Calculating the Change in Weight of a Concentrated Sucrose Solution Through the Use of Osmosis and Diffusion

Calculating the Change in Weight of a Concentrated Sucrose Solution Through the Use of Osmosis and Diffusion Abstract Dialysis tubing is used to represent an artificial cell by demonstrating the effects of variables on the rate of osmosis. By filling tubes with 20 mL of different concentrations of sucrose solution, the rate of osmosis can be measured to determine how the diffusion of water molecules works in living organisms’ cells. Five dialysis tubes containing different concentrations from 0.2 M to 1.0 M sucrose solutions along with one control tube, were placed in five individual beakers filled with water for a period of fifteen minutes. Each tube was placed under the same circumstances. The cell weights were recorded before submerging the dialysis tubes and after, which showed results of the 1.0 M sucrose solution gaining double the weight of the 0.2 M sucrose solution. Therefore, the results showed that the dialysis tubes containing the 1.0 M sucrose solution diffused faster, had a greater rate of osmosis, and gained more weight in grams, due to the tubes containing a more hypotonic solution and lower concentration of water molecules in comparison to the others. Introduction The procedure conducted tested the percent change in mass when osmosis occurred. The lab required dialysis tubing with a variety of sucrose concentrations, which made a hypertonic artificial cell. When placed in a beaker of water, the tubes were expected to swell with water. Diffusion is the movement of particles from an area of high concentration to low concentration. A more specified form of diffusion is osmosis, which is 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. The main objective of this lab was to obtain a better understanding of osmosis by seeing it in action. My hypothesis was that if the solute has a high concentration, water will move into the hypertonic cell through the semi-permeable membrane, which will make the cell swell and become isotonic. Method and Materials For this experiment, five, 8-inch pieces of dialysis tubing were cut and filled with five solutions of varying sucrose concentrations. After I cut five pieces of the dialysis tubing, I set them aside until further instruction was given. I began to prepare the sucrose solutions by weighing out the desired amount of sucrose using a weigh boat on a scale. I proceeded by measuring 20 mL of water in a graduated cylinder and poured it into a flask. I added the measured sucrose to the labeled corresponding flask and mixed until it dissolved. I repeated this step for each sucrose concentration. I took my dialysis tubing and tied one end of the tubing closed. Using a transfer pipette, I placed approximately 20 mL of the first sucrose solution from the labeled flask into the tubing and tied the open end closed. I repeated this step for the next four sucrose solutions. After I transferred the sucrose solutions to the dialysis tubing and tied it close, I weighed each dialysis bag and recorded the initial weight. I then placed the dialysis bag into a fresh beaker of water. I labeled each beaker with the corresponding concentration of the solution in the dialysis bag. Once each dialysis bag was placed in a beaker of water, I allowed them to soak in the water for 15 minutes. After the bags soaked for 15 minutes, I removed them and dried them off. I proceeded to weigh them and recorded their final weight. Calculations to find the change in weight were obtained by subtracting the initial weight from the final weight. I found the percent change in weight by dividing the change in weight by the initial weight, then proceeded to multiply by 100. Results Overall, my hypothesis was correct. As I submerged the dialysis tubing filled with various concentrated sucrose solutions, the water would go inside the bag. My results from 0.0 mol, 0.6 mol, and 0.8 mol seem to be outliers in terms of the mass decreasing. After pulling out the distilled water dialysis tubing, I observed a slight error in the tying of the knot which may have corrupted my results and allowed water to pass through the top. Besides my three outliers, the data almost forms a linear trend, as the sucrose increases, so does the final mass of the bag. My results may also be slightly skewed due to the different sizes and inaccurate measurements of the dialysis tubing. Concentration Initial weight (g) Final Weight (g) 0.0 mol 0.2 mol 0.6 mol 0.8 mol 1.0 mol 15.81 g 15.93 g 19.83 g 19.13 g 16.45 g 13.51 g 16.52 g 18.97 g 18.42 g 18.36 g Discussion Change in weight (g) -2.3 g .59 g -.86 g -.71 g 1.91 g % Change in weight -14.5% 3.7% -4.3% -3.7% 11.6% Osmosis is the diffusion of water, in which water moves to areas with high solute concentrations. This finding agrees with my hypothesis that the semi-permeable bag with the 1.0 mol of sucrose will have the most water movement, and will gradient down to the 0.0 mol, which will have no water movement. All the water movement will be water going inside the bag. My results were not what I expected though. One of the highest percentages of mass change was in the 0.0 mol of sucrose solution (just water). However, I realized that I had a few errors occur in tying my dialysis tubing correctly as well as inaccurate measurements, which is what caused some of the results to be skewed. The purpose of this lab was to test osmosis. Although the results contained errors, 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.