Water is a chemical compound with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at temperatures above 0 °C (273.15 K, 32 °F) at sea level, but it often co-exists on Earth with its solid state, ice, and gaseous state (water vapor or steam). Water also exists in a liquid crystal state near hydrophilic surfaces.
Water covers 71% of the Earth's surface, and is vital for all known forms of life. On Earth, 96.5% of the planet's water is found in oceans, 1.7% in groundwater, 1.7% in glaciers and the ice caps of Antarctica and Greenland, a small fraction in other large water bodies, and 0.001% in the air as vapor, clouds (formed of solid and liquid water particles suspended in air), and precipitation. Only 2.5% of the Earth's water is freshwater, and 98.8% of that water is in ice and groundwater. Less than 0.3% of all freshwater is in rivers, lakes, and the atmosphere, and an even smaller amount of the Earth's freshwater (0.003%) is contained within biological bodies and manufactured products.
The color of water is colorless to the human eye in small amounts, but when it's in large quantities, it has a blue hue. Most people (including teachers) say that the ocean is blue because it reflects the blue sky. While this is one of the reason why it's blue, it's not the main reason. And also, while covering water is slightly blue, air is also slightly blue. More on that later. Or the next post. ;)
Interesting fact of the day: The only animal that has 4 knees is the elephant.
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