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An Investigation to Find out the Solute Concentration of Potato Cells by Osmosis.

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Introduction

An Investigation to Find out the Solute Concentration of Potato Cells by Osmosis. Background information Here is a definition of osmosis: * Osmosis is the net flow of water through a selectively permeable membrane. In this investigation we will be watching osmosis at work on potato cells and different concentrations of sucrose. Plan Variables Available to Test * Temperature - Temperature could be a main factor as it could speed up the movement of the water molecules, and therefore speed up osmosis. * Size of Potato - The size of the potato could effect the amount of water molecules that are able to diffuse through into the surrounding sucrose solution. * Sucrose Concentration - The sucrose concentration, if high would allow more water molecules through and, if low wouldn't let many molecules through at all. Osmosis only works if the surrounding sucrose solution concentration is higher than the concentration the molecules start in. We chose to use sucrose concentration to investigate osmosis, as osmosis is mainly to do with diffusing from one concentration to another. Method 1. Peal a potato using a knife but remember to push the blade away from you, because if you slipped then you could cut yourself. 2. Using a corer cut out cylinder shaped pieces from the potato. Make sure you use the same sized corer each time so you don't get different sized potato pieces. 3. Measure out the pieces to the length you want (3cm). ...read more.

Middle

How we are going to make the tests fair To make sure the investigation is fairly conducted we will: * Keep the temperature the same (room temp 23�C) * Make sure the concentrations are divided up carefully, using a measuring cylinder * Make sure the potato pieces are the same size * Take the potato pieces from the same potato * Use the same sized corer to make the potato pieces * Give each test 40 minutes to work Prediction I predict that the water molecules in a potato piece in a higher concentration of sucrose solution than of in the potato piece will diffuse into the surrounding higher sucrose concentration by osmosis. This is because of the basic laws of osmosis; osmosis is the movement of water molecules from a substance of a sucrose concentration to a substance of higher sucrose concentration. If the surrounding sucrose solution has a lower concentration than in the potato piece then the water molecules in the sucrose solution will diffuse into the potato piece by osmosis. If the potato piece absorbed water molecules by osmosis then I would expect it to weigh more and maybe increase in size. If the potato piece's sucrose concentration was lower than the surrounding sucrose solution's I would expect it to weigh less and decrease in size because of it's water molecules diffusing out of it and into the surrounding sucrose solution. ...read more.

Conclusion

In all the correct results the potato piece starts to lose weight or size between 5 and 10. This tends to suggest that our guess of around 8.5% is correct. Whether or not our results agree with our predictions I would say that our results did agree with our predictions. In the prediction I predicted that if the potato piece was put in a surrounding sucrose concentration that is higher than that of the potato piece's then the water molecules inside the potato piece would diffuse into the surrounding sucrose concentration by osmosis. And if the potato piece has a higher sucrose concentration than the surrounding sucrose concentration then water molecules will diffuse via osmosis into the potato piece cause the potato piece to increase in size and weight. This did happen. In all the correct results you could see that osmosis was taking place and the potato piece was getting lighter or heavier. Our results followed the simple laws of osmosis: If something is put in surrounding higher sucrose concentration than it, molecules will diffuse from the object into the surrounding sucrose solution. In our investigation this law was proved. Our average result for surface area change with a potato piece in a surrounding sucrose solution concentration of 20% clearly states this. The surface area of the potato piece decreased by 0.4cm�. This is because the sucrose solution surrounding the potato piece had a higher concentration than the potato piece, so the water molecules in the potato piece diffused into the surrounding sucrose concentration. ...read more.

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