water

Water is a transparent and nearly colorless chemical substance that is the main constituent of Earth's streams, lakes, and oceans, and the fluids of most living organisms. Its chemical formula is H2O, meaning that its molecule contains one oxygen and two hydrogen atoms, that are connected by covalent bonds. Water strictly refers to the liquid state of that substance, that prevails at standard ambient temperature and pressure; but it often refers also to its solid state (ice) or its gaseous state (steam or water vapor). It also occurs in nature as snow, glaciers, ice packs and icebergs, clouds, fog, dew, aquifers, and atmospheric humidity.
Water covers 71% of the Earth's surface. It is vital for all known forms of life. On Earth, 96.5% of the planet's crust water is found in seas and 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 ice and liquid water suspended in air), and precipitation. Only 2.5% of this water is freshwater, and 98.8% of that water is in ice (excepting ice in clouds) 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. A greater quantity of water is found in the earth's interior.
Water on Earth moves continually through the water cycle of evaporation and transpiration (evapotranspiration), condensation, precipitation, and runoff, usually reaching the sea. Evaporation and transpiration contribute to the precipitation over land. Large amounts of water are also chemically combined or adsorbed in hydrated minerals.
Safe drinking water is essential to humans and other lifeforms even though it provides no calories or organic nutrients. Access to safe drinking water has improved over the last decades in almost every part of the world, but approximately one billion people still lack access to safe water and over 2.5 billion lack access to adequate sanitation. There is a clear correlation between access to safe water and gross domestic product per capita. However, some observers have estimated that by 2025 more than half of the world population will be facing water-based vulnerability. A report, issued in November 2009, suggests that by 2030, in some developing regions of the world, water demand will exceed supply by 50%.
Water plays an important role in the world economy. Approximately 70% of the freshwater used by humans goes to agriculture. Fishing in salt and fresh water bodies is a major source of food for many parts of the world. Much of long-distance trade of commodities (such as oil and natural gas) and manufactured products is transported by boats through seas, rivers, lakes, and canals. Large quantities of water, ice, and steam are used for cooling and heating, in industry and homes. Water is an excellent solvent for a wide variety of chemical substances; as such it is widely used in industrial processes, and in cooking and washing. Water is also central to many sports and other forms of entertainment, such as swimming, pleasure boating, boat racing, surfing, sport fishing, and diving.

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  1. C

    Managed to boil my hot water tank with immersion heater...

    Woke up at 6AM to the sound of my hot water tank boiling and a cold sweat as I realised I'd left the immersion on since 6PM the night before. Immediately turned it off and opened the taps in the bath to drain the tank, temporarily turning my bathroom into a steam shower - still not sure if this...
  2. J

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  3. F

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  4. K

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  5. C

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  6. S

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  7. M

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  8. S

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  9. S

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  10. S

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  11. J

    Sewer storm water back up problems

    hi.We have a holiday property ( on condominium) with a basement approx 10feet below ground level). In the basement there are 2 rooms - one en suite with toilet and shower.The condo relies on a cesspit . Last week we had an horrendous storm with extremely heavy and long landing rains. W e...
  12. K

    Neighbour refusing to fix her noisy Water supply pipes

    Hello there, I'm new on here and would like to ask if anyone has practical advice. I live in a converted house hence I live in the flat on the first floor and my neighbor on the ground floor. The water supply is via a single supply from the street which splits (either underground or in the...
  13. M

    Hot Water Mystery

    I'm hoping someone can shed light on this mystery for me. My son has moved into a rental flat and, not being very savvy with central heating controllers, I'm trying to help him understand how it works. And I'm trying to help him remotely which is making it very difficult. His flat has a combi...
  14. T

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    Evening all, hope someone can give advice. I have a Baxi duo etc 24 HE A combi boiler and over night the hot water is not going above the digital display of approx 48 degrees. The burner and light does come and goes off, this still happens when the hot water dial setting is at max but the temp...
  15. Bogart

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  16. A

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    Suggestions please. I have an puzzling problem. I switched off hot water and CH in Summer. Baxi boiler. After a short period of turning hot watertap on the water was scalding. Assuming hot water coming from hot water tank? I switched on hot water and CH but hot water is still scalding and...
  17. P

    Hot water not getting into heating system

    Hello, I am look some advice. Our boiler heats the water for the radiators, but the hot water only makes it as far as this component ( pump is above it). It has a temperature sensor in it reading air temperature in the void, but I think it must have a cross over in it from the central heating...
  18. KenLM

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    Hey folks, I’m moving into a 2 storey house built in 1970s, and water pressure upstairs is really bad. The current system: cold water supplied from mains, good pressure. Cold water is stored in a tank in the attic. Downstairs there’s a boiler, however it’s the first time I see one like that...
  19. H

    Water Hammer?

    Hi, My pipes keep making suddent bang noises every now and then, like someone's suddenly stopping a tap. All my taps are turned off. I had an engineer come in the other day and he drained all the central heating radiators. I myself turned the water off from the mains and drained all the taps...
  20. T

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