A critical analysis of research done to identify conceptual difficulties in acid-base chemistry.
The literature review shows that student alternative conceptions or misconceptions are important for teaching and learning. Causes of such student difficulties may include the counter-intuitive nature of some chemistry concepts or to instruction itself. However, over 30 years research into student conceptual difficulties has had little impact on teaching and learning chemistry. In this study, a critical analysis and synthesis of published research into student conceptions in acid-base chemistry was carried out in the naturalist nomothetic paradigm using a constructivist framework. Historical models which were included were an operational macroscopic model and the theoretical Arrhenius and Brønsted models. Firstly, a comprehensive search strategy with defined inclusion/exclusion criteria identified 42 suitable reports which were mostly peer-reviewed. The identified research was not limited to Anglophone countries although Africa and South America were underrepresented and research among secondary students predominated. Then a critique of the research showed it was of variable quality and often poorly reported. An outcome was a set of guidelines for research into student conceptions. The variable quality and reporting of research then also necessitated a four-level framework to reflect the stability of descriptions of student difficulties. A new method for synthesis of descriptions of student conceptual difficulties was developed which entailed mapping qualitative data on the difficulties, which had been extracted from research publications, to propositional knowledge statements derived in this study. This was an iterative process which simultaneously honed descriptions of difficulties and illuminated propositional knowledge implicated in them. The second major outcome was synthesized descriptions of 10 student difficulties with acid-base species, 26 difficulties with acid-base properties and 17 difficulties concerning terminology and symbolism particular to acid-base chemistry. Some conceptions were also found to have been mis-reported as ‘misconceptions’. The difficulties could be broadly due to student conceptions concerning acid-base models, or students not relating empirical observations to theoretical models or their poor understanding of underlying chemical principles. Some difficulties were found to have been over-researched, while further work was needed to clarify the nature some difficulties with conceptions of bases, acid-base reactions, and symbolism used in acid-base chemistry. The third major outcome from the synthesis was 218 propositional knowledge statements which were shown to be suitable for teaching high-school students, avoided hybrid historical models and were acceptable to expert chemists. These propositional statements were integrated as a set of 11 concept maps. The maps showed the hierarchy and interconnectedness of concepts as well as the propositional links which had been implicated in the difficulties. Furthermore the concept maps indicated critical concepts where teaching in each topic should focus as well as cross-linked concepts that can be used to integrate different aspects of the topic. Accordingly they contribute to PCK in the acidbase topic as they represent the fine-grained yet well integrated conceptual knowledge characteristic of a teacher with highly developed PCK.