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Introduction
Water is without a doubt the most important substance known to mankind. It is an essential to life, being involved in practically every process that occurs in plants, animals and humans. While the molecules of water are simple in structure (H2O), the chemical and physical properties of the compound are quite complicated and unique. It is because of its unique and complex properties that water is able to support life.
Chemical Structure
The water molecule has two lone pairs of electrons. These two pairs along with the two hydrogen atoms give the molecule a tetrahedral shape (see figure 1). These lone pairs of electrons are very negative and repel the hydrogen atoms. This repulsion causes the hydrogen atoms to move closer together and gives the molecule its bent shape. If water did not have this bent shape all of its properties as we know them would change. A property of water that would be affected is that of its polarity.
Polarity
Water is a polar molecule as the oxygen has a higher electronegativity than that of the hydrogen. Oxygen’s higher electronegativity causes the electrons to spend more time around it resulting in a slight negative charge around the oxygen atom. Slight positive charges also exist around the hydrogen atoms. (The University of Arizona, 2003) If the water molecule was straight these charges would cancel out and it would not be polar. If water was not polar life as we know it would not exist.

Hydrogen Bonding
Due to polarisation, nearby water molecules have Intermolecular bonds, otherwise known as hydrogen bonds. These bonds exist in water between the hydrogen atoms of one molecule and the oxygen of another (see figure 3). Hydrogen bonds in water are not as strong as ionic, covalent and metallic bonds, however they are stronger than Van der Waals forces. Many of the unique properties of water result from Hydrogen Bonding.

Unique Properties
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