Water

Water is a chemical compound and polar molecule, which is liquid at standard temperature and pressure. It has the chemical formula H2O, meaning that one molecule of water is composed of two hydrogen atoms and one oxygen atom. Water is found almost everywhere on earth and is required by all known life. About 70% of the Earth's surface is covered by water. Water is known to exist, in ice form, on several other bodies in the solar system and beyond. The importance of water to terrestrial life has led many to surmise that its existence in liquid form anywhere besides Earth could provide a viable habitat for extraterrestrial life. The solid state of water is known as ice; the gaseous state is known as water vapor (or steam). The units of temperature (formerly the degree Celsius and now the Kelvin) are defined in terms of the triple point of water, 273.16 K (0.01 °C) and 611.2 Pa, the temperature and pressure at which solid, liquid, and gaseous water coexist in equilibrium. Water exhibits some very strange behaviors, including the formation of states such as vitreous ice, a noncrystalline (glassy), solid state of water. At temperatures greater than 647 K and pressures greater than 22.064 MPa, a collection of water molecules assumes a supercritical condition, in which liquid-like clusters float within a vapor-like phase.

Deficiency symptoms:

Dehydration is a deficiency of water in the body. Vomiting, diarrhea, excessive sweating, burns, kidney failure, and use of diuretics may cause dehydration. People feel thirsty, and as dehydration worsens, they may sweat less and excrete less urine. If dehydration is severe, people may be confused or feel light-headed.

Overdose symptoms:

Water intoxication, also known as water poisoning, hyperhydration, overhydration, or water toxemia, is a potentially fatal disturbance in brain functions that results when the normal balance of electrolytes in the body is pushed outside safe limits by excessive water intake. At the onset of this condition, fluid outside the cells has an excessively low amount of solutes, such as sodium and other electrolytes, in comparison to fluid inside the cells, causing the fluid to move into the cells to balance its concentration. This causes the cells to swell. In the brain, this swelling increases intracranial pressure (ICP), which leads to the first observable symptoms of water intoxication: headache, personality changes, changes in behavior, confusion, irritability, and drowsiness. These are sometimes followed by difficulty breathing during exertion, muscle weakness & pain, twitching, or cramping, nausea, vomiting, thirst, and a dulled ability to perceive and interpret sensory information. As the condition persists, papillary and vital signs may result including bradycardia and widened pulse pressure. The cells in the brain may swell to the point where blood flow is interrupted resulting in cerebral edema. Swollen brain cells may also apply pressure to the brain stem causing central nervous system dysfunction. Both cerebral edema and interference with the central nervous system are dangerous and could result in seizures, brain damage, coma or death.

Recommended daily intake:

	Males	Females	Pregnancy	Lactation
0-6 months	700g*	700g*
6-12 months	800g*	800g*
1-3 years	1.3kg*	1.3kg*
4-8 years	1.7kg*	1.7kg*
9-13 years	2.4kg*	2.1kg*
14-18 years	3.3kg*	2.3kg*	3kg*	3.8kg*
19-30 years	3.7kg*	2.7kg*	3kg*	3.8kg*
31-50 years	3.7kg*	2.7kg*	3kg*	3.8kg*
51-70 years	3.7kg*	2.7kg*
>70 years	3.7kg*	2.7kg*