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To find out the concentration of cell sap

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Introduction

Aim of the Experiment: To find out the concentration of cell sap Scientific Background Osmosis is the net movement of solvent molecules (water) through a semi permeable from an area of high water concentration (hypotonic solution) to an area of low water concentration (hypertonic solution). A semi-permeable membrane/partially permeable membrane is the one with tiny holes that are just big enough to let small water molecules through. Bigger molecules such as glucose can't pass through the semi-permeable membrane. In osmosis water molecules pass both ways through the membrane but the overall movement is from a hypotonic solution to a hypertonic solution. The diagram below shows osmosis in action: Osmosis occurs in plants. Plants need water in order to survive. They use this water in keeping cool, making glucose in photosynthesis, transporting food and mineral and keeping upright and rigid. The plant takes in this water through the roots. When the water level in the root cells decrease the solution in cell sap such as in the root hair cells becomes hypertonic and this causes water from the soil to move into the root hair cell. This water is then transported around the plant cell by cell by osmosis. For example, if the root hair cell has a lot of water and the cells next to it don't then the water will move to these cells. Plant cells always have a strong cell wall surrounding them. When they take up water by osmosis they start to swell, but the cell wall prevents them from bursting. ...read more.

Middle

Cork Borer are also sharp, care needs to be taken when they are used. Plan 1. Take a potato that's healthy and hard. 2. Drill a hole into the potato using 10mm cork corer. Take the drilled piece of potato and cut it to a length of 2 cm using the ruler. Cut another 4 potato pieces the same way. 3. Take five beakers and label the 1, 0.8, 0.6, 0.4 and 0.2. Now measure 50 cm3 of 1 molar sucrose solution using a 100 cm3 measuring cylinder and place the solution into the corresponding beaker. Repeat this with the rest of the four molar solutions left. 4. Now place the potato pieces into each of the molar solutions and start stopwatch. 5. Run the experiment for 60 minutes. 6. Then fish out all the potato pieces with a tong and lightly roll them on the tissue paper to remove excess water. 7. Then weigh each potato piece on an electronic weighing scale and record the change in mass (if any). 8. Repeat the experiment again to get reliable results. Results 1 m Solution Molarity Before mass in gm After mass in gm Total gain or loss in gm 1st attempt 1.7 1.1 -0.6 2nd attempt 1.7 1.2 -0.5 Average -0.55 0.8 m Solution Molarity Before mass in gm After mass in gm Total gain or loss in gm 1st attempt 1.7 1.0 -0.7 2nd attempt 1.7 1.1 -0.6 Average -0.65 0.6 m Solution Molarity Before mass in gm After mass in gm Total gain or loss in ...read more.

Conclusion

Not all the potato pieces were cut to exactly the same length. Some were cut at a slanted angel, so therefore only one side measured 2cms. Cutting carefully and slowly straight down with a scalpel angled at roughly 90� could have prevented this. Not all the weight measurements were that accurate as the weighing scale wasn't that sensitive and only measured accurately to 0.1 of a gram. Using a more sensitive weighing scale could have prevented this. The sucrose solution wasn't measured to extreme accuracy. Reading the measurements at eye level and getting someone else to check the volume could have prevented this. The results matched the prediction completely as regards to the gain and loss in mass in different types of solutions. But the results don't show a definitive molarity of the potato piece. The results only suggest that the molarity is above 0.2. The evidence obtained is sufficient enough to match the prediction regarding weight loss and gain. But there isn't enough evidence to show what the real molarity of the potato pieces is. There are various ways in which the experiment could have been extended to get reliable, accurate and definitive results. Firstly, the experiments could be repeated several more time to get accurate figures. The moralities of the solutions could have been narrowed down further to between 0.2 and 0.3. To get accurate results a wide range of moralities between 0.2 and 0.3 could be tested, i.e. 0.205, 0.201, 0.215, 0.220, etc. Also in addition to measuring the mass the length and diameter of the potato pieces could be measured to look for any changes in different moralities of sucrose solution. ...read more.

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