Rough method
First of all I will begin with the core borer to slice 18 slices of potatoes which will be 5cm each in length. We will try our best to make sure that each potato slice is the same size with the use of a scalpel to slice potato chips to equal sizes. We will then weigh three potato chips to get their initial mass and then place the chips into six 100ml beakers. Thereafter we will label each beaker to identify the different amount of solution and water in each beaker and leave them for 24 hours. Our results will go into this table below.
Preliminary
To make sure that the experiment will be a fair test I will compare each potato to all of the others to make sure all potato slices are equal size. To also create a fair test certain aspects of the experiment will have to be kept the same whilst one key variable is changed. I have chosen to vary the concentration of the sugar solution and water. This will give me a very varied set of results from which I hope to make a decent conclusion. If any of the non-variables below are not kept constant it would mean it would not be a fair test:
- I will be carrying out this experiment at room temperature.
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To keep the water potential of the potato initially will be kept the same by using the same type of potato, which have been treated in the same way, e.g. have all been cut without being washed and peeled.
- The mass of the potato is a dependent variable, and this means that it will be measured throughout the experiment. I will measure the mass in grams. The potato chip will be measured before it is put in the solution, and after. This will allow us to see whether osmosis has taken place, and to what extent.
- I am also going to use the same balance to weigh my potato chips. This is because the measurements may slightly vary between scales.
All of my results will be recorded in this table below.
Preliminary results table
Method
- We will take one average sized potatoes and use a core borer to get 18 potato chips.
- We will do this on a white tile to make sure we do not damage the tables because the core borer is extremely sharp.
- Thereafter we will use a scalpel to cut each chip precisely to 3 cm long using a 30cm ruler.
- We will then use a test tube rack and place 5 test tubes in it and label them: 0 molar, 0.25 molar, 0.5 molar, 0.75 molar and 1 molar.
- Using a measuring cylinder I will measure the different amounts of sucrose solutions and water that needs to be placed into the 100ml beakers.
- I will place one sticker label on all the beakers used to identify the different amount of solutions in each beaker.
- But before pouring in the solutions in the 100ml beakers I will weigh the chips each to get their initial mass in grams and record the results onto a table.
- I will then pour in the solutions and place 3 chips in each beaker to get an average score to make my results more reliable and accurate, these results will also be recorded on the results table.
- I will wait for 24 hours and then soak off the solutions on the chips using paper towels.
10. Finally the chips will be weighed and recorded on my table; I then received all the initial mass, final mass and the change in mass including the averages. (As shown on page 4)
Final Results Table
Conclusion
In conclusion, my final results graph tells me that when the sucrose solution was above 0.25 molars the mass decreased and when the sucrose solution was below 0.25 the mass increased. I can therefore conclude that the movement of water through the semi-permeable membrane of a potato is certainly affected by the concentration of the sucrose solution and that the higher the concentration, the more the mass of the potato chips decrease. Because water molecules have kinetic energy the keep randomly moving around, that’s why the more water poured into the solution the more total kinetic energy and the higher the water potential. This means that as the sucrose solution increases, the amount of water decreases reducing the amount of kinetic energy and lessening the amount of movement between the solutions by osmosis. Basically, as the concentration of glucose in each solution increases, the water in that solution is less able to move to the potato, causing water from the potato to move to the solution, decreasing its weight.
Evaluation
The problems that had occurred throughout the experiment was mainly effecting the reliability of the results like when we measured the potatoes we had to remove the water by using paper towels but when we did this we could have removed the water that was originally in the potato chips reducing the mass unnecessarily which would have changed the results. Also because we used a scalpel to slice the potato chips using a ruler to measure the measurement could have been slightly incorrect because I only measured the first piece accurately and the rest I tried to compare them to the first piece which I could have got wrong but that was entirely because of human error. If I was to repeat this same experiment again I would use a more accurate instrument to measure my chips to get more accurate results. Also I would make sure that the potatoes I use will not be crippled or dodgy potato, I will try to get a big accurately circular shaped potato so that the potato chips would not have all the slightly crooked shapes. Also I would try to clean and wipe off the bits of water that were still on the weighing scale and make sure that it is dry to make sure that these water particles do not alter my results. These improving methods that I could use and the problems we had, suggest that the results were reliable but could have been a lot more reliable if I were to improve the experiment with the ideas that I gave above. My results
table above shows the two outliers highlighted and that is all the outliers I received and the outliers both reflected on my graph. Also, my graph showed me that my results were reliable as I received several small error bars, increasing the reliability; also I noticed the line of best fit changing at the end of the graph, this was showing me that plasmolysis occurred in my potato slices. Plasmolysis is the loss of water from a cell, in this case a potato cell, causing it to contract and deform.
