Michal Drechsler

Textbooks’ and teachers’ understanding of acid-base models used in chemistry teaching

Acid-base reactions can be described in several ways: by formula equations as reactions between substances, or by ionic equations as proton transfer reactions according to Bronsted‘s model. Both models are introduced in chemistry teaching at Swedish secondary schools. The aim of this study was to determine how textbooks and teachers handle the different models to explain acid-base reactions. First, chemistry textbooks most widely used in Swedish upper secondary schools were examined. Second, semi-structured interviews were conducted with six chemistry teachers. The textbooks neither described the differences between the models used to explain acid-base reactions nor clarified why the Bronsted model was introduced. Teachers were well aware of the importance of using models in their lessons. However, they seemed to have difficulties in applying this view with respect to acids and bases. There was no clear distinction between the models, some teachers had even not reflected on the differences between them. They seemed to rely on the content of chemistry textbooks. Implications for textbook writers, teachers and further research are discussed. [Chem. Educ. Res. Pract., 2005, 6 (1), 19-35]

Upper Secondary Teachers' Knowledge for Teaching Chemical Bonding Models.

ABSTRACT Researchers have shown a growing interest in science teachers’ professional knowledge in recent decades. The article focuses on how chemistry teachers impart chemical bonding, one of the most important topics covered in upper secondary school chemistry courses. Chemical bonding is primarily taught using models, which are key for understanding science. However, many studies have determined that the use of models in science education can contribute to students’ difficulties understanding the topic, and that students generally find chemical bonding a challenging topic. The aim of this study is to investigate teachers’ knowledge of teaching chemical bonding. The study focuses on three essential components of pedagogical content knowledge (PCK): (1) the students’ understanding, (2) representations, and (3) instructional strategies. We analyzed lesson plans about chemical bonding generated by 10 chemistry teachers with whom we also conducted semi-structured interviews about their teaching. Our results revealed that the teachers were generally unaware of how the representations of models they used affected student comprehension. The teachers had trouble specifying students’ difficulties in understanding. Moreover, most of the instructional strategies described were generic and insufficient for promoting student understanding. Additionally, the teachers’ rationale for choosing a specific representation or activity was seldom directed at addressing students’ understanding. Our results indicate that both PCK components require improvement, and suggest that the two components should be connected. Implications for the professional development of pre-service and in-service teachers are discussed.