Physics and Chemistry of the Water Molecule

Physicsand Chemistry of the Water Molecule

Bent’srule gives a description of the relationship between the orbitalhybridisations of atoms in molecules as well as theelectronegativities of the substituents. The rule states “Atomic scharacter concentrates in orbitals directed toward electropositivesubstituents.” The structure of every molecule is related to itsreactivity and properties. Molecular structures are the result ofcovalent bonds between atoms. Every bond is made up of two hybridizedatomic orbital that overlap one another. According to bent’s rule,a centralized atom that is bonded to several other groups canhybridise making the orbitals with more s character to be directedtowards the electropositive groups. The orbitals with more pcharacter are then directed towards the electronegative groups[ CITATION Sha07 l 1033 ].

Therule is illustrated perfectly in the structure of the water molecule.The molecule is a combination of two hydrogen atoms and an oxygenatom. Oxygen is the centralized atom. Since the atom is highlyelectronegative, an electrostatic attraction forms between the oxygenatom and the hydrogen atom. This attraction is known as the hydrogenbond. The resulting structure of the water molecule is tetrahedral inshape. The structure of the water molecule is also responsible forthe many fascinating behaviors of water.

Thestrong hydrogen bonds in the water molecule lead to the formation ofthe cohesive and adhesive forces. Water may form a thin film on aclean glass because the adhesive forces are stronger than thecohesive forces. Water has cohesion and adhesion properties that helpin the survival of plants. In biological cells, water is usually incontact with the membranes and protein surfaces that happen to behydrophilic. Therefore, plants can pull water from the soil up thestem and to the leaves[ CITATION Eis05 l 1033 ].

Wateris at times called the universal solvent because, more substancesdissolve in water than in any other chemical. The polarity of watermakes it a good solvent. Substances that dissolve in water can easilymatch or overcome the attractive forces generated by the watermolecules. If a substance lacks the ability to overcome these forces,the molecules of such a substance are pushed out from the water, thusfailing to dissolve. When ionic substances like table salt are mixedwith water, they are dissociated into their individual positive andnegative ions. The oxygen atoms in water attract the positive ionswhile the negative ones are attracted to the hydrogen side[ CITATION Eis05 l 1033 ].

Amongall the heteroatomic substances, water has the second highestspecific heat capacity as well as a very high heat of vaporization.The properties are the result of hydrogen bonding between theindividual molecules. The two uncommon properties enable water tomoderate earth’s climate through the buffering of the largefluctuations in temperatures[CITATION Cas07 l 1033 ].

Thelarge volumes of water in the oceans have been said to be absorbing athousand times more heat than the air, and hold approximately 85% ofthe global warming heat. Were it not for the high specific heatcapacity properties of water, all the heat in the earth would beradiated back into space. The ocean is responsible for thedistribution of heat around the world. The water in the ocean isevaporating, increasing the temperatures and humidity of thesurrounding air leading to the formation of rain and storms. Heatabsorption and evaporation is highest around the tropical areas[CITATION Cas07 l 1033 ].

References

Casper, Julie Kerr. Water and Atmosphere: The Lifeblood of Natural Systems. New York: Infobase Publishing, 2007.

Eisenberg, D and W Kauzmann. The Structure and Properties of Water. Oxford: OUP Oxford, 2005.

Sharma, R K. Text Book of Coordination Chemistry. Delhi: Discovery Publishing House, 2007.