The Heat is On

Setup

The materials I chose for this experiment were brown paper, cheese cloth, a cotton washcloth, and a plastic ziplock bag.  I anticipated the plastic bag and the washcloth being the best insulators.  I hypothesized the plastic bag would trap in the most heat as it is similar to plastic wrap, a material used for locking in heat and preserving food.  Also, I figured the wash cloth would work similarly as cloths are sometimes used in place of pot holders to pick up hot food.  I hypothesized that the mug with the cheesecloth would be the coolest of the four because it was covered with the most porous material.  I also expected that each of the materials would be slightly dampened by rising heat.  

Results

I was correct in hypothesizing the plastic bag would retain the most heat as that mug dropped the smallest amount of degrees (see Appendix A).  I was incorrect in guessing though, that the cheesecloth would let out the most heat.  It was the second hottest mug after thirty minutes.  I was also incorrect in guessing the materials would become moist from the rising heat.  The water must not have been hot enough to cause the heat to rise up as steam.  

If I was choosing one of these four materials to insulate something I wanted to keep warm, I would choose the plastic.  If however, I was trying to cool down a substance,  the brown paper would be the most effective or no insulator at all.  “Heat is the measure of of the internal energy that has been absorbed or transferred from one body to another” (Tillery, Enger, & Ross, 2008).  The brown paper was able to better decrease the internal energy of the water in the mug while the plastic served as a better insulator, maintaining the internal energy.  

Questions

Which of the three methods of heat transfer did the materials encourage or discourage? How do you know? Support your response with evidence from the resources.

Conduction

The ceramic mug would have acted as a conductor for the transfer of the heat from the water.  The mug was cooler than the water inside so some of the heat transferred into it, cooling down the temperature of the water and heating up the mug.  “Anytime there is a temperature difference, there is a natural transfer of heat from the region of higher temperature to the region of lower temperature” (Tillery, Enger, & Ross, 2008).  Since I measured a temperature change, I know that conduction took place.  

Convection

Convection took place in the water.  As the water cooled, it became denser and fell.  The hot water rose to the top.  “In fluids, expansion sents the stage for convection.  Warm, less- dense fluid is pushed upward by the cooler, more -dense fluid around it” (Tillery, Enger, & Ross, 2008).  

What other materials might you choose if you were to repeat the experiment? Which of these do you believe would be the best insulators? Why?

I would like to try foil versus plastic wrap.  I think the foil would be more effective at insulating the mug over the plastic because the plastic is more porous.  I would also like to try a piece of white paper versus a piece of black paper.  I know that white reflects sunlight which is why we wear lighter colors in the summer, but would it also reflect heat?  

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

Engaging in Guided Scientific Inquiry

I chose to investigate the question: How do different surfaces affect the momentum of marbles? For this experiment, I set up a ramp against the edge of my coffee table. The ramp consisted of a turned over cardboard box with another upturned cardboard box positioned underneath it to close the gap between the edge of the first box and the floor. I set a third box at the end of the ramp to act as a barrier for the marble. I used the cardboard as one testing surface. I also used pieces of felt, foam, and sandpaper as surfaces. I laid the pieces over top of the ramp to test them.

One of the challenges I thought I would face was finding a way to keep the marble in a straight path all the way down the ramp. I thought that with the rougher surfaces, especially, the marble would stray to the side, thus traveling a farther distance. However, the mass of the marble propelled it in a straight line in each trial, so this was not a problem. Another challenge was making sure I hit the start and stop on the stop watch at the exact moment the marble hit the ramp and then hit the barrier at the end of the ramp. I had to do a few practice trials to get it right.

I predicted that the cardboard surface would give the marble the most momentum because of its smooth surface. I also predicted the sandpaper would cause the marble to lose the most momentum out of the materials I used due to its rough surface. From the trials I conducted (See Appendix A), I discovered that the felt most inhibited the momentum of the marble. The sandpaper actually had the second fastest trial which was a surprise to me. This could have been because it was not a particularly thick brand of sandpaper. I would probably repeat this experiment using a rougher, thicker type of sandpaper and compare the results. From the results I concluded the fiber of the felt is what slowed the marble the most. From what I know about forces and momentum, I have to conclude that the felt provided the most amount of friction against the marble. I had to wonder if this is why felt is used on pool tables. Perhaps if the tables were made out of different materials, the balls would fly right off the table.

I think the experiment might have worked better if my ramp was not as steep. I might use a more gradual incline so that the marble would not travel as quickly. I might get more accurate measurements with the stop watch this way. Also, it would be interesting to try the same experiment with different types of balls other than marbles. A plastic ball would cause more friction than a marble because of static.

If I was doing this in a classroom, I would provide my students with a list of questions to choose from just as we were. Then, each group would be doing experiments about a similar concept but exploring different aspects of it. I would probably have the students then present their findings to the class after their experiment so that all the groups can share their discoveries. This would be a good way to incorporate technology into the lesson as the students can present their information in the form of graphs or photo presentations.

I would ask the students to make real world connections with the experiments they did. We could then use those connections to further this assignment turning it into an engineering lesson. For example, if the students discovered that the more friction a surface provides, the slower the momentum and they connect that to the fact that they might not go as fast down a grassy hill than down a paved hill, I might ask them to construct a model racetrack using materials that would be conducive to biking quickly, yet safe to ride on.

I would want students to discover the various forces that are acting on the marble that cause it to gain or lose momentum. I want them to realize what aspects of a material will cause it to cause more friction than another material. Also, I would want them to practice the proper way of going through the process of designing and implementing an experiment.

Appendix A

Time (seconds)
Material	Trial 1	Trial 2	Trial 3	Average
Cardboard	0.65	0.59	0.49	0.577
Felt	0.86	0.79	0.86	0.837
Foam	0.80	0.64	0.65	0.697
Sandpaper	0.75	0.49	0.50	0.580