Heat Transfer and Insulators

For our inquiry experience this week, we were asked to choose 4 different household materials to test for their effectiveness in insulating hot water. The materials I chose were aluminum foil, a micro fiber cloth, a wool ski sock and a piece of printer paper (at the urging of my son). I chose the aluminum foil as I thought it would be the best insulator because there are no air pockets to allow for the release of the warm air and that the metallic nature of the foil would help hold in and reflect some heat back into the water. Contrary to my initial beliefs but after reading the course text, I chose the micro fiber cloth and the wool ski sock to test because they are constructed in such a way that they contain many small air spaces that should prevent heat loss through conduction as the air spaces make the vibration of heated molecules more difficult (Tillery, Enger & Ross, 2008). I predicted that the printer paper would make the worst insulator because condensation would saturate the paper allowing the paper to cool and thus allowing the air under the paper to cool faster, cooling the water below.

One of the challenges I faced when completing this activity was that my coffee mugs do not have a lip at the top to allow for the materials to be secured at the top. I had to completely wrap the materials around the mug and handle securing the materials at the bottom of the mug, which allowed for a large air pocket under each insulator, as shown below. Because I was not sure of the accuracy of the results I obtained because of this problem, I chose to complete the experiment a second time using four identical drinking glasses.





The results of both trials in my experiment were as I had expected. The aluminum foil and micro fiber cloth topped the list as the best insulators, with the wool ski sock right behind. As expected, the paper proved to be the least effective at keeping the water warm. However, I was surprised by how close all the results were, including the results of the printer paper.

Amount of Heat Loss Trial 1-With Coffee Mugs

Insulating material	Initial temp. in ̊C	Final temp. in ̊C	Change in temp. in ̊C
Aluminum foil	56.3̊ C	39.8̊ C	-16.5̊ C
Micro fiber cloth	56.3̊ C	38.9̊ C	-17.4̊ C
Wool ski sock	56.3̊ C	38.4̊ C	-17.9̊ C
Printer paper	56.3̊ C	37.7̊ C	-18.6̊ C

Amount of Heat Loss Trial 2-With Drinking Glasses

Insulating material	Initial temp. in ̊C	Final temp. in ̊C	Change in temp. in ̊C
Aluminum foil	66.8̊ C	44.6̊ C	-22.2̊ C
Micro fiber cloth	66.8̊ C	44.8̊ C	-22.0̊ C
Wool ski sock	66.8̊ C	43.4̊ C	-23.4̊ C
Printer paper	66.8̊ C	41.7̊ C	-25.1̊ C

Even though the results were as expected, I gained many insights about heat transfer through this activity. I was able to observe all three modes of heat transfer; conduction, convection and radiation, thus deepening my understanding of all three. Conduction was observed by the heating of the aluminum foil above the hot water, as energy was transferred from the hot water to the cooler foil causing the foil to heat up (Tillery, Enger & Ross, 2008). The heating of the air above the water in all of the mugs or glasses demonstrated convection (Tillery, Enger & Ross, 2008). Convection currents were also experienced with the difference in temperature between the warmer water on top and the cooler water on bottom, which presented another challenge that I resolved by stirring the water before taking the final temperature of all samples (Tillery, Enger & Ross, 2008). Radiant energy was emitted from all samples and was easily felt in the air above and around the mugs or glasses.

I felt that this inquiry activity accomplished what it was meant to. I feel I have a better understanding of the three modes of heat transfer explored and the properties of a good insulator. I believe this inquiry activity would be engaging for younger students as they would probably enjoy just predicting what they believe would happen, making the observations and seeing if their predictions were correct. Older children may be more engaged with a more challenging scenario, such as developing the best container to keep food hot during transport.

References:

Tillery, B.W., Enger, E.D., & Ross, F.C. (2008). Integrated science. Boston, MA: McGraw Hill .

Pendulum Guided Inquiry Activity

For the application assignment in my Exploring the Physical World class, we were asked to choose a question to explore on momentum. The question I chose was "Which pendulum will come to rest more quickly—a lighter pendulum or heavier pendulum?" To investigate the answer to this question I used the following materials and procedures.

Materials-
long piece of string
3 washers of different sizes
stopwatch
notebook

Procedures-
1. Make a pendulum by putting the string through the hole in the small washer and grabbing the two ends of the string at the top with the washer hanging straight down. Raise the washer and string so the string is taut and the washer is at the same level as the hand holding the ends of the string and release. Observe the pendulum in motion and time the motion from when the washer was released until it comes to a stop. Record the time in your journal. Repeat two more times.
2. Repeat the above procedures with the medium and large sized washers.

Through my investigation, I found that the larger the washer was, the longer the pendulum stayed in motion, confirming my understanding that an item with more mass has more momentum, will remain in motion longer and takes more force (in this case, gravity) to stop its motion.

This was an easy guided inquiry activity to conduct and feel that it would be effective in helping students understand how mass effects momentum.