Özet:

The research on science education has an important place in the development of education systems. The data obtained from the researches has contributed to the emergence of different teaching approaches, strategies, models, and practices, and to further development of existing approaches. One of these approaches is the context-based approach. In recent years, it has been widely used in many countries in the world to improve the quality of education. Several context-based approaches have been developed, for example, Salters Advanced Chemistry in the UK (Barker and Millar, 2000; Bennett and Lubben, 2006), Chemistry in Context in the USA (Schwartz, 2006), Industrial Chemistry in Israel (Hofstein and Kesner, 2006), Chemistry in Context in Germany (Parchmann et al. , 2006), and the Context-concept Approach in the Netherlands (Bulte et al., 2006). The cognitive and constructivist learning theories constitutes the foundation of the context-based approaches (Ingram, 2003). Context-based learning tries to answer to the question "Why do I need to learn this?, by linking learning settings in schools with events and situations encountered in everyday life. This approach has three basic principles (Kegley, Stacy and Carroll, 1996): (i) to increase students' interest in science courses, (ii) to help students see connections between science and events in everyday life, (iii) to help students develop a more comparative understanding of science. In parallel to these developments in our country, secondary science curricula (chemistry and physics) were revised in accordance with context-based approach. When the science education literature was examined, it was seen that in schools, it was not given enough attention to establish connections between science concepts and events in everyday life, and science teaching in schools was unsuccessful in increasing andining students' interest in real world events (Winther and Volk, 1994; Banks, 1997; Barker and Millar, 1999; Yager and Weld, 1999; Tsai, 2000; Bennett, 2005). This approach is thought to fill an important gap in science education. The REACT model has often been preferred for integrating it to the process of learning-teaching. The model consists of five steps; Relating, Experiencing, Applying, Cooperating, and Transferring. The activities based on the model were increasingly used in science education (House, 1996; Tanner and Chism, 1996; Crawford and Witte, 1999; Crafford, 2001; Ingram, 2003; Demircioğlu, 2008; Coştu, 2009; Demircioğlu, Demircioğlu and Çalık, 2009). However, activities based on this model for gifted students were not found in Turkey. The context-based approach has actually emerged from the idea of increasing the number of individuals who have leadership potential to give them direction to the development of communities, have abilities to make discoveries and have enough knowledge to interest in the science and technology topics. Education of the gifted students is vital for the progress and development of countries. In the literature, there is a lot of research on the concepts of acid and base with students in different learning levels (ranged from primary to university). (Cros et al., 1986; Ross and Munby, 1991; Schmidt, 1991; Nakhleh and Krajcik, 1994; Geban, Ertepınar and Tansel, 1998; Bradley and Mosimege, 1998; Toplis, 1998; Ayas and Özmen, 1998; Demircioğlu, Özmen and Ayas, 2000; Demircioğlu et al., 2001; Özmen and Demircioğlu, 2003; Çetingül and Geban, 2005; Özeken and Yıldırım, 2011). The research was shown that many students at all levels had difficulty in understanding these concepts and the student-centered approaches were more successful than traditional approachesThe Purpose: The aim of this study is to investigate the effect of a teaching material developed based on the REACT model on gifted students' understanding of the neutralization concept. The Method: The study was conducted in 2010-2011 academic year at Ardu Science and Art Center. The sample consisted of 18 gifted students who are willing to participate in this study and enrolled in the seventh and eighth grade level. It was determined as the action research. This research method can be defined as a procedure by which the teacher recognizes a problem in his/her class, monitors a scientific way to solve the problem, and shares his results with colleagues. A teaching material was developed based on the REACT model and applied to the sample. The application lasted for 3x45 minutes. The Instruments: In this study, it was used two instruments; the word association test, and a questionnaire. The word association test (WAT) was used to reveal the scientific conceptual structures about the neutralization concept. In order to construct the WAT, six words were selected. The selected words were; acid, base, neutralization, salt, water and pH. Each key word was written at the top of the page in WAT. Students were required to write responses for each key word. It was given 60 seconds for each word. In the analysis procedure of WAT, students' responses were counted for each key word and then the frequency table was prepared. To draw concept maps from the frequency table, the cut-off point was determined (Bahar et al., 1999) to be 9-up. Next, this cut-off point was lowered three times and concept maps were drawn for each cut-off point. A questionnaire consisting of three open-ended questions was used to determine the sample' views about the application process. The Results: Before the treatment, while the total number of associations was 205 for seventh grade students, it was 294 for eight grade students. After treatment, while the total number of associations was 274 for seventh grade students, it was 343 for eight grade students. The results showed that eighth-grade students were more successful than the seventh grade students, but the constructed knowledge of the seventh grade students is more meaningful and integrated than the other group. From this, it was concluded that the model used in the present study made a significant contribution to teaching the neutralization concept

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