Osmosis Experiment of Selectively Permeable Membranes Introduction:
Osmosis Experiment of Selectively Permeable Membranes
Introduction:
Osmosis is the movement of a solvent through a selectively permeable membrane. Water is a solvent, can pass through a selectively permeable membrane, while larger solutes are unable to pass through, such as sucrose. For example, a bag filled with sucrose solution is placed inside a container of water, the water will try to enter the membrane of the bag, to equalize the concentration of water on both sides of the membrane, the bag in this case is hypertonic. The water entering the bag will cause the bag to swell.
A hypotonic bag, filled with water, will shrink in size when placed in a sucrose solution. The water inside the bag will travel out of the membrane, in attempts to equalize the concentration of water on both sides. A bag is considered Isotonic when both sides of the membrane are already equal, for example a bag of water placed into a solution of water. Water may travel back and forth through the membrane but no change in side will occur. Dialysis tubing is a selectively permeable membrane which allows less concentrated solutions to flow through but does not allow larger concentrated solutions to pass through the membrane. This experiment will demonstrate osmosis in bags that are hypertonic, hypotonic, and isotonic.
Understanding the definition of osmosis, I believe that the following hypotheses will be tested to be true during this experiment. Bag one will have no change as the bag is isotonic. Bag two, three, and four will gain in weight as the solvent tries to equalize the concentration of water within the membrane. Water will enter the membrane and bags two through four will be found to be hypertonic. Bag five which is filled with water will shrink in size when placed in the sucrose solution. The water will try to equalize the concentration on each side of the membrane thus making the bag shrink as water leaves the membrane, this deems the bag to be hypotonic.
Materials and Methods:
Electronic Scale
Dialysis Tubing (5 strips) referred to as “bags”
Twist Ties (10)
20% sucrose solution (15 ml)
40% sucrose solution (15 ml)
60% sucrose solution (415 ml)
Water (1615 ml)
5 beakers (400ml)
1 graduated Cylinder (25ml)
1 pipette
Paper Towels
Electronic Scale
Clock
In the beginning of the experiment four beakers were filled with 400 ml of water. The beakers were placed on the workbench in a line. The fifth beaker was filled with 400 ml of 60% sucrose solution, this was placed at the end of the line of beakers. In efforts to ensure the dialysis bags would not leak, the end of the bags were twisted, folded over, and a twist tie was placed around the bottom of the bag. This process was repeated for the remaining four dialysis bags. A paper towel was placed in front of each beaker and labeled specific to what solution would be in the bag and numbered one through five. In order from left to right, each paper towel read: 1. water, 2. 20% sucrose, 3. 40% sucrose, 4. 60% sucrose, 5. water. The numbering represented the order that the results were recorded.
A graduated cylinder was filled with 30 ml of water. A clean pipette was used to put 15 ml of water in the first bag, then the open end of the bag was secured in the same nature as the end of the bag. The remaining 15 ml of water in the graduated cylinder was placed into the second bag and secured. One bag was placed on the paper towel numbered one, the second bag was laid on the paper towel numbered five. At the work station, the graduated cylinder was filled with 15 ml of 20% sucrose solution. Using a clean pipette, the sucrose solution in the graduated cylinder was pipped into the open end of the third dialysis tube. Once the graduated cylinder was emptied, it was rinsed with water along with the pipette. The graduated cylinder was filled with 40% sucrose solution and that was pipped into the fourth bag using the clean pipette. The same steps were taken for the 60% sucrose solution being pipped into the last dialysis tube. All tubes were laid on the paper towels which were numbered and marked with their solution.
The Electronic scale covered with a paper towel was turned on and zeroed. Once we observed that the bags were not leaking we weighed each bag and recorded their weight in grams. The time was observed as each bag was placed in beakers 1-5. After 15 minutes, each bag was removed from the beaker, dried using the paper towel, and weighed. The time and weight was recorded. The bags were removed from the beakers and weighted every 15 minutes for 45 minutes. Once the final reading was completed the experiment was complete. The work bench was cleaned and sucrose solution was poured into a collection jar and water was poured into the sink. The work bench was wiped down after the experiment to ensure a clean workstation.
