The Chemical and Physical Properties of Water.
Water consists of two volumes of hydrogen to one volume of oxygen. The hydrogen atoms are arranged at a bonding angle of 105 degrees. This makes the water molecule polar because the shape of the molecule is such that it has a positive end and a negative end. This polarity accounts for the strong bonding between the molecules and peculiar properties of water, e.g. Relatively high melting and boiling point, expands when freezes. Because of its polarity water is a good solvent, attracting both the positive and negative charges of other solutions. This is very important because all chemical reactions in cells take place in aqueous solution. .
Water has a pH of 7, which makes it a neutral liquid medium. It's neutrality ensures that reactions taking place within living organisms are not disturbed by being too acidic or basic. Blood in animals and sap in plants consist largely of water. It's serves as a transport medium for food and removal waste materials within living organisms. Water is transparent allowing for sunlight to penetrate deep into water bodies. If it were not, photosynthesis would not take place and few organisms would be able to survive. Transparency also allows for organisms to see in water.
Water has a high specific heat, meaning that it takes large amounts of energy to cause a change in temperature. Because so much energy is needed to raise or lower the temperature, oceans and other bodies of water remain at a relatively constant temperature, ensuring that the organisms that they house are provided with a constant environmental temperature. The same is true for organisms living on land. A constant body temperature is crucial because rates of chemical reactions are greatly affected by temperature. Water also helps minimise temperature fluctuations. Without this property, living organisms would overheat or freeze to death with the slightest change in temperature.