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