Why does water diffuse?

[scilearner]

Hello everyone,

 

Ok I'm confused again (surprise). Let's say there is a semipermeable membrane and on one side there was 100 percent water. On the other side there are solutes mixed with water. Now water should move from high to low, but where is the water from 100 percent side going to move into. There are no gaps on other side, other side is full of water mixed with solutes. So why does it diffuse. Thanks

[mississippichem]

You're describing osmosis. Solutes or gases tend to move from areas of high concentration to low concentration which is diffusion. Solvents tend to move from areas of low solute concentration to areas of high solute concentration; that's osmosis. Remember when the solute concentration is higher, the solvent concentration is lower.

[timo]

Having a substance somewhere is not a binary property, but a gradual one. You are just going to end up to have more water on the right side side with the solutes, i.e. a higher density.

Edited December 13, 2010 by timo

[alpha2cen]

Hello everyone,

 

Ok I'm confused again (surprise). Let's say there is a semipermeable membrane and on one side there was 100 percent water. On the other side there are solutes mixed with water. Now water should move from high to low, but where is the water from 100 percent side going to move into. There are no gaps on other side, other side is full of water mixed with solutes. So why does it diffuse. Thanks

 

This phenomena is called osmosis .

If we see it more detail, we can see this phenomena.

The solvent molecules which are not mixed with solute are more active than the solvent molecules mixed with solute.

The molecular movement of no solute part is more fast than the other solute mixed part.

So the solvent molecules should have to move form pure solvent to the mixed solution.

From this movement the pressure is created, and we call it osmosis pressure.

The solution should be ionic solution (NaCl, H2SO4, ... solution)or so. It reduces solvent molecule movement.

Edited December 19, 2010 by alpha2cen

[steevey]

Won't let me delete it

Edited December 19, 2010 by steevey