Models play an important and central role in science as well as in science education. Chemical bonding is one of the most important topics in upper secondary school chemistry, and this topic is dominated by the use of models. In the past decade, research has shown that chemical bonding is a topic that students find difficult, and therefore, a wide range of alternative conceptions are developed by students. This study focuses on analyzing the models of chemical bonding in chemistry textbooks at upper secondary level and aims to investigate the content of chemical bonding presented in chemistry textbooks related to students' alternative conceptions and difficulties in understanding. Chapters concerning chemical bonding in five chemistry textbooks at upper secondary level in Sweden were analyzed. The results showed that the models of chemical bonding represented in the school textbooks might cause students to have alternative conceptions and difficulties in understanding chemical bonding, which matched the findings found by other recent studies. Thereby, the results indicate a need for filling in the gap between research and textbook writers. Implications for textbook authors and teachers are addressed.

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We investigated the pedagogical content knowledge (PCK) of nine experienced chemistry teachers. The teachers took part in a teacher training course on students' difficulties and the use of models in teaching acid-base chemistry, electrochemistry, and redox reactions. Two years after the course, the teachers were interviewed about their PCK of (1) students' difficulties in understanding acid-base chemistry and (2) models of acids and bases in their teaching practice. In the interviews, the teachers were asked to comment on authentic student responses collected in a previous study that included student interviews about their understanding of acids and bases. Further, the teachers drew story-lines representing their level of satisfaction with their acid-base teaching. The results show that, although all teachers recognised some of the students' difficulties as confusion between models, only a few chose to emphasise the different models of acids and bases. Most of the teachers thought it was sufficient to distinguish clearly between the phenomenological level and the particle level. The ways the teachers reflected on their teaching, in order to improve it, also differed. Some teachers reflected more on students' difficulties; others were more concerned about their own performance. Implications for chemistry (teacher) education are discussed.

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This thesis reports an investigation of how acid-base models are taught and understood in Swedish upper secondary school. Historically, the definition of the concepts of acids and bases has evolved from a phenomenological level to an abstract level. Several models of acids and bases are introduced in Swedish secondary school. Among them an ancient model, the Arrhenius model and the Brønsted model. The aim of this study was to determine how teachers handle these models in their teaching. Further, to investigate Swedish upper secondary students' ideas about the role of chemistry models, in general, and more specific, of models of acids and bases.