Osmosis Coursework - Osmosis with Potato Chips
Aim:
To investigate the effect of concentration on the amount of osmotic activity between the solution and a potato chip of a fixed size.
Prediction:
Osmosis is the net movement of water molecules from a place where they are in a higher concentration to a place where the water molecules are in a lower concentration, through a partially permeable membrane such as a cell wall, which lets smaller molecules such as water through but does not allow bigger molecules such as salt to pass through. This occurs down a concentration gradient. The molecules will continue to diffuse until the area in which they are found reaches a state of equilibrium, which means that the molecules are randomly distributed throughout an object, with no area having a higher or lower concentration than any other.
For this particular investigation I predict that the lower the concentration of the salt solution in the test tube, the higher the mass of the potato chip will be after osmosis has occurred. This is because the water molecules pass from a high concentration, i.e. in the water itself, to a low concentration, i.e. in the potato chip. Therefore, the chips in the lower salt concentrations will have a larger mass than in higher salt concentrations.
I predict that in a 0% salt solution the mass of the potato chip will go up, in a 1% salt solution it will stay roughly the same as there is about a 1% concentration of salt in potatoes, in a 2-5% salt solution it will go down in mass decreasing more as the concentration of the salt in the solution gets higher.
Further Information (which helped me make my prediction)
Plant cells always have a strong cell wall surrounding them. When they take up water by osmosis they start to swell, but the cell wall prevents them from bursting. Plant cells become "turgid" when they are put in dilute solutions. Turgid means swollen and hard. The pressure inside the cell rises and eventually the internal pressure of the cell is so high that no more water can enter the cell. This liquid or hydrostatic pressure works against osmosis. Turgidity is very important to plants because this is what make the green parts of the plant "stand up" into the sunlight. This leaves the cells with a bigger area for osmosis to occur which leads to it getting a higher mass.
When plant cells are placed in concentrated salt solutions they lose water by osmosis and they become "flaccid." This is the exact opposite of "turgid". The content of water in the potato cells shrinks and pulls away from the cell wall. These cells are said to be plasmolysed. This leaves the cell with a smaller area for osmosis to occur which results in a lower mass.
When plant cells are placed in a solution, which has exactly the same osmotic strength as the cells they are in a state between turgidity and flaccidity. We call this incipient plasmolysis. "Incipient" means "about to be".
Preliminary Experiment:
Aim:
To investigate the effects of tap water compared to salt water on the mass of potato discs.
Prediction:
I predict that in the pure water solution the potato chip will increase in mass because there is a lower concentration in the potato.
I predict that in the salt water tube the potato will decrease in mass because water in the potato will have a higher concentration.
Method:
. Cut the potato cylinders (on the white tile, using a scalpel) into 5mm thick pieces.
2. Divide the discs into two equal batches.
3. Dry the batches with blotting paper.
4. Place the discs into the beaker after labeling one salt and the other tap water and leave for 17 minutes.
5. Using blotting paper, blot dry the discs and then with them.
6. Record your results.
Results:
Batch
Start mass (g)
Aim:
To investigate the effect of concentration on the amount of osmotic activity between the solution and a potato chip of a fixed size.
Prediction:
Osmosis is the net movement of water molecules from a place where they are in a higher concentration to a place where the water molecules are in a lower concentration, through a partially permeable membrane such as a cell wall, which lets smaller molecules such as water through but does not allow bigger molecules such as salt to pass through. This occurs down a concentration gradient. The molecules will continue to diffuse until the area in which they are found reaches a state of equilibrium, which means that the molecules are randomly distributed throughout an object, with no area having a higher or lower concentration than any other.
For this particular investigation I predict that the lower the concentration of the salt solution in the test tube, the higher the mass of the potato chip will be after osmosis has occurred. This is because the water molecules pass from a high concentration, i.e. in the water itself, to a low concentration, i.e. in the potato chip. Therefore, the chips in the lower salt concentrations will have a larger mass than in higher salt concentrations.
I predict that in a 0% salt solution the mass of the potato chip will go up, in a 1% salt solution it will stay roughly the same as there is about a 1% concentration of salt in potatoes, in a 2-5% salt solution it will go down in mass decreasing more as the concentration of the salt in the solution gets higher.
Further Information (which helped me make my prediction)
Plant cells always have a strong cell wall surrounding them. When they take up water by osmosis they start to swell, but the cell wall prevents them from bursting. Plant cells become "turgid" when they are put in dilute solutions. Turgid means swollen and hard. The pressure inside the cell rises and eventually the internal pressure of the cell is so high that no more water can enter the cell. This liquid or hydrostatic pressure works against osmosis. Turgidity is very important to plants because this is what make the green parts of the plant "stand up" into the sunlight. This leaves the cells with a bigger area for osmosis to occur which leads to it getting a higher mass.
When plant cells are placed in concentrated salt solutions they lose water by osmosis and they become "flaccid." This is the exact opposite of "turgid". The content of water in the potato cells shrinks and pulls away from the cell wall. These cells are said to be plasmolysed. This leaves the cell with a smaller area for osmosis to occur which results in a lower mass.
When plant cells are placed in a solution, which has exactly the same osmotic strength as the cells they are in a state between turgidity and flaccidity. We call this incipient plasmolysis. "Incipient" means "about to be".
Preliminary Experiment:
Aim:
To investigate the effects of tap water compared to salt water on the mass of potato discs.
Prediction:
I predict that in the pure water solution the potato chip will increase in mass because there is a lower concentration in the potato.
I predict that in the salt water tube the potato will decrease in mass because water in the potato will have a higher concentration.
Method:
. Cut the potato cylinders (on the white tile, using a scalpel) into 5mm thick pieces.
2. Divide the discs into two equal batches.
3. Dry the batches with blotting paper.
4. Place the discs into the beaker after labeling one salt and the other tap water and leave for 17 minutes.
5. Using blotting paper, blot dry the discs and then with them.
6. Record your results.
Results:
Batch
Start mass (g)
