diffusion & osmosis - michigan.gov · what is diffusion? diffusion is the net movement of...
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E X P L O R E L A B S C I E N C E
DIFFUSION & OSMOSIS
WHAT IS DIFFUSION?
Diffusion is the net movement of molecules from areas
of high concentration to areas of low concentration
of that molecule. This random movement, or Brownian
motion, is the result of collisions with other molecules in
the medium.
To see diffusion in action, put a drop of food
coloring into a glass of water and see how it
behaves.
GRADIENTS
The movement of particles from high to low
concentration is called “moving down the
concentration gradient.”
High concentrationLow concentration
EQUILIBRIUM
Molecules will continue to diffuse like this until they
reach equilibrium, or until there are equal
concentrations of that molecule throughout the
whole medium.
This is why the food coloring particles disperse until the
water is the same color all the way through.
OSMOSIS
Osmosis is a specialized
type of diffusion that
describes the movement
of water molecules.
Osmosis occurs when you
have membrane with
unequal concentrations of
water molecules on either
side. Water molecules will
diffuse across the
membrane until
equilibrium is reached.
SEMIPERMEABLE MEMBRANES
When you made
your naked eggs,
you removed their
shell. Now they are
surrounded by a semipermeable membrane.
What is let across the membrane is determined by the
size, shape, or charge of the molecule and the
characteristics of the membrane’s pores.
The egg membrane is only permeable water in your
experiments, so all the changes you see are because
of the movement of water across the membrane.
NAKED EGG EXPERIMENT
If you put your naked egg in
water, you probably noticed
that it got bigger.
But if you put your egg in
corn syrup or salt water, it
became shriveled.
NAKED EGG EXPERIMENT
In a glass of water, the inside of the egg is going to have a lowerconcentration of water. Water is going to cross the membrane into the egg and make it swell.
But in corn syrup or salt water, the concentration of water is higher inside the egg. So in this case, water is going to leave the egg and make it shrivel up.
H2O H2O
H2O H2O
BLOOD CELLS
The membrane of
your blood cells
acts in the same way
as the egg
membrane when
placed in different solutions.
When placed in high water concentrations (hypotonic
solutions), blood cells will accept water until they
burst. In low water concentrations (hypertonic
solutions), water will exit the blood cell until it shrivels.
KIDNEYS
Your kidneys have a critical function: to filter waste
products from your blood and regulate the balance
of nutrients and water in your body. The functional
units of the kidney, nephrons, keep the body in
homeostasis via diffusion and osmosis.
WATER PURIFICATION
Osmosis is also
utilized for water
purification, which is
crucial for the
preservation of water
quality and public
health.
Reverse osmosis is a processes used to remove impurities from water by using extreme pressure to force it to against its concentration gradient. You can use this process in your own home to purify your drinking water.
REFERENCES
• http://leavingbio.net/osmosis%20and%20diffusion.ht
m
• http://www.imaginationstationtoledo.org/educator
/activities/how-to-make-a-naked-egg
• http://kidsactivitiesblog.com/19496/egg-
experiment-3
• http://www.biology-pages.info/K/Kidney.html
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