Generally speaking when we talk of “pure water”, we say that it is a tasteless, colorless and odorless liquid compound composed of two gases; hydrogen gas which is a very light gas; and oxygen gas which is a heavier, active gas. As matter, we already know that water exists in three different states: as a liquid, as a solid (called ice), and as a gas (called water vapor).
But when it comes to the various properties of water, we will discover that “pure water” never occur pure in the true sense in nature. Water in nature contains several impurities including dissolvedminerals, dissolved gasses, and many times even living organisms. Therefore, it is very rare to encounter just “pure water” in our everyday living.
Chemically treated “pure water” is tasteless. But oftentimes that we also knew that for every glass of water we drink, we experienced a slight taste of water. One reason for this is the presence of certain impurities dissolved in the water. For example, rain water which falls through the atmosphere absorb some of the atmospheric gases though which they pass.
We also know that oxygen is one of the most important gases that exist on earth. It is oxygen in water that makes it possible for living things to live under water. Aside from oxygen, another important gas which dissolved in water is carbon dioxide. Dissolved carbon dioxide (called carbonic acid) in water is the main cause of eroding limestone rocks and forming caves and sinkholes.
Because of the dissolved lime, magnesium carbonates and calcium in water due to the chemical reaction of carbonic acidin the water make up“hard water”. We can say that the water is hard when it does not produce a soapy lather easily. Another characteristic of a “hard water” is that if boiled, it leaves a lime coating (carbonates) on the inside part of kettles.
Dissolve salts is also abundant in most of the water on our planet. Inorganic particles are also likely to be seen in river and lake water.
But what about “soft water”? When water is chemically treated so that only the positively charge ions is left on it (which is sodium), the water is called “soft water”.
Furthermore, water is being distributed over the earth in one of the greatest energy cycle we know – the water cycle (also called hydrologic cycle). As the sun heats up the earth’s surface, water vapor is evaporated (evaporation) and gathers in the clouds (condensation) . It is then distributed to different parts of the earth as rain, hail, snow, or dew (precipitation). As water seeks its own level, it works its way back to the sea and the great energy cycle begins again.
notes: reposted article.