Odorless? Tasteless? Water is a transparent liquid that is colorless in small amounts but exhibits a bluish tinge in large quantities. It is the most familiar and abundant liquid on earth. In solid form (ice) and liquid form it covers about 70% of the earth’s surface. It is present in varying amounts in the atmosphere. Most of the living tissue of a human being is made up of water. Water constitutes about 92% of blood plasma, about 80% of muscle tissue, about 60% of red blood cells, and over half of most other tissues. Well, how about that? Most of us is water.

Water is also an important component of the tissues of most other living things.

Let's investigate its chemical and physical properties.

Chemically, water is a compound of hydrogen and oxygen -- the familiar H2O. It is chemically active, reacting with certain metals and metal oxides to form bases, and with certain oxides of nonmetals to form acids. It reacts with certain organic compounds to form a variety of products, e.g., alcohols from alkenes. Because water is a polar compound, it is a good solvent. Although completely pure water is a poor conductor of electricity, it is a much better conductor than most other pure liquids because of its self-ionization. Self-ionization is the ability of two water molecules to react to form a hydroxide ion, OH-, and a hydronium ion, H3O+. Its polarity and ionization are both due to the high dielectric constant of water. Interesting isn't it? Remember that when we talk about water, we're also talking about our bodies. Water is 70% of us!

Water has interesting thermal properties. When heated from 0°C, its melting point, to 4°C, it contracts and becomes more dense; most other substances expand and become less dense when heated. Conversely, when water is cooled in this temperature range, it expands. It expands greatly as it freezes; as a consequence, ice is less dense than water and floats on it. Because of hydrogen bonding between water molecules, the latent heats of fusion and of evaporation and the heat capacity of water are all unusually high. For these reasons, water serves both as a heat-transfer medium (e.g., ice for cooling and steam for heating) and as a temperature regulator (the water in lakes and oceans helps regulate the climate).

Well, well, well! This water that makes up our bodies comes from outside of us then it is taken into us to constitute 70% of that part of us we call our bodies. Are you beginning to see a faint picture?

Hope so. Meet you at the next issue. This series continues. We continue this marvelous re-discovery of our bodies, minds and spirits - that's us @ U-Shine. Here is a parting question. How long does it take for a glass of water to get completely out of our system?

One of UShine OnLine's experts, Chirstos Moundrizas, is doing a series of essays on water. Go to the first essay.