Water 

Combinations of atoms can create molecules.  The atomic chain lengthens from particles to atoms to molecules.  Water molecules formed in a combination of two hydrogen atoms and one oxygen atom represented as H₂O contain three atoms total.  Water covers two-thirds of the earth’s surface.  The other surface is solid.  The whole thing is enveloped in gas.  Liquid, solid, gas.  Sea, land and air.  That’s our world.  Of all the water on the surface only 3% is fresh water.  Of that three per cent, 2% is locked up in ice and 1% flows freely as streams and rivers and creates ponds and lakes.  There is a lot of water on our planet and not much anywhere else in the universe, we think.  These three atoms in their unique combination sustain all life.  

“Water is the strangest, most ubiquitous substance on earth.  Its solid form is less dense than its liquid form, which is why ice floats.  It can absorb large amounts of heat without changing very much, which is why coastal towns have moderate temperatures.  And, it has a ‘skin,’ a thin layer of molecules that try to stick together at the surface.

“Water’s unusual properties are the result of its shape….It looks like Mickey Mouse: the two hydrogen atoms are the ears, and the oxygen atom is the head.  Because electrons aren’t distributed evenly in the water molecule, the ears are positively charged and the head is negatively charged.  Since opposites attract, the ears of one molecule are attracted to the chin of another water molecule, forming a hydrogen bond.  In ice, water molecules bond together stably to form a tetrahedron, a four-sided pyramid.  But in liquid the structure of the water molecules is looser.  Hydrogen bonds are constantly breaking up and getting back together.  In fact, the average hydrogen bond lasts only a fraction of a second.”  Elsewhere on earth and perhaps nowhere else in our expanding universe are we concerned with life, life forms and living things, most of which require water in some form for sustenance.