Diffusion





Diffusion 2871
Photo by: Lansera

Diffusion is the movement of molecules from a region of high concentration to one of low concentration. If you have ever opened a bottle of cologne or perfume, you have witnessed diffusion. Molecules of the scent escape from the container, where they are present in very high concentration. They spread outward in every direction to regions where they are in low concentration. Your nose is able to detect the smell of the cologne or perfume even if you are quite a distance from the bottle that has been opened.

Diffusion occurs in all states of matter: solid, liquid, and gas. It occurs rapidly enough to be observable in a reasonable period of time, however, only in liquids and gases.

You can demonstrate diffusion easily in your home. Fill a glass with water. Then add 10 drops of ink (any color) to the water very carefully. The ink sinks to the bottom of the glass because it is more dense than water. Place the glass in a place where it will not be disturbed and make observations of it every day. Over time, the colored ink at the bottom of the glass spreads upward. It moves from a region of high concentration to one of low concentration.

Eventually, the water in the glass is the same shade: a grey, light blue, or pink throughout. The original black, blue, or red ink has been diluted with water to produce the paler shade. Diffusion eventually stops because no region of high ink concentration remains. The concentration of ink and water is the same throughout the glass. That rule applies to all cases of diffusion. When differences in concentration no longer exist, diffusion stops.

Osmosis

Osmosis is diffusion through a membrane. The membrane acts as a barrier between two solutions of different concentration. One substance (usually water) travels from an area of high concentration to one of low concentration. Osmosis can be compared to the examples of diffusion given above involving perfume and ink. In those cases, no barrier was present to separate perfume from air or ink from water. Diffusion took place directly between two materials.

In contrast, a barrier is always present with osmosis. That barrier is usually called a semipermeable membrane because it allows some kinds of materials to pass through, but not others.

The most familiar example of osmosis through a semipermeable membrane may be a living cell. Cells contain semipermeable membranes

Carbon dioxide vapor diffusing from an open gas jar. The vapor molecules are traveling from the area of high concentration (the jar) to the area of low concentration (the open air). (Reproduced by permission of Photo Researchers, Inc.)
Carbon dioxide vapor diffusing from an open gas jar. The vapor molecules are traveling from the area of high concentration (the jar) to the area of low concentration (the open air). (Reproduced by permission of
Photo Researchers, Inc.
)

that act something like a plastic baggy holding cell contents inside. The cell membrane is not a solid material, however, but a thin sheet containing many tiny holes. (Imagine a self-sealing sandwich bag—its surface dotted with minuscule holes—then filled with water.) The holes allow small molecules and ions (such as molecules of water and sodium ions) to pass through, but trap larger molecules (such as proteins) inside the cell.

[ See also Dialysis ]



User Contributions:

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Aug 2, 2010 @ 5:05 am
can you give more examples of the diffusion process nad can you give me the debate between the osmosis and the diffusion. thats alll thank you.
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Sep 16, 2010 @ 8:08 am
What are some more examples of Diffusion and Osmosis that you use everyday life?:)
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Sep 19, 2010 @ 5:17 pm
can you show more examples of diffusion other than that gret explnaion
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Nov 1, 2010 @ 1:13 pm
I need more examples of Diffusion, please! Thank you!
Je m'apelle
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Dec 1, 2010 @ 4:16 pm
Why is diffusion important or how can it be useful in everyday life?
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Jan 30, 2011 @ 8:08 am
a better explanation of perfume diffusion is needed.
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Aug 3, 2011 @ 12:00 am
what are the more examples of diffusion and osmosis thank you! i need more examples of diffusion
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Aug 18, 2011 @ 11:23 pm
I love this! It is a big help! I just really need more examples of diffusion of gases! Please!
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Oct 6, 2011 @ 6:06 am
i need more examples !! but thanks... this helps a lot :D
elena
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Feb 19, 2012 @ 1:01 am
please anybody tell me if diffusion happens then how can smell remain on person body
?
sunday
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Apr 15, 2012 @ 12:12 pm
How does diffusion occur in human body?and what are the signs to know that diffusion is occuring?
alona lozano asube
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Aug 1, 2012 @ 2:02 am
the idea is good but i want more about diffusion what i is all about
destiny
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Sep 17, 2012 @ 9:21 pm
thank you very much. this information was very beneficial, juzt need some more examples on gas.
makayla thomas
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Oct 6, 2012 @ 9:09 am
i need to know more about diffusion what is it all about i still dont get it
dallas
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Mar 14, 2013 @ 2:02 am
I need to know much about the processes of diffusion
Ankita Arya
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Jul 10, 2013 @ 12:12 pm
thanks for providing the examples i need some more examples!
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Jun 25, 2014 @ 10:10 am
I WANT EXAMPLES OF DIFFUSION IN DAILY LIFE, PLESASE GIVE ME THAT SOON
britney
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Sep 26, 2014 @ 9:21 pm
I WANT EXAMPLES OF DIFFUSION IN DAILY LIFE, PLESASE GIVE ME THAT SOON
Skittlez
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Oct 10, 2014 @ 9:21 pm
Thanks! This really helped! But I need more examples.

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