Osmosis Diffusion Lab Report
Osmosis and Diffusion:
Percent Difference in Mass Based on Sucrose Solution Concentration
AP Biology, Mod 5
Abstract
The process of osmosis was examined through this experiment using dialysis tubing and potato cores. By filling dialysis tubing with different concentrations of sucrose solution and leaving them in water over a period of time a pattern could be observed. Using this information, another experiment was conducted with potato cores submerged in sucrose solution to further examine osmosis. There were no direct correlations between the findings of both experiments. Therefore, the effect of osmosis is uncorrelated with the kind of solute, but only with the water content of the two solutions.
Introduction
Both labs tested the percent change in mass when osmosis occured. The first lab used dialysis tubes with a variety of sucrose concentrations. When placed in a beaker of water, the tubes were expected to swell with water. This is known as a hypotonic solution. In comparison, a hypertonic solution is just the opposite; the cell has a lower concentration than the solution surrounding it (Campbell Biology 76) so water will flow out of the cell in order to create equilibrium, or a balance between the solute (substance being dissolved) and the solvent (dissolving agent). (Campbell Biology 27) The will cause the cell to shrivel up.The second lab tested the osmosis from a beaker of water to a small wedge of potato with different concentrations of sucrose. The concentrations were unknown and it was up to us to infer which one was which.
Diffusion is the movement of particles from an area of high concentration to low concentration. (Campbell Biology 75) A more specified form of diffusion is osmosis, what was primarily focused on in this lab, and it is the movement of water across a membrane, again from an area of high concentration to low concentration. (Campbell Biology 76) The main objective of this lab was to obtain a better understanding of osmosis by seeing it in action. In the first lab, we expected the dialysis tubes with the high concentration of sucrose to swell. In the second lab with the potato wedges, the expected outcome was that the potato pieces placed in the beakers with a higher concentration of sucrose would also swell due to the hypotonic solution it creates. Our hypothesis was that if a solute has a has a high concentration, it will gain more water than if the solute had a lower concentration.
Methods
Both of the experiments in this lab report were conducted at New Tech High @ Coppell in Mrs. Wootton's AP Biology class. Our experiment was completed with the use of the beakers,dialysis tubing, sucrose solvents and potatoes provided by Mrs. Wootton.
Due to the large amount of work needed we split the group into various roles: Recorder, Weigher, Grabber, Cleaner. As the time was coming to an end the Grabber would pull the dialysis tubing out of the beaker and dry it off. The Weigher then proceeded to weigh the bag and give the data to the recorder. As the data was coming in it was immediately inserted into our data tables to ensure that no data would be missed. After the data was inserted into the data tables the Cleaner began to rinse and dry the beakers and put them back on the tray. After our data was completed and submitted the class data was available to compare our results with other groups in the class.
Results
Overall, for the first lab our hypothesis was correct, as we submerged the dialysis tubing filled with various solvent concentrations the water would go inside the bag. Our results from the Distilled Water and 0.4 mol seem to be our only outliers in terms of the mass decreasing. After pulling out the distilled water dialysis tubing we observed a slight error in the tying of the knot which may have corrupted our results and allowed water to pass through the top. Besides our two outliers the data almost forms a linear trend, as the sucrose increases then then so does the final mass of the bag. Our results may also be slightly skewed due to the time constraints that we were facing.
In the Potato Core experiment the majority of our trials were fairly consistent. Aligning with our predictions the potato in Beaker #4 gained weight of 0.24 g therefore deducting that Beaker #4 is filled with distilled water. Beaker #1 was the most significant change with a percent difference of 42.5 making it almost half of the potatoes mass. From the data obtained we can concur that the most likely result of the loss of mass is due to the water leaving the potato.
Discussion (Nimisha)
Osmosis is the diffusion of water, in which water moves to areas with high solute concentrations. (Campbell Biology 76) This finding agrees with our hypothesis that the semi permeable bag with the 1 mol of sugar will have the most water movement, and will gradient down to the 0 mol (distilled water), which will have no water movement. All the water movement will be water going inside the bag.
Our results were not what we expected though. The highest percentage of mass change was in the distilled water. However, we realized that we had a few errors occur in tying our dialysis tubing correctly, which is what caused some of the results to be skewed.
Conclusion(Jackson)
The purpose of this lab was to test osmosis through two mediums. Although the results contained error the initial hypothesis remains true. The degree to which osmosis occurs is directly related to the molarity of the substances involved. Water molecules transfer through permeable membranes until both sides are equal, this means that the hypotonic to hypertonic flow is directly proportional to the mass increase or decrease. (Campbell Biology 76)
Lab #1: Average Percent Change Comparison Chart
Lab #2: Percent Change of Potato Cores
Works-Cited:
Reece, J. (2012). Campbell biology: Concepts & connections. San Francisco, CA.: Benjamin Cummings.
