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...he increase means the cells within the potato cylinder should be turgid as well. I now predict the outcome of the experiment for the test tube with the 0.2M solution in it. I predict that the percentage change in mass will also be an increase in percentage mass because the concentration of water is greater in the solution surrounding the potato cylinder than in the potato cylinder. The water should move down a concentration gradient and into the potato cylinder therefore increasing the cylinder’s weight, this weight change should not be as great as for the 0.0M or the 0.1M solutions as this solution’s concentration of water has decreased. But the increase means the cells within the potato cylinder should be turgid as well. The diagram below shows a turgid plant cell: I now predict the outcome of the experiment for the test tube with the 0.3M solution in it. I predict that the percentage change in mass will be either a slight increase in percentage mass or a slight decrease in percentage mass because the concentration of water is similar in both the solution surrounding the potato cylinder and the potato cylinder. The water should not move down a concentration gradient therefore the cylinder’s weight should stay roughly the same; this weight change should be relatively small as the concentration of water in the potato cylinders and the concentration of water in the solution is about the same. The diagram shows a plant cell in equilibrium: I now predict the outcome of the experiment for the test tube with the 0.4M solution in it. I predict that the percentage change in mass will also be a decrease in percentage mass because the concentration of water is greater in the potato cylinder than in the solution surrounding the potato cylinder. The water should move down a concentration gradient and out of the potato cylinder therefore decreasing the cylinder’s weight, this weight change should not be as great as for the 0.5M solution as this solution’s concentration of water is greater than for the 0.5M solution. But the increase means the cells within the potato cylinder should be plasmolised. Lastly I will predict the outcome of the experiment for the test tube with the 0.5M solution in it. I predict that the percentage change in mass will be a decrease in percentage mass as the concentration of water is greater in the potato cylinder than the solution surrounding it. The water should move down a concentration gradient and out of the potato cylinder therefore decreasing the cylinder’s weight. The cells within the potato cylinder should become plasmolised. The diagram below shows a plasmolised plant cell: What I am going to do I am going to try and determine what affect each of the different concentrations effect the percentage change in mass for the potato cylinders. Factors affecting the experiment The factors that affect the experiment are • Temperature • Concentration of the sucrose solution • Surface area of the potato cylinder • Time each potato cylinder is left in the sucrose solution. What factor am I going to change? The factor that I am going to change is the concentration of the sucrose solution; the concentrations that I will use during the experiment are 0.0M, 0.1M, 0.2M, 0.3M, 0.4M and 0.5M. What am I going to measure? The factor I will measure is the change in mass of the potato cylinders. I will measure the initial and final masses of each of the potato cylinders which enable me to find the percentage change in mass using the following equation Final mass –Initial mass × 100 Initial mass What am I going to keep the same? The factors that I will keep the same are, • The temperature, I will try to keep the temperature the same for each potato cylinder. • Length of the potato cylinder, I will cut each potato cylinder to 4cm. • The surface area, I will keep this the same by using the same cork borer for each potato cylinder. • The time each potato cylinder is left in solution, I will make sure each potato cylinder is left overnight for the same period of time. • Volume of solution, I will put 15cm³ of each solution into the correct test tube. Fair testing To make sure this is a fair test I will make sure everything is kept the same for each test tube apart from the actual solution put into each test tube. List of apparatus • 12 boiling tubes • 30cm³ of water • 30cm³ of each sucrose solution • cork borer • ruler • scalpel • potato • electronic scales Method 1. Set up boiling tubes with 15cm³ of the correct sucrose solution in each one. 2. Use cork borer to cut 6 potato cylinders. 3. Measure the cylinders to 4cm and cut off the excess potato. 4. Weigh and record each potato cylinder’s mass. 5. Place each of the potato cylinders in a boiling tube. 6. Repeat above steps to improve accuracy of results. 7. Leave potato cylinders overnight. 8. Take out potato cylinders and dry. 9. Weigh and record the mass for each potato cylinder. Safety • Wear safety goggles to prevent sucrose solution from getting in your eyes. • Be careful when using scalpel to cut off excess potato. • Wear an apron to prevent sucrose solution from getting onto your clothes • Be careful when using the cork borer. Strategy for dealing with results I will record my results in a table that looks like the one shown below. Solution concentration Initial mass (g) Final mass (g) Change in mass (g) % change Average % change 0.0M 0.1M 0.2M 0.3M 0.4M 0.5M 0.0M repeat N/A 0.1M repeat N/A 0.2M repeat N/A 0.3M repeat N/A 0.4M repeat N/A 0.5M repeat N/A I will then put the average percentage change results into a graphical form my prediction for what the graph will look like is shown below. Obtaining evidence Table of results Solution concentration Initial mass (g) Final mass (g) Change in mass (g) % change Average % change 0.0M 1.42 1.61 +0.19 +13.38 +16 0.1M 1.49 1.59 +0.1 +6.71 +5.17 0.2M 1.35 1.36 +0.01 +0.74 +1.77 0.3M 0.96 0.88 -0.08 -8.33 -7.77 0.4M 1.49 1.13 -0.36 -24.16 -23.91 0.5M 1.43 0.94 -0.49 -34.27 -32.44 0.0M repeat 1.45 1.72 +0.27 +18.62 N/A 0.1M repeat 1.38 1.43 +0.05 +3.62 N/A 0.2M repeat 1.43 1.47 +0.04 +2.80 N/A 0.3M repeat 1.25 1.16 -0.09 -7.20 N/A 0.4M repeat 0.93 0.71 -0.22 -23.66 N/A 0.5M repeat 1.34 0.93 -0.41 -30.60 N/A + = percentage increase - = percentage decrease Observations 1. Osmosis has occurred within the potato cells. 2. For the solutions 0.0M, 0.1M and 0.2M the cells within the potato cylinders are turgid. 3. For the solutions 0.3M, 0.4M and 0.5M the cells within the potato cylinders are plasmolised. Conclusion Trend From my results I can conclude that as the concentration of the sucrose solution is increased the mass of the potato cylinders decreased. This is clearly shown by my results and my graph, the graph also shows from the way the line of best fit slopes that there is strong negative correlation between the mass of the potato cylinder and the concentration of the sucrose solution. Conclusion For the 0.0M solution the percentage change in mass increased by 16% this was because the concentration of the water in the solution was greater than in the potato cylinder so the water travelled down a concentration gradient and into the cells, as the cells gained water the cell membrane is pushed tighter and tighter against the cell wall, as the cell wall is made of cellulose it causes the cells not to burst but instead the cells become turgid. For the 0.1M solution the percentage change in mass also increased by 5.17% although this time the change was lower than for the 0.0M solution the change was still due to the concentration of water ...