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Students are generally known to memorise and regurgitate chemical equations without sufficient understanding of the changes that occur at the particulate level. In addition, they often fail to recognise the significance of the symbols and formulas that are used to represent chemical reactions. This article describes an evaluation of the ability of 65 Grade 9 students (15-16 years old) from a Singapore secondary school to describe and explain seven types of chemical reactions using macroscopic, submicroscopic and symbolic representations. The study was conducted over nine months using a supplementary teaching program with particular emphasis on the use of multiple levels of representation to describe and explain chemical reactions. Students' proficiency in the use of multiple levels of representation was assessed at the end of the course using a two-tier multiple-choice diagnostic instrument that was previously developed by the authors. In order to evaluate the efficacy of the instructional program, the instrument was also administered to another group of 76 students who were not involved in the supplementary instructional program. The efficacy of the program was evident from the significantly improved scores on the diagnostic instrument of the former group of students. In addition, several student conceptions in the use of multiple levels of representation were identified that could assist teachers in their planning and implementation of classroom instruction.Keywords Chemical reactions . Macroscopic, submicroscopic and symbolic representations . Student conceptions Students' ability to use the macroscopic, submicroscopic and symbolic representations is essential for understanding several chemistry concepts and phenomena. Research has Res Sci Educ (

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Background and purpose: This study investigated Indonesian and Japanese senior high-school students' understanding of electrochemistry concepts. Sample: The questionnaire was administered to 244 Indonesian and 189 Japanese public senior high-school students. Design and methods: An 18-item multiple-choice questionnaire relating to five conceptual categories (reactions occurring during electrolysis, differences between electrolytic and voltaic cells, movement of ions in voltaic cells, poles in voltaic cells, voltaic cell reactions) was administered. Results: The findings of this study show that difficulties and alternative conceptions previously reported in the literature are held equally by students from a developing and developed country, Indonesian and Japan respectively. Conclusions: Collectively, the findings suggest that students' understanding of electrochemistry concepts is relatively weak. Students from both samples shared common difficulties and displayed several alternative conceptions dealing with electrolysis, electricity flow, the voltaic cell and the electrode reactions. Not surprisingly, the students displayed limited consistency in understanding of the concepts in the five categories. This study has implications for teaching and learning, particularly in classroom discussions using models and computer animations in order to reinforce understanding at the sub-microscopic level.

This paper reports on the understanding of three key conceptual categories relating to the kinetic particle theory: (1) intermolecular spacing in solids, liquids and gases, (2) changes of state and intermolecular forces and (3) diffusion in liquids and gases, amongst 148 high school students from Brunei, Australia, Hong Kong and Singapore using 11 multiple-choice items that required students to provide explanations for their selection of particular responses to the items. Students' responses to the items revealed limited understanding of the particle theory concepts, with nine alternative conceptions held by more than 10% of various samples of students. Also, 40.5-78.4% of all students indicated consistent understanding relating to the three conceptual categories based on their responses to the 11 items. However, when their explanations were taken into account, very few students displayed consistent understanding of the related concepts.

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