Teaching an Introductory Course in QualitativeAnalysis in Order to Enhance Learning General Chemistry Ruth Shamal and Ruth Stavy School of Education. Tel Aviv University. Tel Aviv, Israel Many reports describe difficulties that students have in understanding concepts related to the subject of electrolytes, such as solubility, ionic reactions, ionic equilibrium, acid-base euuilibrium. hvdrolvsis. etc. (1. 2). It has been suggested that the difficuity students havein understanding scientific ideas and concepts is a result of their inat~ilitv - to use the strategies of abstract thinking reliably (3,4). Psychologists such as Bruner and Piaget have attempted to define formal or abstract thinking. The work of Inhelder and Piaget (5) is the primary source on formal thinking. Their research presents the characteristics of concrete and formal thinking and develops a variety of tasks designed to elicit the abstract thought processes of formal thinking. Aconcrete-thinking individual uses logic based on his own experiences. He can make simple generalizations and classifications, and follow step-by-step instructions. Since a concrete thinker must have direct experiences, he can understand concepts only in terms of familiar actions and experiences. Finally, he is not spontaneously aware of his own raaaonine. . ---. -. . .u A formal-thinking individual recognizes and interprets functional relationships even in situations described by ahstract variables. He can imagine many possible combinations of theoretical conditions, formulate hypotheses, and devise experimental tests. Finally he is aware of and is able to evaluate his own reasoning. ~e has developed a wide repertoire of problem-solving skills. Many reports have indicated that a large proportion of high school students does not use formal thinking when solvina- oroblems and dealine with conceots related to sci. ence, yet in many science courses concepts and principles are developed through formal-thinkine processes. It is ~ossible. therefore, that tge thinking level o?hany studentshoes not coincide with the level at which conceots are presented (3.4. 6 ) . One approach to this problem is io limit the scope and depth of thecurriculum for those students who think onlv in concrete thinking modes. A second approach is to search for instructional strategies or teaching methods that will make high level concepts more readily attainable for students who have not reached the level of formal thinking. The present study is concerned with the second approach. The purpose of our study was to test whether a short introduction course on uualitative analvsis nrior to teachine the chapters related td the subject o i ele&olytes, woulz enhance students' understandine of the different hieher level concepts and ideas related to this topic. It was expected that handline ionic substances. observing their behavior (dissolving, precipitating, etc.), a n d using chemical symbols to describe them in a problem-solving situation, would serve as a concrete basis on which related higher-level formal concepts could be more readily built up by all students and especially by students who had not yet reached the level of formal thinking.
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Sub)& Seventy-three students (21 males and 52 females) aged 17-18 from an urban high school that draws its students
from an upper middle class population participated in the study. All students were chemistry majors and studied four hours of chemistry per week. oesign A post-test-onlv. control-mouo desien was used. One class was assigned to the experimLntai group and another class to the control e r o u ~Students . were divided into the two classes randomly; the average grades in chemistry prior to the heginning of the experiment were not significantly different (control-77.3%, experimeutal-78.8%). The two classes studied the same course in chemistry: the chapters "homogeneous and heterogeneous equilib;ium" and 'acid-base equilihriurn" according to an accepted high school program in chemistry in IsraeLi
Assessment of Cognltlve Level A Piagetian-based paper and pencil test was used to assess thinkina level. The test. developed . . consists of - hv Lawson (7) 15 multiple choice items in the following domains: conservation of weight, conservation of volume, proportions, isolation and control of variables, combinatarial thinking, and probability. According to Lawson, students who answered fewer than 12 questions were regarded as non-formal. (Most of the students in the study could be classified as transitional rather than concrete thinkers.) No significant difference in the thinking level was found between the two classes (control-64.776, of formal-thinking students, experimental-58.8%).
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Treatment In the experimental class the studv of the two chanters was preceded by an introductory, 25-h course in analvsis. Durina the introductorv course students learned to identify severaiions in the following groups: cations: Group I: Agt, Pb2+,HgZ+ Group 11: CuZ+,Fez+,Znz+,AI3' Group III: CaZ+ Group IV: NH4+,K+ anions: Group I: CI-, Br-, J Group 11: S0.2.. C03g-, P043Group 111: NO3For each group of ions, students were tested by identifying an unknown ion. After recognizing the different ions, students practiced analyzing salts. The course was summarized by a test in which each student had to identify an unknown salt and to describe and formulate the processes of his or her analysis. The average grade was 78.3% (range-67-95%). The control class studied the regular, theoretical course program, without the introduction course.
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Chemistry for high school part II, the Israeli Science Teaching Center, Weizmann Institute of Science. Rehovot, Israel. 1973. Volume 63 Number 8 Augusl1986
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Mean Percents for Achievement Tests
Assessment of Achievement in Chemistry
Students' achievements were assessed by pencil and paper tests. Five tests wereadministered a t the end of studying the subtitles: acids and bases, hydrolysis, acid-base equilibrium, homogeneous equilibrium, and heterogeneous equilihrium. The problems in all the tests were checked by two experienced chemistry teachers (not by the authors) and were found suitable for assessing achievements in these topics. Two other chemistry teachers examined students' tests. No significant differences were found between the grading of the different teachers. In cases of small differences the average grade was used. All the test problems were grouped into four categories: (a) theoretical problems, (b) formulational problems; (c) computational problems; and (d) one general equilibrium problem. Reruns The total average mark of each of the two classes was: control-7090; experimental-82% with a difference of 1.5 standard deviations @
