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An introduction to osmosis.

Extracts from this document...

Introduction

Science Coursework Osmosis Plan An introduction to osmosis. The movement of water molecules from a high concentration of water molecules to a lower concentration of water molecules through a partially permeable membrane is called Osmosis. Under normal conditions, the concentration of water molecules and salts is the same in both cells and plasma. After sweating, water and salts are lost from the plasma and there is a lower concentration of water in the plasma than inside the cells. Water molecules therefore diffuse out from the cells through the cell membrane. We call a membrane like this partially permeable. Water molecules are small, so they pass through the membrane much more easily than salts. Diagram: There are several different types of cells in xylem but the one that transports most water and minerals to the leaves are called xylem vessels. These are formed from dead xylem cells whose end walls have broken down. These form continuous tubes. The xylem vessels act like pipes in transporting water up the plant. Wood is made up of xylem cells; most xylem cells have substances in their walls which strengthen the cells. This is why wood is a strong material. Osmosis in plants The root hairs together increase the surface area of the root. This enables water and mineral ions to be absorbed more quickly. The soil solution is water containing low concentrations of mineral ions. This is a dilute solution. The cytoplasm and the vacuole... Stacey Owen Candidate no: 0126 Hampton Community College of the root hair cell contain a higher concentration of mineral ions, than the soil solution. ...read more.

Middle

Now I can find out whether there has been a decrease or increase in the weight of the potato chip from the original weight. We either had the choose of using 0g,1g,2g,3g,4g,5g of sugar or using 0g, 1/2g, 1g, 11/2g,2g,21/2g. we decided the second option because we were told that half the class should do 1 set of measurements of sugar and the other half should do the other set of measurements of sugar, but we thought most the class would do the first one as it basic, so we done the other set but I then repeated the experiment using the other option. I had to make a measurement of each potato chip before and after osmosis had taken place. I tried to make sure my experiment was as precise as I could make it e.g. I made sure I wrote down the right weights by weighing them again, then checking the people books who I will be working with. Also I will put the measuring cylinder on a flat surface, so I make sure there is the right amount and when transferring the water from the measuring cylinder to the test tubes, I will try not to spill any. I try to use the right measurements e.g. for sugar, I used grams and for water, I used millimeters. Preliminary work For my preliminary work, I did a small experiment using dialysis tubing. I took a length of dialysis tubing and made it into a sac about 10-12cms long. I filled this sac with strong sucrose sugar solution and tied the ends off. ...read more.

Conclusion

My results show quite definitely that as the potato chips are in more sugary water they shrink. I'm happy with the accuracy of my results for two reasons: 1. The results follow my prediction. 2. All the points on the graphs are close to the line of best fit. I could have made my experiment more accurate if I had taken another set of readings or even several more sets of readings, I would have obtained a better average. I'm pretty pleased with the suitability of my experiment for the following reasons: 1. I was able to get a good and valid set of readings using the equipment and time allowed. 2. I made sure that the test was as fair as possible by making sure the amount of water was the same, the potato chips were from the same potato and that there was only one input variable that changed i.e. the amount of sugar. There was only one anomalous result. It was the 5th result in the first set; this was because it was shorter than the others. So it could not take in as much, so it could not give out as much either. So if I was to do the experiment again I would measure the length of the potato and then take this into account when looking at my results. Therefore I'm happy that my evidence is accurate and reliable enough to support my conclusion. To improve and extend this investigation I could use the same method to investigate a greater range of input variables e.g. * Temperature * Bigger potato chips * Sugar (more concentrated) * Use other materials (different fruits) Stacey Owen Candidate no: 0126 Hampton Community College 1 ...read more.

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