Evaluation of long-term effects of a force-based approach on student understanding of chemical bonding

Chemical bonding is an abstract topic that students often find difficult to grasp. This study examines the long-term retention of knowledge about chemical bonding after instruction using a force-based approach, grounded on Coulomb's law. The study involved 15 students from an upper secondary school in Sweden. Using Bernstein's concept of vertical horizontal and vertical hierarchical discourse, students’ conceptual understanding was examined through semi-structured, task-based interviews one year after the instruction. The findings indicate that students who demonstrated solely, or primarily hierarchical discourse when solving the tasks demonstrated a wide range of cognitive strategies – from rote memorization to deep conceptual reasoning – when explaining how and why chemical bonds form. These results highlight the value of introducing fundamental Coulombic concepts early in the teaching of chemical bonding, as all chemical bonds can be linked to these principles. Regardless of knowledge discourse used during the interview, many students struggled to articulate the concept of electronegativity and its role in explaining bond formation. Interestingly, while covalent bonding was often described using a hierarchical discourse, the students tended to shift to a more horizontal discourse when addressing ionic bonding, frequently relying in the octet rule as the main explanatory tool. This trend underscores the need to place greater emphasis on electrostatic interaction between subatomic particles and ions to foster a force-based understanding of bonding and move beyond oversimplified explanations of covalent and ionic bonds.