Chemistry of Water

1
Chemistry of Water

• The characteristics of water that make it
  important to living things.

2
Water FACTS

• Water is the most abundant compound on Earth's
  surface, constituting about 70 of the planet's
  surface.
• In nature it exists in the liquid, solid, and
  gaseous states. Water is the only common
  substance found naturally in all three common
  states of matter and it is essential for life on
  Earth.
• Many substances dissolve in water and it is
  commonly referred to as the universal solvent.
  Because of this, water in nature and in use is
  rarely pure and some of its properties may vary
  slightly from those of the pure substance.
• There are many compounds that are essentially, if
  not completely, insoluble in water.
• Water usually makes up 55 to 78 of the human
  body, averaging 70.

3
Properties and other things to know about Water

• 1.     Chemical Formula
•  2.  Bond
•  3. Storage of Energy
• 4. Attraction
• 5. Effect on Human Body
• 6. Aqueous solution
• 7. Polarity
• 8. Acids and Bases

4
Chemical Formula

• H2O
• Two hydrogen atoms and one
  oxygen atom bonded together.

5
Bond

• Molecule is formed by covalent bonds. The
  electrons in a water molecule are shared by
  oxygen and hydrogen atoms.
• HOWEVER The shared electrons are attracted more
  strongly by the oxygen nucleus than by the
  hydrogen nuclei. (The oxygen nucleus has more
  protons to be attracted to.) This makes the
  oxygen more negative because 10 electrons are
  staying close around its nuclei of 8 protons.

6
Storage of Energy

• Water absorbs heat more slowly and retains this
  energy longer than other substances.
• Ex Humans sweat to release excess heat through
  water evaporation.
• Water vapor lost through the evaporation of sweat
  carries heat away from the body. Helps with
  Homeostasis!

7
Storing Energy

8
Attraction

• The hydrogen bonds between water molecules cause
  the cohesion of liquid water. COHESION is an
  attraction between substances of the SAME kind.
  Because of cohesion water droplets form thin
  films and drops, creating SURFACE TENSION.
• Water molecules are also attracted to many other
  polar substances. ADHESION is an attraction
  between different substances, creating CAPILLARY
  ACTION in plants which moves water from roots to
  leaves. Adhesion can also cause stuff to be wet,
  like a paper towel.

9
Surface Tension (Cohesion)

10
Capillary Action (Adhesion)
11
NO Adhesion? Water would be like this if the
molecules did not stick together.

12
Effects on Human Body

• 70 of your body is made of water.
• 2/3 of molecules in your body are water.
• Your cells are filled with water.
• Water is where most cell events occur.
• Cells are surrounded by water.
• Water helps move nutrients and waste in and out
  of your cells.

13
Aqueous solutions

• Many substances dissolve in water
• Example Salt dissolves in water, making a
  saltwater solution.
• Many substances in the body are dissolved in
  blood or other aqueous fluids.
• Water allows substances to move in and out of
  cells. Like sugars!

14
Aqueous solution

15
polarity

• Water molecules have a partially positive end and
  a partially negative end or poles.
• Partially positive end of one water molecule is
  attracted to the partially negative end of
  another water molecule.
• Attraction between 2 water molecules is called a
  HYDROGEN BOND. It is a weak bond between 2 polar
  molecules.

16
Attraction between two water molecules

• Notice the polarity!

17
Acids and bases

• While bonds in water molecules are strong, at any
  given time, a small fraction of those bonds might
  break, forming a hydrogen ion H or a hydroxide
  ion OH- .
• Pure water has a low concentration of hydrogen
  ions and hydroxide ions present in equal numbers.

18
Acids and Bases

19
ACIDS

• Compounds that form hydrogen ions when dissolved
  in water are called acids.
• When an Acid is added to water, the concentration
  of hydrogen ions in the solution is increased
  above that of pure water.

20
Bases

• Compounds that reduce the concentration of
  hydrogen ions in the solution are called bases.
• Many bases form hydroxide ions when dissolved in
  water.
• This lowers the concentration of hydrogen ions
  because hydroxide ions react with hydrogen ions
  to form water molecules.