Investigating Students’ Reasoning about Acid–Base Reactions

TLDR

Acid–base chemistry underlies many reactions, and understanding its mechanisms should enable students to reason about a wide array of other reactions. The study develops a method to characterize student reasoning about acid–base reactions by analyzing their descriptions of what, how, and why the reactions occur. The method categorizes responses according to the model of acid–base reactivity used and whether students invoke electrostatic causal arguments. The method reliably classifies responses into categories reflecting acid–base reactivity models and electrostatic reasoning, but response quality depends on task prompt structure, and students using a causal mechanistic Lewis model are more likely to produce correct curved‑arrow mechanisms.

Abstract

Acid–base chemistry is central to a wide range of reactions. If students are able to understand how and why acid–base reactions occur, it should provide a basis for reasoning about a host of other reactions. Here, we report the development of a method to characterize student reasoning about acid–base reactions based on their description of what happens during the reaction, how it happens, and why it happens. We show that we can reliably place student responses into categories that reflect the model of acid–base reactivity used and whether the students invoke an electrostatic causal argument. However, the quality of student responses is highly dependent on the structure of the task prompt, which must be structured to provide students with enough information for them to understand what is needed. In general, students who construct responses that invoke a causal mechanistic Lewis model are more likely to draw appropriate curved arrow reaction mechanisms.