Osmosis lab report PDF

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Lab report done on water osmosis with results provided by my professor. ...

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Egg Osmosis Lab Report Tsionawit Hileyesus BIO 2451k 01 Dr. Hanson September 14, 2020

Tsionawit Hileyesus

9/14/2020

1. Introduction Osmosis is a specialized form of diffusion that deals with the net movement of water through a selectively permeable membrane from a less concentrated solution towards a more concentrated one. Diffusion is the movement of particles from a high concentration to a lower concentration as a result of their constant motion. Osmosis causes the concentration inside of a cell to be the same as the concentration outside of a cell. It attempts to balance the concentration on each side of the membrane. Which way water moves depends on what condition the cell is in. There are 3 conditions a cell can be in. Hypertonic (the outside of the cell is more concentrated), hypotonic (the inside of the cell is more concentrated), and isotonic (equal concentration inside and outside of the cell). In this experiment, osmosis was observed by placing a deshelled egg in different solvents with different levels of sucrose concentration. The purpose of this experiment is to show the process of osmosis through a selectively permeable membrane and to calculate the isotonic point of the eggs as well as the sucrose concentration of the unknown sucrose solution. Students used eggs for this experiment because the surface under the egg shell is selectively permeable and resembles the plasma membrane of a cell.

2. Hypothesis Since the eggs are placed in solvents with different levels of sucrose concentration, the egg in the hypertonic solution is expected to lose weight (shrink), while the egg in the hypotonic solution is expected to gain weight (expand). This might occur because the hypertonic solution will have a higher level of sucrose concentration than the inside of the egg while, the hypotonic solution will have a lower level of sucrose concentration that the inside of the egg. The hypertonic solution will cause water to leave the egg in order to reach equilibrium, and the hypotonic solution will cause water to move into the cell in order to reach equilibrium.

3. Methods

For this experiment, a class of A&P student were divided into 6 groups and each group was responsible for collecting data using 2 deshelled eggs and 2 solutions. Before starting the experiment, all of the eggs were left in a bowl of vinegar with 3% acetic acid solution for 4 days in order to remove the protective shell. First, the deshelled eggs were dried using paper towels. Students handling this task wore gloves and were careful not to puncture or burst the egg. Students recorded the weight of each egg respectively by placing a weight boat on a scale, tarring it, and placing the egg on the weight boat. 6 sucrose solutions were prepared with different levels of sucrose concentrations. The concentrations were 0%, 10%, 15%, 20%, 30%, and an unknown amount. 0% solution was the control group since it did not have any sucrose in it. A control group is a group in an experiment that is not receiving the treatment. Next, each group placed one egg into each jars of the same sucrose solution (2 solutions) and began the 2

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timer. After 15 minutes, the eggs were taken out of the jars, dried with paper towel, and weighed. The weight of both of the eggs was recorded. Once the weighing process was done the eggs were placed back into the jars for additional 15 minutes and taken out and weighed again. These steps were repeated until the eggs have been in the jars for a total of 75 minutes while getting weighed at 15-minute intervals. Finally, after each group was done recording their data, it was put in the class data table for the whole class to see. Every group performed this experiment with different concentrations of sucrose. There was also a control group and an unknown one. Students used two jars with identical concentration to make sure they got reliable data and had spare experimental materials (egg and solution) in case of an error. After the weight of all the eggs was collected the average weight of every 2 eggs placed in the same sucrose solution was calculated by adding the two weight together and dividing by 2. The results were put in table 2 and from those results the change in weight Vs. sucrose percentage was calculated and put in table 3. Afterwards, I was able to create graphs 1 and 2 showing the weight change in eggs Vs. time and total weight change in eggs Vs. percentage of each sucrose solution.

4. Results

OsmosisLab Biology 2451K F20 Section 01 Table 1 Time(min 0 15 30 45 60 75

0% #1 82.02 84.19 85.86 86.79 87.43 87.95

0% #2 10% #1 10% #2 15% #1 15% #2 20% #1 20% #2 30% #1 87.18 85.58 89.03 86.44 77.95 86.12 91.18 89.38 85.61 89.27 86.43 77.79 85.58 90.37 91.17 85.79 89.52 86.42 77.73 85.05 89.88 92.45 86.00 89.73 86.30 77.64 84.56 89.37 93.30 86.11 89.81 86.24 77.54 84.12 88.93 93.93 86.41 89.96 86.24 77.52 83.94 88.66

81.07 80.07 79.17 78.48 77.90 77.34

30% #2 Unknown #1 Unknown #2 84.50 81.47 83.74 83.30 80.65 82.93 82.33 79.84 82.00 81.53 79.16 81.59 80.74 78.70 80.94 80.21 78.44 80.55

After conducting the experiment, the data gathered was collected from each group. Table 1 shows the weight of both eggs from each group along with the sucrose concentration percentage and amount of time each egg was submerged in the solution before weighing. As I mentioned above in the methods section, two eggs were used to ensure accuracy and avoid human error and mishaps. Although each group placed both of their eggs in the same sucrose percentage that was assigned to them, there was a difference between the weight of the two eggs. That could be due to a number of reasons, but I assume that it may have occurred because of the naturally different concentration levels inside the eggs.

