Download Osmosis and diffusion

Please take out your science
journal to take notes in!
Diffusion and Osmosis

Cell membrane- selectively permeable,
which means that some substances can
pass through the membrane while others
cannot.
◦ Think of the analogy- The cell membrane is like
a window screen, certain things can pass in
and out of the screen (dust, pollen, rain, etc.)
while other things are kept out (flies, bees,
leaves, etc.).

The cell membrane- allows certain things
to come into and out of the cell such as….
◦ IN
 Oxygen, food, water
OUT
 Waste, Carbon Dioxide
All of these substances must pass
through the cell membrane.

We call this movement – DIFFUSION
◦ Diffusion is the process by which molecules
move from an area of high concentration to an
area of low concentration. The molecules
spread out to fill the space.
Review of Yesterday's Experiment

What causes this to happen?
◦ Molecules are always moving. If there are a lot
of molecules in one area (high concentration)
and they are all moving they will bump into
one another and spread out (to low
concentration) over time.
◦ *Demonstration air freshener
Diffusion in Daily Life
1)
2)
3)
4)
5)
When someone applies perfume or
deodorant, the smell slowly spreads into the
entire room.
If the door of the kitchen is left open, the
odor of food cooking spreads into the
adjacent room.
The smell of a burning incense stick spreads
throughout the room/house.
If a person is smoking in an enclosed area,
its odor spreads in the area.
When a tea bag is kept in a hot cup of
water, its color and aroma diffuses into the
water.

Osmosis is the diffusion of water
molecules through the cell membrane.

Water will move from an area of higher
concentration to an area of lower
concentration.
Concentration
of water
inside the cell
is the same
as outside.
High water
concentration
outside the cell
– during
osmosis, water
moves into the
cell.
Low water
concentration
outside of cell –
during osmosis,
water moves
out of the cell.
Osmosis Video
Gummy Bear Osmosis
Osmosis in Daily Life
1)
2)
3)
4)
A patient with malfunctioning kidneys
undergoes dialysis which used the principle
of osmosis to clear waste from the blood.
Rice or beans are soaked in water for a few
hours before cooking as they take in water
due to osmosis, become soft and hence
take lesser time to cook.
Roots of plants take in water by the process
of osmosis.
Osmosis is also used for preserving fruits
and vegetables.
1) Osmosis is used to dehydrate the produce or pull
the water out of it.
Osmosis vs Diffusion