Osmosis and Colloids

Osmotic Pressure

Another colligative property A solution and a pure solvent are

separated by a semipermeable membrane- membrane allows solvent but not

solute to pass through As time passes, the volume of the

solution increases while the volume of the solvent decreases- stops when equilibrium is reached

Flow of solvent through the semipermeable membrane is called osmosis

Since the liquid levels are different at equilibrium, there is a different fluid pressure

The excess pressure on the solution is called osmotic pressure

The greater the concentration of the solution the greater the osmotic pressure

Reverse Osmosis

Colloids

Small particles can be suspended, without dissolving, in a liquid – don’t settle to the bottom

Can detect these particles by shining an beam of light through the suspension

If the beam is visible from the side, then there are suspended particles scattering light

Called the Tyndall Effect

Suspension of tiny particles is called a colloid

Suspended particles range in size from 1 to 1000nm

They are classified according to the states of the dispersed phase and the dispersing medium

Pg. 550

If heat or an electrolyte is added to a colloid, particles may clump together (called coagulation) and fall to the bottom