Heat Insulators Experiment

           

This week, I performed an experiment on heat transfer. Before the experiment, I learned that heat is transferred by conduction, convection, and radiation. Conduction takes place when two substances are in direct contact with each other and energy transfers from molecule to molecule. Convection is the method of heat transfer in liquids and gases in which heated molecules in fluids and gases gain higher kinetic energy and move in a circular pattern called convection current. Radiation is heat transfer through space via electromagnetic waves. This week’s inquiry assignment deals with insulators and heat conduction. 

I was asked to use scientific inquiry to determine which materials are the best insulators. I began by gathering the materials: four identical mugs, four rubber bands, one thermometer, hot water, and a timer. I chose to test foil, bubble wrap, polyester material, and a cotton cloth. My initial hypotheses were that the aluminum foil would be the worst insulator since metal is a good conductor of heat and electricity, and the polyester cloth (from a scarf) would be the best insulator. Since this thin polyester scarf has kept me warm in cold weather, I thought that it may be a better insulator than the cotton wash cloth or the bubble wrap.

I poured six ounces of hot water into each mug, covered the tops with the four test materials, and secured them with rubber bands. After thirty minutes, I took the temperature of each to determine which water remained the warmest. My results were as follows: the water covered with foil was 46 degrees C, the bubble wrapped covered mug was 47 degrees C, and both the polyester and cotton cloth covered mugs were 48 degrees C. My hypothesis that the foil would be the worst insulator was correct. The bubble wrap was a bit better. I thought that the polyester covered mug would be the best insulator, but actually the cotton wash cloth was just as effective.

           
One difficulty I faced when doing the experiment was that I only had one thermometer. While I took the temperature of the first water mug, the other three mugs were cooling off. If I had to do this experiment again, I would make sure that I had four thermometers. Even though I do not think that my results would have been entirely different, they could have been more accurate.

If I were to test another material to find a good insulator, I would chose polystrene foam. I read that styrofoam (or polystyrene foam) has trapped air pockets which help insulate material. Fiberglass used to insulate homes uses the same method. Since glass and air are good insulators, small fiber of fiberglass trap air pockets which help keep homes warm.

Inquiry Lesson : Law of Conservation of Momentum

This week I have been provided with a question to explore through a guided inquiry investigation. The question is “What is the effect of large objects colliding with smaller objects?”. To find the answer to this question, I gathered the following materials: large marble, small marble, two meter sticks, paper, and pencil. On a table, I taped the meter sticks parallel to each other about an inch apart. I placed a small marble at the center on the “track” and the large marble at on end. I rolled the large marble toward the smaller one and recorded what occurred on a data table after the collision. I repeated this ten times. Each time the large marble hit the stationary small marble, the large one caused the small one to move in its same direction but at a faster speed.

 Next, I asked a friend to help with another marble collision scenario. She stood at one end of the table and I stood at the other. We rolled the large and small marbles toward each other with about the same force. We repeated this ten times, recording the results on a data table. Each time, the smaller marble changed direction and quickly rolled back in the direction it came from after the two marbles collided. The large marble continued in the original direction, but slowed down after striking the smaller marble.

Before performing this experiment, I hypothesized that when the large, more massive marble hit the stationary small marble, they would both move in the same forward direction. I was sure that the smaller marble would roll faster than the larger one because I knew that the momentum of the more massive marble would transfer much energy to the smaller one. My hypothesis was correct for this first experiment.

For the second experiment in which the two marbles move toward each other and collide, I hypothesized that the large marble would stop in place and the small marble would roll in the direction opposite of its original motion. My hypothesis was incorrect because the large marble did slow down, but it did not stop completely. After thinking about this situation, I feel that if the smaller marble had a bit more mass or traveled at a greater velocity, the larger one may have stopped completely. The mass of the small marble was not enough to halt the motion of the large marble.

The experiments were simple and worked out well. When I do this experiment with my eighth grade class, I may modify the experiment by having the students roll the small marble at the stationary large marbleas well to see what happens. I would probably  have the materials on each table ready for the students. For this particular activity, I would give the procedure to the students. There aren't many multiple ways to make this work, so unless the students can come up with the exact experiment procedure on their own, they won't see accurate results.

To make this activity more engaging, I would make momentum relevant to their lives by using examples they can relate to before the activity, such as sports examples and the motion of amusement park rides. By the end of the activity, I want the students to understand that momentum is not lost when a collision occurs (besides some lost to friction), it is just transferred. I think this activity will be successful in the classroom.