An Evaluation of a Teaching Intervention to Promote Students' Ability to Use Multiple Levels of Representation when Describing and Explaining Chemical Reactions

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.