By Cyril Anderson

Water is a substance, that, from a casual glance, is seemingly very ordinary.  This is due to its almost ubiquitous presence.  Indeed, most of us only start to notice the wonder of water when we are lacking it.  But it is not merely its ability to quench our thirst that makes water amazing.  In reality, water is a highly anomalous and unique substance from a chemical standpoint, with a number of extraordinary properties that set it apart from other substances.

·        The specific heat of water, highest of all liquids except ammonia.  (4.18 J/g)  Allows water to hold a lot of heat.  Makes it difficult to change the temperature of large amounts of water.  The vast reserves of water in the oceans act as either a heat sink or a heat reservoir. This acts to moderate the earth’s temperature by preventing the earth’s oceans, covering 75% of the earth’s surface, from overly changing in temperature. This also allows heat to be transported around the earth very effectively through ocean currents.

Similarly, the human body is made up 75% of water. This helps us to keep a relatively constant body temperature, aided of course by other thermo-regulatory controls.

·        Water also has the highest surface tension of any liquid. (7.2x10⁹ N/m)  This has an effect in nature, allowing water to creep into cracks and cause erosion.  Also has an effect in the physiology of cells, affecting surface behavior.

·        It is a polar substance, allowing a number of electrical properties of water.  This is due to the geometry of the water molecule, combined with unequal electron pair sharing on the oxygen hydrogen bonds.  The net result is that the oxygen end of the molecule is relatively negative, while the hydrogen end is relatively positive.  This gives water a strong electric dipole moment.  This allows a number of interesting effects.  For one, this polarization allows for weak attractive forces between oxygen and hydrogen atoms on neighboring molecules known as hydrogen bonding.  In addition, it allows the possibility for water molecules to line up temporarily in an electrical field.  This allows phenomena such as lightning, and is also exploited in microwave ovens, where electromagnetic radiation at the right fine-tuned frequency will cause water molecules to rotate and release heat through friction.  This polar property allows the dissolving of polar substances such as ammonia and of ionic substances like salts, and also accounts for the acid base properties of water.

·        Water has the highest dielectric constant of any liquid except hydrogen peroxide and hydrogen cyanide.  This helps to keep ions separated in solution.

·        Water is unique amongst liquids in that its solid form, ice, is less dense that its liquid form, and thus, ice floats on water.  In all other substances, the solid form sinks in the liquid.  This anomaly prevents ponds from freezing from the bottom, and allows life to persist under ice in the winter in a world dominated by water-based life.

·        The heat of fusion, that is, the energy needed to melt a given amount of a solid, is the highest of all substances except for ammonia.  (333 J/g)  This has a thermostatic effect at freezing due to absorption of heat at melting or release of heat in freezing.  Phase changes occur in a substance at a constant temperature.  For example, the amount of energy needed to simply melt 1.5 kg of ice at a constant temperature of 0^oC will heat 1 kg of steel from 0^o C to 1100^o C.

·        The heat of vaporization, the heat required to turn a substance from liquid to gas, per unit mass, is highest of all liquids.  (2250 J/g).  This plays an important role in heat and water transfer in the atmosphere.

·        The heat conduction of water is the highest of all liquids.

·        The viscosity of water is lower than other liquids at comparable temperatures.  As a result, water flows relatively easily to equalize pressure.

·        Water is a necessity for all forms of life, plants and animals.  On a cellular level, water is the major component of cytoplasm. On a biochemical basis, water features prominently in both photosynthesis and cellular respiration, being a needed reactant in both.  Water also serves as a home for a great number of life forms.