End-of-the-Year Projects and New Possibilities Ken Turner Schaumberg High School, Schaumberg, IL 60194 At the onset of September in my Advanced Placement Chemistry class, I look for an end-of-the-year project that will stimulate interest while simulating (at least in comparison to most high school classes) research or engineering. In the past two years I have been fortunate to team my classes with the Advanced Placement Physics classes. This gives u s a considerable pool of students while distributing our preparation among three teachers. Last year, following the lead of other teachers in this Journal (11, we had the students research, synthesize, and test high-temperature superconductors. This year we chose to investigate the properties of a piezoelectric film called PVDF (polyvinylidene fluoride; 1,l-difluoro ethene is the monomer). This project was chosen because i t satisfied three parts of our "wish list": cutting edge technologies, hands-on activities, and an interdisciplinary approach. We began our activities with a n introductory period. We told the students what we were going to do, divided them into groups, (usually a combination of physics and chemistry students), and informed them of their evaluation. The bulk of their evaluation would be a group journal t h a t needed to contain not only the activities and data of each day, hut also insights a s to new problems or areas they might pursue if time warranted. During this period, we also demonstrated some of the possibilities of PVDF film and the lab equipment students would use. The next two days were spent with oscilloswpes,computers, thermometers, and samples. The students tested the voltage output of the film in a variety of methods and conditions. In no time a t all they were tapping it, warming it, breathing on it, singing across it, and sometimes stomping on it. Soon, they were testing relationships of frequency versus voltage, force versus voltage, etc. Acomputer link allowed them to graph the data almost as soon as they took it. This allowed students to test more than one hypothesis during class time. The next lecture was on the history and theory of piezoelectric materials. This was difficult for us. Although the piezoelectric effect is well documented i n many materials, i t is not exactly common knowledge for high school teachers. We spent a large part of the 1992-1993 school year learning enough about the effect to teach the topic. The next two days were spent by the students in the lab again, this time studying some of the applications of the film. We had access to two infrared detectors as well as a vibrational sensor. We also had access to a frequency generator, speakers, and a tape recorder. (It turns out that this film can be made to act a s either a speaker or a microphone.) The final lecture covered the piezoelectric film as an example of a polymer. General forms of both addition and condensation polymers were discussed as well as many, many examples. (Recycling of plastics is also a n easy tangent.) Finally, the specifics in preparation of PVDF were discussed, including an attempt to explain why pulling and poling were instrumental in obtaining the B configuration of the solid form (which results in the film's extremely high piezoelectric properties). Again, the next two days were spent in the lab. This time the students made and tested three polymers: polyvinyl alcohol, nylon 66, and polystyrene. These polymers were chosen for their ease of preparation in a high school lab. Although none of these will demonstrate appreciable piezoelectric effect, they serve a s simple examples of
polymerization. Thus, the students have a better foundation for understanding the structure of the extraordinary film (PVDF) with which they were working. After this brief "scramble" through piezoelectric effect, student teams chose from the following list the direction of the final five days on the topic. Student Choices 1. Design ar build a circuit that better demonstrated some facet of the piezoelectric film. 2. Design or build a specific application or new product that featured piezoelectric film. 3. Continue to investigate some aspect of the project that you feel requires more time. 4. Develop a molecular model that helps to illustrate the piezoelectric film we worked with.
The designs, from additional power sources located in automobile tires to analysis of the tensions in a tennis racquet to testing the polymers properties in various acid settings, allowed some very creative work by the teams. One of the most excit~ngthings that happened a; a result of this pr+m was the npplicntion ol CHI
