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# Investigation of different molar salt solutions on the rate of osmosis in potato slices.

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Introduction

Investigation of different molar salt solutions on the rate of osmosis in potato slices Section A. Planning and Predicting 1. Practical Procedure In this experiment I am going to try and find out whether or not osmosis occurs in potatoes, and the effect that different molar solutions of salt and water have on the potato. I will use five different molar solutions of salt and water: 0 (100% water), 0.05, 0.10, 0.15, and 0.20. I will then study the effects on the potato by putting three different sized slices of potato into five test tubes containing the above solutions. I will use a small, a medium and a large slice of potato in all five test tubes of different molar solutions. Before putting the potatoes into the test tubes I will weigh each slice and record it. The potatoes will then be left to soak for thirty minutes before taking them out, carefully drying them and then re-weighing them to see if the mass has changed. 2. Collecting Valid Evidence I am going to measure the weight of the slice before and after leaving it to soak. These two results will give me enough information to work out the percentage change and plot a good conclusion. The measurements will tell me if the potato has lost or gained weight whilst it has been left in the test tube, which will help me to conclude whether or not osmosis has occurred. 3. Apparatus The equipment I am going to use includes; Scalpel Cutting tile 5 Test tubes Potato Test tube rack Stopwatch Balance Tissue paper-to dry potatoes with Distilled water Salt and water solutions 25cm3 measuring cylinder I have decided to ...read more.

Middle

The results I record will help me to see how much mass has been gained or lost in the potatoes and how the five different concentrations have affected the potatoes. My results will also help me work out a percentage change. I will then be able to see how the osmosis has affected the potato slices. This is all aimed at testing my prediction. 7. Preliminary work and secondary sources Prior to this experiment I did do a preliminary practical that helped me to decide which molar solutions to use. In this preliminary practical I used distilled water, 0.5 molar and 1.0 molar solution. This made me realise that I had to go a bit lower down to 0.20 rather than 1.0 and put some other different solutions in-between them because there was too big a gap between the results which although they showed a rough pattern did not show the gradual increase and decrease in mass which I predicted. From secondary sources I found that osmosis does not just simply occur in salt and water solutions, it can occur in sugar solutions and many others. 'One important example of osmosis is water entering the roots of plants. If animal cells such as blood cells are placed in different strength solutions they will swell up or shrink depending on whether they gain or lose water via osmosis.' ( extract from 'Collins study and revision guide' for science). Section B. Obtaining Evidence 1. Safety Hazards Control Methods Sharp scalpel The scalpel I will using to slice the potato will be extremely sharp so I will take extra care when handling it in order not to accidentally injure myself or anyone else. ...read more.

Conclusion

influence on the results, the fact that my results clearly demonstrated the prediction shows that this had little influence but if I were doing this again I would improve this aspect. 4. Reliability of Evidence I consider the results I recorded to be very reliable and certainly sufficient enough to support a strong conclusion accounting for one anomaly. The one anomalous result I recorded was only slightly odd but proved to be a large percentage change compared with the other two so I decided to ignore it when producing the graph of averages. This result probably occurred by not drying the potato slice sufficiently compared to the rest of them. The evidence I collected is sufficient enough to support a firm conclusion. Because all of the points are virtually on a straight line they are therefore reliable and there are enough to give a good clear pattern. 5. Further Work To obtain even more reliable results and to support my conclusion more definitively I could record more repeats for each molar solution. I could also make more solutions, maybe five more to go with the five I have already got to make more precise results. If I was to do this experiment again I could use a cork borer to cut the potatoes into cylinders instead of cutting them with a knife into slices. This would make all of the potato pieces the same size that would make the experiment much easier instead of having a small, a medium and a large slice. With this I would put the potato cylinders into fifeteen separate test tubes that would make the experiment much easier to control and less confusing. GCSE Biology Coursework ...read more.

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