Candidate Name: Kangmin Joseph ParkCandidate Number: 2213-077August 10, 2010

Internal Assessment – Investigating the relationship between the change in Albumin

Concentration and the rate of osmosis into a Visking Tube

Research Question:

How will the change of the percentage of Albumin concentration affect the rate of osmosis

(diffusion of water ) into a Visking Tubing measured using a pressure sensor in a Visking

tubing containing different albumin solution ?

Introduction:

Osmosis is a process that results from a difference of concentration between two solutions.

The solution with the lower concentration will allow its solvent to move across to the highly

concentrated solution. This energy that allows a solvent to diffuse from a less concentrated

solution to a highly concentrated one is called the Osmotic Pressure.

To investigate this natural phenomenon, a series of Albumin Concentrations which include

1.25%, 2.5%, 5% and 10% will be used to see how the rate of osmosis would differ in each

circumstance. The Albumin Concentration will be obtained through a serial dilution starting

from 10% all the way to 1.25%. The rate of osmosis can be measured by the change of

pressure over time. The change in pressure will be obtained through a pressure sensor

connected to a visking tubing tied in with Albumin solution. This experiment will be

conducted and concluded with the results of the rate of osmosis in each concentration.

Hypothesis1Osmosis is a natural process of the solvent (water) moving from a solution with a higher

concentration of water molecules (hypotonic) to the lower solution (hypertonic) to maintain

equilibrium. Since it is a passive process we can expect to see osmosis occurring after a long

period of time. The energy that pushes this to happen, osmotic pressure, increases as the

difference in concentration between the two solutions become more extreme.

Rate of Osmosis (Diffusion of Water) = Δ∈PressureTime

Thus, the hypothesis for this experiment is that the rate of osmosis will increase as the

1 http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.html

Candidate Name: Kangmin Joseph ParkCandidate Number: 2213-077August 10, 2010

concentration of albumin increases.

Variables

Variable Measured Method of Control

Independent VariableConcentration of Albumin

Solution

A serial dilution is done on 10% Albumin Concentration to obtain 5%, 2.5%, 1.25% of additional albumin concentrations for the experiment

Dependent VariablePressure of Visking Tube &

Rate of Osmosis

The pressure will be obtained through a pressure sensor connected to one side of the visking tube while the other side of the tube will be tied in a knot to prevent leakage. The rate of osmosis can be calculated by observing the change in pressure over time. Thus, in a pressure vs. time graph the rate of osmosis would be the slope.

Controlled Variable

Size of Beaker

A 500 cm3 beaker will be used for each trial where the different concentrations of albumin solution inserted in visking tubes will be placed in 400 cm3 of distilled water

Length of Visking Tube

The lengths of the 4 visking tubes must be identical (20 cm) so that the surface area would not differ for each visking tube

Time MeasuredEach trial measuring the rate of osmosis will be done in 2000 seconds to gain accurate results

400 cm3 of Distilled Water in Beaker

The amount of distilled water poured into the 500 cm3 beaker will be kept the same to eliminate error

Submergence of Visking Tube

The visking tube will be completely surrounded with distilled water so that the surface area would remain the same for each trial

TemperatureSince temperature affects the rate of osmosis, the experiment will be done in room temperature(25°C)

Candidate Name: Kangmin Joseph ParkCandidate Number: 2213-077August 10, 2010

Table 1: List of Variables

Apparatus and Materials

Gas Pressure Sensor Probe 25 cm3 Pipette ( ± 0.04 cm3 ) Clamp Stand 4 Visking Tube ( 20 cm ) Albumin

Distilled Water (400 cm3) Weight Balance ( ± 0.001 cm3 ) 5 Beakers (500 cm3) Magnetic Stirrer Plastic Clamps

Procedure

Preparation of different albumin solutions

1. 10 grams of Albumin is measured through a weight balance and transferred to a 500 cm3 beaker with 90 cm3 of distilled water to complete the 10% albumin solution.

2. The 10 grams of Albumin and distilled water are mixed by a magnetic stirrer for 1 minute to insure that the solution settles.

3. 50 cm3 of the initial albumin solution is transferred to a beaker with a 25 cm3 pipette filled with 50 cm3 of distilled water and mixed with the use of the magnetic stirrer for 1 minute.

4. Procedure 3 is repeated three times to obtain 5%, 2.5% and 1.25% of albumin solution.

Figure 1: Serial DilutionConducting the Experiment

5. 20 cm3 of the 10% albumin solution is transferred with a 25 cm3 pipette to a prepared visking tube (20cm) with one side tied to prevent leakage.

6. The visking tube is tied to the gas pressure sensor with additional plastic clamps to prevent any leakage from both sides. Check the pressure to see if there are any significant fluctuations.

Candidate Name: Kangmin Joseph ParkCandidate Number: 2213-077August 10, 2010

7. The visking tube is then placed inside a 500 cm3 beaker filled with 400 cm3 of distilled water in a position so that the whole tube is surrounded with water. The moment it is submerged, the gas pressure sensor begins measuring the pressure for 2000 seconds.

