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What is the difference between diffusion and osmosis?

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Quick Answer

Osmosis is a particular type of diffusion in which water crosses a semi-permeable membrane to an area with a greater solute concentration, whereas standard diffusion often allows the free movement of both solutes and solvent toward equilibrium. Diffusion in general is the net movement of molecules in solution from areas of higher concentration to areas of lower concentration. Osmotic pressure is potentially very powerful, with osmotic pressure being the only force necessary to move water from the roots to the tops of the tallest trees in the world.

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What is the difference between diffusion and osmosis?
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Full Answer

When water dissolves another substance, it is because the polar water molecules and the solute attract one another. Each atom, ion or molecule of solute has a charge in at least one region that attracts one side or another of the water molecule. As such, as many water molecules as possible tend to gather around each particle of solvent. In liquid water, all molecules are in constant, random motion around each other. However, because of the attraction, the water molecules are slightly more likely to move toward particles of solute than they are away from them, and solute particles are more likely to move toward water molecules than other particles of solvent. This net movement results, gradually, in an even distribution of the solute. In osmosis, only the water molecules can move to equalize concentrations.

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Related Questions

  • Q:

    How is osmosis different from diffusion?

    A:

    Diffusion is the spontaneous movement of any type of particle or molecule from an area of high concentration to an area of low concentration, while osmosis is the diffusion of water across a semi-permeable membrane. Osmosis only occurs in liquid. Diffusion mainly occurs in a gaseous state, though it also occurs in liquids.

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  • Q:

    Why does osmosis occur?

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    Osmosis occurs because dissolved particles have a higher concentration on one side of a membrane, that only allows the passage of water, than the other. As water molecules randomly drift across the membrane, they tend to stay around the dissolved particles rather than drifting back.

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  • Q:

    Why do potatoes lose weight in high sucrose solutions, through osmosis?

    A:

    Potatoes lose weight when placed in high concentration sucrose solutions because they lose water through osmosis. Osmosis is the process where solvent molecules pass through semi-permeable membranes to equalize the solute concentration on both sides of the membrane.

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  • Q:

    What adaptations do plants and animals have in saltwater biomes?

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    Animals and plants that live in saltwater biomes feature adaptations designed to prevent osmosis from equalizing the salt concentration throughout their bodies while remaining capable of absorbing oxygen from the water. Animals do this through specialized kidneys and gills, while plants do this directly through their cell walls.

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