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Find the concentration of cell sap in potato and to investigate the behaviour of potato in salt solution.

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Introduction

Linsey Belford U5E Aim: To find the concentration of cell sap in potato and to investigate the behaviour of potato in salt solution Aim: The aim of my experiment is to use salt solution to find the concentration of the cell sap in a potato and to see how a piece of potato behaves when placed in different concentrations of salt solutions. In my experiment this will be measuring the mass of the potato before and after the experiment to see if it has gained or loss any mass during osmosis. Prediction: I predict that the higher the concentration of the salt solution, the more water will move out of the cell and the mass will decrease. I think that mass will only decrease up to a certain point. The Science: Osmosis is the diffusion of water through a selectively permeable membrane from a region of high water concentration to a region of low water concentration. Selectively permeable means that the cell membrane allows only some things to pass through it. That is gases and water. It does not allow other things to pass through it. For example salt, sucrose, starch or proteins as their molecules are too big. A region of high concentration water is where there is pure water or a very dilute solution of something like salt. ...read more.

Middle

Size of potato: The large the potato size the more water can diffuse in and out of it. I need to keep the size of the potato the same all the way through the experiment so that the potato cylinders have the same surface area and are under the same conditions. The cylinders diameter will be 10mm and the length of the cylinder will be 20mm. Amount of Solution: The amount of solution needs to be the same so that the entire potato cylinder is covered and has the same amount of solution for the water to diffuse to and from. I will control this by using the same amount of solution and this will be 20 ml. Amount of time: To make this fair the time needs to be kept the same for all the experiments. This is so that the water has the same amount of time in each boiling tube so that the water has the same amount of time for diffusion. If some of the experiment has longer, more water will be able to diffuse in or out of the cell making a difference to the mass. I will control the time by using a stopwatch and keeping the potato cylinders in the boiling tubes for 45minutes. ...read more.

Conclusion

* White Tile * Knife * 20ml Measuring Cylinder * 2 pipettes The equipment will be set up as shown below. My new range of solutions is and they way that I make them is: Final Concentration Volume of 1M salt sol. Volume of water 1 M 20 ml 0 ml 0.8 M 16 ml 4 ml 0.6 M 12 ml 8 ml 0.4 M 8 ml 12 ml 0.2 M 4 ml 16 ml 0 M 0 ml 20 ml Safety: To make my experiment as safe as possible I will use safety goggles and wear a lab coat. This stops any of the salt solution from getting in my eyes and from getting on my clothes. I will also keep my work surface as tidy as possible so none of the experiments become contaminated and I will also tie my hair back Reliability: If I use the same method throughout my experiments then the experiments will have been treated fairly and the only variable will be the concentration. I am measuring the percentage gain/ loss of mass because the potato cylinders were different masses to start with so it would be fairer to do it this way. I am going to do an average of the result so it is fairer and the more results I use in the average the more accurate the results will be as it will take out very minor anomalies. Linsey Belford Page 1 ...read more.

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