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Osmosis investigation.

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Introduction

Osmosis investigation. Background knowledge: The information of the background knowledge comes from my own knowledge and textbooks. Form my own knowledge I that Osmosis is the movement of water molecules, form a region of high water concentration to a region of low water concentration. (Weak to concentrated solution) through a semi permeable membrane until concentrations become uniform (equal on both sides of the membrane). But osmosis also affects other factor such as plant and animal cells. This knowledge has come from a textbook. In animal cells have red blood cells, which contain solutions such as salts and other substances. But when these cells are placed in water they expand. When they are in the water the cells aren't visible. This is because the water has entered the cells by osmosis causing the cells to swell and eventually burst haemolysis. But when the cells are bathed in a concentred solution, the water moves out by osmosis. So the cells shrink and become crinkled, this is know as crenation. When plant cells, are placed in water they increase in size. The water has entered the cells by osmosis, causing them to swell. This is when the vacuole is pressing against the cytoplasm and the cell wall. The cells are now fully turgid. Unlike the animal cells the plant cells don't burst because the cell walls are tough and strong. But when the cells are placed in a salt concentration, the vacuole shrinks. The cytoplasm is pulled away from the cell wall. The cell membrane also pulls away from the cell wall. This is known as plasmolysis. Now the animal cell is now as a plasmolysed cell. This happened because the water from inside the cell has moved out, due to osmosis Aim: My aim is to investigate three factors; those three factors are concentration of solution, mass before and after and length before and after. ...read more.

Middle

The reason you place the chip on the tile is, so that the chip doesn't become contaminated, with what ever was on the table. Then take a reading of each length of every potato and put it into the results table. After you had recorded each potato chip, then you should check each chips mass by putting it on the weighing balance. When weighing the weight of the potato chip on the scales, you must not lean on the bench because it affects the weight. You should do this one chip by one chip so that you don't get the readings mixed up. After you have weighed one chip, put it in the petri dish and label which side you put it on left, centre or right and the solution on the lid using the sticky label. Three potato chips are being placed in each Petri dish so that I can get a better average. There will be five solutions and in every solution there will be three potato chips. Starting the concentration at 0g/l and going up to 200g/l. When you have five complete Petri dishes labelled then you should add, a different solution to everyone. Each solution should be measured before being poured into the dish. This will make my experiment a fair test. You have to make sure that add enough solution that it is covering each potato chip completely leaving no gaps. As this may alter the readings and give me some poor results Once this is done time each Petri dish using the stopwatch for an hour and half. Following after the hour and half open the Petri dish and remove each potato chip carefully and place it on the tile. You Should remove any excess water by rolling the chip on a paper towel, keeping each surface on the towel for 2 seconds, making sure that you do not squeeze the chip so that the results are fair Checks it's length after you have token it out and record it in the results table. ...read more.

Conclusion

This will stop the potatoes and salt solution from evaporating or being contaminated. Once this is done you should place five petri dishes in room temperature, which is about 27 degrees and place the other five dishes in the freezer, which should be about -5 degrees. Time each Petri dish using the stopwatch for an hour and half. Following after the hour and half remove the five dishes out of the freezer and then open the Petri dish and remove each potato chip carefully and place it on the tile. You should remove any excess water by rolling the chip on a paper towel, keeping each surface on the towel for 2 seconds, making sure that you do not squeeze the chip so that the results are fair. Checks it's length after you have token it out and record it in the results table. Do this for all the chips. Still making sure that you don't mix the potato chips up or the solutions they are in. Then you should check each chips mass by placing it on the weighting balance. Take each reading carefully and record it in the results table. You should have two results table one for the room temperature and one for the dishes in the freezer. The results table is the same as the one above. When this is done though the potato chips away and clear your mess up, that you have made. The results table should look half full all you need to do now is to work out the change in mass, the percentage change in mass, the change in length and the percentage change in length. You should repeat this experiment another two times to give you nine results for each solution. At the end of the first experiment you should wash the Petri dishes. This is so that no salt solution is left in them that might change the results or contaminate the next result. Repeating the experiment will help you to get a better set of average results. Kuldeep Jagpal 11 Bennett ...read more.

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