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Osmosis Over Time

By Eliza Normen, Megan Dunlop and Emily Mclean AP Biology Period 6. Osmosis Over Time. Purpose. To study how time effects rate of osmosis. Hypothesis. If the weight of the potato increases over time and the potato is going through the process of osmosis, than time effects rate of osmosis.

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Osmosis Over Time

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  1. By Eliza Normen, Megan Dunlop and Emily Mclean AP Biology Period 6 Osmosis Over Time

  2. Purpose • To study how time effects rate of osmosis

  3. Hypothesis • If the weight of the potato increases over time and the potato is going through the process of osmosis, than time effects rate of osmosis

  4. Procedure • First make a solution of sugar and water • This solution will be 5% sugar • Table sugar is a disaccharide of glucose and fructose • Its chemical formula is C12H22O11 • Add 5 grams of sugar to a graduated cylinder. • Add distilled water until you reach 100 mL of solution. • Poor 25 mL of solution into 4 cups

  5. Procedure (cont.) • Cut 4 potato wedges of relatively equal size • Weigh the potato pieces • Add each potato piece to 25 mL of the sugar solution • Label the cups of solution 1, 2, 3 and 4 • Allow potato 1 to remain in the solution for 10 minutes, potato 2 for 20 minutes, potato 3 for 30 minutes and potato 4 for 40 minutes • Dry off outside of potato piece, weigh and record results

  6. Potato

  7. Experiment Controls Variables • Amount of time potato was in solution • Molarity of the solution • Potato Type/Potato size • Type of sugar used to make solution • Change in weight due to time spent in solution

  8. Experiment Test Tube

  9. Observations • Solution was clear and colorless • Potatoes were light tan in color • After osmosis, potatoes 3 and 4 looked slightly larger than before, as if they had swelled • When potatoes were removed from solution, extra solution remained on the outside

  10. Data

  11. Change in Mass

  12. Graph

  13. ConclusionDoes Time effect Osmosis? • Time does effect osmosis • The longer the potato was in the glucose solution, the more the water went into the potato • The water went from high to low concentration through the process of osmosis to attempt to reach equilibrium

  14. Restate Purpose • The purpose of this experiment was to see if time effects osmosis • From our experiment, we can conclude that the answer is yes

  15. Hypothesis was Correct! • Our hypothesis predicted that time would effect osmosis • If the weight of the potato increased after a certain amount of time in the solution, than time does effect osmosis

  16. Experimental Errors • Human error: The potatoes may not all have been in exactly the same amount of solution • All remaining solution might not have been dried off from outside of potato • Equipment error: The balance beam may not have accurately recorded the weights of the potato

  17. What would we do differently? • Make all the potato pieces the exact same weight and size • Try a different solution, such as salt dissolved in distilled water • Keep potato pieces in solution longer before measuring change in weight • Try a different fruit or vegetable, like an apple • Test to see if there a point at which the potato reaches equilibrium and time no loner effects osmisis

  18. Osmosis • Osmosis is the diffusion of water across a membrane • Water naturally moves from areas with high concentration of water to low concentration • It moves from areas with a low concentration of solute to a high concentration • This process does not use energy

  19. Osmosis Across a Membrane

  20. What we learned • A semi-permeable membrane allows some substances to move into and out of the cell, while it blocks other substances from moving across the cell • The flow of water is regulated by aquaporins (proteins located in the cell membrane) • Time effects osmosis. The longer the potato was in the solution, the more water diffused into it

  21. Aquaporin Side View

  22. The End

  23. Sources for Pictures • http://www.aquapuredrinkingwater.com/reversepic.jpg • http://images.asia.ru/img/alibaba/photo/50353563/Potato.jpg • http://www.made-in-china.com/image/2f0j00EMptukCsgHqvM/Test-Tube-10ml-7ml-5-5ml-G1001-G1002-G1003-.jpg • http://img.tfd.com/wiki/a/a5/Aquaporin-Sideview.png

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