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Tsionawit Hileyesus

9/14/2020

Table 2 Time(min 0 15 30 45 60 75

0% 10% 15% 20% 30% Unknown 84.60 87.31 82.20 88.65 82.79 82.61 86.79 87.44 82.11 87.98 81.69 81.79 88.52 87.66 82.08 87.47 80.76 80.92 89.62 90.37 90.94

87.87 87.96 88.19

81.97 81.89 81.88

86.97 86.53 86.30

80.01 79.32 78.78

80.38 79.82 79.50

Table 2 illustrates the average weight change the eggs exhibited versus time spent submerged in the sucrose solutions. Judging from the table, the longer the eggs stayed in the sucrose solution the more weight they either lost or gained depending on the concentration of the solution. The egg submerged in the 0% sucrose solution exhibited the highest weight gain, while the egg submerged in the 30% sucrose solution exhibited the highest weight loss compared to the other eggs that were in the 10%, 15%, 20%, and unknown amount of sucrose solutions.

Table 3 Time(min 0 15 30 45 60 75

0% 10% 15% 20% 30% Unknown 0.00 0.00 0.00 0.00 0.00 0.00 2.19 0.13 -0.09 -0.67 -1.10 -0.82 3.92 0.35 -0.12 -1.18 -2.03 -1.69 5.02 0.56 -0.23 -1.68 -2.78 -2.23 5.77 0.65 -0.31 -2.12 -3.47 -2.79 6.34 0.88 -0.32 -2.35 -4.01 -3.11

Table 3 gives us a clearer data on how the weight of the eggs changed corresponding with the sucrose concentration percentage. At 0% and 10% sucrose concentration, the weight of the eggs increased. However, at 15%, 20%, 30%, and unknown levels of concentration, the eggs lost weight. If we were to compare the weight change at 0% (control group) with 30%, it is evident that the egg in the 0% sucrose concentration gained a good amount of weigh as opposed to the egg in the 30% sucrose concentration which lost weight compared to the other eggs. This was caused because at 0%, the inside of the egg had a higher concentration meaning it was in a hypotonic condition. This resulted in water molecules moving into the egg causing it to expand and gain weight. At 30% the inside of the egg was a lot less concentrated than the outside, causing the water inside the egg to come out and make the egg shrink (lose weight).

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Tsionawit Hileyesus

9/14/2020

Change in weight Vs. time Graph 1 Changeinweight (g)

8.00 6.00 4.00 2.00 0.00 -2.00 -4.00 -6.00 0

15

30

45

60

75

Time (min) 0%

10%

15%

20%

30%

Unknown

Graph 1 depicts change in weight Vs. time of each egg in each sucrose solution observed in table 3. The graph shows a visual representation of the data. As mentioned above, 0% (control group) exhibited a significant weight change compared to the rest of sucrose concentrations. The line for 15% concentration was the closest to 0 change in weight. This tells us that somewhere above or below 15% is the isotonic point of the egg, meaning the concentration inside the eggs was the same as the sucrose solution outside and has reached equilibrium.

Change in weight (g) at t=75 min Vs. Sucrose concentration (%) 8.00 6.00 4.00 2.00 0.00 -2.00 -4.00 y = -0.3428x + 5.25

-6.00 0

5

10

15

20

25

30

35

Graph 2 depicts total weight change Vs. sucrose concentration. Since the eggs have weighed at 15-minute intervals for a total of 75 minutes, the weights shown at 75 minutes on table 3 are the total weight changes the eggs exhibited. The unknown concentration was not included in this graph because since the concentration is unknown, there would be nothing to put 5

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on the X-axis. Instead, a linear trendline was generated in order to calculate the concentration of the unknown solution and the actual isotonic point of the eggs. From this trendline, I generated a linear equation to use for my calculations that I have included below. To calculate the isotonic point, I used 0 as the value for Y and solved for X. To calculate the concentration of the unknown, I used the total weight change of the egg in the unknown solution at 75 minutes which was -3.11.

Linear equation: y = -0.3428x + 5.25 Calculations: Isotonic point of egg. y = -0.3428x + 5.25 0 = -0.3428x + 5.25 -0.3428x + 5.25 -5.25 -5.25 -5.25 = -0.3428x −5.25 −0.3428 x = −0.3428 −0.3428 X = 15.32

Unknown solution concentration y = -0.3428x + 5.25 -3.11 = -5.25

-5.25

-8.36 = -0.3428x −8.36 −0.3428 x = −0.3428 −0.3428 X = 24.39

5. Discussion

As a final observation, the data from the experiment showed how different concentration levels resulted in the egg either losing or gaining weight through osmosis. As I mentioned in the introduction, osmosis is the movement of water molecules from a low concentration level to a high concentration level. My results correspond with this definition and support my hypothesis because the eggs in a low concentration level gained weight while the ones in the high concentration solution lost weight. We can see these results in depth when looking at graph 1. Graph 1 shows the weight change each egg in each sucrose solution exhibited corresponding with how long it was submerged in the solution. According to the graph, solutions with 0% and 10% sucrose concentration are hypotonic and the rest are hypertonic. 0% and 10% are hypotonic because the egg gained weight when placed in these solutions. This is a direct result of water moving into the egg because it was more concentrated than the solution. Although the solution was hypertonic, the egg that was in the 15% sucrose solution exhibited a small weight difference compared to the other eggs because it was the closest to the calculated isotonic point of the eggs. The calculated isotonic point was 15.32%. 15%, 20%, 30% and unknown (24.4%) solutions are 6

Tsionawit Hileyesus

9/14/2020

hypertonic because the eggs in those solutions lost weight. If an egg was put into a beaker containing 50% sucrose solution, I believe the egg would shrink due to the high concentration level of the solution. The 50% sucrose solution would create a hypertonic environment causing the water inside the egg to move into the sucrose solution in order to reach equilibrium. Although this experiment was good way to show how osmosis occurs in a cell, errors might have altered the results. In my opinion, although some precautions were taken, human error is hard to avoid and it may have occurred during the experiment or during the data calculation.

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