Analysis
My first graph is a line graph to show the percentage change of the first set of boiling tubes:
This graph shows that at the first boiling tube that contained 100% sugar solution, the change was in the negative region, suggesting that the potato cylinders were becoming lighter. This means that the water has moved out of the cells and into the solution. I expected this to be the case because research shows that water moves towards a region of low water concentration, from a region of high water concentration. The percentages after the 100% sugar solution show that the mass is varying by a few grams being gained and lost. This tells me that the potato cells are constantly gaining and losing mass due to water moving in and out of the potatoes. I expected that the mass should gradually increase and not vary as much as the concentration of distilled water is growing. After 40% sugar solution, the mass increases greatly, which is what I had expected because there would now be more distilled water that could move into the potato cells. By 100% distilled water, I can see that the mass has been gained as I had expected. The line of best fit backs up my prediction as generally, as the concentration of water increases, the mass increases showing water has moved into the potato cells when more distilled water is present.
My second graph is for the second set of results I took:
My second set of data showed that the 100% sugar solution had lost the most mass as the water would move out of the potato cells and into the high sugar concentration. This was as I had expected. I can see that the mass continues at a steady increase. Unexpectedly, the 40% sugar solution contained the highest mass. I would have expected the 100% distilled water to contain the highest mass because there would be more water to move into the cells and less to move out of the cells. My line of best fit shows that as the amount of sugar decreases, the mass increases, which is what I had expected.
My third graph was for the final set of results I plotted.
The third set of data I took showed that the 100% sugar solution had one of the lowest masses, but the 60% sugar solution contained the lowest. This was unexpected because I would have thought that a lower sugar solution and a higher water concentration would mean a higher mass as the water would slowly move into the cells. After this anomaly, the percentage change continues on the predicted course and increases in mass. By the 100% distilled water, the mass has been significantly gained. This is what I had expected to happen, as the water would move into the potato cells. These results are also backed up by the trend line.
The last graph I plotted is the average percentage change for all three experiments.
This graph shows that on average, the data is following a certain trend. This is that as the concentration of water increases, so does the mass of the potato. We can see that on average, by 80% sugar, the mass has increased slightly, but then drops down again to –20%. The change then increases dramatically and at 40% sugar solution, the potato has gained extra mass. On average, we can see that the 100% distilled water shows that the mass is lost again. I had expected that the results would not have been so varied from the 100% sugar solution to the 40% sugar solution. I did expect however, that the mass would start to rise at 40% sugar solution, as more water would be moving into the cells. I did not expect that the 100% distilled water on average should have fallen. This is because more water would be present to move into the cells and therefore a greater mass would be achieved. The average trend line shows that there is a pattern , which is that as the concentration of sugar decreases, the mass increases as water is moving into the cells of the potato.
Conclusion
To conclude I can say that there is a trend osmosis follows when it is in different concentrations of water. The percentage change in mass is very slow, but the cells definitely get heavier as the concentrations of sugar get weaker. This would tell me that if I had left them in for longer, there would be a definite change in mass by 100% distilled water. I can confidently say that my prediction was partially correct as there was an increase in mass and therefore the pattern in osmosis is as I had expected it to be.
Evaluation
The graphs I have obtained show a great resemblance to my predictions. This shows that I cannot have been extremely inaccurate in collecting my data.
If I were to improve this experiment, I would definitely try it with many more repeats, so I would have solutions to 100% water in multiples of five. This would give me extremely accurate results and a more reliable average. If I were to improve even more, I change the time that the potatoes stayed in the solution to somewhere around one hour. This would ensure that osmosis has enough time to act on the potato. I could also see if different types of plants other than potatoes have an effect on the rate of osmosis. I used distilled water specifically in the experiment to ensure that there were no impurities in the water that could obscure my results. I could also measure the temperature of the different solutions, as this would allow me to see if osmosis varies in rate with different temperatures. If I was able to change the solution type to something other than sugar, this would give me a varied result and I could conclude if the different solute matched the sugar solution. The amount I dried the potato must be measured also as this may not give me an accurate result if there was still liquid left on the outside of the potato cylinder. I would need to think of some way to make sure that each potato cylinder was given enough time to dry and the same amount for each. I would also try to ensure I place the different solutions in the boiling tubes more accurately. Perhaps if I had enough time and money, I could use a computer to place an exact measurement of the different liquids.
Evaluation Method
- Place an apple on a white tile and remove 60 cylinders using two different sized borers
- Cut to 4cm equally
- Measure weight to 4 decimal places. Repeat for accuracy
- Record in a table and fill 60 boiling tubes with the different solutions of sugar. Use intervals of 5%
- Mix boiling tubes for 10 seconds each
- Measure temperatures of each tube
- Use a machine to place all the apple cylinders in the test tubes at the same time
- Wait for 2 hours
- Remove using machine at exactly the same time and place onto a mat in order
- Dab at the cylinders 20 times each with paper tissue
- Weigh each cylinder to 4 decimal places and repeat for accuracy.
- Find the percentage change
I believe that overall my experiment was pretty fair and the only way I could really improve is if I had more time and access to machinery and unlimited funds.