In this experiment to make it a fair test all the chips must be exactly the same shape, size and length. To do this I will use a knife to cut the potato, then use the scalpel to cut the potato into equal strips and with the help of a ruler, cut them into the same length.
Osmosis is the diffusion of water molecules from a region of high water concentration to a low water concentration. Every cell has a cell membrane. This membrane separates the contents of the cell from the outside. The cell membrane is partially permeable, which means it has tiny holes in which allow small molecules to pass though but not large ones. When a partially permeable membrane separates two solutions and one solution is stronger than the other, osmosis will occur. The water molecules pass through the partially permeable membrane from the weak solution into the stronger solution. The greater the concentration of water in the salt solution the greater the amount of water that enters the potato by osmosis. The smaller the concentration of water in the salt solution the greater the amount of water that leaves the potato. However, there will be a point where the concentrations of water inside and outside the potato will be equal. At this point there will be no osmosis occurring.
I predict that a strip of potato put in 0.5% salt solution will increase in size and that a strip of potato put in 5%salt solution will decrease in size. Also at a certain concentration of salt solution the strip of potato will remain the same in size.
Obtaining Evidence
For this experiment I will use a scalpel so I can get the strips of potato the same size in length. I have to be careful because it is sharp. I will use it on a cutting tile to protect the bench.
I will not have to repeat the experiment because I put two pieces of potato in each petri dish, and I will get an average.
Concentration (%) Both Chips Chip1 Chip2
Before (mm) After (mm) After (mm)
0.5 50 57 56
1 50 54 55
1.5 50 52 53
2 50 52 52
2.5 50 50 50
3 50 48 47
3.5 50 47 46
4 50 46 45
4.5 50 45 45
5 50 45 44
Analysing And Considering Evidence
Averages
Salt solution
concentration (%) Average (mm)
0.5 56.5
1 54.5
1.5 52.5
2 52
2.5 50
3 47.5
3.5 46.5
4 45.5
4.5 45
5 44.5
From the table at 2.5% salt solution the strip of potato remains the same length. At lower concentrations of salt solutions the strip of potato increases in length and at higher concentrations of salt solution the strip of potato decreases in length.
From the graph we can see from the line of best fit that my results were quite accurate, and I never got any anomalous results. We can see that the strips of potato put in the lower concentrations of salt solution increased in size, and the ones put in the higher concentrations of salt solution shrunk in size. Therefore this supports my prediction and shows that water molecules pass from a weaker solution into a stronger solution through a partially permeable membrane.
Evaluating
To improve my experiment I could have used more accurate equipment. I could have used a borer or even better a micrometer screw gauge to get the diameter of all the chips exactly the same. I could also use more concentrations of salt solutions. My results are reliable as they show clearly that the length of a potato chip is related to the concentration of the salt solution. To extend my investigation I could use different varieties of potato or different plant cells.
