GROUP VI

Osmosis and Osmotic

Pressure

Connection of Osmosis to the Osmotic

Pressure

What do you think about “Osmosis”?

allow some species through it but not others.

Osmosis occurs when two solutions of different concentrations are

separated by a membrane which will selectively

Then, material flows from the less concentrated to the more concentrated side of the membrane. A membrane which is selective in the way just described is said to be semipermeable.

What is semipermeable?

When two water (or other solvent) volumes are separated by a semi-permeable membrane,

water will flow from the volume of low solute concentration, to the

volume of high solute concentration. The flow may be stopped, or even reversed by

applying external pressure on the volume of higher concentration.

In such a case the phenomenon is called reverse osmosis.

*ALWAYS REMEMBER *

• If there are solute molecules only in one volume of the system, then the pressure on it, that stops the flow, is called the osmotic pressure.

Look The Illustration

To Be More Clearer

Here Is Another Illustration (•(I)•)

Imporatnce of

osmosis In terms of Biology

For the Part 2 of the report

SOLUTIONS AS

ELECTROLYTES

Some solutions, because they contain ions, also serve as electrolytes. In the human body, the transfer of nerve impulses from various receptors to the brain involve a flow of ions in a liquid medium.

•Substances that give ions when dissolved in water are called electrolytes. They can be divided into acids, bases, and salts, because they all give ions when dissolved in water. These solutions conduct electricity due to the mobility of the positive and negative ions, which are called cations and anions respectively. • Strong electrolytes completely ionize when dissolved, and no neutral molecules are formed in solution.

•Many industrial products also use electrolytes. These include dry cells for radios, flashlights, and other electrical devices; storage batteries for cars; and, fuel cells for rockets. Industrial manufacturing process use this property of solutions in the electroplating of car parts and in the manufacture of rubber products.