¶ … Size and Temperature on Diffusion
In this experiment is expected that after 30 minutes, the diameter of the diffused dye ring will increase in size when placed at 37°C.
Time (minutes)
Distance (cm)
Janus Green at room temperature
Janus Green at 37°C
Potassium Permanganate at room temperature
Potassium Permanganate at 37°C
Measurement of diffusion of Janus Green and Potassium Permanganate at different temperatures.
Consistent with the expectations, potassium permanganate molecules spread further, 1.0 cm at room temperature and 1.1 at 37°C. This was longer compared to those of Janus Green that spread 0.3 cm at room temperature and 0.5cm at 37°C. It is evident that both molecules spread further at 37°C than at room temperature.
Effect of solute concentration on osmosis
Bag Contents (10ml)
Beaker Contents (200ml)
min
min
Total Mass Change
1
10% sucrose dH2O
+0.8
dH2O
10% sucrose
-0.7
3
10% sucrose
10% sucrose
10.2
10.3
+0.1
Figure 2. Quantifying changes in the mass of dialysis bags due to osmosis.
During this experiment it was concluded that a 10ml bag increased in mass up to 7.4% when placed in a hypotonic solution, for 40 minutes. When placed in a hypertonic solution, the same 10ml bag decreased 7% to 9.3 ml. Nonetheless, when placed in an isotonic solution, the change was negligible at 10.3 from 10.2.
6.3 Selective Permeability of Membranes
Test tube #
Solution
Ion/Molecule tested for Result (+ or -)
1
Sodium Chloride
Chloride ion (Cl-)
2
Sodium Sulfate
Sulfate ion (SO42-)
3
Glucose
Glucose
4
Starch
Starch
5
Protein
Protein
6
Mixture
Chloride ion (Cl-)
7
Mixture
Sulfate ion (SO42-)
8
Mixture
Glucose
9
Mixture
Starch
10
Mixture
Protein
Figure 3. Determining which molecules of varying sizes may permeate a selectively permeable membrane.
During this experiment, the Mixture Solution from test-tube 6 and 7 tested positive for chloride and sulfate ions respectively indicating presence of these molecules in the solution. On the other hand, glucose and protein tests were negative, an indication that these molecules were absent in the solution.
6.4 Osmosis with red blood cells...
Morphological changes in erythrocytes in response to solutions of differing tonicities.
In the comparison of the appearance of the leaf cells that were soaked in water to those that were soaked in NaCl, it was discovered that, the appearance changed slightly when placed in a solution with 4 drops blood and 15ml 0.9% NaCl (Isotonic solution) . The change was minimal. The leaf shriveled and seemed to have spikes when placed in a solution of 4 drops blood and 15ml 10% NaCl (Hypertonic solution), but when in a solution of 4 drops blood and 15ml 0.45% NaCl (hypotonic solution), the leaf cells had burst.
6.5 Osmosis with plant cells (cells with cell walls)
20% NaCl
diH20
Figure 5. Differences in Elodea cells due to solutions of different tonicity.
It was discovered that the cells swell and become turgid in a hypotonic solution as compared to the one placed in a hypertonic solution, which shrinks leaving the cell membrane detached from the cell wall.
Discussion
In the first experiment (6.1) investigating the effect of size and temperature on diffusion, it was noticed that potassium Permanganate molecules, which are smaller, move faster than the bigger Janus Green both at 37°C and room temperature. Therefore, the rate of diffusion is determined by the molecular mass, the smaller the molecule the more the kinetic energy it has as compared to a large molecule. It concluded that the smaller molecules move faster than larger ones. The other deduction was that temperature is also a determinant of diffusion speeds. At higher temperatures, it appears as though molecules absorb energy resulting in increased kinetic energy and movement causing increased rate of diffusion. This is practical in human bodies and specifically hormones, when triggered, their size elicit faster response.
In the second experiment (6.2) investigating the effect of solute concentration on osmosis, it was discovered that there was varied change in the weight of the bag either, increased, decreased or minimal change depending upon the concentration of the solution. In the experiment, at points where the bag had higher water concentration compared to the solution (hypertonic), water spilled into the solution from the bag thereby lessening the weight of the bag and its content. In the same line, with a lower water concentration compared to the…
