One of the main purposes of science education is to develop scientific understanding and inquiry along with problem solving skills. Such higher order abilities have been considered by constructivism. Constructivism is a learning theory describing knowledge construction as an active process by individuals through experience. In this theory, prior knowledge is important in dealing with complex problems (Driscoll, 2005). However, if students’ prior knowledge does not reflect scientific phenomena, students will have difficulty in understanding new concepts. Students’ ideas about how the world works different than that of the scientists are called as misconceptions (Dykstra, Boyle, & Monarch, 1992). Unfortunately, students have several misconceptions about different scientific concepts. One of them is states of matter. Especially, students had difficulties in understanding condensation and particulate nature of matter (Osborne & Cosgrove, 1983; Brook, Briggs and Driver, 1984; Bar & Travis, 1991; Gopal, Kleinsmidt, & Case, 2004; Hatzinikita & Koulaidis, 1997). In order to eliminate students’ misconceptions, conceptual change model, consisting of four steps as dissatisfaction, intelligibility, plausibility, and fruitfulness, was proposed by Posner et al. (1982). In the context of states of matter, case-based instruction based on conceptual change model was used in this study. Case-based instruction is a teaching technique where real-world problems or scenarios are used in order to encourage students to think deeply in societal and environmental issues and to promote students’ problem solving skills and collaboration (Naumes & Naumes, 1999; Wassermann, 1994). Purpose The present study aimed to investigate the effect of cased-based instruction on 6th grade students’ understanding of states of matter concepts. Mainly, evaporation, condensation, sublimation, and particulate nature of matter in the context of states of matter concepts were covered.

Sample Two classes of sixth grade students instructed by the same teacher participated in the study. One of the classes was randomly assigned as experimental group where case-based instruction was employed. On the other hand, students in the other class, assigned as control group, were instructed traditionally where the teacher was dominant throughout the instruction and class discussions and activities were mainly directed by the teacher. Instrumentation States of Matter Concept test, developed by the researchers, was used to assess students’ understanding of states of matter concepts. The reliability of the test was found as 0.80. This test was administered to both experimental and control groups as a pre and post test. Treatment A non-equivalent pretest-posttest group design was used. For the experimental group, four cases about evaporation, sublimation and condensation of water were developed. Each case involved a scenario and related questions about this scenario. At the beginning of the class, each student read the scenario and tried to answer the questions individually and then in groups. The purpose of this step was to create dissatisfaction among students. After that, to provide intelligibility and plausibility steps, class discussion took place and with the guidance of the teacher in class, students constructed the related concepts and correct answers of the questions. For fruitfulness step, each case involved a question about the application of the learned topic to new situations. Analysis Analysis of Covariance was run to compare the effectiveness of case-based instruction over traditional instruction when students’ prior knowledge on states of matter concepts was controlled.

Results indicated that cased-based instruction produced significantly better acquisition of states of matter concepts than traditional instruction when students’ prior knowledge on states of matter concepts was statistically controlled (F=11.82, p<0.05, η2=0.143). The experimental group scored significantly higher than the control group (Mexperimental= 11; Mcontrol=8). Therefore, it can be said that considering students’ prior knowledge and giving students opportunity to interact with each other might help students construct their own knowledge. The findings of this study suggest that case-based instruction can be used as a supplement to instruction to foster students’ understanding science concepts and to teach science in a more relevant and meaningful way.