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Science Coursework: Investigating Osmosis in potato tissue

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Introduction

Science Coursework: Investigating Osmosis in potato tissue What is Osmosis? Osmosis is the passage water takes from as dilute concentration to a more concentrated solution via a semi/selectively permeable membrane. Water molecules will diffuse from the Dilute Solution into the more concentrated solution through the selectively permeable membrane. How will we use this in our experiment? We will use osmosis in our experiment by measuring how much water moves from the dilute solution of either the water in the potato cells cytoplasm or the concentrated solution outside of the potato into the more concentrated solution. What we are investigating We will be investigating the effect of osmosis in potato tissue. We will be investigating to see whether or not, if we change certain factors, the mass/size of the potato will be affected by osmosis. Factors that affect osmosis in potato tissue are as follows: * Type of potato (whether it's a sweet, King Edward, Maris piper.) This could affect it because of how concentrate the water is in the cytoplasm in the cells of the potato. * Concentration of water solution outside of the potato. (Whether its 2 spatulas worth of salt or 5 could make a big difference.) * Shape (surface area) * Size (mass) * Whether the potato has been peeled or not (potato skin is waterproof) * Time you leave the potato in the solution for. * Temperature of the water. (Heat makes water particles vibrate and travel faster; this could affect the rate of osmosis and therefore our results.) We will be investigating the concentration of the solution outside of the potato. To keep the experiment fair we will have to keep all of the factors the same apart from the level of salt concentrate. We will do this by having 6 different solutions of different concentrate with bits of potato in of equal size, and therefore an almost equal mass. ...read more.

Middle

Method The technicians in the prep rooms had already made us 3 slat solutions worth: 0.25%, 2% and 5%. We had to make 5 solutions of different concentrate salt and 1 solution of pure water. We only had 3 solutions of salt and we needed 5 so we halved the 5% and the 2% to give us 2.5% and 1% concentrate solutions. We halved them by measuring out 50ml of the given solution .e.g. 5% and then we added 50ml of water to dilute it, so it was 50ml salt concentrate and 50ml water. After doing this and putting the solutions into the boiling tubes we cut up, weighed and measured 6 pieces of potato that were going into the boiling tubes. Equal size and mass to keep it a fair test, this we have had to do on all as a fair test is very important. Then we placed the pieces of potato into their respective solutions and started the test. Sadly we never finished the test as lesson time ran out. But the above method will be the method used when we do the real experiment after the half term. Proper Experiment In this I will try to prove my prediction that the higher the concentration in the beaker the potato's mass and size will decrease and the lower the concentration in the beaker the potato's mass and size will increase. Apparatus * 6 x boiling tubes - test tubes would be impractical. * 6 x measuring cylinder - to get the same amount of water for each boiling tube. And for a fair test. 25 ml for each boiling tube. * 1 x test tube rack - to put the boiling tubes in. * 1 x spatula - to get salt from the salt container into the solutions. * 6 x bits of potato - equal size (for a fair test as surface area is a factor that effects osmosis - we only want to change one factor, the concentration) ...read more.

Conclusion

the higher the concentrate the more osmosis is taking place (apart from the anomaly of the 0.5% salt solution). Sadly we don't have enough time to conduct another repeat experiment to see if we can prove better our prediction. Evaluation I do believe that we have set out what we wanted to achieve. I am confident that my results were accurate and that I took enough of them so that my results are reliable. I believe my results are accurate because I used: * A measuring cylinder which had measurements of millimetres so that we could get it accurately. * The scales we used to weigh and find out the mass of the potato pieces had an accuracy of 2 decimal places. * We left the experiment over-night so that there was more than enough time for a recorded change of osmosis in the potato. * We used a ruler which had millimetre measurements on it and we measured to exactly 2.5 cm. Improvement * The water we used could have been pure water - not tap water that may contain chemicals which will affect the process of osmosis. * We could have kept the temperature in the lab constant when we left them over night as the temperature fluctuated during the night (at night the temperature drops considerably) this may have affected the rate of osmosis. Extension * We could use a different substance in the water to make the solution such as sugar or even pepper. * We could use another type of food or vegetable, like a carrot to see if we get the same results as the potato. * We could also find the amount of concentration of salt in the potato by fine tuning the solution outside the potato. * We could increase the amount of concentrations from six to ten solutions in order to get more results and therefore more reliable results that could prove/disprove my prediction that the higher the concentration in the beaker the potato's mass and size will decrease and the lower the concentration in the beaker the potato's mass and size will increase. ...read more.

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Here's what a teacher thought of this essay

4 star(s)

This is a good report that has clearly been written with care and attention.
1. The introduction is good and uses diagrams well to back up the ideas.
2. The preliminary tests are needed and well carried out.
3. The language used is good but inconsistent.
4. The conclusion could be improved to analyze the data and then try to explain it.
**** (4 stars)

Marked by teacher Luke Smithen 01/05/2013

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