Water (a.k.a. H2O) is one of the four L.A.W.S. of nature. (the 'W') At the molecular level, water is simply made up of 2 hydrogen atoms and 1 oxygen atom held together by covalent bonds. Since oxygen is a polar atom, the water molecule creates a specific structure (Fig 1.1) that allows it to have unique characteristics. Like most molecules, when water is heated, the molecules move quickly. If it gets hot enough (212oF/0oC) the molecules break apart and are released into the atmosphere (a process known as evaporation). When water is cooled, the molecules gather closer together (a process known as condensation). If it gets cold enough (32oF/0oC), the water freezes and forms ice. Due to its unique shape (Fig 1.2), pockets of air form between bonds allowing it to be less dense than liquid water. Liquid water exists between 33o Fahrenheit (0o Celcius) and 211o Fahrenheit (100o Celcius)
71% of the Earth is covered in water. It is essential to the survival of all living things on Earth. Only 2.5% of all the water in the world is fresh water. The availability of freshwater is a huge factor in the types of ecosystems that are created. (i.e. deserts have a very limited amount of water and wetlands have an abundance of water)
Water does not stay in one place, it moves through a watershed and flows through the water cycle that allows it to be refreshed and reused constantly. The water that exists today, is the same water that the Dinosaurs, Ancient Romans/Greeks, and the Early Colonialists drank and bathed in.
The amount of information available about water is practically infinite.
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