Water (H2O)

                                           

IUPAC name: Water, Oxidane

Other names: Hydrogen oxide, Dihydrogen monoxide (DHMO), Hydrogen monoxide, Dihydrogen oxide, Hydrogen hydroxide (HH or HOH), Hydric acid, Hydrohydroxic acid, Hydroxic acid, Hydroxylic acid, Hydroxilic acid, Hydrol, μ-Oxido dihydrogen.


Properties:
Molecular formula: H₂O 

Molar mass: 18.01528(33) g/mol

Appearance:  white solid or almost colorless, transparent, with a slight hint of blue, crystalline solid or liquid

Density:  1000 kg/m³, liquid (4 °C) (62.4 lb/cu. ft) 917 kg/m³, solid

Melting point: 0 °C, 32 °F, (273.15 K)

Boiling point: 99.98 °C, 211.97 °F (373.13 K)

Acidity (pK_a): 15.74 ~35–36

Basicity (pK_b): 15.74

Refractive index (n_D): 1.3330

Viscosity: 0.001 Pa s at 20 °C
Crystal structure: Hexagonal

Molecular shape: Bent
Dipole moment: 1.85 D

Some more fact:

Water is the chemical substance with chemical formula H₂O: one molecule of water has two hydrogen atoms covalently bonded to a single oxygen atom. Water is a tasteless, odorless liquid at ambient temperature and pressure, and appears colorless in small quantities, although it has its own intrinsic very light blue hue. Ice also appears colorless, and water vapor is essentially invisible as a gas. Water is primarily a liquid under standard conditions, which is not predicted from its relationship to other analogous hydrides of the oxygen family in the periodic table, which are gases such as hydrogen sulfide. The elements surrounding oxygen in the periodic table, nitrogen, fluorine, phosphorus, sulfur and chlorine, all combine with hydrogen to produce gases under standard conditions. The reason that water forms a liquid is that oxygen is more electronegative than all of these elements with the exception of fluorine. Oxygen attracts electrons much more strongly than hydrogen, resulting in a net positive charge on the hydrogen atoms, and a net negative charge on the oxygen atom. The presence of a charge on each of these atoms gives each water molecule a net dipole moment. Electrical attraction between water molecules due to this dipole pulls individual molecules closer together, making it more difficult to separate the molecules and therefore raising the boiling point. This attraction is known as hydrogen bonding. The molecules of water are constantly moving in relation to each other, and the hydrogen bonds are continually breaking and reforming at timescales faster than 200 femtoseconds. However, this bond is sufficiently strong to create many of the peculiar properties of water, such as those that make it integral to life. Water can be described as a polar liquid that slightly dissociates disproportionately into the hydronium ion (H₃O⁺(aq)) and an associated hydroxide ion (OH⁻(aq)).

2 H₂O (l) H₃O⁺ (aq) + OH⁻ (aq)

The dissociation constant for this dissociation is commonly symbolized as K_w and has a value of about 10⁻¹⁴ at 25 °C