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Notes on All about Water

190 / June-06-2021 23:03:55 By- srijan /

Introduction

Water is the very important for all animals as well as plants. To drink and and for our daily activities, water is very esserntial and no any animals and plants can survive without it.
Almost 4 part of earth 3 parts is covered by water. Likewise water makes up seventy percent of our body weight. At birth, a child's body weight comprises of eighty % of water
From this chapter we gonna study about sources of water, properties, use and ways to remove hardness of water.

Henry Cavendish was the first scientist to proposed that we can form water by igniting hydrogen and oxygen in the ratio 2:1.

2H2 + O2 → 2H2O
So water has the chemical formula H2O

Sources of Water

The place from where water is available in the community or regions, for agriculture, industries, for daily use and for different function, they are called sources of water.

On the basis of the place water resouces it is divided into two types:

  1. Surface Water Resources
     
    • Ocean :
      It cover 97 of water resources of the earth. The water in the Ocean is salty. This water is not used for our daily life but is it useful to produce electricity.
       
    • RIvers, Ponds, Lake, etc:
      These are found in the surface of the earth aand the water obtained fron these sources are used in different activities. These water is helpful for agriculture, to use in factories and industries, to produce electricity and to perform daily home activities.
  2. Under Ground Water Resources
    The water which is found underground in the cracks and spaces in soil, sand and rock is called underground water. It is stored in and moves slowly through geologic formations of soil, sand and rocks which is called as aquifers. In this acquifer hundred times more water is being collected than in sea, river, waterfall, pond, lake, etc and the surface inside the ground is called water table.

Properties of Water

  1. Physical Properties of Water
    Among the substances in the earth, water is only the substance which is present in all three states(solid, Liquid and gas). Water is present in the solid state at mountain etc, in liquid state at river and in gas state at the atmosphere.
    • Pure water is tasteless, odourless and colourless.
    • Water can dissolves wide varieties of chemical substances that is why, water is called as universal solvent.
    • Pure water donot conduct electricity.
    • Pure Water freezes at 00 C.
    • Water in pure form has a neutral PH i.e., 7 , which means it is neither acidic nor basic.

  2. Chemical Properties of Water
    • Pure water does not conduct electricity. But if water is impure with any dissolved solute then conducts electricity. Water has high capacity to conduct electricity than other liquid substances.
    • Metals like lithium, sodium, potassium, calcium, etc reacts with water and form hydroxide of metal.

      2Li + 2H2O → 2LiOH + H2
      2Na + 2H2O → 2NaOH + H2
      Ca + 2H2O → Ca(OH)2 + H2

       
    • When we dissolve acid, base and soluble salts in water, their aqueous solution is formed and breaks down into ions.
      HCL → H+ + CL-
      KOH → K+ + OH-

Uses of Water

  • It is used to generate hydroelectricity.
  • It is used to run industries.
  • It is used for the means of transportation(ships).
  • Used for our daily activities like drinking, washing, bathing, etc.
  • It is used for fishary.

Types of water

On the basis of nature and use, water are catagorised into two types:
i) Hard Water
ii) Soft Water


Hard Water: The water which does not produce lather with soap easily is called hard water.
There is the preseent of sobuble of calcium and magnesium like calcium sulphate, calcium chloride , calcium bicarbonate, etc. Usually, well water, river water, ground water are the example of hard water.
On the basis of the types of Ca and Mg salts contained in water, there are two types of hardness of water.

  1. Temporary Hardness of Water: Temporary hardness is caused in presence of bicarbonates of calcium or magnesium. these hardness can be easily removed by boiling and by treating with lime water.
  2. Permanent Hardness of Water: This hardness is caused in the presence of chloride or sulphate of calcium or magnesium. The hardness cannot be removed.

Soft Water: The water which produce lather with soap easily is called soft water.
There is not presence of soluble salts of calcium and magnesium which brings the hardness of water like calcium sulphate, Calcium chloride, calcium bicarbonate, magnesium chloride, magnesium bicarbonate, etc are not dissolved in water. Rain water is the best example of soft water.

Advantage of hard water:

  • It is used in breweries to manufacture beer.
  • The salt present in hard water makes the water testy to drink.
  • The calsium salt present in water, makes our bone strong.


Disadvantage of hard water:

  • It consumes more soap since it doesnot form lather with soap easily.
  • It decrease the brightness of with clothes if dipped into water.


Methods of removing temporary hardness of water

a) Boiling:
    While boiling water the dissolved bicarbonate converts into insoluble carbonate. These insoluble compounds are separated from filter method. The water achieved in this way is soft water.

b) By Clark's Method:
In this process, the hard water is treated with slaked lime(calcium hydroxide), the slaked lime reacts with the bicarbonates of the calcium or magnesium and it forms insoluble carbonates of calcium and magnesium and water.about-btnDue to this temporary hardness changes into soft water.



Methods of removing permanent hardness of water

a) By the Additional of Washing Soda : Washing soda is sodium carbonate(Na2CO3).
When it is mixed with hard water, a chemical reactions takes place between the washing soda or chloride and sulphate of calcium or magnesium of hard water. It forms sodium salts and calcium or magnesiu carbonate due to which permanent hardness is removed.



b) By Permutit Process:
    It is the most common method of removing both temporary and permanent hardness of water. Sodium in permutit is hydrated sodium aluminium silicate, Na2(Al2Si2O8.9H2O) and is also called sodium zeolite.