Determining The Molarity Of a Potato Cytoplasm

When the salt in NaCl dissolves in the water Osmosis occurs. This then causes the concentration to proceed from high concentration to low concentration decreasing the mass of the potato core.

Most of the results of the experiment show that as the molarity of sucrose in the solution increases, the percent change in mass of the potato decreases. This is due to osmosis, water moves from a higher water concentration area to a lower water concentration area. From the results table, one can see that the mass of potato in the 0.1M sucrose solution increased by 13%, and the mass decreased by 28% in the 1.0M sucrose solution.

The ends were trimmed of each core to 3 centimeters in length. The cores were blotted dry and weighed each to the nearest one hundredth of a gram and results were recorded. 20 ml of each sucrose solution were poured in the labeled, 50 ml beakers (0.0m-0.8). Placed one white potato and one sweet potato core in each beaker. The potato cores were left in sucrose solution for one hour.

This was because not all of them looked the same in shape. Also, for at least two of the slices we used the curved ends of the potatoes, this meant parts that should have been there were already not present for a cube shape. This was bad because much mass was eliminated in comparison with the cube shaped ones actually coming from the middle area of the potato, where you get a sufficient amount of the potato to actually use. This could remove more mass. Also, we only peeled off enough skin as we could, although we did not have too. Some parts were too hard to peel, therefore, a few potatoes had most of their skin removed, whereas, others mostly had at least half of their skin remaining. This would also have a role in causing various wrong masses for the initial masses of the potato, also affecting the final mass after it had been placed into the solution.

The purpose of this lab was to find the water potential and osmolality of potato cores after being soaked in NaCl and sucrose solutions and to compare them to each other and the expected water potentials and osmolalities from the literature. We did this by weighing potato cores, soaking them in the NaCl and sucrose solutions, and then weighing them again. This information was used to find the percent weight change of the potato cores. The potato core’s water potential mean for sucrose was -9.86 bars and for NaCl it was -10.72 bars. The osmolality that produced zero weight change in potato cores for sucrose was 0.401 and for NaCl it was 0.439. Our experiment found that the there was no significant statistical difference in the water potential and osmolality of the potato cores soaked in the sucrose and NaCl solutions.

An anomaly will be that when the mass of the potato was measured for 6% of sugar solution, the mass at time 5minutes was high then it decreased sharply at times 10 minutes to time 20 minutes this shows that the pressure with which the potato shrunk made the potato less rigid which made the cell membrane of the potato start shrink from the cell itself therefore causing the mass to decrease, also from 20% to 60% of sugar solution was used the mass of the potato decreased sharply as time went on which also shows that the cell membrane of the potato has plasmolysed which shows that the cell membrane has pulled away from the cell which shows with the shrinkage of the potato.

However, there are also some errors in this experiment. Firstly, the potato pieces were not exactly the same size despite the care taken to cut them. A solution to this would be to use a form cutter, which would cut exactly equal shapes. Secondly, the temperature is not exactly a constant variable as it fluctuated throughout the experiment as the test tubes were even put in a refrigerator with a much lower temperature than in the room. A solution for improving could be to place the test tubes into an electric cooler in the beginning to make the temperature stable and put potato pieces when the test tubes are in the cooler. Also, errors could be decreased by using a more precise beaker. Finally, repeating the experiment several times would allow as to take the average results and have a more adequate result.

This could have affected the results because the potatoes might absorb the solutions in different because of their different attributes. Also, the timing was a little off between Test 1 and Tests 2 through 5 because through certain limitations on time and various constraints, Test 1 soaked in solutions for 28 hours whereas Tests 2 through 5 soaked for about 26.5 hours. This could have caused some problems with the collected data, but overall, Tests 2 through 5 follow similar trends to the initial test, so discrepancies were kept minimal. In addition to the timing being slightly off, the potato cubes from all of the tests were cut at the same time; however, only Test 1 used the freshly cut potatoes due to time constraints. Tests 2 through 5 used drier potatoes, which could have affected the data.

Cast the potato cylinders 5. Place all seven potato samples in a petri dish, and keep them close to avert their drying out. 6. Remove a cylinder from the petri dish and place it between the pleads of paper 7. Weight to nearest 0.01g on the aluminum sheet on the balance.

Table 1. Coursewide data comparing means of water potentials and osmolalities required to produce zero weight change of potato cores in three treatment solutions. Also includes chi-square and P-values for each set of data.

Pour 40ml of sodium thiosulphate into the 50ml-measuring cylinder then transfer the sodium thiosulphate into the conical flask. Place conical flask right above the dot on the

Pour distilled water into the volumetric flask until the meniscus hits the white line at 20.0 ml

After soaking, the cylinders were reweighed to determine their final weights. The initial weights were then subtracted from the final weights to find the change in weights. To determine the percentage of change in the potato, the values for change in weight were divided by the initial weights of the cylinder. I used the values for percentage of change and the different sucrose concentrations to create a scatter plot In Excel, which also calculated the y-intercept equation and the R-squared value. I also added a trend line, which helped me determine what concentration of sucrose was isotonic (same concentration of solutes) to the potato. By setting the y-intercept to 0 and inputting the values for the slope in the equation, I was able to solve for x and determine that the osmolarity of the potato was .48 (M). Therefore, if placed in a solution of .48(M) of sucrose there should be no net change in the weight of the potato. The results of the studies supported my prediction that hypotonic solutions will increase the weight of the potato and hypertonic solutions will decrease the weight of the

Place an Agar bottle into the 1000 ml beaker with the water slightly over the top of the

After conducting the experiment, the hypothesis “if a cell experiences osmosis, then it will shrink, or enlarge depending on the type of solution,” is proven incorrect. In both the distilled water and 1% salt solution, water from the potato cores’ surroundings moved into the cores causing them to gain mass. The cores gained water mass due to the fact that they were hypertonic while their surroundings were hypotonic. On the other hand, in the 3% salt solution and the 5% salt solution water from the potato cores moved out to their surroundings. The cores lost water mass because they were hypotonic while their surroundings were hypertonic.