As seen in the resulting data, sucrose solutions cause an effect on the mass of the potato cores. As the Molarity of the sucrose solutions increase, the mass of the potato cores decrease. In 0.2M sucrose solution, there was a 8.5% increase; 0.4M sucrose solution, 3.9% increase; 0.6M sucrose solution, 22.1% decrease; 0.8M sucrose solution,
24.0% decrease; and 1.0M sucrose solution, 27.9% decrease. When the potato core was placed in a distilled water solution, it gained a 15.0% increase in mass. Because the concentration of water is lower in the potato than in the pure water, osmosis causes water to diffuse into the cores. Osmosis is the process of water diffusing from higher concentrations of water to that of a lower concentration. Although far from the expected
21.4% mass increase, it can be easily explained through the multiple uncertainties and errors when dealing with multiple groups input and processing. Processing errors may include inaccurate measurements or the many differences in significant figure from group to group. Uncertainties lie in the mass measurements each group has taken. See ***
Other errors that have caused outliers such as that found in trial 4 of the 0.4M sucrose solution testing may create wide ranges in the found values causing an in accurate class average, hence, a value far from that of the expected value.
Observations indicate that changes in the addition of distilled water to water and
NaCl back to distilled water have apparent affects on the onion cells’ shape. From the three stages, the shape of the cells seemed to have been fully boxed-shaped to shriveled and then back to being full and round. The last stage seemed to have caused the cell to become fuller than before. At the initial wet mount, the cells were full of pigment, and seemed to be very detailed as to their cell wall, nucleus and their content, as well as being well defined from other neighboring cells. Once NaCl was added to the slide without removal of the previous distilled water, the cells began to shrivel, there was a loss of pigment and the distance between the cells began to grow. This is easily explained knowing that because the concentration outside of the cells decreased, the cells began to shrivel. This implies that the concentration of water in the cell was much greater than that of outside the cell. The process of osmosis then takes water from inside of the cell and releases it into the solution attempting to regain equilibrium amongst the solution and the cell. Once distilled water was re-added to the slide without the presence of NaCl, the cells became overly-filled. They began to regain the pigment that was disappearing in the previous submerge. The cells seemed, in most cases, to be larger than the initial addition of distilled water. They also became more packed and closer to the neighboring cells.
This is because now, the concentration of water is at a high outside of the cell, so the rapid occurrence of osmosis causes water to diffuse into the cell to once again achieve equilibrium with its surrounding. Errors may lie in misinterpreting the cells’ physical features when sketching the process seen. Uncertainties lie in fact that we are using the naked eye to try to process what is occurring in the cells. Although we may not be exact, we can see only certain basic features that are occurring in this case of osmosis.
The set of resulting data indicates that as the Molarity of sucrose solution within the bags increases, the final change in mass of the bags also increases. Osmosis, as stated,

is the process of diffusion of areas of higher water concentration to that of a lower water concentration. Because the Molarity of the bags increases, this means that in the same distilled water solution, the water concentration of the bags begins to decrease because there is now more sucrose present within them. Having said so, the bags must gain mass because there is now a lower water concentration in the bags meaning water will now diffuse into the bags. In the presence of distilled water in the water solution, the bags seemed to lose 2.68% mass. Although this seems unlikely because we know that water should be diffusing into the bag. The expected value was a gain in 1.2% change in mass.
Errors such as a whole in the bag or not tying the bag efficiently causing a leak may have occurred in this situation. When the dialysis bag had 0.2M of sucrose solution, the percent change in its mass was 3.3%, relatively close to the expected value of 3.1% change. 0.4M sucrose solution bag had a change in 8.9%; 0.6M sucrose solution, 9.2%;
0.8M sucrose solution, 13.5%; 1.0M sucrose solution, 14.8%. These results were relatively close to the expected values. Although the 1.0M solution was a little off from the expected value, we can explain this through our many uncertainties and errors. Errors including the mis-processing of the data amongst the many, many groups as well as mistakes such as not tying the bag tightly, or putting in different amounts of solutions into the bag due to inaccurate measurements of the solutions used. Uncertainties lie in inaccurate measurements, values interpreted at different significant figures and possible errors in rounding the measurements taken.
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The data indicates that the dialysis bag, a selectively permeable membrane, allows glucose and iodine to diffuse through, but not starch. The starch molecules clearly were too larger to diffuse our of the dialysis bag. Unlike starch, glucose and iodine are relatively smaller, allowing them to diffuse across the dialysis bag’s membrane. We can imply that both glucose and iodine diffused across the membrane because there was a presence of both molecules in areas they were not initially present. From the Benedict solution, were able to confirm that initially, there was no presence of glucose in the
H
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0+IKI solution. After the experiment, in the
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The reaction of iodine and starch produces a purplish-black precipitate. Because the final solution color of the dialysis bag turned purple, this implies that iodine must have diffused into the bag because clearly, starch is too large to do so or else the outer solution will also attain a purple color when it remains amber. Iodine can be concluded that it is a molecule small enough to cross the dialysis bag’s membrane and diffuse into the bag because there is a higher concentration of iodine outside of the bag. Errors may lie in not tying the bag tight enough allowing the glucose and starch solution to leak and produce a purple color outside of the dialysis bag. Also, because this reaction calls for more time, some bags may not have been able to fully diffuse to produce a physical change in coloring of their bags.

