Chapter 3 - Water

  • Water is a polar molecule and because of its polarity, it may create hydrogen bonds.
      * These hydrogen bondings provide water with qualities that are necessary for life on Earth.
  • Covalent bonds (shared electrons) exist between the oxygen and hydrogen atoms in water.
      * %%Oxygen has a high electronegativity (ability to attract electrons), whereas hydrogen has a low electronegativity.%%
      * Because of this difference in electronegativity, electrons in the covalent link between oxygen and hydrogen are unequally shared, with electrons spending more time around the oxygen atom.
      * As a result, a polar covalent bond is formed with a partial negative charge around the oxygen atom and a partial positive charge around the hydrogen atom, as seen in the image attached.
      * As a result, the partial negative charge on an oxygen atom in one water molecule attracts the partial positive charge on a hydrogen atom in another water molecule, forming a hydrogen bond.
      * As a result, water molecules are attracted to one another.

   

  • Because water molecules can form hydrogen bonds, they have qualities that aid in the survival of life on Earth, such as the image attached above.
      * %%Water molecules are "sticky," exhibiting cohesive and adhesive properties.%%
      * They are attracted to other water molecules as well as other polar compounds.
      * This is what gives water its distinct qualities, such as its high surface tension and ability to do so.
  • Because of the negative sign in the pH formula, a greater [H+] value results in a lower pH value, and a lower [H+] value results in a higher pH value.
      * As a result, a solution with a pH of 3 has a greater [H+] than a solution with a pH of 5.
      * @@Furthermore, because the pH scale is logarithmic, a one-unit change in pH translates to a tenfold variation in H+ concentration.@@
  • A pH of 3 has ten times the H+ concentration of a pH of 4 and one hundred times the concentration of a pH of 5.
      * The pH of a water-based solution is determined by the quantity of dissociated water molecules (split into H+ ions and OH– ions) and the relative quantities of these ions.
  • Pure water will dissociate and create equal amounts of H+ and OH– ions, yielding a pH of 7.
      * @@Acids raise the relative concentration of H+ ions in a solution, whereas bases raise the concentration of OH– ions in a solution.@@
      * Biological systems can be extremely sensitive to pH fluctuations. Buffers are essential for keeping pH levels in live cells generally constant.
  • If the pH of a cell falls too low (excess H+), the process will shift to the left, allowing the basic bicarbonate ions to neutralize the excess H+ ions and restore the cell to its original state.
      * When the pH of a cell becomes too high (excess OH–), the reaction swings to the right, introducing additional H+ ions into the cell to neutralize the excess OH–, lowering the pH down to normal levels.
      * Within a water molecule, oxygen and hydrogen atoms form covalent connections.
      * Because oxygen has a higher electronegativity than hydrogen, the electrons in this link are shared unequally, resulting in a polar covalent bond.