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This study aims to compare the effectiveness of case-based instruction over traditional instruction in improving 11th grade students' understanding of electrochemistry concepts, attitudes toward chemistry, chemistry self-efficacy beliefs, and motivation to learn chemistry. In total, 113 students (47 males and 66 females) from three high schools participated in this study. Two of the classes from each school were randomly assigned to be either the experimental or control group. The experimental group was instructed by case-based instruction while the control group was taught by traditionally designed instruction. The Electrochemistry Concept Test, Attitude toward Chemistry Scale, High School Chemistry Self-efficacy Scale, and Chemistry Motivation Questionnaire were applied as pre- and post-tests to students in both groups. Moreover, a feedback form was administered to students in the experimental group at the end of the study to get students' opinions about the case-based instruction. One-way Multivariate Analysis of Variance (MANOVA) revealed that case-based instruction was an effective method to improve students' understanding of electrochemistry concepts, attitude toward chemistry, and intrinsic motivation to learn chemistry. The qualitative data gathered from the feedback forms also supported the results of the inferential statistics. Students reported that chemistry lessons were more interesting and enjoyableviacase-based instruction.

We examined the interactions among pedagogical content knowledge (PCK) components of novice and experienced chemistry teachers in teaching reaction rate and chemical equilibrium topics in this qualitative multiple-case design study. For this aim, three chemistry teachers who had different levels of teaching experience in chemistry teaching were selected through a process of purposeful sampling. Multiple types of data were gathered through more than two months. In order to collect and triangulate data, a card-sorting activity, a Content Representation (CoRe) tool, semi-structured interviews, observation of instruction, and field notes were utilized. Data were analyzed through three approaches: in-depth analysis of explicit PCK, the enumerative approach, and constant comparative methods. The results revealed eight characteristics of the interactions of the PCK components: (a) the novice teacher's orientations towards science, in contrast to the experienced teachers’, were more broad and non-specific, which impeded the interactions among the components, (b) the interplay of the PCK components was idiosyncratic and topic specific, (c) the novice teacher's PCK maps were fragmented while the experienced teachers’ PCK maps were integrated, (d) the experienced teachers, in contrast to the novice teacher, interacted more than two PCK components in most of their teaching fragments, (e) knowledge of learner, knowledge of curriculum and knowledge of instructional strategies were central in the interplays of all teacher maps, (f) the experienced teachers were more successful than the novice teacher in translating their knowledge into practice in terms of the integration among PCK components, (g) teacher self-efficacy appeared to play a role in their use of PCK components and constructing interactions among them, and (h) all teachers taught the same topics with similar lesson plans and the same instructional materials; however, they differed in terms of how they connect the PCK components. Implications and suggestions for teacher education and science education research are presented.

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