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How is osmosis affected by the concentration of salt that we use?

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Introduction

Biology Coursework Osmosis and potato cores 11/16/2007 Alex Tanner BIOLOGY COURSEWORK How is osmosis affected by the concentration of salt that we use? INTRODUCTION We are carrying out an investigation to see how the concentration of water will affect osmosis within a potato core. We were given a choice whether to decrease the water concentration with a salt or sugar solution, we thought; it was easier to work with salt solution though as the sugar solution became sticky when we decreased the water solution. I will use two sets of results to see how an increase in salt solution affects osmosis. STRATEGY We will use potatoes to show that osmosis is occurring, we have to use the same potatoes as water density's may change as will other things if you vary between potatoes, we will place a 4cm long core of potato (from the same potato) into different concentration of salt in water. Before the potato is placed in the solution, the weight and length will be recorded. It is highly important that we use the same length potato as the surface area would affect the osmosis. This is important as it increases the reliability and accuracy as the only variable is still the salt concentration. We will have 6 different measurements of salt concentration, In Ml: 0 salt/ 100 DW, 20 salt/ 80DW, 40 salt/ 80 DW, 60 salt/ ...read more.

Middle

So for our actual recording for coursework we took our repetitions from a different potato as there is more variation and ensure accuracy. We did start to use volumes. However results were inconclusive and it deteriorated the reliability as the potato core had got wet and even though we dried it is no 100% that it is completely dry, this could affect osmosis when we place it in the test tube. EQUIPMENT 1. 10 TEST TUBES 2. SPACHULA 3. PIPETTE 4. SCALES 5. CHOPPING BOARD 6. KNIFE 7. POTATO CORER 8. POTATO We did our preliminary work to try out our initial ideas but after we saw some of the problems that this involved we improved it, we increased accuracy and reliability by using more concentrates. This ensures that if we get different results from different potatoes it will help us come to a conclusion, if we only have results from one potato in effect we are reviewing osmosis in that potato not on more of a general scale. In my experiment I have changed the concentration of the salt, kept the time the same (24 hours), the length of the potato core is consistently the same, although we cannot control the weight. The length is a consistent 2.1 cm, the weight varies from 1.78 to 1.88, and this shows the variation in density among different potatoes, although this is only 0.1 of a gram. ...read more.

Conclusion

The fact that it is in order for example the first % change is the largest % change in its group and the last in its group is the smallest. CONCLUSION The potato cores have increased in weight when the water concentration in the solution is higher than that in the potato. The weight in the potato core decreases when the water concentration in the solution is lower then that in the potato, this happen as the water molecules diffuse from the potato cells into the solution. On the other hand when the weight increases the water concentration in the solution is higher than that in the potato, so osmosis occurs and the water travels into the cells and makes the cells increase in weight and size. We choose to use weight as the main way to investigate osmosis, this is because in our preliminary the results were better, and also I feel it was more accurate as they were getting measured by scales and to two decimal places. This conclusively would make our percentage change more accurate. From our results we know that the concentration of water in a potato is between 40 and 60% but roughly 45%. We can see that we have a curve that is reliable and accurate. % Change 9.7826 7.5676 3.8251 -2.1978 -3.8462 -5.9783 10.1124 6.9519 1.6216 -1.5957 -6.5574 -8.7432 EVALUATION ?? ?? ?? ?? 4 | Biology Coursework ...read more.

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