March 22, 2010

Water: the chemistry aspect

Water: the chemistry aspect
The chemistry formula for water is H2O. Water contains strong covalent bonds that hold the two hydrogen atoms and one oxygen atoms together.

The oxygen can be regarded to be at the center of tetrahedron, with a bond angle of 105 degree between the two hydrogen atoms in liquid water and larger angle of 109 degree 6’ between the hydrogens in ice.

The bonds between oxygen and each hydrogen atom are polar bonds, having a 40% partial ionic character. This means that the outer shell electrons are unequally shared between the oxygen and hydrogen atoms, the oxygen atom attracting them more strongly than each hydrogen atom.

As a result, each hydrogen atom is slightly positively charged and each oxygen atom is slightly negatively charged. Therefore they are able to form hydrogen bonds.

A hydrogen bond is a weak bond between polar compounds where a hydrogen atom of one molecule is attracted to an electromagnetic atom of another molecule.

It is a weak bond relative to other types of chemical binds such as covalent or ironic bonds, but it is very important because it usually occurs in large numbers and therefore, has a significant cumulative effect on the properties of the substance in which it is found.

Water can form up to four hydrogen bonds (oxygen can hydrogen bond with two other hydrogen atoms).

Water would b expected to be gas at room temperature if compared with similar compounds in terms of their positions in the periodic table, but because of the many hydrogen bonds it contains, it is liquid.

Hydrogen bonds between hydrogen and oxygen are common, not just between water molecules, but between many other types of molecules that are important in foods such as sugars, starches pectins, and proteins.
Water: the chemistry aspect

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