Teacher Demonstration: Thinking about the Movement of Water

The distinction between diffusion and osmosis is not clear to many students. Observing coloured particles (such as food dye) diffuse in water shows direct evidence of diffusion, but the movement of water particles is not so easily observed. This demonstration prepares students for an understanding of osmosis, the diffusion of water across a selectively permeable membrane. Students have been seen diffusion, the movement of particles in from an area of high concentration to areas of low concentration. This demonstration allows students to observe the movement of water to an area of low concentration.