In ancient times water was considered as an element, but in 1781 Henry cavendish clearly proved that water is a compound of hydrogen and oxygen, because
In water, hydrogen and oxygen always remain in a fixed ratio (2: 1).
The properties of water are completely different from those of hydrogen and oxygen.
The components of water (Hydrogen and Oxygen) cannot be separated by physical methods.
For these reasons it is clear that water is not a homogeneous or heterogeneous mixture, but a compound. For the first time in 1842, Duma found the ratio of hydrogen and oxygen present in water by weight. after which chemists found the mass and volumetric composition of water and told that its molecular formula is H2O.
So we can say that water is the monoxide of hydrogen.
Occurrence: Water is a natural substance, about 75% of the earth is water. It is the main component of the animal and plant world. About 70% water is found in the human body. The water which is found in the main state in nature is called natural water.
Sources of water in nature:
In nature, water is found in three states – solid, liquid and gas. Water is mainly obtained from the following sources –
Rain water: – This is the purest natural water. It is obtained by evaporation and liquefaction of water of river, sea etc. In addition to gases like ammonia (NH3), carbon dioxide (CO2), nitrogen dioxide (NO2), 0005 % solid impurities are also found.
Rain water being pure, it is used for making medicines and in place of distilled water in the laboratory.
River or Spring water: River water comes due to rain and melted snow on the mountains, this water is also pure near the mountains, but due to continuous flowing on the ground, some solid impurities dissolve in it and insoluble impurities arise. The water of the river becomes muddy due to impurities like soil etc.
Sea water: – This is the most impure water. Usually 3 – 5% solid impurities are dissolved in it. Which about 26% common salt (NaCl) is dissolved.
Apart from this magnesium salt, potassium chloride, bromide and iodide salt etc. are also found in abundance.
Mineral Water: – Due to seepage into the porous surface of the earth, almost all the impurities dissolved in rain water get separated. When this water collects in such places, from where it cannot go down, sometimes it starts coming out of the earth in the form of a waterfall.
It contains dissolved salts of various solid impurities – sodium, potassium and calcium etc. Some of these also have medicinal properties. Such water of springs is called mineral water and it is used as water for medicine.
Well Water: Some part of the rain water is filtered through the sandy pebble layers of the land and collects below. In this water insoluble substances are less, but soluble substances are in more quantity. The properties of this water depend on the chemical composition of the land.
In some places this water is obtained by digging deep wells.
The water used for drinking is called potable water or potable water. Natural water is not good for drinking, because in addition to many soluble and insoluble substances, it contains microscopic bacteria and germs. Due to which various diseases such as cholera, intermittent fever, dysentery etc. occur, so the drinking water should be absolutely pure.
The following properties should be present in drinking water –
It should be transparent, colorless and odorless.
Let it be clean.
It does not contain germs and germs.
It does not contain harmful solute substances: – such as nitrate, nitrite, ammonium salt etc.
It is very important to have some essential minerals salt and air dissolved in drinking water. This makes it tasty and healthy.
Purification of Drinking Water :
The following 5 steps are used for the purification of drinking water –
Insoluble impurities are removed by decantation or filtration.
Water is made colorless and odorless by filtering it with coal.
Water is made free from harmful micro-organisms by mixing air, ozone, chlorine, potassium parmagnate, tutia, bleaching poweder etc.
Alum is added to the impure water, due to which the suspended impurities coagulate and settle down, then the water is carried away to other ponds.
Drained water is filtered from sand, bricks, pebbles etc.
Drinking water treatment in cities
Industrial method: – The system of purifying water in cities is different. For this, water works are constructed in cities.
In which the following methods of water purification are used.
Aggregation and coagulation – First of all, the water of river, pond and lake is filled in big pucca tanks, in which there are layers of pebbles, sand, fine sand and coal. These tanks are also called setting tanks.
In these, many suspended substances settle down, those suspended substances are in collide state, for them, alum is added to the water. Due to this the collide impurities precipitate and settle down.
Some germs also get destroyed by the use of alum and sit down. The remaining germs are destroyed by sunlight. This type of precipitation of collide substances is called coagulation.
Filtration: After the stabilization tanks, the water is taken to the big filtrate tanks. These tanks have thick layers of sand, gravel, pebbles and charcoal.
This method is similar to the method of four pots. Water is slowly filtered from these layers and is fed into the tanks through the taps installed in the tanks.
Sterilization of water: After filtering the water, the germs and bacteria present in it are destroyed by the following methods –
By boiling – By boiling the filtered water, the germs present in it are destroyed. This method is mostly used in homes.
Chlorination: Chlorine is a bactericidal substance. An appropriate amount of liquid chlorine bleaching powder is used to destroy the bacteria in the water.
Ozonization: – Ozone is also a bactericidal gas. If ozonization makes oxygen flow into water, then the germs present in it are destroyed.
By Ultra Violet rays: Ultra violet rays are also a good means of killing bacteria. These rays are received from Mercury lamp and flowed on the stream of water. This kills the bacteria in a very short time and no inappropriate odor or taste is produced in the water.