Demonstration of Diffusion

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Demonstration of Diffusion Osmosis using an
Artificial Membrane
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TLSAMP '07

• Group members
• Tiffany Pewitt- HillCrest High
• Alana Antoine- St.Vincent Girls High
• Danielle Chatman - Whitehaven High
• Rachel Randle- Central High
• 
  
  
• 
  
• 
  

• Alyasha Robinson- Hillcrest High

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Theorem

• The dialysis bag containing distilled water will
  not change significantly in weight unlike the
  1.0M and 0.6M dialysis bag containing sucrose.
• All three dialysis bags will turn red after 40
  minutes indicating diffusion of sodium hydroxide
  from outside of the dialysis bag.

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Definitions
Osmosis is the net movement of water, through a
semi-permeable membrane from a high water
concentration (dilute solution) to a lower water
concentration (more concentrated solution).
Diffusion Movement of molecules from a high
concentration to an area of low concentration.


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• When does osmosis occur?
• If two solutions are separated by a partially
  permeable membrane and the water potential (i.e.
  the kinetic energy of the water molecules) of
  each solution is different, osmosis will occur.
• All the membranes in a cell are partially
  permeable and allow water through by osmosis.
• If there is a difference in water potential
  between adjacent solutions osmosis will take
  place, it cannot be stopped.

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When Does Osmosis Occur? (2)

• Water molecules pass in both directions but there
  is a net movement of water molecules from a
  higher to a lower water potential.
• Only when the water potential of two adjacent
  solutions is the same, will osmosis stop and
  there will be no further net movement of water
  molecules.
• Water will then move equally between the
  solutions.

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• Osmosis occurs within 3 types of solutions
• Hypotonic
• Hypertonic
• Isotonic

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• Hypotonic solution The solution surrounding
  a cell may have a lower solute concentration
  (e.g. sugar molecules) and therefore a higher
  water potential than the cell. Water passes from
  the solution into the cell by osmosis. Solutions
  with a lower solute concentration are described
  as hypotonic.
• Hypertonic solution The solution
  surrounding a cell may have a higher solute
  concentration and therefore a lower water
  potential than the cell. Water will pass out of
  the cell by osmosis. Solutions with a higher
  solute concentration are described as hypertonic.
• Isotonic solution If the solution
  surrounding a cell has the same solute
  concentration as the cell, water will pass
  equally between them. There will be no net
  movement of water. They have the same water
  potential. When a solution has the same solute
  concentration s the cell, it is described as
  isotonic.

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Experimental Materials

• 3 strips of dialysis tubing
• 8 pieces string
• graduated cylinder
• 1 sucrose (15mL)
• 25 sucrose (15mL)
• 50 sucrose (15mL and 200mL)
• balance
• 3 500mL beakers

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• Procedure Osmosis (Diffusion of water) across an
  artificial membrane
• Three strips of dialysis tubing (15cm long were
  used in these experiments.
• 
  Bag 1 20mL of
  1.0M sucrose
• 
  Bag 2 20mL of 0.6M
  sucrose
• 
  Bag 3 20mL distilled
  water
• In all the three bags 6 drops of Phenolphthalein
  base indicator were added.
• The open end of the bag was tied with string so
  that no air in the bag is left and the bag was
  filled enough so that it will not fold up, but
  not so much that the bag is stiff.
• 
  

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Procedure Osmosis (Diffusion of water) across an
artificial membrane (2)

• Each of the three dialysis bags were immersed in
  three separate 500 mL beaker containing 300 ml
  distilled water and 20 drops of 1N NaOH.
• Trim the strings on each end of the closed
  dialysis bags. Then weight each bag and record in
  given Table 1.1
• Be sure the bags are completely submerged.
  If they are not , add enough of the appropriate
  solution to submerge them.
• Weigh the bags at 10 minute intervals.
• Take at least 5 weights following the initial
  weighing.
• Record times and weights in Table1.1 then graph
  your results.

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Hypothesis Testing(1)
H0 Osmosis shows no effect on the weight of the
distilled water and 0.6M dialysis bags. Ha
Osmosis shows significant change on the distilled
water and 0.6M dialysis bags.
t-Test Paired Two Sample for Means    
  Distilled H2O 0.6M Sucrose
Mean 21.09 28.42
Variance 0.01 6.92
Observations 10 10
Pearson Correlation 0.882  
Hypothesized Mean Difference 0  
df 9  
t Stat -9.178207  
P(Tltt) one-tail 0.000004  
t Critical one-tail 1.833113  
P(Tltt) two-tail 0.000007  
t Critical two-tail 2.262157  
p-valuelt 0.05(significant level)
Reject H0
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Hypothesis Testing (2)
H0 Osmosis shows no effect on the weight of the
0.6M and 1.0M dialysis bags. Ha Osmosis shows
significant change on the 0.6M and 1.0M dialysis
bags.
t-Test Paired Two Sample for Means    
  0.6M Sucrose 1.0M Sucrose
Mean 28.42 30.12
Variance 6.92 12.15
Observations 10 10
Pearson Correlation 0.998  
Hypothesized Mean Difference 0  
df 9  
t Stat -6.16152  
P(Tltt) one-tail 0.00008  
t Critical one-tail 1.83311  
P(Tltt) two-tail 0.00017  
t Critical two-tail 2.26216  
p-valuelt 0.05
Reject H0
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Results

• As expected from the stated hypothesis the
  dialysis bag with 1.0M gained the most weight
  followed by the bag with 0.6M.
• The bag with distilled water did not changed
  significantly.
• All three bags turned red after about 40 minutes
  indicating the diffusion of NaOH from outside to
  inside of the dialysis bag.

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Table 1.1
Weight of Dialysis Bag (Artificial Cell Membrane) Weight of Dialysis Bag (Artificial Cell Membrane) Weight of Dialysis Bag (Artificial Cell Membrane) Weight of Dialysis Bag (Artificial Cell Membrane)
Time in minutes Distilled H2O 0.6M Sucrose 1.0M Sucrose
0 20.81 23.23 23.60
10 21.01 25.79 26.33
20 21.08 27.00 27.98
30 21.08 27.60 29.12
40 21.12 28.47 30.10
50 21.21 29.21 31.19
60 21.06 29.47 31.44
70 21.20 30.14 32.40
80 21.15 31.48 34.36
90 21.20 31.84 34.68
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Data Analysis by Graph
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Conclusion

• As expected according to the hypothesis, there is
  no gain in weight of the dialysis bag in isotonic
  solution.
• When the dialysis bag had the hypertonic solution
  there was a significant weight gain by osmosis.

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AcknowledgementsA special thank you to the
TLSAMP Agency that funded this program. On
behalf of group 2 members I will like to say
thank you to Dr. Rafique Uddin, Dr. John Harris,
Dr. Valerie Chu, Dr.Rajagopolan and Dr. Muhammad
Shafi for all the assistance and support they
have given us to make this project a success.