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The purpose of this study was to investigate Thai students' understanding of dilution and related concepts. The literature suggests that a complete understanding of chemistry concepts such as dilution entails understanding of and the ability to integrate mental models across three levels of representation: the macroscopic, sub-microscopic and symbolic. In this work students' understanding was probed using the interview about events (IAE) approach employing open-ended questions, and also by analysis of student descriptions, and drawings. The research findings suggest that all students were able to answer open-ended questions related to dilution and related concepts. Less able students presented representations at the symbolic level and subsequently described events at the submicroscopic and macroscopic levels. However, these latter representations typically were unrelated to the representations presented at the symbolic level. In contrast, more able students were able to present consistent representations of dilution at each level of representation. (Contains 9 figures.)

The research reported in this study consisted of an investigation of student learning experiences in Thai chemistry laboratories using the Jigsaw IV method. A hands-on experiment based on the Jigsaw IV method using a real life example based on green tea beverage was designed to improve student affective variables for studying topics related to dilution. Earlier work by the authors and other published work suggest Thai students' do not much enjoy studying topics such as dilution chemistry and stoichiometry, and the authors wished to develop learning experiences for such topics that students might enjoy more. The Jigsaw method is, however, reasonably complex and the approach used is radically different to normal teaching approaches used in Thai science classes, but is the type of teaching approach recommended in the current Thai science curriculum. Here we reported on 244 Thai first year undergraduate students' learning approaches; their past learning approaches and their learning experiences with a new cooperative learning approach based on the Jigsaw IV method. The research findings, based on self-completion questionnaires and classroom observations suggest that in the past these students did not particularly enjoy learning in chemistry practical classes, and they reported using highly formulaic approaches to solve chemistry problems for dilution. In contrast they enjoyed the more interactive nature of the Jigsaw IV approach, and in particular acting as an "expert" in front of their peers, which enhanced their self-confidence about chemistry learning in practical classes. They did, however, struggle to understand the purpose of the new teaching approach based on the Jigsaw IV method. (Contains 3 tables.)