Symposium: lecture and learning: Rre They Compatible?
Use of the Particle Nature of Matter in Developing Conceptual Understanding Dorothy L. Gabel Indiana University, Bloomington, IN 47405
Several years ago, a paper was presented at a conference bv Rrenner ( 1 , who described a studv about 5- and 6-vear;ids in a cit; environment who hadlearned to go the grocerv store to Durchase soft drinks. ~opsicles,and the like. ~ h ; children'handed ? the clerks quakers and dollars for their purchases, and the clerks and other customers made certain the children received the proper change. These children then entered first grade and began their formal study of mathematics (arithmetic). In the unit on money (included in first made to make arithmetic relevant and useful) they started with pennies. This was quite new to the children because they had not dealt with pennies before. When a picture was shown of a cup of lemonade that was labeled "5 cents", the children thought that the nickel was for the cup alone! After all, in their experience, they never could buy much of anything for five cents, let alone a cup of a beverage. They knew that if they used pennies to buy the confections in their local deli, the clerk would not be happy about having to count out all of the money, nor would the persons behind them in line waiting to check out. From their practical experience, the children became "dollar wise" and were not "penny foolish." The children did learn about pennies however. They knew that they would be tested onit, and they also wanted to please their teachers. What the children did was to compartmentalize their learning. School learning went into memow and real-life leaminp one art of the lone-term .. into another. It was not until their teachers opened a store in their classroom in which children trctuallv sold candv, etc. that the children were able to relate these two kinds of knowledge. Chemistry Learning and Teaching This study has much to say about how students learn chemistry and about how chemistry is taught. For several years, Johnstone (2)has been discussing the three levels on which chemistry can be taught: atomslmolecules (microscopic level), sensory (macroscopic level), and the symbolic level. Using an equilateral triangle with a level a t each vertex, any point within the triangle can represent the percentage of time allocated to using a given level in the teaching of chemistry. As Johnstone has pointed out, a t the present time most chemistry courses are taught a t the symbolic level with little emphasis on the microscopic and the macroscopic levels. There are many research studies that a t least indirectly substantiate Johnstone's claim (3-9). The few examples given here illustrate the point. Sawrey (6) found that when chemistry problems emphasizing either the microscopic level or the symbolic level were administered to students in a n introductory chemistry course, signilicantly more students were able~solvethe ~roblrmsthat used svmbolii and numbers than could solve Fmm interviews of students who ihose depicting had solved problems aloud, Bunce and Gahel(7) found that students used a "Rolodex" approach to problem solving. Students indicated that they flipped through the formulas
in their mind until they came upon one that fit the conditions of the problem. They rarely, if ever, thought about the phenomena itself. A study by Osborne and Cosgove (8)showed how little students in New Zealand a t several age levels (7-17) understood about the particle nature of matter or about chemical phenomena in their everyday lives. What is surprising about the results of their study is that some of the explanations that students gave to common phenomena, such as, that when water boils, the bubbles seen in the liquid are "air" or "a mixture of hydrogen and oxygen," are ideas that they have formulated after formal school instruction. Bodner (9) sought to determine how prevalent these ideas were among the graduate students entering the doctoral Droeram a t Purdue University. He asked enteringgraduite kudents for the past sever& years some of the same questions used hv Osborne and Cosmove. His findings indicate that someof the same nonscikific explanations persist for some students even aRer a n undergraduate major in chemistry. There are several oossible ex~lanationsfor the findinm from the aforementioned studies. The simplest one is t h i t chemistry teaching emphasizes the symbolic level and problem-solving a t the expense of the phenomena and particle levels. Another explanation is that even though it is taught a t the three levels, insufficient connections are made between the three levels and the information remains compartmentalized in the long-term memories of students. A third explanation is that even if chemistry was taught on the three ievels and the relationships among the levels were emphasized, the phenomena considered were not related to the students' everyday life. Students compartmentalized the knowledge as that learned in school versus that needed in everyday life, just as the children who had become dollar-wise had, and a s a result, the knowledge was not readily retrieved. Teaching about the Particulate Nature of Matter In an effort to determine whether students' understanding of chemistry would increase if the particulate nature of matter was emphasized, a study involving high school students enrolled in an intmductorv chemistrv course was conducted. It was hypothesized chat by emphasizing the particle nature of matter, chemistry achievement on all three levels would improve. The reasoning behind this was that when the particle level is emphasized in instruction, this cannot be done in isolation &om the sensory level or its symbolic representation. At least one of the other two levels must simultaneously be included in the instruction. Hence in stressing the particulate nature of matter, students would relate knowledge a t two or three levels. The s a m ~ l consisted e of three chemistrv classes in a consolidated &hool district in the midwest."~heteacher who had six years of teaching experience randomly selected one class as a control class and two as treatment classes. After eliminatinp students for whom data were incomplete or for permission was not obtained, 90% of the whom
Volume 70 Number 3 March 1993
193
Mean Scores of Responses by Students with and without Particle Nature of Matter Instruction Treatment Class 1 (n =_20) Total score Symbolic score Sensory score Particle score GALT score
Control
Class 2 (n =-23)
Class 3 (n =_23)
x
X
X
22.85 8.10 7.70 7.60 7.50
23.26 8.30 8.08 7.43 6.48
17.96 6.40 5.87 5.65 6.04
Maximum total score = 60; each subscore maximum = 20. Maximum GALT Score = 12.
