Although diffusion is a pervasive concept in chemistry, minimal discussion in chemical education literature provides intuitive explanation of diffusion and mass transport. Explanation of diffusion is often given as a dichotomy: (1) a drunken sailor described by a discrete binomial distribution and (2) a continuous solution of the diffusion (heat) equation. As the dichotomy suggests, there is a persistent dislocation between the drunken sailor and error functions as the two explanations do not align to provide a unified and intuitive explanation of this important and fundamental concept.

Here, we present an introduction to diffusion through models and demonstrations to bridge the intuition gap of diffusion in the classroom. Discrete diffusion is explained initially with the classic drunken sailor narrative and also by the Galton board (Figure 1). The Galton board provides a much improved and intuitive explanation of discrete diffusion via hands-on demonstration of the binomial probabilities.

Transition into continuous diffusion evolves from an explanation of flux (Figure 2.) and concentration gradients, the drivers of diffusion. Finally, we provide a demonstration suitable for any classroom with diffusion of physical therapy putty. The broadening of a physical therapy putty disk with time is modeled with the diffusion equation. Time dependence of the putty radius is observed and compared with the standard diffusion length metric.