Earth is sometimes named the “Blue Planet” due to the large amount of water present on its surface. Oceans and seas cover more than 70% of the earth surface.
The volume of water on earth is evaluated in the table below:
|Water Reserve||Volume in km3||Volume (%)|
|Oceans and seas||1 320 000 000||97.2|
|Ice (glaciers, ice caps)||25 000 000||1.8|
|Ground Water||13 000 000||0.9|
|Surface Water (Lakes, swamps, rivers)||250 000||0.02|
|Atmospheric Water (clouds, rain)||13 000||0.001|
Water is a very simple molecule (two hydrogen atoms combined with one oxygen atom), but that simple combination allows the emergence of exceptional properties that have made water the most important solvent on earth and an essential support to the development of life.
For many physico-chemical parameters, water has outstanding values; many of these values can be explained by the hydrogen bonds that link water molecules together.
Some key parameters of high purity water are listed below:
Ultrapure Water Value
|Boiling Point||100||°C||at 1 kg/cm²|
|Density (liquid)||997.07||g/L||at 25°C|
|Density (liquid)||999.97||g/L||at 4°C|
|Density (liquid)||999.83||g/L||at 0°C|
|Dielectric Constant||78.4||at 25°C|
|Ebullioscopic constant||0.51||K kg/mol|
|Entropy of vaporization||109|
|Heat of fusion||5.98|
|Heat of vaporization||40.7|
|pH||7||pH units||at 25°C|
|Surface Tension||72.75||mJ/m²||at 20°C|
|Triple Point||0.01||°C||at 611.73 Pa|
The water molecule has another interesting characteristic: its ability to dissociate itself.