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

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 pKa 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.