Importance of Water
Water a wonderful liquid
We cannot live without water. We use water for bating, drinking and washing. We cook our food with it. Plants and animals too cannot live without water. We can say that earth would have been lifeless without this wonderful liquid.
It is important also because it dissolves a large number of materials.
A liquid that contain a material dissolved in it is called a solution. In a solution there are two components:-
a) solvent – which dissolves the material
b) solute- the material which is dissolved in the solvent
Water the best solvent
Water is known to the best solvent. Water dissolves a number of materials such as sugar, common salt, colors, inks, medicines, fertilizers etc.
there are some materials which do not dissolves in water e.g., coal power, wood powder, coal tar, sand, chalk power etc. coal tar can be dissolved in kerosene oil.
A given quantity of water can dissolve only a certain amount of common salt any other solute.
Some solids dissolve quickly in water than others.
Conditions favorable for dissolving solids
a) string helps in dissolving the solids faster
b) heat helps in dissolving the solids more quickly
c) hot water generally dissolves a greater amount of solid than cold water
d) small particles of a solid dissolve faster than large ones
Separation of materials
There is problem of separating one material from another. But still we can separate them. For example, if we want to separate salt from the sand, we can do it by dissolving the mixture in water. The sand does not dissolve and settles down at the bottom. The salt dissolves. The salt solution can be poured slowly into another container, from which the salt can be recovered by heating,
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