VIII.+Why+does+water+have+such+a+high+boiling+point?



The water molecule is angular in shape, forming negative and positive charges on opposite sides. This means that the H2O molecule is highly polar. Because of this high polarity H20 molecules form hydrogen bonds which are very strong. This is when hydrogen atoms in one water molecule are attracted to the non-bonding electron pairs of the oxygen atom in another H20 molecule. These strong hydrogen bonds mean that water has a very high boiling point because it takes a lot more energy to overcome them and release H2O molecules from the liquid into the gaseous phase. The polarity of the molecules determines the forces of attraction between the molecules in the liquid state. Polar molecules are attracted by the opposite charge effect (the positive end of one molecule is attracted to the negative end of another molecule. Molecules have different degrees of polarity as determined by the functional group present. Principle: The greater the forces of attraction the higher the boiling point or the greater the polarity the higher the boiling point.
 * Polarity and Boiling Point:**

In the case of water, hydrogen bonding, which is a special case of polar dipole forces exerts a very strong effect to keep the molecules in a liquid state until a fairly high temperature is reached.

This is shown in the graphic on the left for a similar set of molecules in Group VI of the periodic table. If water behaved as a normal polar molecule it would have boiled at about - 100 C (shown in red). The other molecules are slightly polar and show the increase in boiling point with molecular weight which is normal.

__**Instead, water boils at +100 C, which is very abnormal. The major reason for this abnormal behavior is the strong attractions afforded by the hydrogen bonds. It takes a lot more kinetic energy in an increased temperature to break the hydrogen bonds to free the water molecules as the gas.**__ More normal behavior is seen in dimethyl ether (CH3)2O which has no hydrogen bonds possible.

http://www.africanwater.org/waterbasics.htm and http://www.elmhurst.edu/~chm/vchembook/163boilingpt.html

PEACE!! this will answers the question if u take the time to read it