Why water is called as a miracle of nature

Some unique properties of water:

When we study the properties of water its seems such a strange and unique physical and chemical property that scientist says it is a Miracle of Nature.

1-    Did you ever think if saltish water comes in raining:     

Scientist says water is a universal solvent and is a miraculous property of water that it can dissolve almost everything but unlike the other solvent it did not carry any contaminants when it evaporates only pure water components go into the vapors, that is why we get soft and drinkable water is raining.

Just imagine if water evaporates along with its salts and raining all along the surface of earth making a saltish surface which does not let anything to grow and unable to drink.

2-    Freezing of water: It is a universal fact that heat expands the size of almost everything and cooling reduces the size. In case of water when it is cool down up to 04 C⁰ it follows the universal rule and shrinks but when the temperature goes down below 04C⁰ it expands and comes in the shape of ice. This is a very unique property of water which really seems to have a great advantage for marine life. It’s a physical phenomenon that things float on water when its weight is less than its replacing water which certainly depends on its size, So below 04 ^oC when its size increases it freezes and because of increased size ice float on water. Imagine if ice does not float and settle under the water on the bottom then what would happen to our marine life and this ice would never be melted again.

Surface tension

The surface tension of water is 71.99 mN/m at 25 C⁰, it's because of strong cohesion force between its own water molecules, this the highest of the common non-ionic, non-metallic liquids.

Capillary waves is another effect of surface tension when surface ripples that form around the impacts of drops on the surface of the water. The overall elasticity due to surface tension drives the wave.

Capillary action

Due to the forces of adhesion and surface tension water plays capillary action and rises into the narrow tubes adhering to inside walls and causing a surface rise and more and more pulled up as can be seen in the plants. Cohesion is actually intermolecular attraction holding the water column to the xylem and preventing the tension rupture by an intermolecular pull to supply water up to any height of the plant. 

The property of the surface of a liquid that allows it to resist an external force, due to the cohesive nature of its molecules.

The Cohesive forces between liquid molecules are responsible for the phenomenon known as surface tension. It is not really true that a "skin" forms on the water surface; the stronger cohesion between the water molecules as opposed to the attraction of the water molecules to the air makes it more difficult to move an object through the surface than to move it when it is completely submerged.

cohesion and Surface Tension

Surface tension could be defined as the property of the surface of a liquid that allows it to resist an external force, due to the cohesive nature of the water molecules.

Surface tension at a molecular level

Water molecules want to cling to each other. At the surface, however, there are fewer water molecules to cling to since there is air above (thus, no water molecules). This results in a stronger bond between those molecules that actually do come in contact with one another, and a layer of strongly bonded water (see diagram). This surface layer (held together by surface tension) creates a considerable barrier between the atmosphere and the water. In fact, other than mercury, water has the greatest surface tension of any liquid. (Source: Lakes of Missouri)

However, for a molecule on the surface of the liquid, there will be a net inward force since there will be no attractive force acting from above. This inward net force causes the molecules on the surface to contract and to resist being stretched or broken. Thus the surface is under tension, which is probably where the name "surface tension" came from. (Source: Woodrow Wilson Foundation).                                

Due to the surface tension, small objects will "float" on the surface of a fluid, as long as the object cannot break through and separate the top layer of water molecules. When an object is on the surface of the fluid, the surface under tension will behave like an elastic membrane.

Example of surface tension

                                                  

Walking on water: Small insects such as the water strider can walk on water because their weight is not enough to penetrate the surface.

Floating a needle: A carefully placed small needle can be made to float on the surface of water even though it is several times as dense as water. If the surface is agitated to break up the surface tension, then the needle will quickly sink.

Soaps and detergents: These help the cleaning of clothes by lowering the surface tension of the water so that it more readily soaks into pores and soiled areas.

Water as solvent

Water is also a good solvent due to its polarity and the things dissolve in water are known as Hydrophilic (water-loving). While the things do not dissolve (like fats and oil) are called as hydrophobic (water-fearing). The ability of the substance to dissolve in water can be determined by the similar or strong attraction force that water molecules generate between other water molecules. A substance does not allow to overcome these strong molecular forces, it pushed out from water and do not dissolve.

In general ionic and polar substances like acids, alcohols and salts are soluble and nonpolar such as oils and fats are not soluble in water.