"When the well is dry, we know the worth of water."-Benjamin Franklin (Poor Richard Almanac, 1746)
Water is a polar molecule with covalent bonding between the electronegative oxygen atom and the hydrogen atoms. Plainly stated, polarity refers to how polar a chemical bond is. To find the polarity one must take the difference between the electronegativities. If the result is below 1.8 and above 0.3, the bond is polar. Thus the attraction of polarity is electrical, slightly positive hydrogen of one molecule is attracted to the slightly negative oxygen of a nearby molecule. The two molecules are thus held together by a hydrogen bond. Each water molecule can form bonds with up to four neighbors. This property of water enables life to exist on Earth.
Oceans and lakes don't freeze solid because ice floats. As water-cools it expands at 0oC it is becomes hydrogen bonded to four other molecules creating spacing between the molecules.
Ice is less dense than liquid water, and therefore it floats. The floating of ice insulates the water below, allowing marine life to exist. A higher level of structural organization occurs in water when a hydrogen bond is formed between the hydrogen atoms of one water molecule with the oxygen atom of the water molecule, these hydrogen bonds are only 1/20th of as strong as the covalent bonds and continuously forming. This hydrogen bonds hold substance together by phenomena called cohesion. By cohesion water is transported in plants against gravity from root through vessels in different parts of the tree. The adhesion of water molecules to the walls of plant vessel contributes to the water transport. Hydrogen bonding between water molecules produces a high surface tension at the interface between water and air. Biologically this property of water helps some animals to walk stand and run...