The Uniqueness of Water

Water is a natural substance that all of us encounter on a daily basis.  We rinse with it to clean ourselves and we drink it to stay healthy.  In addition, more than 60% of the human body is comprised of water.  But have you ever stopped to consider the uniqueness of this molecule that plays an intricate part of our lives and bodies?

H2O Molecule
Diagram of a water molecule. Figure by Melyssa Smith

Perhaps the beauty of water begins with the simplicity of its molecule, H2O.  It is made-up of only two elements: two hydrogen atoms (H2) and one oxygen atom (O).  The H atoms create a slight positive electrical charge on one end of the molecule (a positive pole), while the O atom creates a slight negative charge (a negative pole).  This polarity helps liquid water attract to, surround and break apart more substances than any other known liquid.  Thus, scientists call water a “universal solvent” – something that many other substances (e.g. salt, sugar, powdered hot cocoa) can dissolve into.  This attractive quality is how water is able to transport many vital minerals and nutrients throughout our soils, plants and environment.

Waterstrider_wiki
A Water Strider, kept afloat by the surface tension of water. https://upload.wikimedia.org/wikipedia/commons/1/1a/WaterstriderEnWiki.jpg

Not only does water bind easily to other substances (adhesion), but it also sticks well to itself (cohesion).  The positive and negative ends of water molecules attract to each other and form water droplets.  These dual properties help explain how water can ascent up the trunks of trees – water clings to the inner walls of the xylem in tree trunks and pulls other water molecules along, travelling up against the forces of gravity.  You can observe water’s cohesive forces by filling up a glass of water slightly over the rim; water will hold onto itself and not spill over the sides.  Similarly, surface tension enables spiders and insects, such as the water strider, to walk on the surface of the water.  And so this seemingly simple molecule is capable of amazing feats.

Water has special physical qualities as well.  Unlike any other material on Earth, water can exist in solid, liquid and gaseous forms naturally.  The gas form floats freely in the air we breathe, with many molecules moving haphazardly far away from each other.  This vapor can condense into clouds and return water to the earth as either rain or snow.  When we hear the word “water” we usually think of the liquid form, and that’s probably because ~70% of our planet is covered in oceans.  Snow and ice are examples of water’s solid phase, with molecules tightly packed and organized into crystalline structures.  Unlike most other materials, the solid phase of water is less dense than its liquid form, which means ice can float atop liquid water.  This property is useful in lakes during the wintertime, as surface ice acts as an insulating layer for the water below, shielding aquatic life from extremely cold temperatures.  Clearly, water is a necessary ingredient for survival.

2013 letchworth falls downstream winter
A frozen Letchworth Falls, Letchworth State Park, Castile, NY. All three physical states of water are present: solid (ice and snow), gas (air) and liquid (stream below). Photo by OPRHP

New York State has more than 70,000 miles of rivers and streams and around 7,600 lakes, ponds and reservoirs.  Additionally, we are fortunate to share our borders with two Great Lakes, Lake Erie and Lake Ontario.  Whether flowing, still, above or below ground, water is a ubiquitous feature in New York State Parks.  It supports life and creates habitats for aquatic plants and animals.  At the same time, water provides endless opportunities for recreation.

Many of our State Parks offer outdoor activities which involve water.  Check out the 2016 Empire Passport to learn more about how you can access our state parks in any season.  From swimming, boating and water skiing in the summer, to snowshoeing, sledding and cross-country skiing in the winter, to fishing (ice, fly or reel) year round — there is water-filled fun for every age all year long.  The unusual chemical and physical properties that make water so valuable are also what make water so unique and enjoyable.

Post by Melyssa Smith and Erin Lennon (OPRHP Water Quality team)

Resources:

Water as a universal solvent – http://water.usgs.gov/edu/solvent.html

New York State’s land and water resources – http://www.dec.ny.gov/61.html

Unusual properties of water – http://chemwiki.ucdavis.edu/Physical_Chemistry/Physical_Properties_of_Matter/Bulk_Properties/Unusual_Properties_of_Water

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