Osmosis Over Time

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Osmosis Over Time

• By Eliza Normen, Megan Dunlop and Emily Mclean
• AP Biology Period 6

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Purpose

• To study how time effects rate of osmosis

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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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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

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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

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Potato
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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

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Experiment
Test Tube
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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

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Data
Potato Number Original Weight of Potato (g) Weight After Osmosis (g) Change in Weight (g)
1 5.7 5.8 .1
2 5.4 5.5 .1
3 5.3 5.45 .15
4 5.8 6.0 .2
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Change in Mass
Potato Number Original Weight (g) Change in Weight (g) Percent change in Weight
1 5.7 .1 1.75
2 5.4 .1 1.85
3 5.3 .15 2.83
4 5.8 .2 3.45
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Graph
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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

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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

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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

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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

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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

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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

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Osmosis Across a Membrane
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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

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Aquaporin
Side View
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The End
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Sources for Pictures

• http//www.aquapuredrinkingwater.com/reversepic.jp
  g
• http//images.asia.ru/img/alibaba/photo/50353563/P
  otato.jpg
• http//www.made-in-china.com/image/2f0j00EMptukCsg
  HqvM/Test-Tube-10ml-7ml-5-5ml-G1001-G1002-G1003-.j
  pg
• http//img.tfd.com/wiki/a/a5/Aquaporin-Sideview.pn
  g