When a thirsty stranger arrives at an oasis after a long march through the Sahara desert, the locals warn him not to drink too much water. When fishers want to preserve the fish they catch, they add plenty of salt to it. When you fill one balloon with helium, and another balloon with air, the first one quickly loses its shape and size, whereas the second remains inflated. Is there anything in common between these phenomena? Apparently, yes: diffusion and osmosis.
In this introductory-level semilab, we will explore principles and real-life applications of diffusion and osmosis. Diffusion is the movement of particles from an area of high concentration to an area of low concentration, and osmosis is a particular case of diffusion when particles of water are moving through thin films with microscopic pores. It is amazing that such a simple phenomenon is the basis of the ancient methods of food preservation by salt, cleaning of the blood of waste materials in kidneys, and the ability of plants to absorb water from the soil. In this lab, we will explore the diffusion of gases and particles in solutions, learn how to measure a rate of diffusion, and what is the effect of temperature and size of particles on the diffusion rate. We will deal with the diffusion of odors and food coloring, acids, and bases, chemical reactions between them, and color indicators used to detect acidity, osmosis in plant and animal tissues, and dialysis in the semi-permeable membranes.