Pre-Service Chemistry Teachers’ Ideas about Reaction Mechanism Özgecan TAŞTAN 16 , Eylem YALÇINKAYA 2 , Yezdan BOZ 3 , 1 Lecturer Dr., Çukurova University, Education Faculty, Dept. of Elementary Science Edu., Adana- TURKEY 2 PhD, Middle East Technical University, Education Faculty, Dept. of Sec. Sci. and Math. Edu., Ankara- TURKEY 3 Assist. Prof. Dr., Middle East Technical University, Education Faculty, Dept. of Sec. Sci. and Math. Edu., Ankara-TURKEY Received: 12.05.2009 Revised: 10.11.2009 Accepted: 10.12.2009 The original language of article is English (v.7, n.1, March 2010, pp.47-60) ABSTRACT The purpose of this study is to examine Turkish pre-service chemistry teachers’ (N=49) conceptions about the reaction mechanisms for given situations. Participants’ ideas were elicited through the open-ended questions and the semi-structured interviews related to the reaction mechanism. Several conceptual difficulties were exhibited by pre-service chemistry teachers. The outcomes of the study revealed that some of the prospective teachers were not aware that slow step of a reaction mechanism is the rate determining step. They also tried to explain the effect of concentration on the reaction rate by means of Le Chatelier’s principle. It was also found that prospective chemistry teachers had difficulties in writing the mechanism of a reaction from a given potential energy curve. In addition to these, most of the participants could not differentiate between activated complex and reaction intermediate by using the energy values of the substances in a given graph. Key Words: Pre-Service Chemistry Teachers; Chemical Kinetics, Reaction Mechanism; Alternative Conception. INTRODUCTION Chemical kinetics is an important topic in chemistry because students learn how a chemical reaction occurs by means of collision theory, the mechanisms of reactions, the importance of catalyst and also because chemical kinetics has many industrial applications such as manufacturing of medicine and synthesis of organic and/ inorganic compounds. On the other hand, in the literature, number of studies related to students’ conceptions of chemical kinetics is very limited (Boujaoude, 1993; Justi, 2002; Bozkoyun, 2004; Çakmakçı, 2005; Çakmakçı et al., 2006; Kolomuç, 2009). In fact, some of them were cited in the literature under the heading of chemical equilibrium (Quilez & Solaz, 1995; Huddle & Pillay, 1996; Doymuş, 2008) and some are not broadly reachable because of language limitations 6 Corresponding Author email: ozge.deniz@gmail.com TÜRK FEN EĞİTİMİ DERGİSİ Yıl 7, Sayı 1, Mart 2010 Journal of TURKISH SCIENCE EDUCATION Volume 7, Issue 1, March 2010 http://www.tused.org