Osmosis and Diffusion

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Osmosis and Diffusion: Introduction: In this experiment the principles of osmosis and diffusion were demonstrated. Osmosis is defined as the diffusion of free water (or other liquids) across a selectively permeable membrane from areas of high concentration to areas of lower concentration. The osmosis experiment used 1%, 20%, 40% sucrose solutions in dialysis tubing placed in water to demonstrate the diffusion of water. Diffusion is defined as the spontaneous movement of a substance down its concentration or electrochemical gradient, from an area of high concentration to an area of low concentration1. In the diffusion experiment, phenolphthalein was added to a beaker full of water. A .5 molar solution of NaOH was added, contained in a dialysis bag. The phenolphthalein dyed the water in the dialysis bag. This demonstrated the diffusion of substances across a selectively permeable membrane. The NaOH molecule was small enough to pass across the bag membrane, while the phenolphthalein molecule was too large. Materials and Methods: Diffusion: The materials for the diffusion experiment include; Dialysis bag/tubing, 500 ml beaker, phenolphthalein, water, and .5 molar solution of NaOH. The procedure was as follows: Fill the beaker with 400ml of water, wet the dialysis bag, tie one end of the bag, fill the bag with 10ml of water, add three drops of phenolphthalein to the bag along with the water, tie the other end of the bag tightly, wash it off, put the bag in the beaker with the water. Add 4ml of the .5 molar solution of NaOH to the water. Observe the color change. Osmosis: The materials needed for the osmosis experiment include: 1%, 20%, and 40% sucrose solutions, a 100ml beaker, pipettes, 3 dialysis bags/tubing, scales, and weigh boats. The procedure was a follows; Place the 1% sucrose solution into a beaker. Next, fill one dialysis bag with 1% sucrose
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