Page 6 - Curriculum Visions Dynamic Book

Water is not evenly distributed as a global resource. Over 97% of it is in the oceans and just over 2% more in the ice caps. That leaves just about 1% for lakes, rivers, rocks, soils, and the air. But when used carefully, that is more than enough for the needs of all living things.
A transporting medium
One of the main things that water does is to carry other materials with it. Some of this material is in solution (see below), but some also is in suspension. This is extremely common. For example, blood is a suspension of blood cells in water. On a larger scale sewage is transferred from homes to sewage plants in suspension.
A chemical
Water is extremely abundant and also very chemically reactive. As a result, it is the most important and most common of all chemical compounds on the Earth’s surface.
Water is called the “universal solvent.” A vast array of substances is dissolved in it naturally, which is why we have salty ocean water and “hard” fresh water that is difficult to lather. It is also a splendid means of getting chemicals to large numbers of living things cheaply, which is why fertilizers are put in irrigation systems on farmland and why fluoride is added to many drinking water supplies to protect whole populations from tooth decay.
Because it is such a good solvent, water is rarely pure. Pure water can be prepared in a laboratory
by boiling it and collecting the water vapour that
is given off. The closest parallel to this in nature is evaporation. But water vapour in the air is not often pure because it can dissolve or react with other gases in the atmosphere. It can form weak acids that can be damaging to trees and animals.
If you follow the water cycle, you can also see that it is a chemical scavenging cycle too. Once water
(Above) Our drinking water is not pure. It contains many dissolved substances, some of which are beneficial and others harmful. It is the job of water companies to help produce a combination that is safe to drink.
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