Results:
The recorded data of the experiment was expected and coincides with my hypothesis on the process of osmosis through a selectively permeable membrane. Table 1 refers to the weight of the dialysis tubing over time during the experiment.
| Table 1. – Weight of Dialysis Tubing in grams | ||||
| Time – 0 | Time – 15 mins | Time – 30 mins | Time – 45 mins | |
| Weight of: Bag 1 | 15.0 | 15.1 | 15.1 | 15.1 |
| Bag 2 | 15.0 | 16.2 | 17.0 | 17.4 |
| Bag 3 | 15.0 | 18.1 | 19.1 | 20.8 |
| Bag 4 | 15.0 | 16.9 | 20.0 | 20.9 |
| Bag 5 | 15.0 | 13.3 | 12.4 | 10.8 |
During the experiment, I noticed that bag one stayed relatively the same while submerged in 400 ml of water. There was a very slight difference during between time zero and the other recorded readings as shown in Table 1, this may be due to a variance in the electronic scale. The results of the experiment agreed with my hypothesis of bags two through five, as there was weight gain in the bag. Bag 5 showed a decrease in weight which also was predicted to happen in my hypothesis. There were changes in the weight of bags two through five during every time reading during the experiment.
| Table 2. Weight Change of Dialysis Tubing in grams | |||||
| Time: | Weight Change Of Bag 1 | Weight Change Of Bag 2 | Weight Change Of Bag 3 | Weight Change Of Bag 4 | Weight Change Of Bag 5 |
| 0 | 0 | 0 | 0 | 0 | 0 |
| 15 min | 0.1 | 1.2 | 3.1 | 1.9 | -1.7 |
| 30 min | 0.1 | 2.0 | 4.1 | 5.0 | -2.6 |
| 45 mins | 0.1 | 2.4 | 5.8 | 5.9 | -4.2 |
Bag 1 had a very minimal weight change as shown in Table 2. The weight change of bag 2 after 45 minutes of being in the beaker of water was 2.4 grams. The largest weight change of the bags, after 45 minutes, was in bag 4. Bag 4 had an overall weight change of 5.9 grams. Bag 5 shows a decrease in weight per Table 2. Bag five lost 4.2 grams after 45 minutes in the solution. Each bag had results that were expected in the hypothesis of the experiment.
Figure 1 gives a visual look at the change of each bag during the experiment. Bag three and four had the closest outcome after 45 minutes, although there was more than one gram difference after the 15-minute weight check. You can see the difference between a hypertonic and hypotonic bag by the direction on the graph that bag two three and four moved vs. bag five. Bag five’s line moved in a negative direction due to the bag shrinking in size. Bag four moved the most of bags that had positive weight changes. Bag one stayed the same on the graph as an example of how a isotonic bag will look on a line graph.
Discussion:
The data collected during the experiment supports the hypotheses formed before the experiment.In Table 1 each bag was weighed before the experiment then weighed every 15 minutes during the experiment. As demonstrated a hypertonic bag is a bag that swells when placed in a hypotonic solution. According to Table 2, bags two through four all had a weight gain which proves they are hypertonic. The bags contains the solute sucrose and beaker containswater which is a solvent. The water travels through the membrane of the bag and the bag begins to swell. Weighing the bags at different times shows the possibility of gradual change as seen in Table 2.Figure 1 shows that bag one had a 0.1 gain in weight during the test, this may be an error of the first reading at time zero. The scale could have been slightly off when the bag was originally weighed. Since bag one stayed the same weight consistently throughout the experiment, it has been proven to be isotonic. Isotonic membranes still allow the flow of water to pass the membrane however, the concentration is already equal so we will see no change. As for bag 5, as seen in Figure 2, shrank in size. Bag 5 has been proven to be hypotonic due to the water leaving the membrane to try to equalize the concentration on each side.
Conclusion:
During osmosis, membranes allow less concentrated solvents such as water to flow through the membrane in hopes to equalize the concentration of each side. This experiment has successfully demonstrated what an isotonic, hypotonic, and hypertonic cell is. Using dialysis tubing and testing the hypotheses we have shown how cells operate during osmosis.
The outcome of the experiment supporting the hypotheses demonstrates comprehension of the concept of osmosis. A hypertonic bag will swell where water is flowing into the membrane. A hypotonic bag containing water will shrink in sucrose solution, and an isotonic bag will allow water to flow but have no weight changes.
Looking for a Similar Assignment? Order now and Get 10% Discount! Use Coupon Code "Newclient"
