Using Density Tanks to Understand Student Sensemaking of How Fluids of Different Densities Behave

Understanding density is important to understanding atmospheric processes such as atmospheric stability and undergirds a deeper understanding of processes critical to learning meteorology. Density tanks can be a teaching tool in meteorology classes to support learning fundamental concepts by modeling how fluids of different densities behave when combined. We worked with over 40 students in individual, semi-structured interviews using density tanks with contrasting colored water of different densities (hot and cold, and salty and fresh). After observing the demonstration, we collected student predictions about how the fluids would behave after we raised a barrier between the two fluids of different densities and captured their sense making. We analyzed the interview data using emergent coding of the transcribed interviews to understand better student mental models, how these mental models form, and how receptive the mental models are to changing with instruction. Our results suggest that many students arrive in courses with inaccurate conceptions of fluid behavior. What these students grasp from common classroom demonstrations may differ from what instructors expect or assume. Everyday experiences with turbulent mixing, such as adding creamer to coffee, playing in swimming pools, and even popular social media seem to lead to an assumption that fluids exist as homogenous bodies with uniform characteristics throughout. Students' tendency to reason from these experiences serves students poorly when applied to large-scale atmospheric processes. We suggest that efforts to scaffold students learning and promote conceptional understanding before moving to more complex fluid behavior will develop a deeper student understanding of the atmosphere.