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The Effect of Sucrose Concentration on Osmosis.

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The Effect of Sucrose Concentration on Osmosis Aims: The aim of this experiment is to find out the effect sucrose concentration has on the mass of a potato cell and the rate of osmosis. We also want to find the concentration of the cell sap in a potato. Introduction: This experiment is centred on osmosis. Osmosis is a specific form of diffusion that only affects water molecules. It is the movement of water molecules from an area of high concentration (many water molecules in one area) to an area of low concentration (fewer water molecules in one area) through a partially permeable membrane. Before Osmosis After Osmosis Osmosis occurs most commonly in plants. They use osmosis to take in water through root hair cells. This water can then be used by the plant in photosynthesis and can also supply the plant with some energy. The experiment we will be carrying out involves investigating osmosis in a potato cell. We will be studying the rate of osmosis in a potato cell when it is immersed in a sucrose solution of weak concentration, and also in various other concentrations of sucrose solution. Our results should be able to tell us the effect that sucrose concentration has on osmosis. We will be measuring the rate of osmosis by looking at the mass change in the potato cell. If the mass increases, then we will know that the potato has taken in water, and has a sucrose concentration lower than that of the solution. If the mass decreases, we will know that it has given out water and has a sucrose concentration higher than that of the solution. ...read more.


5. Drop one in each test tube and time for 30 minutes. 6. Record results of change in mass. 7. Repeat steps 2 to 6 using a cube shape instead of a fat cylinder. 8. Repeat steps 2 to 6 using a cylinder shape. 9. Choose the shape that gives the best results. Results: Shape of potato Mass change pure water, from starting mass (grams) Mass change 80% sucrose, from starting mass (grams) Fat Cylinder +0.25 -0.15 Cube +0.26 -0.17 Cylinder +0.22 -0.21 We have chosen to use the cylindrical shape because it shows a good amount of change in mass in both pure water and 80% sucrose, and the results show that it is a relatively equal change in mass in both solutions. Choosing the concentration range Method: 1. Set up apparatus needed in preliminary work. 2. Measure out 25cm� of sucrose solution with a concentration of 0.01%. 3. Using your chosen shape of potato cut a chunk out and drop it into the solution. 4. Time for 30 minutes then measure change in mass and record results. 5. Repeat steps 2 to 4 using concentrations 0.1%, 1%, 10%, and 80%. 6. Choose the most effective concentration and centre your range on it. Results: Concentration of sucrose solution Mass change, from starting mass (grams) 0.01 +0.21 0.1 +0.15 1 +0.14 10 +0.21* 80 -0.12 *Anomalous result We have chosen to use a range of results going from 5% to 15% sucrose. We have chosen this range of concentrations because we want to find the sucrose concentrations nearest to that of the actual concentration in the potato. To do this, we need the percentages that are nearest to 0. ...read more.


you have more results to use to check it. Our immersion time was also adequate, as we were able to find the information we needed from it. It made sure that we got a wide enough range of results, but was not too long, as we were able to complete the experiment easily. When we were doing our preliminary experiment, some of the potato cylinders did sink to the bottom of the test tube, making them hard to retrieve when the time came to measure the change in mass. This could be avoided in the future by making the potato cylinders smaller so that they could float in the solution. To extend this study, there are other investigations one could carry out. To find out about osmosis in plant roots and cells, you could do a detailed study over a period of time measuring the change in mass of a plant potted in some soil. To do this you would need to take a cutting from a plant (including the roots) and measure its mass at the start. Then you would plant this in a small pot of earth with a certain amount of water poured over it. This would need to be covered during the investigation to stop the water from evaporating away. The water would merely re-circulate if it had nowhere else to go. A specific environment would need to be maintained in order for the experiment to be successful. The amount of water would need to be decided on and kept the same throughout the experiment. After a fixed period of time, longer than in this investigation of course, you would take out the plant and measure the change in mass. This would tell us more about osmosis and how it works in plants, including the rate of osmosis in plants. Jess Cave 10B1 1 ...read more.

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