Changes

==Introduction==

==Introduction==

 

Osmosis is the passive movement of water across a semi permeable membrane.  It occurs in the opposite direction to diffusion of ions.  Water moves from a region of low solute concentration and therefore high water concentration to a region of high solute concentration and low water concentration.

Osmosis is the passive movement of water across a semi permeable membrane.  It occurs in the opposite direction to diffusion of ions.  Water moves from a region of low solute concentration and therefore high water concentration to a region of high solute concentration and low water concentration.

==Pressure and Water Movement==

==Pressure and Water Movement==

 

If you have two bodies of water, one pure and one with a solute dissolved in it, separated by a membrane permeable to water but not the solute then water molecules from the pure water move to the side with the solute.  This movement of water causes a fluid pressure difference at the entrance and exits of the holes in the membrane.  At the side with the solute the fluid pressure is lower than at the side without however this pressure difference is only at the exit of the hole and not in the solution as a whole.  This pressure difference is the actual cause of the movement of water.   

If you have two bodies of water, one pure and one with a solute dissolved in it, separated by a membrane permeable to water but not the solute then water molecules from the pure water move to the side with the solute.  This movement of water causes a fluid pressure difference at the entrance and exits of the holes in the membrane.  At the side with the solute the fluid pressure is lower than at the side without however this pressure difference is only at the exit of the hole and not in the solution as a whole.  This pressure difference is the actual cause of the movement of water.