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Biology Coursework

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PLANNING INTRODUCTION- During this investigation I am going to find out how osmosis affects potato cells. Osmosis is the diffusion of water -or any other solution- through a semi-permeable membrane, from a region with high water concentration to a region with a low water concentration. The movement will take place across a cell wall- a semi-permeable membrane; in this case the potato cell, which lets smaller molecules such as water through but does not allow bigger molecules to pass through. So I will investigate this by using 5 slices of potatoes of the same mass and inserting them into 5 different concentrations of a sugar solution. At the end of the investigation I hope to see how much of the sugar solution is absorbed into the potato slices. EQUIPMENT- * 3 potatoes * Scales * Ruler * Knife * Chopping slate * 10 Test tubes * 2 Test tube racks * 5 concentrations of a sugar solution. (Ranging from 0%-10%) METHOD- I will set up 10 test tubes, because in order to save time, I intend on doing the test twice so that I can calculate the average result, making it more accurate. After I set up the ten test tubes in the two test tube racks (5 each) I will label each test tube. Both racks will have a test tube labelled 0%, 2.5%, 5%, 7%, 10% and either test 1 or test 2. ...read more.


Room temperature is roughly 20 degrees Celsius. The length and mass of the potato slices are a prime factor in the experiment. The lengths and mass of the potato slices have to be the same in order for the experiment to be a fair test; these variables shall not be changed unlike the concentration. PREDICTION- I predict that the lower the concentration the sugar solution is, the larger the mass of the potato slice shall be, because more water will be diffusing into the potato if the concentration of the solution is lower than that of the potato. Also, the higher the concentration of sugar solution is, the less the potato slice shall weigh because water will be diffusing through the potato into the solution as it has a higher concentration then the potato has. Also the longer the potato slices are inside the sugar solution the more water shall be diffused by the potato slice either increasing the mass of the potato or decreasing it. OBSERVING Recording- In my results table I will show that the mass of the potato before the experiment and after. I will also show if it was Test 1 or 2 and the concentration of the solution as well as the change in mass. Units- The units for my results will be grams (g) ...read more.


EVALUATION Reflecting- My experiment worked well because I managed to get an average result making it more accurate. There were no anomalies in my table or my graph. I know my results were reliable because it was a fair test and as I did each test twice and made sure the mass of the potatoes in grams were the same making it more accurate. I could improve the experiment by maybe doing it three times instead of two so that I would have a better average result, making it more reliable. I would describe my experiment as being successful because it does show that as the concentration of the sugar solution increases, the mass of the potato slices decrease and when the concentration of the sugar solution decreases the mass of the potato slice increases. Therefore I can say my conclusion is that the higher the concentration of the sugar the more the mass decreases, this is because the water present in the potato diffused through the cell wall and into the sugar solution as it is a region of lower water concentration. I know this because in my experiment the opposite happened to the potatoes placed in the lower concentrations of the sugar solution; the potatoes gained mass because the potatoes had a lower concentration of water then the solution so water molecules diffused through the cell wall and into the potato. The support and evidence for my conclusion comes from my results table, graphs and scientific explanation. ?? ?? ?? ?? BIOLOGY COURSEWORK ...read more.

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