Giving students the opportunity to extract, manipulate and visualise DNA molecules enhances a constructivist approach to learning about modern techniques in biology and biotechnology Visualisation usually requires agarose gel electrophoresis and staining. In this article, we report on an alternative DNA stain, Nile Blue A, that may be used in the…

Describes a conceptual typology of models to help teachers select models appropriate to the cognitive ability of their students. Presents an example of how the systematic presentation of analogical models enhanced an 11th-grade chemistry student's understanding of atoms and molecules. Makes recommendations for teachers. Contains 28 references.…

Chemistry is commonly portrayed at three different levels of representation--macroscopic, submicroscopic and symbolic--that combine to enrich the explanations of chemical concepts. In this article, we examine the use of submicroscopic and symbolic representations in chemical explanations and ascertain how they provide meaning. Of specific interest…