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GARYE. DUNKLEBEROER Garroll County Public Schwls
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Integrating an Instrumental Approach in High School Chemistry R. Chrls Rohde Chippewa Falls Sr. High School, Chippewa Falls, WI 54729 The most vexing issues in teaching high school chemistry tend to focus on either content or the aooroach used to oresent the subject matter. Perhaps equal att&ion should de given to the laboratom Droeram. An effort to use instruments effectively during the experimental process can be most worthwhile. The utilization of instrumentation adds a new dimension to problem solving. It helps the students relate the subject matter to modern experimentation in chemistry. Instruments also provide a motivational approach that enhances learning, but most imuortantlv a forum to teach . thev-~rovide . the process of science. Typically,the use of laboratory instruments in a high school chemistry course is limited. This is partly caused by the small budgets available to teachers for the laboratory portions of their courses. It is also caused by a general belief that the level of laboratory work in high school does not warrant an instrumental approach. As a result, instruments such as pH meters are seldom used for more than demonstration purposes. Equipment is often viewed as a novelty or a gadget which has true value only when used by the "real chemists." As the advent of technology has expanded rapidly the use of instruments in universities. research. and industrv. the eaD between high school chemist& and the modern chekicaliab has widened. Several of mv former students have commented on this disparity. Their remarks reflect a growing need for better lab preparation at the high school level. The "future shock" that s&dents experience-in chemistry labs after high ~choolis somethina of which teachers should he aware and should attempt to alleviate. For some time I have considered ways to correct this situation when planning my laboratory program. However, I was initially confronted hy several problems. First, budget restrictions precluded the purchase of large quantities of high quality instruments. Secondly, I believe in the inherent value of most high schwl laboratory experiences. It is important for each student to master the basic lab skills and techniques presented in an introductory course. A lab program which emphasizes an instrumental approach might comprise student achievement in this area. Finally, to plan an experiment around a particular piece of equipment merely exaggerates the novelty of its use. The solution is to continue to emphasize desired experimental ohjectives and to utilize available instruments when they can contribute to the achievement of those outcomes. Another successfulapproach has been to intearate more than one instrument to ill&rate the complement& roles they play in research. Surprisingly, this is easier to accomplishthan one might expect.
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Garden. Glen, "The Delicate Balance. An Environmemal Chemistry Module." 1st ed., Harper 8 Row, Publishers, New York, 1973, p. 21.
This was first revealed to me by a group of students, enthusiastically caught up in an actual chemical study which they had initiated themselves. As they found themselves confronted by one complex problem after another, they were able to use an instrument to solve the particular problem. Rather than developing discrete lessons around specific instruments, this approach maintains a steady focus on the objectives of the experiment while incorporating invtruments at strategic times when they prove useful. Instead of a series of demonstrations of isolated instruments. this method r e v.d-a more realistically how various instruments are used during research. Uslng Instruments to Achieve Experimental Objectives The students' project involved a variation of the IAC experiment "Don't Feed the Algae."' This experiment involves making qualitative observations of algae growth in various nutrient-poor solutions and then relating the results to environmental pohtion. The purpose of the students' uroiect was to see if they could improve upon this experimeni lthas decided that their first task would he to quantify the obsena-
Chrls Rohde has been teaching a1 the secondary level for nine years, the last seven at Chippewa Falls Sr. High School. He teachers sections of Chem-Study and General Chemisby. Fw the past three years. he has also served as Secondary Science Curriculum Assistant. He received his BA from the University of New Hampshire in 1975. end his ME from the University of Wisconsin-Eau Claire in 1979. He is a member of the Wisconsin Society of Science Teachers, the National Science Teachers Association, and Phi Delta Kappa.
