An investigation of 16 to 18-year-old students' difficulties with thermochemistry calculations

Abstract

Thermochemistry calculations have been described as stumbling blocks for many students of chemistry. This study set out to investigate the difficulties encountered by students when working out these calculations. The method adopted included collection of written responses to six graded pencil-and-paper items from 55 students. These responses were analysed and were then used to identify a group of 19 students of mixed abilities who participated in the second part of the study. These 19 students were given another set of graded questions to work out in a one-to-one session with the interviewer and were instructed to talk as they work, explaining what they were doing and if possible what they were thinking. The verbatim transcript of each interview together with the written solution produced as they worked made up the interview protocol. The interview protocols provided information about the processes used as well as the way each student performed in the graded items. The method used was found to yield rich data. The different errors observed in students' responses could be grouped under four categories: the errors that were not chemical but mathematical in origin; general chemical errors; errors showing deficiency in thermochemistry; and random errors related to procedure that could have been avoided by appropriate attention to the steps required. The analysis carried out on the interview data has highlighted characteristics in the way students work out calculations and how these may influence success or failure in arriving at a correct answer. Successful students were found to spend more time in understanding the situation, were more likely to check the solution and used a greater variety of ways of representation. This study has improved existing problem solving models and successfully developed and applied a model of problem solving to this investigation of students' difficulties with thermochemistry calculations.