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Water
Water is the most common liquid on Earth. It covers about 71.4% of the Earth.[1] Pure water has no smell, taste, or color. Lakes, oceans, and rivers are made of water. Rain is water that falls from clouds in the sky. If water gets very cold (below 0 degrees Celsius), it freezes and becomes ice. Frozen rain can be ice or snow if conditions permit. If water gets very hot (above 100 degrees Celsius), it boils and becomes steam. Water is very important for life.[2] However, some studies suggest that by 2025 more than half of the people around the world will not have enough water.[3]
Water is a fluid. Water is the only substance on earth that exists naturally in three states. People know of over 40 anomalies about water.[4][5] When water freezes, it expands by about 9%.[6][7][8] This expansion can cause pipes to break if the water inside them freezes.
Uses of water
Plants and animals (including people) are mostly water inside, and must drink water to live. It gives a medium for chemical reactions to take place, and is the main part of blood. It keeps the body temperature the same by sweating from the skin. Water helps blood carry nutrients from the stomach to all parts of the body to keep the body alive. Water also helps the blood carry oxygen from the lungs to the body. Saliva, which helps animals and people digest food, is mostly water. Water helps make urine. Urine helps remove bad chemicals from the body. The human body is between 60% and 70% water.
Water is the main component of drinks like milk, juice, and wine. Each type of drink also has other things that add flavor or nutrients, things like sugar, fruit, and sometimes alcohol. Water that a person can drink is called "potable water" (or "drinking water".) The water in oceans is salt water, but lakes and rivers usually have unsalted water. Only about 3% of all the water on earth is fresh water. The rest is salt water.[9][10]
Many places, including cities and deserts, don't have as much water as people want. They build aqueducts to bring water there.
What water is made of
Water is a molecule made of 2 hydrogen atoms and 1 oxygen atom. Its chemical formula is H2O. Water has a surface tension, so a little water makes drops on a surface, rather than spreading out to wet the surface. Water can also be called 'aqua', which is the Roman word for water. Water is also used for recreational purposes. Though a human being can survive for up to a three weeks without food, they can only survive for a day or two without water. A few desert animals can get enough water from their food, but the others must drink.
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References
- ↑ "CIA- The world fact book". Central Intelligence Agency. https://www.cia.gov/library/publications/the-world-factbook/geos/xx.html#Geo. Retrieved 2008-12-20.
- ↑ "United Nations". Un.org. 2005-03-22. http://www.un.org/waterforlifedecade/background.html. Retrieved 2010-07-25.
- ↑ Kulshreshtha, S.N (1998). "A Global Outlook for Water Resources to the Year 2025". Water Resources Management 12 (3): 167–184. .
- ↑ "Anomalous properties of water". lsbu.ac.uk. 2011 [last update]. http://www.lsbu.ac.uk/water/anmlies.html. Retrieved September 1, 2011.
- ↑ "Forty-one Anomalies of Water « Fairy LoRe". fathersergio.wordpress.com. 2011 [last update]. http://fathersergio.wordpress.com/2006/01/29/forty-one-anomalies-of-water/. Retrieved September 1, 2011.
- ↑ "8(a) Physical Properties of Water". physicalgeography.net. 2011 [last update]. http://www.physicalgeography.net/fundamentals/8a.html. Retrieved August 31, 2011. "pan"
- ↑ "Understanding the Processes of Erosion". mountainnature.com. 2009 [last update]. http://www.mountainnature.com/geology/erosion.htm. Retrieved August 31, 2011.
- ↑ "iapws.org". iapws.org. 2000 [last update]. http://www.iapws.org/faq1/freeze.htm. Retrieved August 31, 2011.
- ↑ "Percentage of water". http://ga.water.usgs.gov/edu/earthwherewater.html.
- ↑ "Fresh water percentage (2)". http://www.cdli.ca/CITE/water.htm.
Other websites
- Water Citizendium