Volume 61 Number 8 August 1984
711
tions. T o do this, they made use of our student spectrophotometer. As in any scientific investigation, they soon discovered that solving one problem usually leads to another. To gain greater experimental control, they used unialgal cultures which led to the need for sterilization and the use of the autoclave. T o achieve greater accuracy, an analytical balance was used to prepare the nutrient solutions. A pH meter was added t o monitor the acidity of the media during the course of the experiment. A filtering apparatus allowed the students to exnand the narameters of the exneriment and to draw conclu;ions abobt the levels of pollut'ion in local water supplies. Besides the excitement of learnine and discove~.one of the most valuable aspects of the project was the way so many different nieces of eouinment were inteerated into the roblem-solving process. %students realizeb that they couid not have comnleted their investigations without the instruments which gave them confidence in the accuracy and reliahility of their findines. ~ l t h o u g h t h i is s an isolated example which involved only a small group of students. it is possible to incorporate an instrumeital approach in &no& any high schobl chemistry lab. Obtaining Equipment for a High School Lab
One of the first concerns is the availability and practicality of the necessary equipment. I t is possible that much of the equipment desired is available already. Many high school chemistry labs have the basics, such as a pH meter, a centrifuge, a hotplatelstirrer, and an analytical balance. Other equipment can be borrowed from the biology and physics classes: a sterilizer or autoclave. an ultraviolet source. a spectrometer and discharge tubes, various camera equipment, a Geieer-Mueller tube. electronic meters. and perhaps even a laser. Additional items may be desired, including equipment which was previously considered too extravagant or too expensive. Fortunately, the market offers a wide variety of good instruments which most high schools can afford. Usually, these are student models of more precise research instruments. Our high school has a student spectrophotometer which is used extensively. Some of the other equipment we have found valuahle and still affordable are a melting point apparatus, a dry ice maker, and various nucleonics instruments. - ~ ~ - ~ As with any budgeted item, the amount of use must justify the cost involved. fi is wise to develop a long-range plan since it may take several years to accumulate all of the equipment desired. ~
Wide Student Participation
Another important concern when developing an instrumental approach is involving all students. But teachers can
712
Journal of Chemical Education
find ways to involve students without drastically altering the lab program of their course. I t is seldom feasible for all lab groups to use a single piece of equipment in one lab period. However, a classroom set of any one type of instrument is not financially feasible. One useful technique is to provide an instrumental alternative for each of the experiments ordinarily undertaken. One lab group is selected to do this alternate version while the rest of the class follows the usual procedure. The selected lab group gives a brief presentation of their experiment during the nost-lab discussion. In this wav. the entire class can share in ;hat they have learned. his isdone on a rotating basis so that each student will have a t least two or three onnortunities for direct involvement in the instrumental approach during the school vear. o n e bf the experiments we do is a study of phase changes. The students develop a mling/heating curve from their data. The instrumental version of &is experiment uses the melting point apparatus to determine the eutectic curve of a twocomponent mixture. The analytical balance is used to prepare the mixtures. This integrates a complementary piece of equipment and teaches a valuable lesson in the use of significant fipures. noth her simple example is to replace chemical indicators with a pH meter in an acidbase titration. Whenever pwible. the alternative experiments make use of as many pieces of equipment as are appropriateso that each student is familiar - witha wide variety of instruments. I have found that these instrumental versions stimulate interest in the subiect. A comnarison with the usual nrocedure helps to clarify ex~erimentaiobjectivesand emphasizes how the narticular nroblem was solved or ohiective achieved. In addition, the teacher can encourage extra credit, enrichment, and indeoendent studv activities which relv on instrumenmaster s k i , or achieve experimental tation to solve objectives. ~
Integrating an instrumental approach in high school chemistrv can sianificantlv. improve the quality of the labo. ?he students who complete the course have ratory a more realistic understanding of modem chemical lab work. Those who continue their study of chemistry beyond high school are better prepared t o meet the expectations of their college professors. For all students, the problem-solving process is often clarified, sothey learn more about scientific investigations and the subject matter presented. From the teacher's viewpoint, an instrumental approach is an effective technique for arousing student interest. The students learn more when they are motivated by what they are doing. Best of all, an instrumental approach is easy to implement. To start, take the instruments you do have out of their storage areas, dust them off, and begin experimenting!
