Because of its polarity, a molecule of water in the liquid or solid state can form up to four hydrogen bonds with neighboring molecules. Hydrogen bonds are about ten times as strong as the Van der Waals force that attracts molecules to each other in most liquids. This is the reason why the melting and boiling points of water are much higher than those of other analogous compounds like hydrogen sulfide. They also explain its exceptionally high specific heat capacity (about 4.2 J/g/K), heat of fusion (about 333 J/g), heat of vaporization ( 2257 J/g), and thermal conductivity (between 0.561 and 0.679 W/m/K). These properties make water more effective at moderating Earth's climate, by storing heat and transporting it between the oceans and the atmosphere. The hydrogen bonds of water are around 23 kJ/mol (compared to a covalent O-H bond at 492 kJ/mol). Of this, it is estimated that 90% is attributable to electrostatics, while the remaining 10% is partially covalent. [94] In a water molecule, the hydrogen atoms form a 104.5° angle with the oxygen atom. The hydrogen atoms are close to two corners of a tetrahedron centered on the oxygen. At the other two corners are lone pairs of valence electrons that do not participate in the bonding. In a perfect tetrahedron, the atoms would form a 109.5° angle, but the repulsion between the lone pairs is greater than the repulsion between the hydrogen atoms. [90] [91] The O–H bond length is about 0.096nm. [92] Most water comes in plastic bottles; you may even have sipped from one today. Recycling plastic is a lot more complicated, due to the number of different types of plastic and it also requires moreenergy than recycling aluminium. Producing a recycled plastic bottle only takes 25% of the energy to produce a new one but an old plastic bottle will not always be recycled into a newplastic bottle. PET bottles can be recycled into new drinking bottles (though not all of it is) but all other types of plastic bottles are recycled into differentplastic products including plastic furniture, polyester fleece or even synthetic carpets. Chapter 4: Water. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. Washington, D.C. National Academies Press. (2005). As the authors of one study report, out of 488 participants in the 2002 Boston Marathon, 13% had hyponatremia symptoms, and 0.6% had critical hyponatremia, with sodium levels of less than 120 mmol/l.

evaporation from oceans and other water bodies into the air and transpiration from land plants and animals into the air. Carlton, A., & Orr, R. M. (2015, December). The effects of fluid loss on physical performance: A critical review. Journal of Sport and Health Science, 4(4),357-363 The viscosity of water is about 10 −3 Pa· s or 0.01 poise at 20°C (68°F), and the speed of sound in liquid water ranges between 1,400 and 1,540 meters per second (4,600 and 5,100ft/s) depending on temperature. Sound travels long distances in water with little attenuation, especially at low frequencies (roughly 0.03 dB/km for 1 k Hz), a property that is exploited by cetaceans and humans for communication and environment sensing ( sonar). [100] ReactivityOn a pressure/temperature phase diagram (see figure), there are curves separating solid from vapor, vapor from liquid, and liquid from solid. These meet at a single point called the triple point, where all three phases can coexist. The triple point is at a temperature of 273.16K (0.01°C; 32.02°F) and a pressure of 611.657 pascals (0.00604atm; 0.0887psi); [70] it is the lowest pressure at which liquid water can exist. Until 2019, the triple point was used to define the Kelvin temperature scale. [71] [72] The amount of water needed each day varies from person to person, depending on how active they are, how much they sweat, and so on. According to the U.S. National Academies of Sciences, Engineering, and Medicine, the average recommended daily intake of water from both food and drink is: Overhydration and water intoxication happen when a person drinks more water than their kidneys can get rid of via urine.

Saliva helps us digest our food and keeps the mouth, nose, and eyes moist. This prevents friction and damage. Drinking water also keeps the mouth clean. Consumed instead of sweetened beverages, it can also reduce tooth decay. Water is a good polar solvent, dissolving many salts and hydrophilic organic molecules such as sugars and simple alcohols such as ethanol. Water also dissolves many gases, such as oxygen and carbon dioxide—the latter giving the fizz of carbonated beverages, sparkling wines and beers. In addition, many substances in living organisms, such as proteins, DNA and polysaccharides, are dissolved in water. The interactions between water and the subunits of these biomacromolecules shape protein folding, DNA base pairing, and other phenomena crucial to life ( hydrophobic effect).

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Water is an inorganic compound with the chemical formula H 2O. It is a transparent, tasteless, odorless, [c] and nearly colorless chemical substance, and it is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a solvent [20]). It is vital for all known forms of life, despite not providing food energy or organic micronutrients. Its chemical formula, H 2O, indicates that each of its molecules contains one oxygen and two hydrogen atoms, connected by covalent bonds. The hydrogen atoms are attached to the oxygen atom at an angle of 104.45°. [21] "Water" is also the name of the liquid state of H 2O at standard temperature and pressure. The water cycle (known scientifically as the hydrologic cycle) is the continuous exchange of water within the hydrosphere, between the atmosphere, soil water, surface water, groundwater, and plants. Joo, M. A., & Kim, E. Y. (2013). Hyponatremia caused by excessive intake of water as a form of child abuse. Maughan, R. J., & Griffin, J. (2003, December). Caffeine ingestion and fluid balance: a review. Journal of Human Nutrition and Dietetics. 16(6):411-20

Britain, meanwhile, works its way through 13bn plastic bottles a year – a significant portion of which are used for water. Plastic-free gum The authors of the study report that hyponatremia symptoms can develop if a person drinks 3–4 liters of water in a short period, though they do not give a specific time estimate. http://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/multimedia/functions-of-water-in-the-body/img-20005799 However, oxygen is more electronegative than most other elements, so the oxygen atom retains a negative charge while the hydrogen atoms are positively charged. Along with the bent structure, this gives the molecule an electrical dipole moment and it is classified as a polar molecule. [93]In nature, the color may also be modified from blue to green due to the presence of suspended solids or algae.