The purpose of this study is to highlight collectively assimilated knowledge by upper secondary school French students (grades 10 to12) and to identify and describe the students' representations and misconceptions related to the concepts of 'atom' and 'molecule'. In order to understand assimilated knowledge better, the school science curricula and textbooks have been examined so as to identify the intended development of the conceptualisation of these concepts within the school curricula. This study is based on the written answers given by school students to four questions concerning these concepts, submitted a long time after the teaching has taken place. The analysis of the students' answers shows the various representations and misconceptions that concern the concepts of atom and molecule at each student level and allows us to see their evolution over these three years. [Chem.

UPPER SECONDARY FRENCH STUDENTS, CHEMICAL TRANSFORMATIONS AND THE REGISTER OF MODELS: A CROSS-SECTIONAL STUDY AbstractThe purpose of this study is to identify how upper secondary school French students (grade 10 to 12) interpret chemical transformation with regards to the changes within molecules and atoms and in terms of intramolecular and/or intermolecular bond breaking. In order to identify and describe the students' assimilated knowledge, four questions were asked to 930 students using a written questionnaire submitted a long time after the related teaching took place. There is much research into student learning in the concept areas discussed here (atoms and molecules, chemical change, chemical bonding) as reviewed in the paper. The present study presents data from an educational system where limited work has been reported in the international literature. The French system has its own unique curriculum, and is taught in the national language (where much of the existing research has concerned learning in Anglophile systems). The research reported here found that French secondary students experienced many similar difficulties in understanding these key scientific concepts to those that have been reported elsewhere, showing the cross-cultural nature of the key educational issues. For example, many have difficulties in understanding the changes undergone by atoms and molecules in the course of a chemical reaction; many are not able to justify explicitly the breaking of inter-molecular bonds and to interpret the breaking of intra-molecular bonds in terms of reorganization of atoms, the target level of understanding in the curriculum from the end of grade 9. However, it is also suggested that some of the specific characteristics identified here are linked to the ordering and language used in the French curriculum, and such cultural idiosyncrasies may offer useful insights into both problematic and valuable aspects of science pedagogy.

This study aims to assess whether the handling of concrete ball-and-stick molecular models promotes translation between diagrammatic representations and a concrete model (orvice versa) and the coordination of the different types of structural representations of a given molecular structure. Forty-one Algerian undergraduate students were requested to answer a pencil and paper questionnaire at the end of their training for a bachelor's degree in physical sciences to test their abilities to translate from Dash-Wedge or Newman representations to 3D ball-and-stick models (andvice versa) of two molecular structures and from one concrete 3D model to the Fischer projection of the molecule. Our results show that concrete molecular models have the potential to be an effective spatial tool to promote visualization, orientation and rotation abilities. However, the handling of the concrete model did not have the same impact on all students and this effectiveness in promoting the spatial abilities required to translate and coordinate between representations was dependent on the representations: it was greater for Dash-Wedge diagrams than for Newman, and was non-existent for the Fischer projection. An implication of our research is that it may be necessary to work with a model over an extensive period of time to improve the mechanisms by which one translates between various representations when the conventions of these representations are varied in nature.

This work aims to assess the difficulties encountered by students of the Ecole Normale Superieure of Kouba (Algeria) intending to teach physical science in the integration of the hybridization of atomic orbitals. It is a concept that they should use in describing the formation of molecular orbitals (s and p) in organic chemistry and gaps in the mastery of these concepts may represent an obstacle for the interpretation of the reactivity of organic compounds. Several studies have noted that the concept of hybridization is among one of the most difficult to understand for students at all levels of learning chemistry. In this work we try to analyze the alternative conceptions that students have constructed and how they have brought together in a conceptual structure the various concepts related to hybridization. The analysis of responses to a written questionnaire and exchanges between students in group activities sequences shows that for most students, the hybridization is not assimilated correctly. It seems that many students can speak about hybridization only once the bonds are formed and there is confusion between the formation of hybrid orbitals and the formation of molecular orbitals. Moreover, various alternative conceptions for the hybridization and the meaning of the designation of hybrid orbitals (sp, sp 2 , sp 3 ) appear. Finally, from the reasoning used by students in achieving the proposed tasks, we inferred a knowledge structure of their possible integration of the concept of hybridization.

This article describes an empirical study concerning the mastering of the chemical equilibrium concept by prospective physical sciences teachers. The main objective was to check whether the concept of chemical equilibrium had become an integrating and unifying concept for them, that is to say an operational and functional knowledge to explain and predict chemical phenomena involving chemical equilibrium. A quantitative survey was conducted among students from various teacher training institutes of universities in France. We have tried to evaluate the preferred types of discourse used by these students for interpreting experimental situations involving chemical equilibria, to what extent they are aware of the dynamic aspect of the equilibrium state, and to how far their experimental knowledge has been improved by this concept. The results show that the concept of chemical equilibrium has not acquired the status of an integrating and unifying concept for the majority of prospective physical sciences teachers. Few of them master the concept of chemical equilibrium in a systematic and efficient way. They conceptualize chemical phenomena involving chemical equilibrium only through the chemical reaction concept. Moreover, experimental knowledge is partly dissociated from theoretical knowledge.