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Design in Atoms, Molecules, and Water

Modern scientific research depends upon the principle that nature is orderly, characterized by regularities or natural laws which man can discover by repeatable observations and measurements. Indeed, at every level, from the nucleus of the atom to the distant galaxies, structured order and design have been discovered. Consider the design of the water molecule, which consists of two hydrogen atoms chemically bonded to an oxygen atom (H-O-H, usually written H2O).²⁷

The gases hydrogen and oxygen react to form water molecules. The reason for this chemical reaction is the design of the nuclei of hydrogen and oxygen atoms, and the associated arrangement of the electrons which form a structured charge cloud around these two kinds of atoms. The water molecule has a "V" shape with the oxygen atom at the apex of the "V." The oxygen atom is classified as more "electronegative" than the hydrogen atoms, for it attracts electrons toward itself away from the hydrogen atoms in the molecule. Therefore, the oxygen end of the water molecule has more negative charge, the hydrogen atoms more positive charge, although the molecule overall is neutral in charge.

Thus we say that water is a "polar" molecule, for it has negative and positive ends or poles. This is important to the properties of water, for the polar molecules tend to attract each other and to clump together in liquid form. In addition, the hydrogen atoms of water can form a special kind of bond between the oxygen atoms of adjacent molecules. This bond mediated by a hydrogen atom is called a hydrogen bond. Hydrogen bonds are described in more detail in Chapter-4. Because of polar attraction and hydrogen bonding between molecules, it requires considerable energy to separate the molecules in the liquid state from each other to produce water vapor or gas in which the molecules are not in contact with each other. Water thus is said to have a high "heat of vaporization."

When water is frozen, the "V" shape of the water molecule, its polar character, and its ability to form hydrogen bonds cause water to produce a beautiful geometric structure which takes up more space than the liquid water. Thus ice is less dense than the cold liquid water from which it crystallizes. Moreover, the polar character of the molecules causes them to cling together in the ice crystal so that a large amount of energy is required to melt ice (i.e., change solid water into liquid water). Thus water has a high "heat of fusion"(melting).

This singular combination of properties found in the water molecule results from the unique design of the two constituent atoms and the chemical bonds which connect them in the water molecule. Now consider the place of water in the world around us. The polar character of water, combined with its stability and also its very slight tendency to break up (ionize) into two charged ions, H+ and OH-, makes water the ideal solvent for living systems. Water can dissolve a greater variety of substances than any other solvent, but it draws the line at oily (non-polar) substances, which are only very slightly soluble in water. On the other hand, the polar character of water makes it possible for so-called "surface active" molecules which are polar on one end and non-polar on the other to carry oily substances into colloidal suspension in a water system. These capabilities of water are vital to life processes.

figure 1-11. The hydrogen atoms on the right side of this water molecule carry an excess positive charge, whereas the electron clouds on the left side carry excess negative charge.

Now consider the function of water in the oceans and atmosphere. As indicated earlier, water expands about 8.7% when it freezes at a temperature of 0^o Celsius. However, as water is cooled down to about 4^oC its density increases. The water expands ever so slightly, about 0.01% as it cools from 4^o to 0^o Celsius. Only one other pure substance, the metal bismuth, has the characteristic of being denser in the liquid than in the solid state. In a lake that is cooled during winter the water slowly becomes more dense as it cools, with the colder, denser water collecting at the bottom. But any water which becomes cooler than 4^oC rises toward the top. Therefore, upon further cooling of the water, the ice forms at the surface.

What if ice were heavier than water? When winter approached, the circulation in oceans and lakes would slowly cause the entire body of water to cool to the freezing point. If the first ice formed at the surface, it would immediately sink to the bottom. Any ice forming at the bottom would stay there, and the entire body of water would become solid ice from bottom to top. Fish would die. When spring and summer came, it is unlikely that large lakes or oceans would be able to melt before the next winter arrived.

Soon most of the water in the earth would be locked up in frozen lakes and oceans and in great glaciers and ice sheets near the polar regions, never to be released. The rest of the earth's surface would be primarily very hot or cold deserts with little available water. And, of course, life in most bodies of water would be very scarce, for total freezing would kill everything under the surface. However, this bleak chain of events never happens, for ice floats because the Creator designed it that way.

Just as the energy of the sun provides the life energy for all living creatures on the earth, it also powers the circulation of the atmosphere, and thereby produces weather and climate. Air is the principle energy-carrying medium for this engine, but also partially responsible is water vapor, particularly effective because of its high heat of condensation which, as was explained earlier, results from the design of the water molecule.

In addition, a body of water can in the summertime store a great deal of heat energy, which is subsequently released in winter time to moderate the cold weather. Conversely, in the summer such a body of water cooled during the winter can soak up much heat energy and thus moderate hot summer weather nearby. In another important function, water vapor in the atmosphere teams up with carbon dioxide gas to absorb heat radiation from the earth's surface and keep it within the atmosphere. This is a major mechanism for moderating temperature extremes on the surface of the globe. All of these capabilities depend upon the design of the water molecule.

Just an introduction has been given to the important properties of water, deriving from the design of the water molecule, which are essential for the existence of life on the earth. Realizing that the universe's only known concentration of water in the liquid form essential to life is located on the earth, and that the temperatures and pressures required for the existence of water in the liquid form depend upon a finely balanced set of conditions peculiar to the earth, a thoughtful person surely must recognize the there is much evidence for intelligent, purposeful design of the solar system and our unique earth with its vast store of the unique stuff called water.

References

27. Pauling, Linus, Nature of the Chemical Bond, 3rd Edition (Cornell Univ. Press, Ithaca, N.Y., 1960).