Student difficulties with volumetric analysis
Creators: name: Anamuah-Mensah, Jophus
Publisher: name: University of British Columbia
Year: 2010

description: The study was designed to investigate the difficulties that grade 12 chemistry students have with volumetric analysis. In the first part of the study, a model of performance on volumetric analysis calculations was developed from the integration of two theoretical perspectives of intellectual performance, namely, the proportional reasoning schema in Piaget's theory and the cummulative learning theory of Gagne. This integrated model hypothesized some relationships among the variables: direct proportional reasoning, inverse proportional reasoning, prerequisite concepts and performance on volumetric analysis calculations. The second part examined specific conceptual and manual difficulties that the students have with volumetric analysis. Tests developed in a pilot study were used to measure direct proportional reasoning, inverse proportional reasoning, knowledge of subsumed concepts and performance on volumetric analysis calculations. The first three measures were administered to subjects enrolled in the grade 12 chemistry course prior to the teaching of the volumetric analysis unit. After the teachers had taught the volumetric analysis unit, a test measuring performance on volumetric analysis calculations was administered to the students. The final sample size was 328. After administration of the tests, a subsample of 47 subjects was interviewed on a titration task. The test data were analyzed using path analysis techniques. The psychometric properties of the tests were assessed. The internal consistency estimate of reliability for each of the tests was above 0.75. The interview data and the written work of the subjects on the volumetric analysis calculations were analyzed using qualitative procedures (e.g. categorizing the frequency of response patterns or conceptual errors). The relationship between prior number of titrations performed and performance or volumetric analysis calculations was analyzed using correlational analysis. The evaluation of the proposed integrated model revealed that the performance of subjects identified as using algorithms without understanding could be adequately explained by a trimmed integrated model in which direct proportional reasoning and inverse proportional reasoning were assumed to have negligible direct influence on prerequisite concepts and volumetric analysis calculations, respectively. The evaluation of the proposed integrated model for subjects identified as using algorithms with understanding revealed that a trimmed integrated model in which direct proportional reasoning was assumed to have negligible direct effect on prerequisite concepts and volumetric analysis calculations provided a reasonable explanation of their performance. The analysis of the subjects' calculations on the items in the volumetric analysis instrument revealed a number of conceptual errors (e.g. indiscriminate assumption of 1:1 mole ratios) made by the subjects. The analysis of the manipulatory skills of the subjects during the interview revealed that while some skills seemed to be adequately developed, other important skills seemed to be lacking. The analysis of the students' understanding of concepts involved in an acid-base titration revealed that the concepts of pH and indicator behaviour as well as the use of certain scientific terminologies such as endpoint were not well understood. The analysis of the approaches used by the subjects to calculate the concentration of the acid solution from their own data, during the interview, revealed that two main approaches -the Proportional Approach and the Formula Approach - were used by the subjects in their solution. However, the Formula Approach was used by a greater proportion of the subjects. Several implications for chemical education in the secondary school were inferred from the interpretation of the results. Such implications include the development of different instructional strategies reflecting the different path models for students who use algorithms with and without understanding.