SIMPLE
DIFFUSION AND
OSMOSIS
SIMPLE DIFFUSION
WHAT IS DIFFUSION
• Diffusion is the movement of molecules or
particles from a region of high concentration
to a region of low concentration
OR
• We can say molecules or particles move from
an area where there is more particles or
molecules to an area where there is less
HOW DIFFUSION OCCCURS
• Molecules and particles are in constant random
motion.
• This is due to the energy that they posses; this is
known as KINETIC ENERGY
• Solids are closely packed so they vibrate and
contain little kinetic energy
• Liquids move around to occupy the space of the
container and contain more kinetic energy so
they move more
• Gases move about freely in space and contains
lots of kinetic energy so they can move faster
HOW DIFFUSION OCCURS
• When molecules or particles are mixed the
kinetic energy they posses allows them to
move about until they are evenly distributed
• So the amount of kinetic energy a molecule
posses will determine how fast it diffuses
• However there are other factors that will
affect the rate of diffusion or how fast
diffusion occurs
MORE ON DIFFUSION
• Diffusion can occur with:
1. liquids and solids (water and dye)
2. different liquids (water and ink)
3. different gases (gases in the air)
• When particles or molecules are evenly mixed
no more changes occur
• We can compare the rate of diffusion of
different substances
MORE ON DIFFUSION
• Diffusion occurs everywhere but can be
demonstrated in the lab with different chemicals
• The rate of diffusion is affected by the size of the
molecules and temperature
• The larger the molecules the slower it will move
therefore smaller molecules will move faster and
diffuse faster
• At higher temperatures particles or molecules
posses more kinetic energy and therefore the
higher the temperature the faster the rate of
diffusion
EXAMPLES OF DIFFUSION
• When you smell a flower
• When someone sprays perfume on one side of
the room and the person on the other side
smells it
• When we add dye to water in celebrating
Phagwa
• When making cool aid
OSMOSIS
• This is the movement of water particles from a
region of high water concentration to a region
of low water concentration through a
selectively permeable membrane.
WHAT DO YOU OBSERVE IN THE
PICTURE BELOW
• PINK = WATER
PURPLE = SUGAR
• Water molecules are smaller
• The selectively permeable
membrane acts as a barrier for
larger molecules
• Water molecules move across
the selectively permeable
membrane
• The volume in the second half
increases but the concentration
of the water molecules is even
IMPORTANCE OF OSMOSIS
• Cells get water via osmosis
• Osmosis occurs in all living cells and helps to
regulate the amount of water in the cells
• Water is very important for all chemical reactions
occurring in the cell.
• If a cell is placed in too much water it can burst
• If a cell is placed in a concentrated solution it can
shrink and become dehydrated.
• Plant cells have a cell wall that prevents the cells
from bursting.
COMPARING BOTH DIFFUSION AND
OSMOSIS
• Diffusion and Osmosis is the process of moving
particles from a region of high concentration to a
region of low concentration
• Diffusion occurs with any particle
• Osmosis occurs ONLY with water molecules
across a selectively permeable membrane
• Both processes are important to the human body
and living things
• Both can be applied to many processes in science
and everyday life.