CONCLUSION:
In conclusion, we may presume that osmosis occurs when the concentration of water within one thing is higher than the other; water will diffuse from the higher of the two concentrations to that of the lower. Referring back to the first graph relating to the potato core, as the Molarity of the solution increased outside of the core, the core began to lose mass. The graph shows a steady decline in the percent change of mass. This is because as the Molarity of sucrose solution increased, the water concentration of the solution began to decrease. This means that water in the potato core will begin to diffuse out of the core and into solution resulting in a decrease of the mass. At sucrose Molarity of 0.0 (distilled water); the percent change in mass is 15%, whereas at 1.0M of sucrose solution the percent change in mass decreased about 27.9%. This supports the idea presented in this conclusion.
Also, the idea of osmosis is also supported through Part B of this experiment.
When NaCl was added to the wet mount slide, the cells began to shrivel; this is because the concentration of water at that point out side of the cell was decreasing. The addition of NaCl caused the water concentration to decrease outside of the cell, and in comparison, the concentration of water in the cell was higher than that of outside of it.
Hence, causing it to shrivel due to the diffusion of water from the cell into the outer solution. Then as the only distilled water was re-added, the cells once again returned to their rounder, fuller shapes. This is because now, the concentration of water outside of the cell was higher than that of what was inside of the cell, as a result, causing the cell to become larger in size.
In Part C of the experiment, osmosis was once again seen as the dialysis bags began to gain more and more mass as the Molarity of the solution in the bag began to increase. Looking at the second graph, we can see that the graph steadily increases proving that osmosis occurred to cause the mass of the bags to increase. When the 0.2M of sucrose solution bags (the 0.2M bags were a better representation for this experiment because of the mentioned errors and uncertainties with the trials including distilled water) were submerged in water, there was a 3.3% increase in the bag’s mass. When the 1.0M bags were submerged in water, there was a 14.8% increase in the bags mass. Due to the increase in the Molarity of the bags, the concentration of water within the bags began to decrease. Osmosis, trying to regain equilibrium causes water to diffuse from outside the bags into the bags due to the differences in concentration.
Diffusion was the last concept tested in this experiment. The idea of diffusion is that substances, molecules, etc. moving from places of higher concentration to lower concentrations. We viewed two cases of diffusion in this one experiment; the diffusion of iodine into the dialysis bag and the diffusion of glucose out of the bag into the solution. It is concluded that because of the selectively permeable membrane, only smaller molecules such as iodine and glucose were able to diffuse through the membrane, unlike starch. The reaction between iodine and starch which formed a purple precipitate within the bag but not outside it, indicates iodine’s ability to diffuse though the membrane, and starches inability. As well as, the Benedict solution’s indication of glucose present outside of the bag, proving that glucose readily diffused causing a blue color one the indicator was added.

LIMITATIONS AND WEAKNESSES:
Limitations that could not be helped in this experiment include insufficient trials, lack of materials and the many groups. The insufficient trials are a result of the time constraint placed upon the experiment. There was little time to complete many different tests resulting in possible negligence that may occur to detail of the experiment. The lack of material cannot be avoided due to the vast number of students taking the course. A large amount of student required to use a small amount of materials may cause some differences than when working at a larger scale. Also, due to the lack of materials and time constraint, there were multiple groups performing different aspects of the experiment producing the errors and uncertainties addressed in the analysis.
Weaknesses were at abundance in this experiment. Contamination, significant figures, errors in carrying out the process and the use of tap water are the most significant of the weaknesses. Due to the many students using the limited amount of supplies from the same source, events such as using the same dropper for many different solutions may occur. Significant figures were also a reoccurring weakness in our raw data. Different groups interpreted their data differently and rounded to different decimal places to attain a percent change. The inconsistency may cause inaccurate data. Errors when actually carrying out the experiment such as not tying the dialysis bag tightly allowing leaks, holes in the bag, or simply not following the directions correctly and using the wrong solutions or the wrong amount of the solution attributes to outliers and simply unprocessed results. The use of tap water may produce results that are not accurate because tap water may include other substance. Tap water is simply not as pure at distilled water and may lower the concentration of water.
IMPROVEMENTS:
Limitations are simply events our of our control in this experiment and although they can be improved by simply allowing more time to perform the experiment, or having a more excessive abundance of material, the experiment may be able to be carried throughout for just one group. Meaning that one group can do all six trials by themselves allowing a more accurate result. But, clearly, we cannot help these limitations.
Our weaknesses are easily changed through re-manipulation of the procedures.
Contamination can easily be fixed by changing the directions so that contamination is a clear factor to be looked out for. And it should be noted that solutions must strictly be kept separate. It is not enough o assume that contamination will be looked out for. The procedures could also specify how many significant figures should be used in the experiment. I found it best to only carry out the values to one decimal point because the expected results that we were given were only carried out to one decimal point. Errors lie in the many different ranges of significant figures used amongst the groups. Although not as common, rounding errors may occur. A general rule may be considered to be added to the procedure to specify how to round. The use of tap water can easily be fixed by specifying that it is a requirement that distilled water should be used. The use of distilled water can attribute to producing more accurate results.