Investigating Students’ Reasoning about Acid–Base Reactions

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.

Assessment in Chemistry Education

“…There are many factors that contribute to the ways by which students receive and respond to the messages given by assessment prompts (including prior knowledge, attitude, and what they believe is being asked). Additionally, prompt structure can powerfully affect how similar groups of students respond . Should a prompt be too structured, it may give away the answer and thereby overestimate student understanding.…”

“…Our own work concerning molecular‐level understanding at the college‐level makes substantial use of “coding schemes” to describe patterns of thinking for large numbers of students and make comparisons between matched cohorts. For example, we have developed a coding scheme to analyze student responses to a prompt that asks them to explain how and why acid base reactions occur . This coding scheme allowed us to discover that student thinking elicited by our assessment item was very responsive to prompt structure.…”

Chewing Gum and pH Level of the Mouth: A Model-based Inquiry Sequence to Promote Scientific Practices

“…Studies performed by Nakhleh [1], Carlton [2], provide a variety of activities on what acid-base models are. More recently, this matter can be found in different pieces of work [3], where ICTs are included [4], and providing depth to the ideas shown by the students [5]. Furthermore, most of the recent proposals are focused on working in inquiry by using Acid-Base Chemistry [6].…”

Teaching progressions and learning progressions

“…The questions were based initially on the Molecular Life Sciences Concept Inventory from Howitt et al [34] and modified following interviews with students and content experts. The differences between scores for students after general chemistry and biochemistry showed relatively large gains for [17][18][19][20] Are able to define strong /weak acid/base but have difficulty identifying examples beyond periodic trends and memorization [21,22] After organic chemistry, students:…”

“…Are able to identify conjugate pairs, protonate and deprotonate with arrow pushing mechanism of Brønsted-Lowry H + movement and Lewis model electrophiles and nucleophiles [19,[23][24][25] Are able to identify strongest/weakest acid/base from structure through periodic trends, electronegativity, inductive effect, resonance [19,[22][23][24][25][26] After biochemistry, students:…”