Water and the Chemistry of Life

1
Water and the Chemistry
of Life
2
Water Facts

• There is the same amount of water on Earth today
  as there was 3 billion years ago.
• Three percent of the water on Earth is freshwater
  and only 1 is avaiIable for human consumption.
• Sixty-six percent of a human being is water.
• Seventy-five percent of the human brain is water.
  
• Seventy-five percent of a living tree is water.
• You could survive about a month without food, but
  only 5 to 7 days without water.

3
Water Facts

• Recall some of the water facts in slide one.
• Jot these down.
• Turn to your partner and explain the
  importance of water in your life.

4
The Water Molecule

• The water molecule contains one oxygen atom and
  two hydrogen atoms.

5
Properties of Water
6
Water is Polar

• Water is polar because oxygen is a bully and
  does not share the electrons.

7
Water is Polar

• Oxygen is negative with more electrons and
  Hydrogen is positive with less electrons.

8
Water Forms Hydrogen Bonds

• Water molecules attract each other because of
  Oxygens (-) charge and Hydrogens () charge.
• Hydrogen bonds hold water molecules together.

9
Water Forms Hydrogen Bonds

• 2. Draw one water molecule and label the
• ( H) and the (- O).
• Draw two more water molecules and show them
  connected together with hydrogen bonds

10
Hydrogen Bonds and the Titanic

• Hydrogen bonds sank the Titanic.
• The reason ice floats is because of hydrogen
  bonding.    In other words, ice is less dense
  than liquid water and will float on the surface
  of the liquid.  Throw in one really big chunk of
  ice and a cruise ship, and you begin to see the
  problems that can arise.  

11
Cohesion

• Cohesion is the attraction of the same type of
  molecules to each other.
• Water molecules stick together and hold hands
  with hydrogen bonds

12
Cohesion

• Cohesion explains wetness. Water molecules
  stick together and form drops.
• Cohesion explains why insects can walk on a
  lakes surface.

13
Adhesion

• Adhesion is the attraction of molecules between
  two different substances.
• Example The attraction of water molecules to a
  glass.

14
Adhesion

• Adhesion causes this.
• 3. Name the line and the equipment.)
• Adhesion causes water to rise in a straw

15
Adhesion or Cohesion??

• Your teacher will put a drop or two of water on
  your desk.
• 4. The water clinging to your desk is an example
  of ____________
• 5 The water forming drops is an example of
  __________________

16
Adhesion or Cohesion??

• 6 Water rising in plants from roots to leaves.
• 7 Animals walking on surface water tension.
• 8 Colored celery leaves.

17
Water is the Universal Solvent

• Water is polar and can dissolve both salts,
  sugars, and other molecules.

18
Water is the Universal Solvent

• 9 Why is water such a good solvent?
• 10 What could you do to dissolve a solute in
  water faster?
• OR how could you speed up the dissolving of
  sugar in water?

19
Water Molecules Can Split

• A water molecule can split and form ions.
• H20 H OH-
• An ion is a charged atom. ( or -)

20
Water Molecules Can Split

• 11 What is the charge of the (H )ion?
• 12 What is the charge of the (OH) ion?

21
Water and Acids

• Acids form H ions in a water solution.
• Acid solutions have high concentrations of H
  ions and have a pH value less than 7 .

22
Water and Bases

• Bases form OH- ions in a water solution.
• Basic solutions have high concentrations of OH-
  ions and have a pH value greater than 7 .

23
Acids and Bases

• 13. Acids form _____ions
• 14. Bases form _____ions
• 15. Draw this number line and label acids,
  bases, and neutral. Write examples of acids and
  bases along your number line.

1
14
24
The Water Cycle
25
The Water Cycle

• Earth's water is always in movement, and the
  water cycle, also known as the hydrologic cycle,
  describes the continuous movement of water on,
  above, and below the surface of the Earth. Since
  the water cycle is truly a "cycle," there is no
  beginning or end. Water can change states among
  liquid, vapor, and ice at various places in the
  water cycle, with these processes happening in
  the blink of an eye and over millions of years.

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The Water Cycle

• 16 Write some of the stages in the water
  cycle.
• Turn to your partner and explain how water cycles
  from drop to drop.

27
The Water Cycle

• Although the balance of water on Earth remains
  fairly constant over time, individual water
  molecules can come and go in a hurry. The water
  in the apple you ate yesterday may have fallen as
  rain half-way around the world last year or could
  have been used 100 million years ago by Mama
  Dinosaur to give her baby a bath.

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HOMEWORK-Chapter 2.2
1. Complete the following four square analogy for
water
2. Write a summary about the properties of water
using the following words Polar Hydrogen
bonds Cohesion Adhesion Solvent Surface Tension