In this study, we defined and quantified the degree of cognitive conflict induced by a discrepant event from a cognitive perspective. Based on the scheme developed, we investigated the relationship between cognitive conflict and conceptual change, and the influences of students' cognitive characteristics on conflict in learning the concept of density. Subjects were 171 seventh-grade girls from two city middle schools in Korea. Tests regarding logical thinking ability, field dependence/independence, and meaningful learning approach were administered. A preconception test and a test of responses to a discrepant event were also administered. Computer-assisted instruction was then provided to students as a conceptual change intervention. A conception test was administered as a posttest. In analyzing students' responses to the discrepant event, seven types of responses were identified: Rejection, reinterpretation, exclusion, uncertainty, peripheral belief change, belief decrease, and belief change. These types were then ordered into four levels. The results indicated that there existed a significant correlation between cognitive conflict and conceptual change. t-test results revealed that there were statistically significant differences in the degree of cognitive conflict by the levels of students' logical thinking ability and field dependence/independence. Meaningful learning approach, however, was found to have no statistically significant effect on cognitive conflict. Educational implications are discussed.

ABSTRACT:In this study, students' views on the nature of science (NOS) were investigated with the use of a large-scale survey. An empirically derived multiple-choice format questionnaire was administered to 1702 Korean 6th, 8th, and 10th graders. The questionnaire consisted of five items that respectively examined students' views on five constructs concerning the NOS: purpose of science, definition of scientific theory, nature of models, tentativeness of scientific theory, and origin of scientific theory. Students were also asked to respond to an accompanying open-ended section for each item in order to collect information about the rationale(s) for their choices. The results indicated that the majority of Korean students possessed an absolutist/empiricist perspective about the NOS. It was also found that, on the whole, there were no clear differences in the distributions of 6th, 8th, and 10th graders' views on the NOS. In some questions, distinct differences between Korean students and those of Western countries were found. Educational implications are discussed.C

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The instructional influence upon students' conceptions and problem-solving ability of presenting pictures at the molecular level when introducing chemistry concepts and solving chemistry problems was investigated. Before instruction, the Group Assessment of Logical Thinking (GALT) was administered and its score was used as a covariate. For the treatment group, 31 pictorial materials were used during 21 hours of Korean academic high school chemistry classes. For the control group, traditional instruction was used. Six classroom observations (1 hour each in duration) for each group were made. After instruction, the Chemistry Conceptions Test, and the Chemistry Problem-Solving Test (CPST) consisting of 10 pairs of pictorial and algorithmic problems, were administered. Korean students' success on pictorial questions from the CPST was higher than that reported in the literature for college students; however, Korean students did very poorly on algorithmic questions. The GALT score was significantly correlated with students' conceptions and problem-solving ability. Analysis of covariance results indicated that instruction with pictorial materials at the molecular level helped students construct more scientifically correct conceptions than traditional instruction. However, use of the pictorial materials had no facilitating effect on problem-solving ability.

A new and efficient preparation of anti-o,o‘-dibenzene 1 has been achieved in three steps from cis-3,5-cyclohexadiene-1,2-diol 25. Utilizing a method for deoxygenation of 1,2-diols developed in our laboratory, anti-tetraol 23 was converted to 1 in 65% yield on a 0.5 g scale. This has allowed us to explore the chemistry of anti-dibenzenes extensively. The kinetics for thermal reversion of 1 to benzene have been studied in three different solvents. The direct photolysis of 1 to benzene has been found to form excited benzene in unit efficiency. This high efficiency of adiabatic photon up-conversion in the singlet manifold is unprecedented. No light was detected in the thermal dissociation of 1 in solution using various sensitizers. The chemiluminescence spectrum from the thermolysis of 1 in the presence of perylene has been recorded and found to correspond to the emission of perylene excimer. Although the efficiency of the chemiluminescent process was very low, it has proven to be one of a very few examples of chemiluminescent reactions from pure hydrocarbons. The possible mechanisms were discussed. Benzene 1,4-endoperoxide 36 was formed during the photolysis of monoperoxide 34 at low temperature. Peroxide 36 underwent a quantitative concerted retrocycloaddition to benzene and singlet oxygen. The half-life of 36 was determined to be 29 min at −30 °C.