An Activity-Based Approach to Chemistry I Mkhael J. Demchlk and Virginia C. Demchik Jefferson High School, Shenandoah Junction, WV 25442
At Jefferson High School students have come to Chemistry I with little or no laboratory experience. Rather than teach a traditional program and start the school year with textbook orientations to measurement and the traditional initiating topics, we start the school year with a rather intense activitv-based proeram. In this nromam students are in the laboratory daiiy, either for all of ihe class period or some part of it, during the first six weeks of the course. Thev perfoim experiments and develop "initiator concepts" foi later use in this course and other courses that follow such as Chemistry I1 and Physics. The "initiator concepts" are those that we feel are preliminary to the development of a strong foundation in the physical sciences. Many of the concepts that are taught in the early sections of a traditional course are incornorated into this format. The coke has had a strong impact on both students who have had lab experiences and those who have not. In this paper we will provide an overview of the course. Those requesting additional information can contact one of the authors. The course is first-year chemistry taught to students in the 11th and 12th grades. The size of the classes averages 22 students. Six or seven classes each year have been taught in this manner over the last three vears. The laboratory procedure h& been reduced to six weeks this year, although when it was first initiated the process took students more time. Initially stress is placed on listeninr! skills and all orelab information is nresented verballv. ~ i e r are e no "cookbook" directions. ti dents begin by 06serving a "black liquid". After written observations are made,they are askedto take their observations to a friend or a former teacher to determine whether their observations are good enough to identify the liquid. Needless to say, the observations, while they may be good, are not enough to identify the material. From this point, the students embark on the task of identifying the liquid through physicalproperties and se~arationtechniaues. The black liquid is filteied to determine if there are any solids that are suspended. While no solid is found to be on the filter paper, students find evidence of various colors emerging from the black liquid. The discovery lends itself to paper and column chromatography. Other physical properties such as density, boiling.. point, and freezing are .point . attempted. Density is determined by the standard methods, and a histoeram of the resultine data is made. The freezine noint is founz to be lower than th;? students had expected. TGliquid is distilled to determine its boiling point. Students find that there are two plateaus, one at 66 "C and the other at 100 OC. Samples of each distillate are collected. The sticky black residue in the distillation flask is air dried and tested later. This indicates at least three components to the mixture. The density and freezing point for each distillate is then determined. The high-boiling component is determined from its physical properties to be water. An initial reading of the lower component is also taken and found tomatch that of methyl alcohol. Students are told when heating the sample not to beat it to complete dryness.
The result is a sticky black mass. I t is allowed to drv and later is ground. ~ a c r b s c o ~and i c microscopic examination of the hlack residue is attemped with no success. There appears to be no fixed melting point when macromelting and micromelting are attempted. In order to see how the melting and micromelting gave definite melting points, phenyl salicylate (44 'C) was used. Part of the residue was checked tosee if the sample would dissolve in water and alcohol. senaratelv. A rhrknatograph of the alcohol solution and thea&ous shution of the reridue is com~leted.It orovides R,value~for the different components. The residue (more needs to be nreoared at this noint). is then placed into the hood and heaied:~lmost an immediate decomposition is observed. The vapor eiven off has a definite odor. It raises questions aboutthenature of gases and vapors. This leads to the study of gases. At this point the properties of gases are examined but the problem is not solved here by wbat they learn.
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Impasse For students the oroiect amears to be at an imnasse. Full separation of the & ~ < ~ risnot e accomplished at this time. Students are told that tbev needed to learn more than wbat they know at this point t o be able to solve the problem totally. They are challenged to look for a solution as the year progresses. They are reminded of what they accomplished and the techniques they used.
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Accountability All of the accomplishments are an admirable start into Chemistry I. During these activities students kept journal entries. They received a daily in-class lab grade as well as a grade for their journal entries. At the end of the six weeks of work, they prepared a full-scale laboratory report for which they received an additional grade. The teachers write a lab report, and the students compare theirs to the teacher's. Testing for this section of work is a situational-type format based on the processes involved. Questions are develoned that are of the application type. N ~ Wsituations are d&eloped and students respond by using the processes learned throughout the course. The Search Goes On After completion of this segment students move to a slightly more content-oriented program, all of the time keeping an eye open for something that will help them solve the black liquid riddle. At a later noint in the vear. after much more traditional content is covered, students c&ry out some additional practical chemistry: labs, including determination of aspirin content in various products, vitamin C in orange juices, antacids in various products, and various dyes used in dye products. In each case, the economics of producing the most value for the money is included. Attempts a t solution to the black liquid problem are made again at this time. Students are told that the answer is within reach. Manvalreadv know that the samoles can besenarated both on the basis of physical and selectedchemical reactions. The CRC Handbook and the Merck Index Volume 66
Number 11 November 1989
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provide much of the needed information. Actual separation is a moot ooint at this staee - of the ~rocess. Student Success
The experiences are very useful for setting the stage for those who will go on to Chemisry I1 and Physics. But even those who do not go on to advanced courses have had the opportunity to attempt to solve a problem. They have all
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gained insight into the practical application of and even had a little fun being a "chemical detective". The faculty end students both indicate a successful venture. We have even found that there is on the average 12percentile increase in student scores. Posttest data from the Science form (form 4T) of the Comprehensive Test of Basic Skills was compared to pretest data taken early in the year, showed an average percentile change from the 83rd to the 95th.
