Master of Arts

The purpose of this study is to develop a pen and paper diagnostic instrument to assess junior college students' (17-18 years old) understanding of and difficulties in acid-base equilibria, a topic in the GCE A-level H2 Chemistry syllabus. There are numerous studies of students' understanding of chemical equilibria as well as acids and bases given the central role of these topics in chemistry. However, there are few studies at the interface between these two topics acid-base equilibria. Thus, research is required to determine the understanding and difficulties students have in learning acid-base equilibria in order to design teaching approaches to address and scaffold students' understanding more systematically and meaningfully.

A concept map and a list of propositional knowledge statements on acid-base equilibria, based on the requirements of the GCE A-level H2 Chemistry syllabus defined the content boundaries for the investigations in this study, and a review of literature was undertaken to determine students' difficulties and alternative conceptions in acid-base equilibria, acids, bases and salts, and chemical equilibria. The development of the diagnostic instrument on acid-base equilibria followed the procedures prescribed by Treagust (1988) and was guided by the literature review, this author’s own teaching experience and past year GCE A-level examination questions.

Two equivalent 10-item test instruments (Instrument QA and Instrument QB) comprising multiple-choice questions, restricted response questions and extended response questions were initially developed and administered to two classes of 21 JC1 students, each from a Junior College in Singapore. The data obtained guided the refinement of the items to produce a final ten-item test instrument (Instrument QC) on acid-base equilibria, which was administered to 115 JC2 students from one JC.

The results of the Instrument QC showed that Singapore Grade 12 students had several alternative conceptions in acid-base equilibria, and these were grouped under the following sub-sections: Conjugate acid-base pairs, Particulate nature, dissociation of molecules and types of reactions, Properties of salt solutions, Strengths of acids and bases, as well as, Acid dissociation constant, hydrogen ion concentration and pH.

This study indicates that is it important, during teaching, to discuss with students the evolution of, and the similarities and differences between the various models of acids and bases. This study also shows that it is important for teachers to explicitly show the relationship between the macroscopic, sub-microscopic and symbolic representations of acids and bases and their reactions during instruction. These steps taken will help to minimize or address students' alternative conceptions in the learning of acid-base equilibria.