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What is Water?
Over 70% percent of the earth is covered in water, and nearly 70% of our adult bodies are comprised of water.1 As abundant as water is, less than 1% (.03% to be exact), is potable or "drinkable" by humans.2 Although the amount of water on the planet is plentiful for study, its unique chemical properties make it so complicated that after years of research, we still do not understand it fully. Water simply does not behave like other liquids.
For example, if you drop an ice cube into a glass of water, it floats. That is because water expands as it freezes, and becomes less dense than its liquid form. Most all other liquids do exactly the opposite, shrinking and becoming denser as they freeze. If water behaved this way, ice formed in cold temperatures in lakes would sink to the bottom. It would then have difficulty thawing in the spring, and adversely affect aquatic life.3
Another curious characteristic of water is that it boils at a very high temperature - 100˚ Celsius at sea level. If water behaved like other liquids, in the temperature and pressure of the earth's atmosphere, it would exist as a gas - and life as we know it could not exist.3
Water has a simple molecular structure of 2 parts Hydrogen, and 1 part Oxygen, [see Diagram A]. Its peculiar properties, however, can be attributed to how these elements are bound to one another. Hydrogen and Oxygen share a pair of electrons, creating what is called a covalent bond. However, Oxygen also has two unshared pairs of electrons. An electrostatic attraction between the partial positive charge near the hydrogen atoms and the partial negative charge near the oxygen results in the formation of a hydrogen bond. Therefore, Oxygen is an "electronegative" or electron "loving" atom compared with hydrogen. This imbalance of electrons between the 2 elements makes water a "polar" molecule, meaning that there is an uneven distribution of electron density. As a result, water is always acting as a "magnet," attracted to and always seeking other chemicals and minerals with which to bond. Herein lies the issue of water's natural propensity to become polluted or "impure."
While water is classified as polar, it could more easily understood as bi-polar, meaning it has the ability to attract positive or negative charged ions, and even neutral based compounds. Because of its polarity, water can and will attract chemicals such as Chlorine and Fluoride, minerals such as Lead and Mercury, as well as Volatile Organic Compounds (VOCs) such as found in pesticides and petroleum. This is why water is commonly referred to as the earth's greatest solvent.
1 http://www.allaboutwater.org - How Much do You Know About Water?, 20 Interesting Facts about Water, March 27, 2009.
2 National Groundwater Association - http://www.ngwa.org, Services - Educator Resources, Distribution of the Earth's Water.
3 National Science Foundation - http://www.nsf.gov, A Special Report - The Chemistry of Water, July 12, 2008. |
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