Heat Transfer

I set up this experiment by using only three insulators instead of the four that we were told to use.  I did this because of a lack of supplies, primarily beakers, and because of the need for a control in this experiment.  I used cheesecloth, a hand towel, and aluminum foil for my insulators.  The water that I used had an initial temperature of 25°C, meaning that this is the temperature that the water could possibly cool down to after being heated, if given enough time to do so.  I heated the water to 72°C and put 200mL of water into four separate beakers (instead of mugs).  I put each insulator tightly on separate beakers, put a rubber band around it, and waited 30 minutes.  After 30 minutes, the control beaker’s temperature cooled to 39°C, the cheesecloth to 41°C, the hand cloth to 47°C, and the foil to 51°C.  Based on just this information alone, I could adequately conclude that the aluminum foil served as the best insulator. 

Additionally, however, I noticed that the beaker that had the foil over it also produced the most condensation.  Condensation decreased as the difference between initial and end temperatures increased.  This was due to the following reasons, as the water cooled, thus meaning that heat energy was released, condensation occurred.  But, as this cooling process continued, condensation exceeded the rate of evaporation, thus reverting water molecules that were in the gaseous states as a result of the hot water releasing steam back to the liquid state.  Because there is little room for these molecules to move, the water molecules, in the liquid state, stick to the sides of the beaker.  Therefore, the efficiency of each insulator was shown through the end temperature and the degree of condensation. 

All in all, this experiment was a simple demonstration of conduction and an easy way to test the efficiency of a variety of insulators.  Conduction occurs when heat energy is transferred from a warm area to a cooler area, from molecule to molecule.  In this experiment, heat energy was simply transferred from the water in the beaker to the outside environment.  The water was warmer than the outside environment temperature, and therefore “escaped” from the water into the air. 

It makes sense to me, and I could be wrong, to say that the reason that the foil was the best insulator is due to the fact that it is the most solid insulator.  In other words, the foil’s structural molecules are the closest together, thus trapping the heat energy, and any gaseous water in the beaker at the greatest rate. 

Although I did not test this, I would hypothesize that these insulators would work the same, or relatively similarly on alternative substances.  In other words, foil would keep heat energy in these materials most efficiently, just like it did for water.  The overall ability of these materials to retain heat, however, is a much more difficult question, as it brings in the concepts of heat capacity and the first law of thermodynamics.  A substance with a higher specific takes longer to heat up because more energy is required in order to raise its temperature 1°.  Due to this fact, a substance with a higher specific heat heats up slowly, holds a greater amount of energy, and cools down slowly.  Therefore, if we were to test the efficiency of insulators on alternative substances, such as spaghetti or a hot dog, those substances with higher a specific heat will naturally take longer to cool down.  

Engaging in Guided Inquiry with Marbles!

During this guided inquiry experience, I chose to discover answers to the following question: How do different surfaces affect the momentum of marbles?  Initially, my head started spinning with possibilities regarding this question.  Although I did not test this, I even played around with the idea of testing on hot and cold surfaces.  Instead, I took the generic route, due to a time crunch in the past few days, and tested two marbles, varying in mass and size, on four household surfaces; carpet, a bed comforter, a smooth hardwood floor, and a tiled kitchen floor.  As I brainstorm ideas for this experiment and started going through the different variables that would be relevant, I soon discovered that I would need to have a very specific set of parameters for each test.  For example, when I tested each marble, it was rolled, with no exerted force from me, down a folder that was propped up against a 1.5-inch book.  To ensure that the folder was placed at the exact same spot for each test, thus ensuring the same exact slope each time, I marked the sides of folder at 9.5 inches, designating where to place it on the book.  Additionally, I used this same mark as my placement from which to begin rolling the marbles.  I rolled each marble individually, and started with the front of the marble placed on the line on the folder.  Lastly, I placed a yardstick at the base of the folder (where it meets the floor).  I measured all tests in centimeters and kept record of how far the marbles rolled according to the rear of the marble.  I performed trials for each marble on each surface three times, then calculated an average for each.  I recorded this data in an Excel chart (found below, modified for formatting reasons). 

After compiling my data and performing each trial, I came to the following conclusion.  When these two marbles, varying in size and overall mass, are rolled from a constant position on the folder, thus allowing for acceleration to build up from a consistent distance, the marble with the greater mass will travel a greater distance on any of the surfaces tested.  This is primarily due to its higher mass, which causes it to gain more velocity while it is traveling down the slope of the folder, thus gaining more momentum when it hits the base of the folder.  This momentum is then carried off the slope onto whichever surface and is transferred to distance. 

In addition, after this experiment was complete, I found a few variables that were not efficiently controlled in this experiment that could very well have affected my results.  For example, the marble almost never traveled in a straight line.  Also, the marble did not always leave the folder at the same spot, thus causing it to travel a different path on the tested surfaces.  Both of these variances could have easily affected my results.  Now, I would not conclude that these variances would have affected my overall conclusions, however.  Regardless, if I were to perform this experiment again, I would modify by setup in order to account for these obstacles. 

In the classroom, students would highly benefit from an experiment on momentum like this.  The guided inquiry process, which only supplies students with a question to study, truly allows students to take control of their learning and make their own discoveries in science.  When this is achieved, the retention of knowledge is much more likely.  If this were a classroom activity, I might make the question more open to the use of a variety of materials.  For instance, rewording it to state, “How is momentum affected by different surfaces?”  This gives students the opportunity to still design an experiment, but does not hold them to using only marbles.  Additionally, if marbles were used, I would have students calculate the mass of each marble and analyze how the specific mass affects momentum (as observed through distance traveled).  Is there a ratio in play here?  To further analyze this question, a more varying range of marbles could be provided as well. 

Data: (in centimeters to the nearest half)

Blue Marble (on carpet)

1: 48.5

2: 43

3: 48.5

Average: 46.7

Green Marble (on carpet)

1: 61.5

2: 58.5

3: 56

Average: 58.7

Blue Marble (on comforter)

1: 10.5

2: 16

3: 16

Average: 14.2

Green Marble (on comforter)

1: 16.5

2: 17.5

3: 15

Average: 16.3

Blue Marble (on smooth floor)

1: 224.5

2: 232

3: 224

Average: 226.8

Green Marble (on smooth floor)

1: 270.5

2: 283

3: 278.5

Average: 277.3

Blue Marble (on tiled floor)

1: 169

2: 184

3: 172

Average: 175

Green Marble (on tiled floor)

1: 202

2: 215

3: 217.5

Average: 211.5