enrolled students were included in the study with 23 in the control group and 20 and 23 in each of the treatment groups. 1&tmction in the control class used the same approach that the teacher had used over the past few years. For use in the treatment classes. the teacher was orovided with 25 different worksheets that required students to link the particulate nature of matter to either physical phenomena andfor to chemical symbols. In addition, a set of 20 overhead transparencies that portrayed the particulate nature of matter was supplied. This gave the teacher 45 opportunities throughout the year to emphasize particles with the treatment classes that went beyond those given in their text. Visits to the classrooms on two occasions showed the teacher using the transparencies, worksheets, and even circle cutouts representing atoms and molecules held on the blackboard using magnets. Because the study occurred with previously formed, intact classes, there was no assurance that the students in the control and treatment groups were equivalent in leaming ability. To control for this, the Group Test of Logical Thinking (GALTI devised by Roadrangka et al. (10)was administered to students during thefirst month of the school year. Data from this 12-item test could then be used as a covariate in the analysis of the students' achievement. Since the major objective of the study was to determine whether there was 'difference in achievement on each of the three levels (macroscopic,microscopic, and sensory) for the control and treatment classes, test items on each level were written resulting in a triad for each of the 25 areas for which there were worksheets. These were administered to students as part of their unit tests throughout the school
194
Journal of Chemical Education
year. The data on which this study is based consists of 20 triads or 60 items because when the data were summarized, only 80% of the instruction had occurred. The KR-20 reliability was 0.71. Data from the study are summarized in the table. Examination of the table shows that the treatment classes performed higher on not only the microscopic level which might have been predicted because of the additional instruction that they received, but also on the macroscopic and on the symbolic levels. Although the control group had a slightly lower GALT mean score, this would probably not account for differences in chemistry achievement. In fad, for the two treatment groups, the one with the lower GALT score outperformed the other. When the overall achievement scores were analvzed wine an analvsis of covariance with GALT scores as the covari&, the dkference between the control and treatments m u ~ was s simificant (F = 4.1) a t the 0.02 level. Although this study was small in scope, and needs to be redicated on a much larger scale, it seems to indicate that instruction on the p a r t i d a t e nature of matter is effective in helping students make connections between the three levelsonkhich chemistry can be both taught and understood. Disappointing, however, is the overall low mean scores that students had on each of the levels of chemistry. In no case was the mean a t even the 50% level. Whether this is because the triads were based on the content that is traditionally included in a chemistry course and students see little connection between it and the real world is not known. Perhaps emphasizing the three levels of chemist~y to describe common, evervdav ~henomenato which students could relate would mak;! the instruction more effective. Or perhaps, there is just so much content included in thc traditionai c h e r n i ~ t ~ ~ othat u r ~students e can only be cxwcted to leam ahout 50rll of it. No matter what the explanation, this study and those cited earlier show that chemistry educators have a long way to go to improve the understanding of chemical concepts a t the introductory level.
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Literature Clted 1. Bmnner, M. E. NARSTAnnual Conf~renoe,unpublished result;r,l%89. 2. Johnstone.A.ACS Meetinn. WashinntotonDC. unmbliahed resdta. 1990.
7. B-&D. M.; Gabel, D. L. J Rer 5%. &ch. lW1.28.505-521. 8. 0sbmne.R. J.; Coagoue, M. M. J a s . Sci. TPmh 1983,20,825-838. 9. Bodner, O. M., submitted for publiestion in J Chem. Edw. 10. Roadrangks, V.; Yeany R. H.; Padilla, J. M. NARS'I Annual Canference, unpublished paper, 1983.
