A Design for Implementing Mastery Learning on Recrystallization, A Chemistry Experimental Technique Author: Cheng-Hsin Wang, Jhy-Ming Horng(Department of Chemistry, National Taiwan Normal University)

Abstract：

Chemistry research supervisors are often frustrated by the fact that students are not well equipped with the necessry laboratory techniques at the start of their research programs. The purpose of this study is to design a method of implement-ing mastery learning of the recrystallization technique to develop students' ability in performing it correctly, as well as using the technique to solve chemistry problems they will encounter later, in other words, achieving transfer of learning. Instruction-al materials and strategies were developed and organized to bring the students up to three successively higher learning levels: concrete, identity, and classificatory. The instruction was assessed by the degree of learning progress, which in turn was eval-uated by positive correlations between two consecutive tests, between task perfor-mance and test results, and among the results of a set of laboratory assignments. Progress of learning was observed in the rightward shifts of the S-curves and the downward shifts of the P-curves during a set of assignments. CPj. values of all items were less than 0.40. In the plots of Pj vs. CPj , all items were in upper left quadrant. These results indicate that all items were of good quality. An acceptably small degree of anomalous item patterns reflected unambiguous instruction. In each post-test 2 for the three levels all the CSi values for individual students were less than 0.40 and all the three D* values were less than 0.3896. Small CSi and D* val-ues indicate an acceptably small degree of learning difficulties and erratic studies (careless mistakes, copying or guessing responses) after instruction. Those students (100% for both the concrete and the identity levels and 91.3% for the classifictory level) with high scores in the paper-pencil test indeed obtained high yield and high purity. These facts were consistent with the learning gain shown in individual per-formance profiles. Once the students mastered the technique, they kept the ability. The progress of learning observed as discussed above indicated the effectiveness of our implementation method for mastery learning of recrystallization technique. These instructional materials and strategies were satisfactory for the college introductory organic chemistry labortory course. The methodology used in this study can be ex-tended advantageously to the study of instruction on other chemistry experimental techniques.

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