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What Is Water?
Water is a colourless, tasteless and odourless substance that is vital for all known forms of life and is the most niversal solvent Water is an abundant substance on Earth that exists in many places and forms: mostly in the oceans and polar ice caps, as well as clouds, rain water, rivers or freshwaters and sea ice. On the entire planet, water is continuously moving through a cycle known as the water cycle which involves processes such as evaporation, condensation, precipiation and runoff to the sea. All known forms of life require water. Humans consume "drinking water" - water with qualities compatible with the human body. This natural resource has become scarce with the growing world population, and its availability is a large major social and economic concern.  Changing Appearances Water can take on many different forms on Earth: water vapour and clouds in the sky, waves and icebergs in the sea, glaciers in the mountain, aquifers in the ground, to name a few. From various processes, such as evaporation, precipitation, condensation and runoff, water is continuously switching from one form to another. Because of the importance of precipitation to agriculture, and to mankind in general, we give different names to its various forms: while rain is common in most countries, other phenomena are quite surprising when seen for the first time: hail, snow, fog or dew. When light appropriately enters the water droplets, water droplets in the air can refract the beautiful colours of a rainbow. 
Water runoffs have played great roles in our history: rivers and irrigation brought the water that was required for agriculture. Streams and the seas offered opportunity for travel and commerce. Through erosion, runoffs played a major part in shaping our environment providing river valleys and deltas which provide rich soil and level ground for the establishment of population centres. Not only that, water also infiltrates the ground and goes into aquifers. This groundwater later flows back to the surface in springs, or more spectacularly in hot springs and geysers. Wells built by man extracts groundwater artificially. As water can contain various substances, it can taste or smell very differently. In fact, we have developed our senses so as to be able to evaluate the drinkability of water, therefore we avoid the salty seas and the putrid swamps yet, we like the fresh pure water from a mountain spring. |
