Transcript Diffusion and Osmosis

Diffusion and Osmosis
Diffusion
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The net movement of atoms or
molecules from a region where they
are at a higher concentration to a
region where they are at a lower
concentration is called diffusion.
Concentration refers to the number
of particles per unit volume.
Diffusion Process
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Diffusion continues until the particles
are uniformly distributed
throughout the system.
When this happens, net movement of
particles is zero and the
equilibrium of the system is
reached. At this point, diffusion has
stopped.
Movement of Particles in Diffusion
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Diffusion occurs spontaneously and does not
involve any energy taken in or given out,
i.e. there is no gain or loss of energy.
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The movement of particles during diffusion
is random, with each moving in a different
direction.
Diffusion - Illustrated
Diffusion of Bromine Gas
Critical Thinking
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Which state of matter (solids,
liquids or gases) will diffusion
happens the fastest? Why?
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Hint: Think about movement of the
particles in each state of matter. Which
particles can move the fastest?
Osmosis
Watch video:
http://www.youtube.com/watch?v=sdiJtDRJQEc&NR=1
Osmosis
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Osmosis is the net movement of
water molecules from a region of
their higher concentration to a
region of their lower concentration
through a partially permeable
membrane.
Osmosis
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Given two solutions of the same volume, the solution
with more solute particles implies higher
concentration of solute but lower concentration
of water
Rationale: Particles take up space. To have more
solute particles in the same amount of space (volume),
there must be less water molecules.
Osmosis
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Osmosis through the partially permeable
membrane will continue until the water
concentration is uniformly distributed
between the 2 solutions.
Osmosis stops when the 2 solutions are of
equal water concentration.
Diffusion vs Osmosis
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Osmosis is just a special kind of
diffusion.
In osmosis, water molecules diffuse
through a partially permeable
membrane.
On the other hand, diffusion generally
involves any type of molecules and a
partially permeable membrane need or
need not be present.
Types of Solutions
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Isotonic solution:
“iso” means equal. Isotonic solutions have equal
water concentration.
Hypotonic solution:
Solution has higher concentration of water
(lower concentration of solute) than the other
solution.
Hypertonic solution:
Solution has lower concentration of water
(higher concentration of solute) than the other
solution.
Animation on Osmosis
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http://highered.mcgrawhill.com/sites/0072495855/student_
view0/chapter2/animation__how_os
mosis_works.html
Osmosis and Living Things
(Look at notes)
Recap…
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In which organ in our body does the
exchange of oxygen and carbon
dioxide between our body and the
surrounding air take place?
Effect of different types of
solutions on living cells
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Animal Cell in Hypotonic
solution (eg. pure water)
Higher water concentration in
extracellular solution than
intracellular solution
Water enters animal cell via
osmosis and it swells.
Net gain of water from
extracellular solution into the
cell.
If a large amount of water
enters the cell, it will burst and
release contents of the cell.
Effect of different types of
solutions on living cells
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2) Animal Cell in
Hypertonic solution (eg.
salt solution)
Lower water concentration
in extracellular solution than
intracellular solution
Water exits animal cell via
osmosis and it shrinks.
Net loss of water from cell
into extracellular solution.
If a large amount of water
exits the cell, it will become
shriveled.
Effect of different types of
solutions on living cells
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3) Animal Cell in
Isotonic solution
Equal water
concentration in
extracellular solution and
intracellular solution
No net gain or loss of
water.
Animal cell prefers to be
in isotonic solution.
Effect of different types of
solutions on living cells
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Plant Cell in solution with higher
water concentration (eg. pure
water)
Higher water concentration in
extracellular solution than
intracellular solution
Net gain of water from
extracellular solution into the cell.
Central vacuole increases in size
and plant cell start to swells.
Plant cells do not burst due to its
cell wall.
When the cell wall is stretched to
its maximum, the plant cell cannot
take in any more water and are
said to be turgid.
Plant cell
prefers to be in
hypotonic
solution.
Effect of different types of
solutions on living cells
2) Plant Cell in solution with
lower water concentration
(eg. salt solution)
 Lower water concentration in
extracellular solution than
intracellular solution
 Net loss of water from cell into
extracellular solution.
 Central vacuole decreases in
size before the cell membrane
start to pull away from the cell
wall.
 This leaves a visible gap
between cell wall and cell
membrane. This process is
Plants with
plasmolyzed cells
will wilt.
Effect of different types of
solutions on living cells
3)Plant Cell in solution
with same water
concentration
 Equal water
concentration in
extracellular solution
and intracellular
solution
 No net gain or loss of
water.
 Cell appearance is
described as flaccid.
Possible ACE Assignments
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Critical Thinking Qn 3
Processes of Reverse Osmosis and
Desalination