Water

Introduction

In its purest form, it's odorless, nearly colorless and tasteless. It's in your body, the food you eat and the beverages you drink. You use it to clean yourself, your clothes, your dishes, your car and everything else around you. You can travel on it or jump in it to cool off on hot summer days. Many of the products that you use every day contain it or were manufactured using it. All forms of life need it, and if they don't get enough of it, they die. Political disputes have centered around it. In some places, it's treasured and incredibly difficult to get. In others, it's incredibly easy to get and then squandered. What substance is more necessary to our existence than any other? Water.

At its most basic, water is a molecule with one oxygen atom and two hydrogen atoms, bonded together by shared electrons. It is a V-shaped polar molecule, which means that it's charged positively near the hydrogen atoms and negatively near the oxygen atom. Water molecules are naturally attracted and stick to each other because of this polarity, forming a hydrogen bond. This hydrogen bond is the reason behind many of water's special properties, such as the fact that it's denser in its liquid state than in its solid state (ice floats on water). We'll look closer at these special properties later.

Water is the only substance that occurs naturally as a solid (ice), a liquid and a gas (water vapor). It covers about 70 percent of the Earth for a total of approximately 332.5 million cubic miles (1,386 million cubic kilometers) [source: U.S. Geological Survey]. If you're familiar with the lines "Water, water, everywhere, nor any drop to drink" from the poem "The Rime of the Ancient Mariner," you'll understand that most of this water -- 97 percent of it -- is undrinkable because it's saltwater (see illustration on next page). Only 3 percent of the world's water supply is freshwater, and 77 percent of that is frozen. Of the 23 percent that is not frozen, only a half a percent is available to supply every plant, animal and person on Earth with all the water they need to survive  [source: National Geographic].

So water is pretty simple, right? Actually, there ar­e a lot of things about it that scientists still don't fully understand. And the problem of making sure that enough clean, drinkable water is available to everyone and everything that needs it is anything but simple. In this article, we'll look at some of these problems. We'll also explore exactly what plants, animals and people do with water and learn more about what makes water so special.­

How Much Water is There on Earth

There's a whole lot of water on Earth! Something like 326,000,000,000,000,000,000 gallons (326 million trillion gallons) of the stuff (roughly 1,260,000,000,000,000,000,000 liters) can be found on our planet. This water is in a constant cycle -- it evaporates from the ocean, travels through the air, rains down on the land and then flows back to the ocean.

The oceans are huge. About 70 percent of the planet is covered in ocean, and the average depth of the ocean is several thousand feet (about 1,000 meters). Ninety-eight percent of the water on the planet is in the oceans, and therefore is unusable for drinking because of the salt. About 2 percent of the planet's water is fresh, but 1.6 percent of the planet's water is locked up in the polar ice caps and glaciers. Another 0.36 percent is found underground in aquifers and wells. Only about 0.036 percent of the planet's total water supply is found in lakes and rivers. That's still thousands of trillions of gallons, but it's a very small amount compared to all the water available.

The rest of the water on the planet is either floating in the air as clouds and water vapor, or is locked up in plants and animals (your body is 65 percent water, so if you weigh 100 pounds, 65 pounds of you is water!). There's also all the soda pop, milk and orange juice you see at the store and in your refrigerator… There's probably several billion gallons of water sitting on a shelf at any one time!

Why can't we manufacture water?

Water is becoming an increasingly important issue in the developed world. But this issue is nothing new for other, less developed nations. For centuries, clean drinking water has been hard to come by for many populations, especially the poor. In some areas, water may be available, but it's often disease-ridden, and drinking it can be fatal. In other areas, a viable water supply is sim­ply not available at all.

A 2006 United Nations report estimated that as much as 20 percent of the world's population doesn't have access to clean drinking water [source: BBC]. This leads us to wonder: If we need it so badly, why can't we jus­t make it?

Water is made of two hydrogen atoms attached to an oxygen atom. This seems like pretty basic chemistry, so why don't we just smash them together and solve the world­'s water ills? Theoretically, this is possible, but it would be an extrem­ely dangerous process, too.

To create water, oxygen and hydrogen atoms must be present. Mixing them together doesn't help; you're still left with just separate hydrogen and oxygen atoms. The orbits of each atom's electrons must become linked, and to do that we must have a sudden burst of energy to get these shy things to hook up.

Since hydrogen is extremely flammable and oxygen supports combustion, it wouldn't take much to create this force. Pretty much all we need is a spark -- not even a flame -- and boom! We've got water. The hydrogen and oxygen atoms' electrons' orbits have been conjoined.

But we also have an explosion and -- if our experiment was big enough, a deadly one. The ill-fated blimp, the Hindenburg, was filled with hydrogen to keep it afloat. As it approached New Jersey on May 6, 1937, to land after a trans-Atlantic voyage, static electricity (or an act of sabotage, according to some) caused the hydrogen to spark. When mixed with the ambient oxygen in the air, the hydrogen exploded, enveloping the Hindenburg in a ball of fire that completely destroyed the ship within half a minute.

There was, however, also a lot of water created by this explosion.

To create enough drinking water to sustain the global population, a very dangerous and incredibly large-scale process would be required. Still, over a century ago the thought ­of an internal combustion engine -- with its controlled repeated explosions -- seemed dangerously mad. And as water becomes scarcer, the process of joining hydrogen atoms to oxygen atoms may become more attractive than it is currently. Necessity, after all, is the mother of invention.

But there are safer ways of creating water out of thin air, and projects to do just that are already underway. Read the next page to learn about a few mad scientists who may end up solving the world's impending water crisis.