Ap Biology Osmosis And Diffusion Lab Report

Patrick McCrystal Diffusion Lab Report Diffusion and Osmosis: Migrant Molecules This lab experiment exemplified two different types of passive transport: diffusion and osmosis. Diffusion is the property of liquid or gas molecules that allow them to move down a concentration gradient in a solution. Osmosis is almost identical to diffusion, but it involves a semi-permeable membrane. The lab also defined hypertonic, hypotonic and isotonic solutions and clearly distinguished between them. Hypertonic solutions contain a higher concentration of solute when compared to another solution, and hypotonic solutions are the opposite. Isotonic solutions are equal in their concentrations of solute and solvent. During the experiment, I explored the effect of solute concentration on water potential as it related to living plant tissues. The higher the solute concentration in a solution, the greater its water potential will be. I observed water and IKI diffuse into a bag that had a lower concentration of the two substances inside it. This was confirmed when the IKI tested positive for the starch that was inside the bag, turning the solution purple. I also observed water move into a bag which contained a sucrose solution, recording the mass of the bag both before and after its immersion. Since the bag contained less water than the outside solution, the water moved through the semipermeable membrane and increased the mass of the bag by as much as 14.2%. Table 1.1

Initial Contents !5% Glucose, 1% Starch H2O + IKI

Solution Color Initial Final

Glucose Test Results Initial Final

Clear

Purple

1/10

1/2

Gold

Gold

-

1/4

Table 1.2 Contents in Dialysis Bag Distilled Water .2M Sucrose .4M Sucrose .6M Sucrose .8M Sucrose 1M Sucrose

Initial Mass

Final Mass

Change in Mass

Percent Change in Mass

20.9 24.5 21.8 24.1 24.9 26.7

20.7 25.6 23.9 26.5 28.1 31.1

-0.2 1.1 2.1 2.4 3.2 4.4

-0.96% 4.30% 8.79% 9.10% 11.40% 14.15%

Table 1.3 Contents in Beaker Distilled Water .2M Sucrose .4M Sucrose .6M Sucrose .8M Sucrose 1M Sucrose 1M Salt

Temp.

Initial Mass

Final Mass

Change in Mass

Percent Change in Mass

22.5 22.5 22.5 22.5 22.5 22.5 22.5

6.7 7.3 7.7 7.9 9.2 8.2 8.7

8.4 7.8 7.9 6.9 7 5.8 7.3

1.7 0.5 0.2 -1 -2.2 -2.4 -1.4

25% 7% 3% 15% 24% 29% 16%

% Change = (Final Mass – Initial Mass)/Initial Mass) * 100 Examples can be found in any of the “Percent Change in Mass” columns. Ψ = Ψp + Ψs Examples are found in the lab packet questions.

The “Osmosis and Diffusion” lab confirmed the definitions of osmosis and diffusion that I had already learned. It taught me the difference between hypertonic, hypotonic, and isotonic solutions. One reason why my results may be a bit erroneous is that my partner and I forgot to accurately record the temperatures of the solutions in Table 1.3, so we decided to give them all a uniform room temperature of 22.5°. Our group also could have taken a few bad potato samples, which would have altered our results.