Osmosis in Potato Tissue Experiment
Osmosis can be defined as the movement of water across a
semi-permeable membrane from a region of high water concentration to a region of low water concentration.
The semi-permeable membrane allows small particles through it but does not allow large particles such as sodium chloride. Osmosis will continue until a state of equilibrium is reached i.e. there is no area with a higher or lower concentration than another area.
To land plants, water and osmosis are vital as they play leading roles in the structural support of a plant. Lack of water will lead to a plant wilting (becoming flaccid) and possibly dieing.
Osmotic pressure. If a plant was placed in a waterlogged area, where the external solute to the cell (being less concentrated (or hypertonic) to the cell vacuole contents) the cell will not continue to take in water via osmosis for ever. The cell wall made of cellulose acts as a firm barrier to any more expansion. Once the cell is full of water, it is said to be turgid. This means that the inward force is equal to that of the outward force. The inward pressure is called turgor pressure and the outward force is called osmotic pressure.
The opposite of being turgid is being flaccid. This occurs if the plant is placed in solution that is hypertonic to its contents. So basically, when the solution outside the cell is more concentrated. The cell loses the water content via the process of osmosis. The cytoplasm will eventually cease to exert any force on the cell whatsoever and so the cell becomes flaccid.
In the experiment, the pieces will either become flaccid, stay the same or become turgid depending on the concentration of the solute inside and outside the cells.
The aim of the investigation is to investigate the movement of water in and out of a sample of potato by osmosis.
* Then experiment involves sodium chloride. This is harmful if it splashes into your eyes, and so you must wear safety spectacles at all times during the experiment.
* A razor blade is required in the experiment so you must take care as it could cause a serious wound. You must carry the knife facing downwards. You must also always use it on a tile to avoid damaging the bench.
* A cork borer is required. Do not use this with your hand on the underside of the potato as it may slip surprisingly well though the potato and stab. You must, like the razor, use this piece of apparatus on the tile to avoid damage to yourself and the bench.
* Also before beginning the experiment so as not to contaminate the experiment one must wash their hands.
The experiment will prove the theory of osmosis and will also tell me how much solute there is inside the potato.
I will cut equal sections from a potato, weigh them and place them in different concentrations of sodium chloride. After 24 hours I will take them out and weigh them. The difference in weight will prove the existence of the process of osmosis. The point of equilibrium is the point where the line on the graph crosses the axis. This is also the point where the piece of potato doesn't shrink or increase in mass or length.
A Fair Test
For the results to be accurate and reliable, the experiment must be a fair test. A fair test is when all the non-variables in the experiment are kept the same. This means the factors like surface-area and volume of solution are all kept the same. For it to be a fair test, the following should and will be accounted for:
* The pieces of potato must be the same width length, because they must have the same surface area exposed to the solutions. This means that if one cylinder is exposed to more solution than another cylinder, then the one with the larger surface-area has a larger contact with the solution therefore the probability that osmosis occurs could be...
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