South African Journal of Chemistry
versión On-line ISSN 1996-840X
MARAIS, Fiona y COMBRINCK, Sandra. An approach to dealing with the difficulties undergraduate chemistry students experience with stoichiometry. S.Afr.j.chem. (Online) [online]. 2009, vol.62, pp. 88-96. ISSN 1996-840X.
Chemistry for first year students has been identified by Tshwane University of Technology as one of the subjects with a low pass rate. It is apparent that students often memorize formulae and definitions, without understanding the underlying concepts required to work with abstract units of measure. We have found that the majority of students at this university are unable to balance reaction equations satisfactorily. They are also unable to predict the reaction yield, or identify limiting reagents. It is imperative that these and other related problems are overcome before any meaningful change to the high failure rate at first year level will be realized. All conventional forms of lecture presentation failed to make any significant impact on the success rate. Structured worksheets were developed and used, together with tactile models, to address the problems and the initial findings showed a marked improvement. It was discovered that the students' problems originated from their inability to understand the meaning of subscripts and coefficients in chemical equations. The worksheets and the impact they have made on the students' understanding of stoichiometry are shared in this paper.
Palabras clave : Stoichiometry; limiting reagent; worksheets; tactile models.