osmosis and diffusion

[baggysenior]

i'm really struggling to understand what both osmosis and diffusion mean. Biology is a weak subject of mine, so i really need simpleton terms and an easy example of both (for me to memorise when i go into my exam) if you can help PLEASE can you make it as easy as possible. I really am after one example of each, I've researched and researched but i'm baffled by big words. Many thanks.

[erin-x]

Osmosis is when water moves from an area of high concentration to a lower concentration. I can remember doing an experiment where we left a raisin soaking in water. When you back to it after a while the raisin will have soaked up the water and become fatter. The water has moved into it by osmosis. That okay? :)

[erin-x]

An example of diffusion can be disolving something in water. The substance will 'difuse' from one area until it is distributed evenly in the water.

[baggysenior]

brill! exactly what i was after! thankyou!!!!! raisin it is for osmosis. any idea for diffusion?

[scotman]

From Chambers on-line

osmosis noun 1 chem the spontaneous movement of a solvent, eg water, across a semi-permeable membrane from a more dilute solution to a more concentrated one, which stops when the concentrations of the two solutions are equal, or when an external pressure is applied to the more concentrated solution. 2 a gradual, usually unconscious, process of assimilation or absorption of ideas or knowledge, etc. osmotic adj. osmotically adverb.
ETYMOLOGY: 19c: a Latinized form of osmose; see also -osis.

diffusion noun 1 the act of diffusing or state of being diffused. 2 physics the process whereby a fluid, either a liquid or gas, gradually and spontaneously disperses from a region of high concentration to one of low concentration, as a result of the random movements of its constituent atoms, molecules or ions. 3 anthropol the spread of cultural elements from one community, region, etc, to another.

Obvious, isn't it.

[erin-x]

The only thing that comes to mind would be adding drops of food colouring to water as you can see it moving through the water until it goes the colour of the colouring :)

[Buenchico]

Click 'Start' and read the information:
http://www.bbc.co.uk/...qa/cells/cells4.shtml
This is the key sentence from that page:
"Osmosis is the movement of water from a less concentrated solution to a more concentrated solution through a partially permeable membrane". (Just remember that and you're well on your way to passing your exam!).

You asked for an example of osmosis:
It's the way that plants absorb water through their roots. The cell walls, in the plant's roots, provide a 'partially permeable membrane' (which simply means that water can travel inwards, but not outwards).

Here's the other key bit of information you'll need:
"Diffusion occurs when particles spread. They move from a region where they are in high concentration to a region where they are in low concentration"
That's taken from here:
http://www.bbc.co.uk/...qa/cells/cells3.shtml

As stated on that page, an example of diffusion is when food moves from the gut (where it's in a high concentration) into the blood vessels lining the gut walls (where it's in a lower concentration).

Chris

[gingejbee]

erin's got it going the wrong way- solvent goes from weak solution to strong solution through a membrane.

[erin-x]

Sorry... i meant it goes from the high water concentration through to a lower water concentration :-s

[Buenchico]

I'm glad that someone's properly awake tonight!

Well spotted, Gingejbee!

[gingejbee]

...thanks, Chris and I've been up since 5.30 this a.m.!

[baggysenior]

thanks guys and gals. one thing i do know is that tiredness and ability to learn effectively don't mix. Perhaps i'm overtired, because at present, i want to beat myself up! ha! sleep would be the best solution i guess xxx

[wildwood]

Another easy to remember example of osmosis is when salmon leave the sea and go up river to spawn. They hang around the river mouth so that their system can slowly change from salt water to fresh water through the skin (osmosis). This takes a few days, hence fishing is great around that time.