Transcript Slide 1

Group members:
Tiffany Pewitt- HillCrest High
Alana Antoine- St.Vincent Girls’ High
Danielle Chatman - Whitehaven High
Rachel Randle- Central High
Alyasha Robinson- Hillcrest High
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 o
the dialysis bag.
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.
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.
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.
Osmosis occurs within 3 types of solutions:
1.
Hypotonic
2. Hypertonic
3. Isotonic
 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 .
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
Procedure: Osmosis (Diffusion of water) across an
artificial membrane
1. 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
2.
In all the three bags 6 drops of Phenolphthalein base
indicator were added.
3. 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.
Procedure: Osmosis (Diffusion of water) across an artificial
membrane (2)
4. 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.
5. 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.
6. Weigh the bags at 10 minute intervals.
7. Take at least 5 weights following the initial weighing.
8. Record times and weights in Table1.1; then graph your results.
Hypothesis Testing(1)
H0: Osmosis shows no effect on
the weight of the distilled water
and 0.6M dialysis bags.
t-Test: Paired Two Sample for
Means
Distilled H2O
Mean
Variance
Observations
Pearson Correlation
21.09
28.42
0.01
6.92
10
10
0
df
9
P(T<=t) one-tail
Ha: Osmosis shows significant
change on the distilled water and
0.6M dialysis bags.
0.882
Hypothesized Mean Difference
t Stat
0.6M Sucrose
p-value< 0.05(significant level)
-9.178207
0.000004
t Critical one-tail
1.833113
P(T<=t) two-tail
0.000007
t Critical two-tail
2.262157
Reject H0
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
Mean
Variance
Observations
Pearson Correlation
1.0M Sucrose
28.42
30.12
6.92
12.15
10
10
0.998
Hypothesized Mean Difference
0
df
9
t Stat
-6.16152
P(T<=t) one-tail
0.00008
t Critical one-tail
1.83311
P(T<=t) two-tail
0.00017
t Critical two-tail
2.26216
p-value< 0.05
Reject H0
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.
Table 1.1
Weight of Dialysis Bag (Artificial Cell Membrane)
Time in
0.6M
1.0M
minutes
Distilled H2O Sucrose
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
50
60
21.12
21.21
21.06
28.47
29.21
29.47
30.10
31.19
31.44
70
80
90
21.20
21.15
21.20
30.14
31.48
31.84
32.40
34.36
34.68
Data Analysis by Graph:
Dialysis Bag (Artificial Cell Membrane)
Weights in gm
40.00
35.00
Distilled H2O
30.00
0.6M Sucrose
25.00
1.0M Sucrose
20.00
15.00
0 10 20 30 40 50 60 70 80 90
Time in Minutes
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.
Acknowledgements:
A 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.