Chemistry of water -Part 2-

Since water is the densest at +4 °C, it expands like other liquids when heated above this point, but it also does so when its temperature drops below this point. In contrast to most compounds, water also expands when it freezes, which is why ice is lighter than water.
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Density of ice and water as a function of temperature

Because of the strong electronegativity of the oxygen atom, the water molecule is polar, and this polarity leads to a rise in its dielectric constant, which makes water play a very important role as a solvant for polar and ionic compounds. In addition, this results in the formation of hydrogen bonds between water molecules, which are responsible for the molecules interconnection and for the fact that water is a liquid rather than steam under normal heat and pressure conditions.

Permanent dipoles in the water molecule

The water molecule's positive and negative charge centers of gravity are separate, and the water molecule's total dipole moment is 1.85, the unshared pair of electrons most likely adds to the significance of this dipole moment.
The water molecule forms hydrates with the widest range of ions with ease. The hydroxonium (or oxonium) ion H3O+ is one of these hydration reactions' particularly significant products. This ion is found in any aqueous solution that has protons-detaching bodies. Although the affinity of the water molecule for the proton is relatively strong, we only know its value in the gaseous state, which is 169 kcal/mol, the affinity for the proton of other molecules is even stronger; thus, for ammonia, it is 206 kcal/mol, which explains how the ammonia molecule is able to take the protons from the water molecules by producing ammonium ions.

Bibliographic references:

• [General and inorganic chemistry book- M. Shkhashirou- H. Birqdad- Y. Qodsi- University publications. Algeria]

• Kada, Imene- Double ionisation de la molécule d’eau par impact d’électrons- Phd thesis

• Pezzella, Marco. Molecular dynamics at water interfaces: from astrophysical to biochemical applications. 2020, Phd Thesis no:13717, University of Basel, Faculty of Science.

• [Book- Chimie moderne- L.Nikolaiv]

• Berend Ensing; geboren te Delfzijl- Chemistry in Water. Phd Thesis. University of Amsterdam- 2003

• Igor Shvab- MOLECULAR DYNAMICS SIMULATION OF WATER AND AQUEOUS SOLUTIONS- Centre for Molecular Simulation Faculty of Information and Communication Technologies Swinburne University of Technology February 2014

• [Smith, Jared D.; Christopher D. Cappa; Kevin R. Wilson; Ronald C. Cohen; Phillip L. Geissler; Richard J. Saykally (2005). "Unified description of temperature-dependent hydrogen bond rearrangements in liquid water" (PDF). Proc. Natl. Acad. Sci. USA. 102 (40): 14171–14174. Bibcode:2005PNAS..10214171S. doi:10.1073/pnas.0506899102. PMC 1242322. PMID 16179387.]

• [Smail Meziane: Livre Chimie générale- Structure de la matiére. Berti edition, Alger, 2006]

• [Livre- Chimie génerale- R.Ouahes]