Water - H2O

Water - H2O

1. Inorganic chemical compound formed by two atoms of hydrogen (H) and one of oxygen (O).

2. Molecular structure.

   • Hydrogen joins oxygen through a covalent bond.

3. Physical properties.

   • Boiling point: 100 ° C
   • Melting point: 0 ° C
   • Density: 1g / cm3.
   • Dielectric constant at 20 ° C, D 80.
     • Water is a better insulator than similar chemicals.
     • Small amounts of salts in solution make water a good conductor.
   • High heat of vaporization / Large heat reservoir.
   • Surface tension: It is caused by the forces of hydrogen bonds within water molecules.
     • As the temperature increases, the thermal agitation increases, decreasing the forces of hydrogen bonds and the surface tension.
   • Odorless, colorless, and tasteless.

4. Chemical properties.

   • La molécula de agua es polar.
     • It has two electronic pairs on one side and two protons on the other side.
   • It can form hydrogen bonds
     • Hydrogen atoms are partially charged (+) and interact with oxygen atoms in other partially charged water molecules (-).
   • The polarity of water and its ability to form H bonds make it a solvent for any charged or polar molecule.
   • Is cohesive.
     • In the liquid state, groups of molecules joined by hydrogen bonds are grouped and broken.
   • Pure water has a pH of 7.0, that is, it is neither acidic nor basic.
   • Almost universal solvent.
     • Inorganic salts.
     • Gases.
     • Organic compounds.
       • Polar in nature.
       • Those that form H bonds with the water molecule.
   • Stability in liquid and solid state due to the high degree of intermolecular interaction.

5. Intermolecular forces.

   • Hydrogen bond or bridge.
   • Ion-ion interaction
     • Saline bond where a metal and a non-metal element come together, looking for electronic stability.
       • NaCl, KBr.
   • Ion - dipole interaction.
     • The ions of a substance interact with the dipoles of a polar covalent molecule.
   • Van Der Waals forces.
     • Attractive or repulsive forces between molecules other than those due to intermolecular bonding.
       • It is based on the distribution of electric charge around an atom, there will be regions with partial charge (+) and others with partial charge (-).

6. Intramolecular forces.

   • Covalent bond.
     • It is produced in two atoms that join together, to reach the "stable octet", and share electrons of the last energy level.

7. Biological function.

   • Thermal behavior.
     • Maintains constant body temperature regardless of environment and metabolic activity.
       • Its high specific heat is the consequence of the great capacity for storing energy in hydrogen bonds, converts it in an exceptional shock absorber and shift regulator thermals.
       • Muscle contraction is a major contributor to the body's heat load, since the transformation of chemical energy (ATP) into mechanical energy is very ineffective.
   • Surface tension.
     • Bile salts improve digestibility and also the absorption of fat and other nutrients.
   • Solvent.
     • Water is a highly reactive molecule, can dissolve a large variety of ionic and molecular (hydrophilic) substances, but it also prevents the dissolution of other apolar (hydrophobic).
   • Its solvent capacity, its high dielectric constant and its low degree of ionization, water is the medium in which all metabolic reactions take place.
     • Hydrolysis, they occur in digestion or oxidation of macronutrients.

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