Osmosis Investigation Essay -- GCSE Biology Osmosis Coursework

Osmosis Investigation How different concentrations of sucrose solution effect potato tissue. Aim How do different concentrations of sucrose solution effect potato tissue. Background Information Osmosis is the movement of water molecules though a partially permeable membrane from an area of high water potential to an area of low water potential. High Concentration Low Concentration The membrane lets small water molecules pass though but not large ones. The flow continues until the concentration becomes the same on the inside as on the outside. This is called equilibrium. Molarity is a measure of concentration. Prediction I predict that the potato will change in mass and in length. I believe this because each Molarity of sucrose will change the potato's water content. This will happen because either the concentration will higher in the sucrose and lower in the Tubas or lower in the sucrose and higher in the Tubers. Therefore water will travel in or out of the potatoes cell though its partial permeable membrane. Preliminary Method ÂÂ · I will firstly get 10 test tubes and to test tube racks ÂÂ · Then I will cut 9 pieces of potato ÂÂ · I will then get 3 different Concentrations of sucrose solution and add 20cm3 to each test tube ÂÂ · Cut a 4 mm in diameter tuba to 1 cm in length ÂÂ · Now I will measure the length and mass ÂÂ · Now place the pieces in ÂÂ · Now leave this for 15 minutes ÂÂ · Now I will measure the length and mass Preliminary Results After we did the Preliminary Test we decided to use 1 cm long 4 mm diameter tubas. We would put them in 25 cm3 sucrose solutions. I don't have any actual results because the potato tubas shrivelled up in the fridge. Method 1. I took two average sized ground potatoes and checked that they were both healthy and hard. 2. Using a standard kitchen knife I peeled the potatoes and used a potato tuba to cut 18 equally size tubas 3. Using a scalpel and ruler I cut the potato into lengths of 4mm by 10mm. I had to be very careful whilst cutting the potato as the scalpel is exceptionally sharp. I then had 18 tubas 4. Taking a test tube rack I placed 18 test tubes in it and then labelled them (0.00M, 0.25M, 0.50M, 1.00M, 1.50M, 2.00M) 5. Using a measuring cylinder I measured out 25cm3. I then poured this carefully into ea... ...the water potential inside the tissue. To measure the tubers I think I would use a digital measurer that goes to two decimal places for accuracy and it would go to the same accuracy level as the top pan balance. I would also increase the amount molar amounts I use, such as 0.25 and 0.75. one explanation for the bad results is when the potato chips were removed from the test tubes and dried I may well have dried some potatoes more thoroughly than others and so some would have more excess water, which would add to the mass. If the experiment was repeated I could find another way to dry the potatoes that would ensure that all were dried in the same way for the same time. I were to repeat the experiment I would have possibly found a machine to cut the potato as it would ensure that all potatoes would be the same weight and dimensions. As well as the potato I could have found a more accurate way to measure out the solutions and to determine the molar concentrations. Perhaps I could have used a burette. This would ensure that I have an accurate amount of fluid in each test tube. I could also weigh each tuber on a more accurate scale, e.g. not to 0.00g but to 0.0000g