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Session 1330

How Chemical Engineering Seniors Think about Mechanisms of Momentum Transport

Ronald L. Miller, Ruth A. Streveler, Barbara M. Olds Colorado School of Mines

Introduction

Faculty members who teach courses in transport sciences often observe that even students who can correctly solve problems in fluid dynamics, heat and mass transfer, or thermodynamics still believe that “processes stop when they reach equilibrium.” These faculty observations are supported by literature suggesting that science and engineering students do not conceptually understand many fundamental molecular-level and atomic-level phenomena including heat, light, diffusion, chemical reactions, and electricity. [1, 2] The problem is more than simply one of confusion or misunderstanding, but instead involves fundamental misconceptions by students about differences in the way that molecular-scale processes differ from observable, macroscopic causal behavior we experience in our daily lives. [3]

Engineering instructors find that molecular-scale phenomena such as viscous fluid flow, conductive heat transfer, diffusional mass transfer, and thermodynamic equilibrium are very difficult for students to learn and, even after instruction, students persist in their misconceptions. For example, engineering students often describe molecular momentum transfer as faster molecules “dragging slow molecules along,” heat as a “substance stored in hot objects” as opposed to cold which is described as a “substance stored in cold objects,” heat transfer as a “flow of hot molecules to cold objects,” and molecular processes as “stopping” when they reach equilibrium. None of these conceptually flawed explanations is correct and each leads to incorrect explanations of other related phenomena (for example, incorrectly predicting the absence of a temperature effect on equilibrium processes or predicting that no molecular diffusion occurs in laminar fluid flow).

Why are these concepts so difficult for students to learn? Part of the reason seems to be that certain beliefs are very entrenched and not easily changed. [4] Based largely on life experience, these beliefs are formed early in a student’s career (perhaps even before the start of formal schooling) and become the basis for future learning via the construction of increasingly complicated mental models. [5] If the student’s prior knowledge is incomplete or incorrect, new concepts are difficult if not impossible to correctly assimilate and a fundamental conceptual change in the student’s mental model will be required before the new concept can be understood.

For many traditional processes, the macroscopic models and metaphors (“heat flows”) still work well and students must still be proficient in their use. However, given the increasing number of engineering systems that explicitly rely upon molecular-level phenomena (e.g. biotechnology, microelectronics, molecular computers, and many others), we argue that students must also

Proceedings of the 2002 American Society for Engineering Education Annual Conference & Exposition Copyright ©2002, American Society for Engineering Education

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Olds, B., & Miller, R., & Streveler, R. (2002, June), How Chemical Engineering Seniors Think About Mechanisms Of Momentum Transport Paper presented at 2002 Annual Conference, Montreal, Canada. 10.18260/1-2--10939