the items must be exactly the same except the materials you are testing. You can discuss how using different mugs might allow the temperature change happen at different rates much like the covers you are testing. It would be important for the students to understand that the density of a material affects its ability to transfer heat and that some metals that are less dense than others may be better insulators than they are conductors much like aluminum.

Reference:

Tillery, B., Enger, E., & Ross, F. (2008). Intergrated Science: Fourth Addition, Boston, MA: Laureate Education Inc.

Marble Momentum

          The activity I chose to investigate was the one that dealt with how different surfaces affect the momentum of a marble? In order to accomplish this activity I first raided my daughter’s toy box to find a marble that would be used to test the different types of surfaces. Next, I located an area in the room to carry out the experiment that gave me plenty of space that had no other obstruction that would affect the outcome of my trials. With the marble and test area decided, gathering the final materials need to carry out this task, I set up my test area. The materials I chose to use consisted of the marble and four different surfaces; two types of carpeting (Shag and Berber) place on a track created with a lined box four meters long and one meter wide. Two other tracks were also created, one filled with a fine sand, and the other with a smooth wood base that were the same size as the two boxes with carpeting in them.  The final item needed to test how the momentum of a marble would be affected by the surfaces it is rolled on, was the ramp that I designed using two, one meter rulers, that have a groove down the center, taped to a wood plank and set at a height of five centimeters.

            The hypothesis that I based this test on was that a marble’s momentum would be adversely affected by a surface that has a greater amount of friction to apply a net unbalanced force in the opposite direction of the momentum of said marble. To test my hypothesis the five centimeter incline plane applied gravitational force to put the marble in motion down the two meter ramp, where it will then come in contact with a surface that is flat and utilizes one of the four surfaces to be tested.  The experiment began with the first trial, which used the smooth wood surface. The marble was able to travel the entire length of the wood surface and then through conservation of momentum hit the end board, a stationary object, which caused the marble’s momentum to reverse and continue back in the opposite direction. The second trial was with the Berber carpet, which had a similar result but only return back toward the ramp a distance of half a meter. The third trial used the shag carpet and had drastically different results. In this trial the marble was only able to advance about one and a half meters in total before coming to rest. The final test utilized the fine sand and much like the Shag carpeting the sand resisted the momentum of the marble and brought it to rest at one meter thirty-seven centimeters. To verify the results I repeated the four trials three different times and then took the average of all three trials to base my information on. My conclusion supported my hypothesis in that the greater the frictional surface the greater the unbalanced net force in the opposite direction causing the marble to stop sooner.

            The outcome of the experiment was what I expected it to be, in that the marble’s momentum was affected by the different surfaces with a varying degree affect. As expected the marble’s momentum allowed it to move the farthest on the smooth wood surface and the least on the shag carpeting. So I wasn’t surprised by the outcome of my experiment.  The final trials of the experiment went very well but it took a lot of time and some searching for the right materials without spending a fortune to build the ramp and runway. Luckily I have a large shed with way too much junk in it. Works great for a struggling science teacher who loves to create things on his own to use in his classroom. If I were to set this up for the classroom I would probably have the students find areas in the school to test different types of surfaces. This would be a less controlled but might be fun for the students. Another would be to have the students create a race with their marbles to see how different masses will produce different results. This test could also show students how momentum will affect them during an accident in a car. Using small cars like in Newtons’s Amusement Park video with Janice Bright (Laureate, 2011) and the momentum of cars. She used quarters on the vehicle to demonstrate how the momentum of the quarter will cause it to continue forward when the car comes to an abrupt stop. It would be my goal to show students how momentum affects motion and  how that can work for us in situations that are controlled but can also work against us in uncontrolled situations such as a car accident. I have used this type of activity with my students and yes I do believe that I have helped them understand this concept about motion.

Reference:

Momentum Land. (Laureate Education Online Streaming, 2011 release).