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.
Related Resources:
Teacher Demo: Osmosis Across a Semi-permeable Membrane
Categories: Teacher Demonstration
Osmosis, the movement of a solvent (usually water) across a semi-permeable membrane from an area of higher solvent concentration to an area of lower solvent concentration, is key in the maintenance... read more
Teacher Demo/Student Activity: Disappearing Volume
Categories: Lab/Student Activity, Teacher Demonstration
In this activity, student mix a given quantity of salt with a fixed volume of water. Mass and volume measurements are made before and after mixing to determine if these quantities change. Students... read more
Teacher Demo/Student Activity: Bending Water
Categories: Lab/Student Activity, Teacher Demonstration
In this demo, a polyethylene rod is charged by rubbing with wool. The charged rod is then used to bend a stream of water flowing from a tap. Different substances have different attractions for... read more