In the Four-Square Diffusion: Vapor Pressure of Liquids and Solids—ChemTopic™ Lab Activity, place a small amount of liquid in one compartment of a partitioned Petri dish, and sprinkle two solids into adjacent compartments. Once enclosed, the solids gradually become “wet” and dissolve into a liquid. The rate at which each solid dissolves illustrates how vapor pressure and intermolecular forces influence diffusion rates. Available as part of the Solids and Liquids—ChemTopic™ Labs digital collection. Click the Price link for digital collection pricing.