What's the difference between osmosis and diffusion?

Question

I know what both osmosis and diffusion means, but I don't really understand what the difference is between them really. Could anyone shed any light?

Thanks.

Answer 1

Osmosis is a special kind of diffusion.  It's diffusion through a semi-permeable barrier, like a cell membrane.

Answer 2

Osmosis is diffusion across a cell membrane.

Answer 3

Diffusion is the spontaneous movement of any molecule from a high to a low concentration.

Osmosis is the movement of water molecules through a living cell membrane.

Answer 4

Diffusion is the spread of "stuff" away from high concentration areas to low concentration areas. Diffusion continues until concentrations have become equalised... Diffusion can occur whether the stuff is in vacuum or in solution... If the stuff is small enough it will spread even through the gaps in an apparent "barrier", in which case the barrier is called permeable because the stuff can get through (and will on average travel from high concentration areas and to low concentration areas as usual).

An interesting thing happens when a) There's stuff in solution (i.e. the stuff is a solute in a solvent); and b) There's a barrier with only small gaps in it. By small gaps we mean that the molecules of stuff can't get through but the molecules of water (or other solvent in which the stuff is dissolved) can get through: Such a barrier is called semi-permeable... In these circumstances the concentrations of stuff cannot become equalised through diffusion of stuff because we've set things up so that the stuff can't move through the barrier (the stuff is too big for the gaps). HOWEVER the concentrations of stuff can become equalised by diffusion of the water (or other solvent) which can get through the gaps. We call this special kind of diffusion of the solvent "osmosis".

N.B. Because the movement of solvent is just like the movement of liquids from high pressure areas to low pressure areas the equalisation of concentrations of stuff by diffusion of the water can be described in terms of a thing called osmotic pressure.

Hope that helps...

Summary:

In DIFFUSION, molecules of stuff travel from areas of high concentration of stuff to areas of low concentration of stuff until concentrations of stuff are equalised.

In OSMOSIS solvent molecules do the travelling not the stuff itself, which stays where it is stuck behind a semi-permeable membrane. The water (or other solvent) travels from areas of low concentration of stuff to the trapped areas of high concentration of stuff until concentrations of stuff are equalised or until the semi-permiable barrier (e.g. a cell membrane) bursts!

Answer 5

In diffusion, molecules of a fluid travel from a higher concentration to the lower concentration. When you put a drop of ink in a glass of water, the spreading of the ink in the water is called diffusion.

In osmosis, molecules travel from lower concentration to a higher concentration and takes place only through a semi-permeable membrane. A cellophane paper is an example of a semi-permeable membrane.

So to give you a simple answer. In diffusion molecules travel from a higher concentration to a lower concentration. In osmosis molecules travel from a lower concentration to a higher concentration.

Answer 6

wot wow this question for nerds by da looks of it haha