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The aim is to find out how osmosis is affected by different concentrations of salt solution, in potato tissue.

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Introduction

An investigation to see how OSMOSIS is affected by different concentrations of salt solution!! AIM: the aim is to find out how osmosis is affected by different concentrations of salt solution, in potato tissue. Diagram: [image004.gif] [image005.gif] [image006.gif] Bung salt solution test tube Potato chip [image007.gif] [image008.gif] [image008.gif] [image008.gif] [image008.gif] [image009.gif] Distilled 0.25% 0.5% 0.75% 1.0% Concentrations of salt solution Safety: v Tie your hair back - because loose hair can interfere with practical work. It might dip into acid etc. v No running- because this will cause lots of accidents, there is more chance of slipping and you may bump into other people. v Clear up any spillages - because other people can slip and some substances can be harmful. v Stand up - so that if there is a spillage or explosion it is easier for you to get away. v Tuck stools under tables - so that people don't bump into them. Equipment: v Test tubes X 15 bungs X 15 v Borer measuring cylinder v Test tubes racks tile v Ruler scales v Knife tissue v Plain sticky labels potato v Five different concentrations of salt solution. The input variable for this investigation was the different concentrations of salt solution. ...read more.

Middle

There are no specific patterns in the way osmosis occurred. For example as the concentration doubled the change in mass did not halve or anything like that. The reason for this is that in the pure water solution the potato chips swell up because water enters them by osmosis, in the rich salt solution water leaves the potato chip by osmosis, and so they shrink in size. Osmosis is trying to balance the amount of water particles on each side of the partially permeable potato membrane. When there is hardly any salt in the salt solution (i.e. it is weak) there is more water in the solution than in the potato so water goes form the solution into the potato. When the salt solution is more concentrated (i.e. 1%) there are more water particles in the potato than in the solution so they leave the potato and enter the solution by osmosis. If you think very technically then there should be a pattern that as the concentration doubles the change in percentage mass should halve. Because at 0.25% there was a + 13% mass change, at 0.5% there was an + 8.8% change, which is nearly half. In the 0.5% salt solution there are twice as many salt particles than in the 0.25% solution, this would mean that there would there is less water in the 0.5% salt solution and therefore less osmosis is needed to reach a water Equilibrium. ...read more.

Conclusion

Also to get very definite end results the experiment could have been left for longer so that all the osmosis that was going to happen would have happened. A water equilibrium would have been reached, and then the mass of the potatoes would be in some sort of proportion to the concentration of the solution and it may have also been possible to come up with a formula or rule that linked the two. This investigation could have been extended for a different variable. Many things affect the rate at which osmosis occurs like, the concentration gradient, the size of the ions or molecules, and the distance over which it occurs. It is possible to extend this particular investigation by using a different substance instead of the potato. Some thing with a much thicker membrane would increase the distance over which osmosis has to occur and consequently the results would be different if the experiment was left set up for the same period of time. This investigation would then be to see what factors affect the rate at which osmosis occurs. Alternatively an investigation could be carried out to see how temperature affects the rate. This could be done by setting up the experiment in the same way as before but instead of simply leaving the test tubes to stand in a test tube rack; they could be put into water baths that are kept at certain constant temperatures. ...read more.

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