Dissolving Salts in Water: Students’ Particulate Explanations of Temperature Changes

摘要

This study investigates how students account for a macroscopic temperature change during the dissolution of ionic salts through particulate level explanations. Semi-structured interviews were conducted with general chemistry, physical chemistry, and biophysical chemistry students. During the interviews, students conducted hands-on tasks that included the touching of beakers containing exothermic or endothermic dissolution processes. Data analysis resulted in categorizing students into groups based on their ideas about bond breaking, bond making, and energy changes. Students’ particulate understandings of the dissolving process did not appear to impact their explanations of the energy changes they observed. Only two students (one from general chemistry and one from biophysical chemistry) correctly described both the dissolving process and the macroscopic energy changes. No students invoked the concepts of potential energy, lattice energy, or enthalpy of hydration to explain their observations.