8. Procedures 5 through 7 are duplicated to obtain the mean.9. Procedures 5 through 8 are repeated for each albumin solution (5%, 2.5%, and

1.25%)

Data Collection and Processing

Quantitative Data

Albumin Concentration / %

Change in Pressure over time for each Trial / ΔkPa s-1

Trial 1 Trial 2

1.25 0.16732 0.144982.5 0.15048 0.133175.0 0.24194 0.2263510.0 0.31721 0.29216

Table 2: Change in pressure over time (2000s) for each concentration

Qualitative Data Albumin Solution was dark yellow in color The Visking Tube became bulky as time passed (Evidence of water entering tube) The color of the Albumin Solution became lighter as time passed

Processed Data

Albumin Concentration / %

CalculationAverage rate(a)

of Osmosis / ΔkPa s-1

Absolute ± SD(b)

1.250.16732+0.14498

20.156 0.156 0.156 ± 0.011

2.50.15048+0.13317

20.142 0.142 0.142 ± 0.009

5.00.24194+0.22635

20.234 0.234 0.234 ± 0.008

10.00.31721+0.29216

20.305 0.305 0.305 ± 0.012

Table 3: Calculation of average rate of osmosis

(a): The average rate of osmosis gained from the mean of the two trials(b): SD represents the Standard Deviation

Data Presentation

Candidate Name: Kangmin Joseph ParkCandidate Number: 2213-077August 10, 2010

Graph 1: Graph of Pressure inside Visking Tube against Time for every trial of the four different Albumin Concentrations

0 2 4 6 8 10 120

0.050.1

0.150.2

0.25

Effect of Albumin Concentration, % against Rate of Osmosis, kPa s-

1

Concentration of Albumin Solution, %

Rate

of

Osm

osis

, kP

a s

-1 (a)

Graph 2: Graph of average rate of osmosis against concentration of albumin solution

Candidate Name: Kangmin Joseph ParkCandidate Number: 2213-077August 10, 2010

Uncertainties

Standard DeviationStandard Deviation was used to represent the calculated uncertainties for the rate of osmosis vs. Albumin Concentration graph

Albumin Concentration,

g/L

Change in pressure over time / ΔkPa s-

1 AverageStandard Deviation

Trial 1 Trial 2

1.25 0.16732 0.14498 0.15615 0.01117

2.5 0.15048 0.13317 0.141825 0.008655

5 0.24194 0.22635 0.234145 0.007795

10 0.31721 0.29216 0.304685 0.012525Table 4: Standard Deviation of different Albumin Concentrations

Calculating Standard Deviation- Albumin Concentration = 1.25%

σ=√ (0.15615−0.16732 )2+(0.15615−0.14498)2

2≈0.01117

- The same calculation is done for each Albumin Concentration

Uncertainty from the process of serial dilutions of Albumin Solution

Albumin Concentration, %

Uncertainties

Volume of Albumin Solution Used / cm3

Volume of Distilled Water

Used / cm3

Total Uncertaint

y / %

Absolute Value, %

1.25 100.00 ± 0.08 cm3 = 100.00 ± 0.08%

50.00 ± 0.08 cm3

= 50.00 ± 0.16%± 0.24% (1.25±0.003)%

2.5 50.00 ± 0.08 cm3 = 50.00 ± 0.16%

50.00 ± 0.08 cm3

= 50.00 ± 0.16%± 0.32% (2.50±0.008)%

5.0 50.00 ± 0.08 cm3 = 50.00 ± 0.16%

50.00 ± 0.08 cm3

= 50.00 ± 0.16%± 0.32% (5.00±0.016)%

10.0 50.00 ± 0.08 cm3 = 50.00 ± 0.16%

50.00 ± 0.08 cm3

= 50.00 ± 0.16%± 0.32% (10.0

0±0.032)%Table 5: Uncertainties of Albumin Solution due to pipette usage

Conclusion

The overall correlation between the Albumin Concentration and the rate of Osmosis is

proven through and shown through the different trials on 1.25%, 2.5%, 5% and 10% of

Candidate Name: Kangmin Joseph ParkCandidate Number: 2213-077August 10, 2010

albumin concentration. The graph clearly shows that the correlation between the albumin

concentrations to the rate of osmosis is a positive one and therefore the concentration of a

solution affects the osmotic pressure.

However, observing Graph 2 we can see that the best fit line does not seem to pass the

origin. When the Albumin Concentration is 0% the rate of osmosis should also be 0 kPa s -1.

Graph 2 does not show this because the Albumin Concentration of 1.25% is slightly off

course due to random error. Nevertheless the linear line still shows a positive correlation

between the change in albumin concentration and the rate of osmosis. Thus, we can conclude

that the hypothesis was proven true.

Evaluation

The hypothesis can be proven from the fact that the graph (Figure 3) had shown a positive

correlation with the concentration of albumin solution to the rate of osmosis. However, the

overall errors due to experimental equipment, such as the pipette and the visking tube, make

the investigation slightly inaccurate.

The 2.5% concentration of albumin solution had been measured incorrectly and the

solution was not properly transferred to the visking tube. As it is seen in Figure 3, the 2.5%

albumin solution has a lower pressure increase than the previous 1.25%.

The following are the errors and suggested improvements that could be made to the

experiment.

Error Effect Improvement

The 2.5% Albumin Solution was not completely tied.

The overall pressure did not increase inside the visking

tube because there was empty space distilled water

could enter without affecting the pressure

Use additional clamps to stabilize the pressure inside the visking tube so that the

change in pressure would be prominent.

Four Visking Tubes were used

There were slight errors in that although they were all 20

centimeters the use of different visking tubes made

the results less accurate

Use of different visking tubes would increase the chance of

obtaining false data. Thus, One visking tube should be used to conduct the whole

experiment.

Pipette (25 cm3) was used This made the uncertainty Using a larger pipette with 50

Candidate Name: Kangmin Joseph ParkCandidate Number: 2213-077August 10, 2010

several times for transferring the Albumin Solution

increase since it has to be used twice to gain 50 cm3.

cm3 would decrease the uncertainty since it would only have to transfer each

solution once.