Does the way charges and transferred electrons are depicted in an oxidation–reduction animation affect students’ explanations?

Abstract

This study compares students’ explanations of the oxidation–reduction reaction between silver nitrate and copper metal after viewing a chemical demonstration and one of four different particulate-level computer animations. The animations differed in the way the ionic charges were depicted (shown or omitted) and the way the transferred electrons were depicted (as discrete “e⁻” particles or as fuzzy electron “halos” around the metal atoms). Students viewing animations explicitly showing the ion charges were better at determining the number of electrons gained by each silver ion and lost by each copper atom and wrote more correct balanced chemical equations for the reaction than students viewing animations with charges omitted. Compared to students who viewed animations depicting the transferred electrons as halos around the metal atoms, students viewing animations depicting transferred electrons as discrete particles provided better explanations for the number of electrons gained by the silver ions and lost by the copper atoms and the relative sizes of the silver/copper atoms and their respective cations. Based on comments from student interviews, it appears that several students did not know the proper charges of the silver, copper(II), and nitrate ions and that animations showing ionic charges provided students with relevant visual information they could use to improve their pictorial models of the reaction, which led to improved student-generated balanced equations for this reaction. Student interview comments also suggested that animations depicting the transferred electrons as discrete particles provided more relevant visual images (the number of electrons being transferred between silver ions and copper atoms and the relative sizes of the metal atoms and their cations) that were not provided by animations depicting the transferred electrons as halos, and this led students to construct more accurate pictorial models of the oxidation–reduction reaction. The results of this study and previous research by our group suggest that, although showing or omitting water molecules in animations depicting simple oxidation–reduction reactions had little effect on students explanations of the oxidation–reduction process, showing ion charges and depicting transferred electrons as particles (instead of halos) led to significant improvement of students’ explanations of the oxidation–reduction process.