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Water



The chemical formula for water is H2O. This means that there are two Hydrogen atoms chemically bonded two each Oxygen atoms. It can be described ionically as HOH, with a hydrogen (H+) ion that is bonded to a hydroxide (OH-) ion.
Water is a polar molecule meaning that one end of the molecule is slightly more negative than the other side, which is slightly positive. This happens because the Oxygen atom atom in the molecule is more electronegative which means it has a stronger pull on the molecules electrons which means there are more electrons surrounding the Oxygen atom. This means that the Oxygen end of the molecule is negative and the Hydrogen end of the molecule is positive.

Diagram showing the polarity of a water molecule

Because of this polarity a water molecule can form a maximum of four hydrogen bonds. A hydrogen bond in water is due to electrostatic forces which create a partial covalent bond.










Water has a high surface tension due to strong cohesion between water molecules. This again is due to the water molecules polarity. The negative end of the molecule is attracted by the positive end of another molecule. These forces of attraction cause surface tension which allows some insects i.e. Water Skater to stand and move about on the surface of the water. This surface tension is also why water forms droplets on smooth nonsoluble surfaces and it allows water to make its way up plant stems.


Water is also a very good solvent and can dissolve many types of polar substances. This is again because water is a polar molecule. When a polar substance is added to water the positve ion is surrounded by the negative ends of the water molecules and vice versa. This depends on that the substance can match or better the attractive forces the water...