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| Absorption and Movement of Water |
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| The movement of the molecules from the region of higher concentration to the region of lower concentration is known as diffusion. |
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| Diffusion of Copper Sulphate in Water |
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 Take a beaker. |
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 Fill about ¾ th of beaker with water. |
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 Add a few crystals of copper sulphate. |
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 Water surrounding the crystals turns dark blue. |
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 The water in the beaker turns light blue in colour (copper suplhate crystals completely dissolve in water). |
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 Diffusion of copper sulphate molecules is due to the reason that molecules are in a state of constant motion (kinetic energy). |
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| The movement of solvent molecules from the region of their higher concentration to the region of their lower concentration through a semi permeable membrane is called osmosis. |
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 Peel off the skin of a large sized potato with a scalpel. |
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 Cut its one end to make the base flat. |
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 Make a hollow cavity in the potato almost up to the bottom. |
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 Add sugar solution into the cavity and mark the level by inserting a pin in the wall of the cavity of the tuber. |
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 Place the potato in the beaker containing water. |
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 After sometime, it will be noticed that the level of solution in the cavity rises. This is due to the phenomenon of osmosis. |
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 This experiment demonstrates that living cells of potato act as differentially permeable membrane. |
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 Water molecules from a region of their higher concentration (water in the beaker) move into a region of their lower concentration (sugar solution in potato cavity) through the differentially permeable cell membrane of the potato cells. |
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| Osmotic pressure is the pressure required to prevent the net movement of pure water into a solution so as to prevent the volume of the solution from increasing. |
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 In the absorption of water by plants |
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 Cell to cell movement of water occurs throughout the plant body |
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 The rigidity of plant organs is maintained |
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 Leaves become turgid and expand due to osmotic pressure |
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 Growing points of root remain turgid and penetrate the soil particles |
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 The resistance of plants to drought and frost |
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 Movement of plants and plant parts |
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 Opening and closing of stomata |
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| Diagram showing relationship of Osmotic Pressure (OP), Turgor Pressure (TP) and Wall Pressure (WP) |
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| The actual pressure exerted by the protoplasm of turgid cell against cell wall is the turgor pressure. |
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| Wall pressure is the pressure which is exerted by the rigid and elastic cell wall and is equal and opposite to turgor pressure. |
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