Investigating chemical change in the laboratory: A curriculum resource for introductory chemistry teachers based on the synthesis, decomposition and analysis of zinc iodide. (Volumes I and II).

摘要

Supported by a constructivist view of learning and epistemology of science, this dissertation describes a curriculum resource for high school and first-year college chemistry teachers. The resource, which contains seven cohesive activities for investigating chemical change in the laboratory, is centered around two colorful and reliable reactions: the synthesis and decomposition of zinc iodide. These reactions have many advantages over the traditional syntheses between elements such as the iron sulfide and magnesium oxide syntheses commonly performed by introductory chemistry students. The primary advantage is that students can synthesize a compound of zinc iodide and decompose that very same sample back into its constituent elements, zinc and iodine. Moreover, this pair of reactions lend themselves to both qualitative and quantitative investigations.;Zinc, iodine and zinc iodide are useful to teachers because they all are commercially available, inexpensive to purchase, safe to use, and can be disposed of readily. Additionally, these substances and their reactions show promise in allowing students to construct fundamental and difficult concepts and laws of chemical change such as excess and limiting reactants, empirical formula, the Law of the Conservation of Mass, and the Law of Constant Composition.;The activities are innovative because they are unified around a few substances and contain improvements not found in existing laboratory manuals. The improvements involve the size of the zinc, the quantity of solvent, the addition of acetic acid, the use of a condensing apparatus, the reclamation of solid iodine, and the overall descriptive detail of the reactions. The resource's activities are structured after Gowin's Epistemological Vee and in a manner that supports a guided inquiry approach.;Eight chemical educators evaluated the activities describing the synthesis and decomposition of zinc iodide. The evaluators, who worked independently from each other, were divided into a formative tier followed by a second tier. Incorporation of their criticisms and comments produced a scientifically and educationally sound resource. All eight evaluators believed the activities would be useful to teachers when teaching about chemical change. Six of the eight (two did not respond) said that they would use these activities themselves or recommend them to others.