Mr. Daniel M. Williams Osan American High School - Home



Diffusion and OsmosisIntroductionDiffusion is the movement of molecules from high to low concentration. This is a natural phenomenon that is constantly occurring around you. For example, if someone were to spray perfume in a corner of the classroom, those molecules of perfume would gradually diffuse through the rest of the room and the other students would smell it.Osmosis is the diffusion of water through a selectively permeable membrane such as that found in cells. The osmosis of water follows the same pattern as diffusion. Look at this example of three solutions of salt and water.The concentration of water is the highest in the ( pure water | dilute solution | concentrated solution ).The concentration of water is the lowest in the ( pure water | dilute solution | concentrated solution ). Another way of remembering how water moves is that it always tends to move towards areas with more solute present. Simply put, “water follows salt.” Osmosis is particularly important when dealing with living cells. Each cell has a certain concentration of water and solutes that it must maintain, or the consequences are likely fatal. An isotonic solution has the same concentration of water (and solute) as the cell. Water will diffuse in and out of the cell at equal rates, resulting in no net change in the cell’s volume.A hypertonic solution has a lower concentration of water and a higher concentration of solute than the cell. There is a net movement of water out of the cell, causing it to shrink.A hypotonic solution has a higher concentration of water and a lower concentration of solute than the cell. There is a net movement of water into the cell, causing it to swell and burst.457263515811500237744016573500106680381000PracticeThis box represents a container that has been injected with gas molecules. 15468606477000Draw an arrow showing the direction that these gas molecules will move in the container. Use the empty box to show what the molecules will look like once they reach equilibrium.150876010033000Is this showing diffusion or osmosis?This is a beaker containing a solution of pure water, and a saltwater solution. They are separated by a semipermeable membrane that allows water through, but not solute. 5301615190500Label the side containing saltwater, and the side containing pure water. Draw arrows showing the direction that water will move.5409565952500Draw what the beaker will look like after reaching equilibrium. Draw arrows showing the movement of water during equilibrium.Does this represent osmosis or diffusion?There are three beakers below, each containing a different concentration of sucrose (sugar) solution and a cell. Based on the concentrations given, draw arrows showing the movement of water. Label each as hypertonic, hypotonic, or isotonic.Indicate whether the cell will be unchanged, will shrink, or burst in this solution.35052013716025336501066804511040160020 Why does a watery syrup appear on the surface of strawberries when you sprinkle them with sugar? Is this an example of osmosis or diffusion?What would you expect to happen to a plant if you watered it with very salty water? Explain why. Is this an example of a hypertonic, hypotonic, or isotonic solution for the plant cells?Many grocery stores spray their produce with fresh (0% salt) to make them more firm and plump. Is this water a hypertonic, hypotonic, or isotonic solution for the plants? What is different about plant cells that prevents them from bursting when exposed to this solution?Ringer’s solution is often given intravenously to patients experiencing dehydration. It contains water, 131mMol/L sodium, and 111mMol/L chloride ions. Why wouldn’t distilled water be used? Why doesn’t the solution contain higher amounts of sodium, chloride, and other electrolytes? ................
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