Osmosis in Potato Tissue Experiment

Topics: Sodium chloride, Osmosis, Concentration Pages: 15 (2272 words) Published: January 22, 2013
Osmosis in Potato Tissue Experiment 

Background Information 

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 

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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