Method:
First I got all the equipment that I needed out and my solutions. I next started to get the strips of potato. I will measure and cut the strips of potato, so all of the strips are 6cm. I next got my solutions, which are in beakers and measured out 40ml of each solution with a measuring cylinder. I wrote on all the test tubes, so then I knew which test tube has got which solution in. Next I poured my solutions into the test tubes, and I put a potato strip in each test tube, so there are two test tubes of each solution with a potato strip in.
After a couple of hours I will measure all the strips of potato and record all of the results.
Diagram:
Measurements:
I’m going to measure how much of each solution I need. I will use a 50ml-measuring cylinder, I need to have 40ml of all the solutions, so it is a fair test. I’m using 40ml of the solutions so the potato is surrounded by the solution.
I will also measure the length of the strips of the potatoes. I will use a ruler and have all the strips of potatoes 6cm’s long. The length of the potatoes is a dependent variable because, I depend on the potatoes to increase and decrease. It is a lot easier and accurate to measure the potatoes when they are fairly long.
Both of these measurements are accurate as long as they are measured on a flat surface.
Results:
Potato strip – 6cm
Solution – 40ml
Potato – King Edward potato
Conclusion:
My results tell me that the potatoes didn’t increase or decrease a lot. The most the potatoes increased was 0.15cm at 0 molar. The most the potatoes decreased was 0.55cm at 1 molar. There is a pattern in my results as the molar increases so does the averages of the differences in length. I can tell this as at 0.2 molar there is no average difference in length and at 0.6 molar the average difference in length is 0.25cm.
My prediction matches my results and I know because I predicted that the potatoes wont grow or shrink that much, and they didn’t. I also predicted that between 0 molar and 0.4 molar the potatoes would increase which did not happen. The potato increased at 0 molar and at 0.2 molar the potatoes neither decreased or increased. The potatoes increased because, water can enter the potatoes cells by osmosis. Osmosis is the movement of water molecules across a partially permeable membrane, from a region of high water concentration to a region of a low water concentration.
In my results from 0.4 molar to 1 molar the potatoes decreased in size and that is roughly what I predicted. 0.4 molar to 1 molar are stronger solutions than 0 molar to 0.4 molar, so that is why they decreased. As the potato had a higher concentration of water inside it, the water molecules passed through the partially permeable membrane out from the potato into the solution so the potato decreased in size as water had gone from it.
From my results I am able to come to the conclusion that the potatoes have a 0.2 molar concentration of cytoplasm in the potato. I can come up with this conclusion, as at 0.2 molar the length of the potatoes did not change. So therefore the concentration outside of the potatoes and in the inside of the potatoes are the same because osmosis did not occur. Osmosis couldn’t occur, as the concentrations of the water molecules were equal so they didn’t have to move.
Evaluation:
I think the test went fine and I think my results are reliable because, I repeated them so I was able to make an average of the difference in the length of the potato, for each solution.
I think the measurements are very accurate as the results were close together and there were no odd results. To improve this investigation I could of done more than two strips of potatoes for each solution.
I don’t think I can improve my method as it is simple and from this method I got reliable and accurate results. Although to achieve more results as well as measuring the length of the potatoes I could also weigh the strips of potatoes, also from these extra results I could draw up some further conclusions.
I can tell from my graphs that my results are accurate as they are close together. To prove the same aim I could weigh the potato strips and then I would find out more about the concentration of cytoplasm in the potato.
