What am I going to do?
Even though I am only going to use six different concentrations of salt solutions, I will need eighteen test tubes because I will repeat each concentration three times. Using a cork borer, I will cut out eighteen pieces of potato, weigh them all and record the masses. My weights will give me quite an accurate measure because the electronic scales are to 2decimal places. The pieces of potato, will then be placed into eitghteen lebelled test tubes, and then each covered in 20ml of salt solution. Iam using 20ml because each piece of potato must be completely covered in salt solutionin order for the reaction to take place. In a previous experiment, the pieces of potato were only left for half an hour, and the results were not very accurate, so the test tubes will be left left for fifty minutes, then the potatoes will be removed, dried, re-weighed and the new mass recorded.
Diagram:
Variables:
Heat is a variable because it speeds up the enzymes, and the reaction will take place faster. I must use the same variety of potatoes throughout the experiment, to ensure it’s a fair test. The pieces of potato should all be roughly the same size because osmosis takes place on the surface of the potato. I must make sure I use the same quantity in each test tube because if there’s more, it will take longer and more osmosis will be able to take place.
Prediction:
Because I know that osmosis will take place during this experiment, I can predict that as the concentration of the salt solution increases, the weight of the potato pieces will decrease.
Results:- Table1
Table2:
Table1 results, plotted onto graph paper:
My graph looks like this because of osmosis. The water moves from where there is more salt to where there is less, and it passes through the semipermeable membrane of the potato. This happens until the concentrations on either side of the membrane are equal.
Evaluation:
This experiment was a good way to obtain results, because they results were the most accurate results that I can achieve. Looking at my graph, I do have a few results that appear to be out of place, but Im unsure of why. I would improve this experiment, by following the same procedure, but using a variety of potatoes, some would be baking potatoes, others would be old ones. Using a variety of potatoes would enable me to see if the variety has an effect on the rate of osmosis.
Conclusion:
After this investiagtion, my conclusion is that different concentrations of salt solutions, does have an effect on osmosis. I can see this by looking at my results table. The weight of the potato pieces decreases as the concentration of the salt solution increases.
*ref:1998 Hutchinson Encyclopedia*
Biology Investigation..
Sarah Harrison
10.2B