Heat Transfer

This week our challenge was to determine the best insulator.  I chose cling wrap, aluminum foil, a wool hat, and newspaper to test this question.  I hypothesized that the wool hat would be the best insulator while the cling wrap would be the worst.  Having tested materials with my students, I knew that wool should be the best insulator due to its many air pockets, while something with more compacted molecules would transfer heat faster.  (Tillery, Enger, & Ross, 2008)  I thought that the cling wrap would be the worst because it had been in my previous experiments, and newspaper is an insulator used by homeless people. 

Based on Tillery, Enger, and Ross (2008), the materials encouraged and discouraged different types of heat transfer.  All of the materials inhibited radiation to some extent, as radiation is the transfer of heat energy across space.  The materials covered the top of the water that is exposed to the air; therefore, some heat energy is trapped as it does not have an unobstructed path.  All of the mugs exhibited conduction as well as convection seeing as the water transferred heat energy to the mug through touch and fluid.

If I were to conduct this experiment again, there are several other materials I would like to test.  Paper towels, dish towels, or even ceramic covers would be interesting to use.  I think that the ceramic cover would probably lose the most heat energy due to the compact nature of the molecules.  The dish towel would most likely retain the most heat energy because of the air pockets and spaces in the material, thus making it more difficult for the energy to transfer throughout the towel.

Testing other materials could be interesting.  I think that hot dogs and spaghetti would probably cool faster depending on where you take the temperature reading.  The middle of the material will be able to retain the heat energy the longest, but they are both solid materials.  Because they are solids, the closeness of the molecules would allow heat energy to transfer much more easily than through a fluid or a gas.

Earlier this year, my students took part in a heat transfer unit where they had to test the insulating abilities of a variety of materials in order to determine which to use for their penguin igloo.  The goal of the inquiry exercise was to keep their ice cube penguin from melting.  The students loved it, and because it was a 5E lesson, we were able to teach the methods of heat transfer in a way that connected it to life.  We talked about why the upper levels of a house are always warmer and how to tell if your house is adequately insulated.  The students loved it and were eager to put their new knowledge into practice.

Tillery B.W, Enger E.D., & Ross F.C. (2008). Integrated Science 4th edition. United States of America: The McGraw-Hill Companies. 

Marble Mayhem

For this week’s blog entry, I decided to take on the conundrum of how different types of surfaces affect the momentum of a marble. My initial hypothesis was the more surface area of a material, the more friction the marble will experience thus slowing down the marble.  As soon as I started to set up this experiment, I realized that controlling all other variables would be difficult.  The first thing I did was to create a ramp using a textbook and a notebook.  This ensured that marble would be consistently traveling at one speed every time it was released.  The next step was to choose materials for the marble to roll across, and I decided to use different household surfaces.  Carpet, tile, concrete, and hardwood were the most readily available thus I went to work.

As I carried out this experiment, I discovered several things.  First, a marble rolls great distances on hardwood, tile, and concrete.  The procedure had to be modified to include a time in order to determine the momentum.  Unfortunately, I did not have access to a stopwatch or have anyone to help me, so my data is inaccurate.  Trying to watch the marble pass a certain point and watch the clock to determine that time was extremely frustrating.  This particular obstacle illustrated why it is beneficial to use partners and teamwork while performing experiments.  (TEACH Engineering)  My second realization was that my hypothesis proved to be correct.  I realize that my data was incomplete, but using what I did collect showed that the marble rolls furthest and fastest on hardwood.  It did not get further than 20 centimeters on carpet.  This was a perfect example of Newton’s first law where it explains that an object in motion tends to stay in motion unless acted upon by an outside force, which in this case is friction.  (Tillery, Enger, & Ross, 2008) 

If I were setting this experiment up in my classroom, I would probably try to create a competition.  Seeing as the final result is the understanding of how momentum is affected by mass, velocity, and friction, I would give the students their choice of marbles along with a meter stick and a stop watch.  The students could go around the room or the building testing various materials and surfaces.  Once completed, the students would put this newfound knowledge to the test by playing a round of “marble golf.”  I would set up a number of holes, obstacles, and “greenways” and the students would have to choose different materials for the marbles to roll across, thus determining the speed needed to reach the hole.  Having never tried this, I am sure there will be some kinks to work out, but I think that the students would enjoy it.

The goal of the experiment is for children to understand how mass, velocity, and momentum all interact in order for movement to occur.  Friction is an important factor in the equation.  I hope that the students will be able to take the information in the experiment and apply it to things like driving on different surfaces or why you can slide in socks on hardwood.  Maybe one student will be able to take the concept and create a car unaffected by friction!

TEACH Engineering: The Engineering Design Process: http://www.teachengineering.org/engrdesignprocess.php

Tillery B.W, Enger E.D., & Ross F.C. (2008). Integrated Science 4th edition. United States of America: The McGraw-Hill Companies.