Osmosis is diffusion of fluid through a partition into another fluid, movement of water molecules from an area of high concentration through a permeable membrane in other words movement of water.

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GCSE Science

Mustafa Rafik

11.7Api

Science coursework

Title:

Osmosis

Mr Bhatwadekar

SCIENTIFIC KNOWLEDGE

Osmosis is diffusion of fluid through a partition into another fluid, movement of water molecules from an area of high concentration through a permeable membrane in other words movement of water.

“Osmosis, in botany and chemistry, the flow of one constituent of a solution through a membrane while the other constituents are blocked and unable to pass through the membrane. Experimentation is necessary to determine which membranes permit selective flow, or osmosis, because not all membranes act in this way. Many membranes allow all or none of the constituents of a solution to pass through; only a few allow a selective flow. In a classic demonstration of osmosis, a vertical tube containing a solution of sugar, with its lower end closed off by a semi-permeable membrane, is placed in a container of water. As the water passes through the membrane into the tube, the level of sugar solution in the tube visibly rises. A semi-permeable membrane that may be used for such a demonstration is the membrane found just inside the shell of an egg, that is, the film that keeps the white of the egg from direct contact with the shell. In this demonstration, the water moves in both directions through the membrane; the flow is greater from the vessel of pure water, however, because the concentration of water is greater there, that is, fewer dissolved substances exist in this solution than in the sugar solution. The level of liquid in the tube of sugar solution will eventually rise until the flow of water from the tube of sugar solution, under the influence of hydrostatic pressure, equals the flow of water into the tube. The hydrostatic pressure establishing this equality of flow is called osmotic pressure. A variety of physical and chemical principles is involved in the phenomenon of osmosis in animals and plants.”

From ‘ENCARTA 99’

Nucleus        Cytoplasm

        It has

Cell        Cell membrane        changed

Wall        (outside line)

(Outside line)

        Vacuole

                

        

          =Water molecules

        

          =Sugar molecules

        Partially permeable membrane

When a plant cell is placed in to a dilute sugar solution it has affect on the cell because it changes the shape of the cell by making it bigger and expand because there is little sugar in a dilute solution and more water making it go into the cell.  This is because the number of water molecules outside in the solution is greater than the number of water molecules inside the cells.  This is called turgid; this is when the plant         cells become swollen, it also becomes heavier in weight.  This is also like hypertonic where the solution with the higher concentrated solutes.  This is because it is making it bigger so we use the term hypertonic.

Dilute        Cell has

        Cell                      Dilute         gone bigger

Sugar                                              Sugar        (Expanded)

Solution                                          Solution

When a plant cell is placed into a concentrated sugar solution it also has affect on the plant cell because it makes the cell go smaller in size and it goes lighter in weight because the water has gone out of the cell this time instead of going in because there is more sugar in a concentrated solution and less water, this is called flacid, this is when the plant cell become shriveled.  This is because the water flows out of the cell and into the solution because osmosis is the movement of water molecules, which are highly concentrated, go into a low concentration.  This is also hypotonic where the solution with the lower concentrated solutes.

Dilute        Cell has

        Cell                      Dilute                                gone smaller

Sugar                                              Sugar                              (Shriveled up)

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Solution                                          Solution

When the concentration of water molecules of the outside of the cell plant is the same as the inside of the cell plant, the cell remains the same because nothing is happening as both sides are the same so nothing will happen, this is called isotonic, this is when both sides are the same and have the same number of molecules.  

Dilute        Cell has

        Cell                      Dilute ...

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Osmosis is diffusion of fluid through a partition into another fluid, movement of water molecules from an area of high concentration through a permeable membrane in other words movement of water.
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