AP Bio Lab Write Up 1
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[edit] Lab One: Diffusion and Osmosis
I Introduction: Diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration. For example, if a bottle of air freshener is sprayed on one side of a room, the fragrance would eventually be able to be smelled on the opposite side of the room. The air freshener diffused from an area of high concentration (where it was first sprayed) to an area of low concentration (the rest of the room). Eventually, an equilibrium will be reached, and the concentration will be uniform throughout the room, and there will be no net movement of molecules. Osmosis is a special case of diffusion, in which water will diffuse across a selectively permeable membrane. Water will diffuse from an area of higher water concentration (low solute concentration), to a lower water concentration (high solute concentration). Water potential is the measure of free energy of water in a solution. Water will always move from an area of higher water potential (more water molecules) to an area of lower water potential (fewer water molecules). Water potential is affected by two factors, the addition of solute and physical pressure. In this lab, we will investigate the processes of diffusion and osmosis in a model membrane system, and investigate the effect of solute concentration on water potential as it relates to living plant tissues.
