Student Conceptions of pH Buffers Using a Resource Framework: Layered Resource Graphs and Levels of Resource Activation

Abstract

pH buffers are used extensively in research and industry making them an important chemistry topic for students to learn. This qualitative study uses the phenomenographic method and a resource theoretical framework to provide the first insights into how students approach conceptual buffer problems. Three scaffolded buffer question sets were designed to promote in-depth conceptual responses during a think aloud interview followed by retrospective reporting. Open-coding for activated resources led to three levels of resource activation: Surface Features, Building Connections, and Interconnected. Layered resource graphs provide a visual representation of a diverse array of activated resources, how resources are connected, and which question type promoted particular activations. Some resources such as Accept or Donate H + were consistently activated in all three questions whereas other resources such as pH relative to pK a were productive only in particular contexts, thereby highlighting the contextual dependence of resource productivity. Challenges were observed in productively activating crucial resources such as Accept or Donate H + and in maintaining activations over time even within the same scaffolded question. Specific suggestions are provided on making connections between resources to promote students to a higher level of resource activation and success with buffer problems. Future research should probe the types of activities that can promote productive resource activations and connections.

Is Your Henderson–Hasselbalch Calculation of Buffer pH Correct?

“…Acid–base chemistry and buffers are of fundamental importance to chemistry and analytical chemistry. , The Analytical Chemistry Anchoring Concepts Content Map (ACCM) states that “ Conceptual and quantitative understanding of buffers is important ” . Recent publications in this Journal have explored how students think about acid–base and buffer concepts, , and suggested various interventions to improve student understanding. ,− The Analytical Chemistry ACCM goes on to state that “ The pH of a buffer solution can be obtained using the Henderson-Hasselbalch equation ”. This paper explores the degree to which that statement is true.…”

Exploring diversity: student's (un-)productive use of resonance in organic chemistry tasks through the lens of the coordination class theory

“…This type of diagram sheds light on the activation of resources in a particular setting and emphasizes the students' task-specific inferential nets. This type of representation has recently been used in chemistry education research to visualize students' ideas of buffers, varied population schema and reaction rate (Rodriguez et al, 2020a;Rodriguez et al, 2020b;Sheppard and Bauer, 2022). In the following, we refer to inferential nets and resource graphs interchangeably, as both describe the types and combinations of activated resources.…”

“…For instance, Richards and colleagues (2018) found that students tend to activate combinations of different resource types when making conceptual breakthroughs in the context of photovoltaic cells. Similarly, a recent study focusing on students' conceptualization of buffers points out that emphasizing relations and connections between resources is valuable for conceptual understanding (Sheppard and Bauer, 2022).…”

Students’ Approaches to Determining the Location of Intermolecular Force between Two Distinct Molecules

“…The learner's goal is to sift through the resources and pick one that fits the context. 29 A particular resource might be misleading depending on the context. For example, solid is denser than liquid, but in the case of water, ice floats instead of sinking in the water.…”

“…Resources are neither right nor wrong. The learner’s goal is to sift through the resources and pick one that fits the context . A particular resource might be misleading depending on the context.…”