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