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Nicos
VALANIDES
ABSTRACT: One-to-one interviews were administered to a sample of thirty female, primary student teachers of different backgrounds in science. A distillation apparatus accompanied by a diagram was presented to each student and its use for distilling liquids was fully discussed. Students were then asked to describe the macroscopic and microscopic changes which would occur when different water solutions were to be distilled. The majority of the students exhibited limited understanding of the particulate nature of matter and the connection between the observable macroscopic changes (i.e., evaporation or liquefaction) and the way molecules move in relation to one another, and how they are held together. They did not also develop appropriate concepts related to boiling point, latent heat of evaporation, and fractional distillation. They had difficulties in realizing the effects of distillation on water solutions and proposed that the product of distillation would not change taste and color, or that its taste and color would be lighter. These difficulties were progressively greater for salt solution, sugar solution, tap water, aqueous alcoholic solution, tea, and coke or wine. Implications of students' conceptions on curriculum planning and teaching practices conducive to conceptual growth are discussed. [Chem. Educ. Res. Pract. Eur.: 2000, 1, 355-364] KEY WORDS: distillation; alternative frameworks; student conceptions; evaporation; liquefaction
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