Water is one of the most fundamental things needed in life by both humans and animals. A large percentage of the earth is made up of water and this goes to show how important it is. There are various sources of water like rain, springs, wells, lakes, seas, and oceans. Natural water like air consists of impurities and some of the impurities include oxygen, carbon(IV) oxide, and dissolved salts of iron, sodium, potassium, calcium, and magnesium.
Water like Air is a mixture and the gases in air are also present in all sources of water. The percentage composition of gases in water volume is as follows: Nitrogen – 63.9%, Oxygen – 33.2%, and Carbon(IV) Oxide- 2.9%. Since the percentage of oxygen in water is higher than the percentage in air, Oxygen is more soluble in water than in air.
Types Of Water
There are different types of water though many are not aware of this. Water can be classified into hard and soft water. Hard water does not produce lather readily with soap solution while soft water produces lather with soap solution readily. Most of the water people use is not pure because it has impurities. Pure water can only be gotten by simple distillation of a water sample. You can read about Simple distillation in the Chemical separation techniques article here.
The water sample is placed in a distillation flask and as the water boils, it changes into steam which condenses on passing through water-cooled liebig condenser, into pure water, called the distillate. The dissolved impurities are left in the distillation flask as the residue and water obtained by distillation is called distilled water.
Physical Properties Of Water
The following are the physical properties of water:
- Pure water is a colourless and odourless liquid
- It has a characteristic insipid liquid
- It boils at 100oC under atmospheric pressure
- It has a maximum density of 1.00gcm-3 at 4oC
Chemical Properties Of Water
The following are the chemical properties of water:
Reaction With Metals: Based on their reactivity, metals can be divided into three namely active, semi-active, and non-reactive metals. Metals such as Potassium, Sodium, and Calcium, react vigorously with cold water to give off colourless and odourless hydrogen gas while metals like Magnesium, Aluminium, Zinc, and Iron do not react with cold/hot water however, they do react readily with steam at red heat, to liberate hydrogen, and produce the corresponding oxide of the metal.
Finally, water does not react with inactive/passive metals. The classification is based to the position of the element in the transition series.
Reaction With Non-Metals: When steam reacts with Carbon, a mixture of Carbon(II) oxide and hydrogen gas is produced while a mixture of Hydrochloric acid and monooxochlorate acid is produced when Chlorine gas is dissolved in water.
Water also reacts with oxides of metals since they are basic and oxides of non-metals. Finally, water reacts with metallic carbides and effervescence occurs; The product of that kind of mixture is a gaseous hydrocarbon and the corresponding hydroxide.
Test For Water: A sample of water will turn white anhydrous CuSO4 blue, or blue anhydrous Cocl2 powder pink
Definition Of Hardness Of Water
When a water is hard, it is due to the presence of soluble salts of calcium, magnesium, and or, iron in wells, rivers, and seas. When it comes to the hardness of water, there are two types of hardness namely temporary hardness and permanent hardness.
Temporary hardness is caused by the presence of hydrogen trioxocarbonate(IV), HClO,3– of Ca, Ca(HClO3)2;Mg, Mg(HCO3)2; or Fe, Fe(HClO,3)2. It is formed when rainwater that contains dissolved carbon(IV) oxide, CO2 flows through a locality where there are deposits of limestone, marble, or chalk. This type of hardness can be removed by boiling.
Permanent hardness cannot be removed by boiling and it is due to the presence of tetraoxosulphate(VI) or chloride of Calcium, Magnesium, or Iron[CaSO4, MgSO4 , FeSO4] in natural water. The other methods used to remove hardness in water include the addition of slaked lime, the addition of washing soda, the addition of crystals of trioxocarbonate(IV) also known as washing soda, distillation, and ion exchange method(Permutit method).