- Cork borer – to extract cylinder shaped pieces of potato out of the potato
- Syringe with measurements imprinted on the side (2) – to add the solution into the test tube accurately. I have one test tube for the distilled water and one for the sucrose solution.
Stickers (12) – to mark onto the 12 test tubes the concentration of sucrose solution
- Electric scales – to weigh the pieces of potato before the experiment to establish there weight and alter I them to have a similar weight for each; and after to gather there osmotic potential
The Key Factors
Surface area – Use the same cork borer to extract pieces of potato with the same surface area meaning the potato piece will absorb a similar amount of water due to the same surface area.
Concentration – The concentration of the sucrose solution compared to the distilled water will affect the results of the osmotic potential. This factor will vary due to the different concentrations used in the experiment. The concentration will be controlled using precise measurements of sucrose and distilled water; this will be achieved by using 2 syringes. One for the sucrose solution and another for the distilled water solution
Temperature – The temperature of the liquid will affect the speed in which the osmotic potential is reached because the particles will move faster in hotter conditions meaning they are more likely to hit the surface of the potato and be absorbed. The temperature will be controlled by simply placing them in the same room next to each other where the temperature will be roughly the same.
The Range of measurements
The range of measurements taken will vary from 0mols. to 10mols. concentrate of sucrose solution. This will go up in 2’s the following measurements for each test tube were
0mols. of water and 1mols. of sucrose solution
0.2mols. of water and 0.8mols. of sucrose solution
0.4mols. of water and 0.6mols. of sucrose solution
0.6mols. of water and 0.4mols. of sucrose solution
0.8mols. of water and 0.2mols. of sucrose solution
1mols. of water and 0mols. of sucrose solution
The data that is collected is accurate because the experiment is repeated
My prediction
My prediction for this investigation is that the more the concentrated sucrose solution there is the less the weight of the potato piece will be due to the hypertonic solution making the cells of the potato piece flaccid because the water particles will diffuse into the medium concentrated potato cells into the high concentrated sucrose solution meaning there will be less water concentrate in the potato cell making it flaccid. On the other end however the more water there is the more the potato piece will weigh this is due to the hypotonic solution where the cells are made turgid, this is because there is such a high concentration of water that the cell reaches its maximum capacity for water. Where the results are similar for example 4mols. of distilled water and 6mols. of sucrose solution, the cells will be more isotonic due to the slightly more equal amounts of solution of distilled water and sucrose solution, this is where water will go in and out of the cell via osmosis.
Results
Graph and Table shown separately
Results/Summary
The following results of the investigation showed that the prediction of the following were within reason supported, that the lower the concentration of sucrose the more the water will move into the potato piece through the process of osmosis and the higher the concentration the more flaccid the potato piece will be due to the water passing out of the potato due to osmosis.
Analysis of the experiment
The Data
The pattern of the graph that was plotted when the final results came through was curved like so. This pattern is sufficient evidence to say that the percentage change in mass decreases as the concentration of sucrose increases. At around 50% the change in mass decreases and radically drops to -30% loss of mass. The big change is around 0.4 mols. to 0.6mols. concentration of sucrose, it radically goes from 45% change in mass to a -30% loss of mass. This has a big difference of 65% change. It reaches its osmotic potential at precisely 0.5mols.
The osmotic potential of the potato is at 0.50mols, so I can conclude that the mass changes are equal. Therefore I conclude that the more concentration of sucrose there is the less the mass there will be.
Explanation
I found these experiments to come to pass because when the concentration of sucrose is at 0.2mols the potato cell becomes completely turgid increasing the mass. The mass decreases as the concentration of sucrose increases. This is due to the sugar particles being to big to get past the selectively permeable membrane, however the water particles are the right size so they are able to get past the selectively permeable membrane, meaning the less the concentration of sucrose and the more water, the more water will diffuse through into the potato cells meaning the mass will increase.
In the opposite result the potato cell becomes almost completely flaccid; this is where the high concentration of sucrose is at 0.8mols. And there is no water except for in the potato piece. What happens is that the potato cells with a medium concentration of water are forced to create equilibrium of water particles, they water diffuses out of the medium concentrated potato cell into the high concentrated sucrose solution, the water particles spread out around the area and create and equal space between themselves in the test tube. This makes the potato piece have a very low concentration of water. It is now flaccid
When the potato has reached its osmotic potential, the water particles are equal on both sides of the selectively permeable membrane with water diffusing in and out of the cell. This was when the sucrose solution was at 0.5mols. and its osmotic potential had been reached
It is now clear the evidence above is sufficient enough to agree with the prediction; the evidence agrees with the theory in that the more the water concentration the more the cells will weigh making the cell turgid, and the more the high concentration of sugar the less the cell will weigh making the cell flaccid.
Evaluation
The results of the experiment were accurate to the analysis in many ways. First the graph showed an s shaped curve. This shows that the 0.2mols. concentration of sucrose and the 0.8mols. drop slowly on the graph meaning that the percentage change in mass is not significant. However there is a big change when the percent change in mass drops radically, this is when there is a 0.4 concentration of sucrose solution and a 0.6 concentration of water. The mass changes so radically because water diffuses out of the potato cell creating equilibrium because the concentration gradient for the water in the potato cell is equal, but not outside. Meaning the mass of the potato cell will become less.
There were no were clear anomalies in my graph however no one else in my class had a graph like mine. My evidence in the graph supports my summary that the lower the concentration of sucrose the more the potato will weigh and the more the sucrose concentration the less the potato will weigh. However the experiment could have been more reliable if I had used more than 5 points (had more potato pieces).
To increase my knowledge of the subject I could have used a different aged potatoes or different vegetables. Using the same apparatus I would perform the investigation having the potato pieces and or the vegetables in a slim shape weighing the same. I would do this because the other vegetable might perform osmosis quicker. After the investigation I would perform the results and compare the average percent change, and take away the differences. Then can compare the osmotic potentials of the other vegetable or the older potato with the original potato.