Examining the effects of laboratory instruction on high school chemistry students' conceptual understanding of chemical equilibrium

摘要

At high school level, students are expected to predict the behavior of the chemical systems at equilibrium. Numerous research studies have evidenced that high school chemistry students presented difficulties with the topic of chemical equilibrium. Likewise, several studies have suggested that laboratory instruction may benefit students by providing concrete situations and practical experiences. Therefore, I investigated how the laboratory instruction about chemical equilibrium might help high school chemistry students to construct and apply meaningful mental models of macroscopic, molecular, and symbolic representational levels and understand this topic. In this study, high school student-constructed concept maps (n= 9) that emerged from pre- & post- laboratory instructional interviews about chemical equilibrium were scored against a teacher map using a rubric. I used these student-constructed concept maps in conjunction with the interviews as way to provide a 2D-representation of: (1) the students' knowledge about chemical equilibrium and (2) the students' use of the three representational levels. A scoring rubric was developed to: (1) holistic analyze the concept map configuration, (2) numeric analyze the accuracy of the links, and (3) classify the links on the map based on three representational levels. Inter-rater reliability for the scoring scheme was high (r= 0.82). Students-constructed concept maps and interviews proved to be helpful tools to assess students' understanding of chemical equilibrium and students' use of the three representational levels. The data analysis of the assessment instruments was performed using Dedoose RTM (an online Web 2.0 software) were emerging trends from the analysis can be observed in a code cloud and bar graphs instantaneously. Results obtained using the quality of understanding scheme (used to score the interviews) and the link accuracy rubric (used to score the concept maps) revealed that after the instruction the students showed partial understanding of the relation between the concepts related to chemical equilibrium. The levels of representations that students utilized to describe their understanding of chemical equilibrium were also classified. After the instruction, the students favored symbolic and macroscopic/symbolic levels of representation to describe chemical equilibrium.