Section 1
Background: The potato experiment was done to find the isotonic point of the potato. As resulting, the experiment reveals the information about osmosis and different solutions. Osmosis is the movement of water from high concentration to low concentration. Therefore, there are 3 different solutions of osmosis, which are hypotonic, hypertonic, and isotonic. Hypotonic has a high concentration of water than salt (pure water); in this case the cell in this solution would explode because of high concentration of water. On the other hand, hypertonic has high concentration of salt than water; in this case the cell in the solution would eventually shrink because of lower concentration of water and high concentration of salt. When the solution has the same concentration of salt and water as the cell then the solution is called isotonic. Therefore, the aim of the experiment is to find the isotonic point for the potato. Hence, by using different amount of salt in water for each beaker would give a concentration of salt in water which equals to concentration of salt in water in the potato.
Hypothesis: If the molar value of salt in water increases then the percent weight change of water would decrease and the isotonic point would be around 0.2mol or 0.4mol. This is because, weight of potatoes depends on the solution, so each molar value has amount of salt added in the beaker.
Therefore, as the concentration of salt increases in different solutions, the weight of potatoes in different solution would decrease. The weight of potatoes would decrease because, the solution would be hypertonic, and it would have high concentration of salt and the movement of water will go out; as a result the potatoes would weigh less than before. The isotonic would be around 0.2mol or 0.4mol because the mole of salt in water for 0.2mol and 0.4mol are does not have that high concentration of salt compared to 0.6mol or 0.8mol of salt in water. So either 0.2mol or 0.4mol of salt in water would be equal to zero so they have equal movement of concentration to the salt in potatoes water.
Equipments: 4 Potatoes
Water
Salt
Knife
Stirrer
Weighing Scale (0.01g) Pencil
6 beakers (200ml) 5% up or down small plate/ beaker
Procedures:
1.
Use a knife to cut the potatoes into circular slices. In total you should have 18 slices, and then arrange the 18 slices into 6 sets,
(3 slices of potatoes in each set).
2.
Fill 6 beakers with 200ml of water, and then arrange the beakers in a line with 6 sets of potatoes. Thus, pair the sets of potatoes with each beaker.
3.
Then, use a pencil and label the pairs of beakers with the potatoes using molar values (mol) (0.0, 0.2, 0.4,0.6,0.8,1.0)
4.
Use a weighing scale 0.01g and weigh each set of potatoes. Keep each sets of potatoes separated, so you don’t switch them.

Record the weight of each set of the potatoes, (the weight of the potatoes before the experiment).
5.
After recording, multiply each molar value by 11.69g. The answer will give you the weight of the salt to put in for each beaker.
6.
Use a plate or a small beaker to pour the salt and measure it on the weighing scale 0.01g. After measuring the weight of salt for molar value, pour it in correct beaker and stir the salt with stirrer until it’s dissolved. Repeat this step for all the beakers.
7.
After you’re done with step 6, now it’s time to put each sets of potatoes into their paired beakers. Make sure you put all the sets of potatoes in the beaker at the same time.
8.
Wait for at least 20 minutes for the reaction to take over.
9.
After 20 minutes take each set of potatoes out from the beakers. Be careful not to mix the sets potatoes with other sets.
10.
Dry the potatoes, and measure the weight of the sets of potatoes, and record the weight.
(The weight of potatoes after the experiment).
11.
Make a data table
12.
Graph your results
13.
Write your conclusion
14.
Write your mistakes in the analysis section
15.
Wash the equipments and throw the potatoes away.
Section 2
Data Table: Potato Osmosis
Molar Value (m)
0.0
0.2
0.4
0.6
0.8
1.0
Uncertainties Table
Potatoes before weight
(g)
Potatoes after weight
(g)
20.58
17.91
23.11
17.97
20.07
28.92
21.90
18.03
21.47
15.73
17.80
24.61
(%)Weight change= weight after– weight before/ weight before
6.41
0.67
-7.10
-12.47
-11.31
-14.90
Beaker
Weighing Scale
+ 5%
+0.01g

Conclusion: The results from the data and the graph proves that my hypothesis was half way correct, if the molar value of salt in water increases then the percent weight change of water would decrease and the isotonic point would be around 0.2mol or 0.4mol. Well, half of my hypothesis was correct because as the molar value of salt in water increased the percent weight change of potatoes did decrease. As for the isotonic point, after getting the results it showed that 0.4mol of salt in water had high concentration of salt and the percent weight change did not equal to zero so my estimate was wrong. But my estimate for 0.2mol of salt in water turned out to be nearly correct because the graph showed the isotonic point of the potato to be nearly 0.26.
The graph of this experiment showed that percent weight changes vs. salt molar value are inversely proportional. As the molar value of salt in H
2
0 increase the percent weight change of potatoes decrease. The graph shows that with 0.0mol of salt in water the percent weight change was highest.
This happened because, the solution was hypotonic, and it was pure water with no salt. Therefore, there was a very high concentration of water than salt, so the movement of water went inside the potato; resulting with a heavier weight that before. But as the molar value of salt started increasing the percent weight change started decreasing. This happened because, as the moles of salt in the water increased, the solution became hypertonic, so it had would high concentration of salt than water and the movement of water went out; as a result the potatoes weight less than before.
The graph also showed the isotonic point for the potato to be near 0.26mol which means that the concentration of 0.26mol of salt in water equals to the same concentration of salt in water in the potato. The isotonic point for 0.26mol of salt in water showed that it had equal movement of concentration of salt in water in the potato. Overall, from this experiment I have learnt the importance of sustainability.
Analysis: Throughout the period our experiment went good, we did our experiment very slowly and tried not to make any mistakes. As we all are a human there is no way that everything is going to be perfect. Hence, our mistakes during the experiment were that we used iodide salt for all the molar value of salt except for 1.0mol this affected the concentration of 1.0mol to be different from the rest. Other mistakes that include in human error were not cutting the potatoes into equal slices, and not fully drying the potatoes after the experiment, so when we measured the weight of potatoes it still had drops of water on it. Other mistake include uncertainties such as, the water in beaker is not exactly filled with 200ml, we did not exactly poured the exact amount of salt in the beaker the salt was still on the surface of the plate, and we also did not put all the potatoes at the exact same time nor took all of them out at the exact same time. As for the graph we had uncertainties in our experiment so the results of the graph are not exactly accurate. Thus, these were the mistakes that occurred during our experiment.