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GCSE: Osmosis Coursewrok

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Introduction

Preliminary work Definition Osmosis is the passage of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration. The definition contains three important statements: 1. Osmosis is the passage of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration. 2. Osmosis is the passage of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration. 3. Osmosis is the passage of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration. It does not matter too much which order you put these statements in. Nor does it matter if you write the definition as one sentence or three sentences. All that matters in your exam is that you make all three points when you explain what osmosis is. Explanation When you put an animal or plant cell into a liquid containing water one of three things will happen. 1. If the medium surrounding the cell has a higher water concentration than the cell (a very dilute solution) the cell will gain water by osmosis. Water molecules are free to pass across the cell membrane in both directions, but more water will come into the cell than will leave. ...read more.

Middle

The process of regulating the amounts of water and mineral salts in the blood is called osmoregulation. My insulin page will tell you more about other homeostatic mechanisms. Animals which live on dry land must conserve water; so must animals which live in the sea (the sea is very salty!), but animals which live in freshwater have the opposite problem; they must get rid of excess water as fast as it gets into their bodies by osmosis. Plasmolysis Plasmolysis occurs when a plant cells membrane shrinks away from its cell wall. This phenomenon occurs when water is drawn out of the cell an into the outside cell fluid. The movement of water occurs across the membrane moving from an area of high water concentration to an area of lower water concentration outside the cell. Plant cells where the water flow into the cell and out of the cell are in equilibrium are not capable of providing the cell with support. Flaccid is a term used to indicate that the cell, although it contains water, does not have enough internal turgor pressure to provide structural support. As mentioned earlier, turgor pressure is the build-up of water within the plant cell. Because of the rigidity of the cell wall, the cell does not rupture, but instead the internal pressure increases. ...read more.

Conclusion

? I noticed a dramatic change in the average when I didn't include group 1. The results were more like my results without group 1. ? Groups 2, 3 and 4 had some similar averages but not all of them were similar. ? Each of the 5 pieces of potato for my group in each tube were fairly similar but they weren't ever all the same length. ? The results I got were not very consistent. Although the majority were, there were some results that I would have expected to be different. For example, I would have expected piece 1 in the 0.75m to be around 1.70cm judging by the other results but it was 1.90. > Safety ? Don't run in the lab. ? Listen carefully to instructions. ? Keep the benches and floor clear of bags and coats. ? Always wear safety goggles when instructed to. ? Tie back loose hair and fasten up loose clothing ? Don't touch gas taps, electrical sockets or other equipment unless instructed. ? Don't eat or drink in the lab. ? Light a Bunsen burner properly on a heatproof mat. ? If you break anything tell your teacher straight away. ? Always clean up spills and put things away. ? Don't distract other pupils while they conducting experiments. ? Be careful when using the borer as it can hurt you because it is sharp. Analysis evaluation ...read more.

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