In nature, we find several types of water. We hardly find it pure. This is because, in water, various other substances are dissolved. So we can say that water is a great solvent, that is, it dissolves many other substances.
It is formed by two or more pure substances.
It consists of only one phase. You cannot differentiate between substances. Example: water + sugar.
It is formed by two or more phases. Substances can be differentiated with the naked eye or with a microscope. Example: water + oil.
It is a homogeneous mixture. The solutions may be gaseous, liquid or solid.
Gaseous solution is a homogeneous mixture formed by gases.
Example: atmospheric air (nitrogen, oxygen…).
Liquid solution is a homogeneous mixture formed by liquids.
Example: hydrated alcohol (alcohol and water).
Solid solution is a homogeneous mixture formed by solids.
Example: common gold (gold and copper).
The solutions are formed by solvents and solutes. Solvent is that which dissolves. Usually it is in larger quantity. Solute is that which is dissolved. It is usually in less quantity.
Water as a universal solvent
Water is known as a universal solvent because it dissolves almost all substances that exist in nature. There are several types of solutions made with this solvent.
- water plus sugar - solvent water / solute sugar
- vinegar - solvent water / solute acetic acid
- bleach - solvent water / solute sodium hypochlorite
- saline - solvent water / solute sodium chloride
- drinking water - solvent water / mineral salts and oxygen solute gas
- sea water - solvent water / solute mineral salts
The substances that dissolve in water are called water soluble. Examples: sugar, alcohol, acetic acid.
Importance of water as a solvent in organisms
- Plants: Mineral salts are only absorbed from the soil by plant roots after they are dissolved in water.
- Blood: It is a heterogeneous mixture. The liquid part (plasma) consists of red blood cells, white blood cells and platelets. This plasma contains water, where other substances such as vitamins and glucose are dissolved. Water serves as a transport of these substances to the rest of the body.
- Urine: Water acts as a transport of bad substances that must be eliminated from the body. These substances are: urea and uric acid.
What happens if you pour sand into a glass of water and then stir it? The sand will not dissolve in water. While the mixture is being stirred, the sand is spreading through the water. We say the sand is suspended in the water. Stopping stirring, the sand quickly separates from the water and settles at the bottom of the glass.
So suspension is a heterogeneous mixture where one of the components is liquid or gaseous.