Revealing Preservice Teachers’ Conceptions, Troublesome Knowledge and Threshold Concept of Chemical Equilibrium through Predict Observe Explain Mental Model Diagnostic Test (POE-MMDT)

Abstract

The purpose of this study is to reveal preservice teacher’ conception of chemical equilibrium concepts which then were further analysed to identify the troublesome knowledge and threshold concept of chemical equilibrium. The participants of this study were 68 preservice chemistry teachers from one of the Teacher Education Institutions in Bandung, Indonesia. Using the descriptive-qualitative design, this research uses a predict-observe-explain mental model diagnostic test consisting of four main questions related to the phenomenon equilibrium process of the decomposition of N2O4 to become NO2. The findings show that most of the preservice teachers’ conceptions about chemical equilibrium are at the level of partial understanding, with five misconceptions has been identified in this study: (1) the reaction in chemical equilibrium is the same as an irreversible reaction; (2) the concentration of reactant and products are the same at equilibrium state; (3) gas with a greater concentration at equilibrium state can be determined from the gas that was first inserted to the container; (4) the concentration ratio at equilibrium is equal with the ratio of the coefficient reaction, and (5) the reactant is the gas which fills the container first. Further analysis shows that there are eight concepts in chemical equilibrium with troublesome knowledge characteristics, namely (1) the concentration of reactants and products in a state of equilibrium; (2) changes in the concentration of reactants and products to a state of equilibrium when starting from any side; (3) reactions that occur in an equilibrium state, (4) chemical equations for equilibrium reaction; (5) the rate of reactions in equilibrium state; (6) the change of reaction rate to reach an equilibrium state; (7) the relationship between Q and K; and (8) the calculation of reactants and products concentration at an equilibrium state. In addition, chemical equilibrium has two threshold concepts: the dynamic characteristic of equilibrium reaction and equilibrium constant. These findings show that the predict-observe-explain instrument has the potential to disclose PSTs’ mental model since it requires the participants to explain the prediction and its corresponding observation result. Besides, this instrument also guides the participants in explaining the macroscopic phenomena, which generates information about their understanding at the submicroscopic and symbolic levels. should be recognised as encompassed by and a form or part of “for all.”