Essay by PaperNerd ContributorCollege, Undergraduate September 2001

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OSMOSIS AND DIFFUSION PURPOSE: To see the effects of a permeable membrane.

HYPOTHESIS: If the water with iodine diffuses through the bag, then i think the starch will change color. The reason why I think that the water will diffuse through the bag because the concentration gradient outside the bag is more than inside the bag.

MATERIALS: Dialysis Bag Starch Solution (Small Beaker) Strings (2) Iodine Beaker PROCEDURE: 1.Get starch solution and put it in the dialysis bag.

2.Tie both sides of the dialysis of the dialysis bag.

3.Put water into the beaker.

4.Put iodine into the beaker with water making a iodine solution.

5.Place dialysis bag into beaker and observe.

6.Record observations.

OBSERVATIONS AND RESULTS: WEIGHT BEFORE WEIGHT AFTER DIFFERENCE IN WEIGHT COLOR BEFORE COLOR AFTER 3.0g 4.9g 1.9g White Purple 8.6g 8.8g 0.2g White Purple 7.9g 7.9g 0.0g White Purple 8.6g 8.8g

0.2g White Purple 8.8g 8.9g 0.1g White Purple 9.3g 13.3g 4.0g White Purple ANALYSIS: The results of my observations are that all the dialysis bags increased in weight, except one. However, all of the dialysis bags did change color. All the iodine in the water diffused into the bag. Some water did get into the bag. None of the iodine was seen inside of the water. My hypothesis was correct because the water outside the bag diffused into the bag changing the color of the starch.

CONCLUSIONS: The membrane of the dialysis bag was permeable to the iodine ,but not to the all the water. Some mistakes in the experiment might be that there could have been more water in the beaker than other or t hat the was more iodine in the water. In the future these mistakes could be prevented if a graduated cylinder be used to accurately...