Developing an understanding of different models of metals - a longitudinal study

Abstract

This paper reports findings from a longitudinal study on students' development of learning from the simple particle model to the electron-sea model of metals. Eighteen students who were taking Year 10 chemistry in Hong Kong (16 years old) were interviewed at four occasions before and after they learned the electron-sea model. This paper reports data from three students, who were a top 5th, a 45th-55th and a bottom 5th percentile student from a middle academic-achieving secondary school in Hong Kong. These data collectively reveal levels of students' development of the simple particle model and the electron-sea model. Generally speaking, the levels progressed from a 'macro' to a 'submicro' understanding of substances (consistent with Johnson, 2013), from regarding attraction between particles as a 'structure' to an 'intangible relationship' (consistent with Chi, 2008, and Cheng & Gilbert, 2014), from understanding metallic bonding as a 'direct phenomenon' to an 'emergent phenomenon' (consistent with Chi, 2005). This paper contributes to the literature by making the above general ideas, with the support of interview data, more specific to the learning of different structural models of metals. For example, although students could regard metallic bonding as an electrostatic force, a lower level understanding saw the electrostatic force merely between a single metal cation and the electron that is orbiting it. It was akin to the understanding of a direct phenomenon. At a higher level, the electrostatic force was regarded as an all-directional interaction (compared with one-to-one-only interaction at the lower level understanding) of all structural constituents. It was akin to an emergent phenomenon. We believe that, given a more thorough analysis of the student sample with the data collected over an extended period of time, such levels can enhance teachers' knowledge of their students' achievement, and facilitate the development of assessment rubrics.