Thursday, February 23, 2012

Just Plain Water

When the restaurant waitress inquires if we would care to have something to drink, I sometimes reply, “I’ll just have plain water.” My reply belies the complex and uniquely wonderful properties of water. Its colorless, odorless, and tasteless qualities have earned it the moniker “just plain water.” But our earth’s most plentiful liquid is far from plain if we carefully study its characteristics.

The successful operation of earth’s water cycle as well as many of our daily activities depends on dozens of unusual and unexpected properties of water. Only a few of water’s unusual properties are well known and appreciated by the average person, but every member of our population benefits from water’s ubiquitous presence in multiple ways every day. Without each of its many properties, life as we know it would be impossible. Beyond our needs, however, knowledge of water’s wonders enhances our sense of awe at God’s created order.

One characteristic of water that inspires wonder is called “surface tension.” This property enables some objects even denser than water to float on its surface. Objects less dense than water such as a piece of cork float owing to buoyant force. Paradoxically, a small steel needle can be made to float on water’s surface because of a tough “film” on its surface. This is the same phenomenon permitting water spiders to walk on a pond’s surface.

Water molecules possess polarity. They act like little magnets, able to attract other water molecules in a variety of ways. The two hydrogen atoms in the water molecule align themselves with the single oxygen molecule at a 105˚ angle. This causes one side of the water molecule to become positively charged while the opposite side becomes negatively charged. Why? The hydrogen atoms share their negative electrons with the oxygen atom, leaving the hydrogen side of the molecule with a net positive charge because hydrogen’s positively charged protons remain in place. The oxygen side of the molecule gains the shared negative electrons from the two hydrogen atoms, thereby acquiring a net negative charge. In my classroom, I used to characterize atoms which either shared or gave away electrons as generous atoms, helping students understand what happens, I hoped.

Surface tension is the tendency of water molecules at the surface to clump together in a dense configuration. Beneath the surface the polarity attracts molecules from every direction. But molecules at the surface attract each other in a tight linear configuration effectively forming a layer of molecules with greater density than the water beneath the surface. This dense layer is able to support water spiders and darning needles. When a drop of “wetting agent” was placed in the water, destroying the surface tension, the needle fell to the bottom. My students enjoyed imagining what would happen to the water spiders if a wetting agent were placed in the pond water.

The surface tension phenomenon, present on every water surface of every ocean, affects evaporation rate, reducing it to a “manageable” and correct rate. Water with no surface tension would support a water cycle with excessive evaporation resulting in uncontrolled rainstorms. We speak of only one of water’s characteristics. Many other characteristics of water, if changed, would not provide appropriate conditions for successful earth life.

Does knowledge of one astonishing characteristic of water enabling earth life as we know it prove the input of a designer? Taken alone, perhaps not. But taken with hundreds of other manifestations of God’s general revelation apparent in our world, we must thoughtfully consider the evidence.