Chapter 2
The Chemical Basis of Life
The Atom
The Periodic Table
Periodic Table
METALS
NONMETALS
Ionic Bonding
• Force of attraction between oppositely charged ions
• Octet rule….compete outer shell
• Cation?
Anion?
Metal to ?
Covalent Bonding
• Shared electrons
• Polar vs nonpolar
Chemical make-up of water
• Water has the chemical formula H2O. A water
molecule contains one oxygen and two
hydrogen atoms connected by covalent bonds.
Hydrogen
Bonding
Weak bonds
between molecules.
polar covalent: O- --- H+
Contributes to the
special properties of
water.
Hydrogen Bonding
• Intermolecular vs Intramolecular
Chemistry: Lesson Plan Day 2
• Hand Back & Review Essays/record results
• HW due dates- review
• Highlight BOTH the properties of water
handout (for water lab) and the buffers
handout (prep for our lab)
• Review Properties of water and relate to the
water lab
• Second Hour- Acids, Bases, Buffers
Tartigrade……Water Bear
Tartigrade ‘tun’
Properties of Water
*The Importance of Water to Organisms
•
•
•
•
High Water Content in living things
Abiotic Factor
Biodiversity
Solvent Properties
Next few slides…for discussion of these topics
Humans
• Up to 60% of the human body is water,
(The brain is composed of 70% water, and
the lungs are nearly 90% water. Lean muscle
tissue contains about 75% water by weight,
as is the brain; body fat contains 10% water
and bone has 22% water. About 83% of our
blood is water, which helps digest our food,
transport waste, and control body
temperature.)
•
Each day humans must replace 2.4 liters
of water, some through drinking and the
rest taken by the body from the foods
eaten.
Water as an Abiotic Factor:
it’s everywhere!
• Water is the key to
our survival on Earth,
it is our source of life
• Water is everywhere!
It makes up about
70% percent of the
Earth’s surface
• Of that water, about
97% is ocean, and
only 3% is fresh
water
Water and Biodiversity
The “Universal Solvent”
Water is capable of dissolving a variety of different substances, which is why it is such
a good solvent. In fact, water is called the "universal solvent" because it dissolves
more substances than any other liquid. This is important to every living thing on earth.
It means that wherever water goes, either through the air, the ground, or through our
bodies, it takes along valuable chemicals, minerals, and nutrients.
*Properties of Water
•
•
•
•
Cohesion
Adhesion
Surface Tension
Capillarity
Discuss each/relate to Water Lab
Definitions
• Cohesion: Molecules have a strong tendency to ‘stick’ to
one another.
-Attraction between like substances
-Water is attracted to Water: spherical shape of the mid
air droplet/dome shape on the penny/in the petri dish
• Adhesion: Molecules have the ability to stick (adhere) to
one another.
-Attraction between like substances
-Water ‘sticks’ to other substances: teardrop shape at
the tip of the pipette/penny/sides of the petri dish/sides of the
capillary tubes
Adhesion and Cohesion
• Adhesion
Cohesion
….and gravity…
Surface Tension
• The property of the surface of a
liquid (water) that allows it to
resist an external force,
(adhesion) due to the cohesive
nature of the (water) molecules.
*Stronger cohesive forces between
surface water molecules (and pull
downward from those below) than
adhesive forces of attraction to the air,
creating a supportive ‘skin’.
*Needle is MORE DENSE than the
water- should NOT float
Capillary Action
• The movement of water (in a
tube) due to the forces of
adhesion, cohesion,
and surface tension.
*When the adhesion to the walls is
stronger than the cohesive forces
between the liquid molecules; limited
by surface tension and gravity.
Importance in Biology?
Plants take advantage of capillary action to pull
water from the into themselves. From the
roots water is drawn through the plant by
another force, transpiration.
Which is greater……A or C?
?
Surface Tension
and
Capillary Action
Hydrogen Bonding explains the way water
responds to changes in temperature
To increase the
temperature,
molecules must
be moving
faster- much of
the energy
added to a
system is used
to break the
H-bonds, only
a portion is
available to
speed up
movement of
the water
molecules…
(Temp = av. KE)
Hydrogen bonds are formed or broken as water changes from one state to another
*High Specific Heat (Heat Capacity)
• Amount of energy required to raise the
temperature of water
1 cal/gH2O/1◦C
Importance in Biology?
BECAUSE WATER REQUIRES SO MUCH HEAT INPUT/LOSS TO CHANGE ITS’ TEMP:
• Oceans and large bodies of water have relatively constant temperatures
• High water content of organisms help them maintain relatively constant internal
temperatures. Biological reactions occur in a relatively narrow temp. range.
*High Heat of Vaporization
• Amount of Heat Energy needed to change 1g of
a substance from a liquid to a gas = phase change
• Water: A calorie is the amount of heat energy
required to raise the temp. of 1g of water 1◦C
• Water’s Heat of Vaporization- very high
compared to other substances due to H-bonds
• Importance in Biology??
Exothermic Reaction: Sweating: Evaporative cooling- dissipate xs heat as sweat.
Nature- leaves stay cool as transpiration occurs
*Polar Molecule (Solvent Properties)
• Water: The ‘Universal Solvent’ that allows
molecules (usually ionic or polar molecules) to
dissociate (separate) into individual ions.
– Example: NaCl salt:dissolved substance is the ‘solute’
*Wherever water goes, either through the air, the ground, or through our
bodies, it takes along valuable chemicals, minerals, & nutrients.
Cushioning: water protects vital organs from jarring
Dissociation of a Water Molecule:
Breaking apart into two ions of
opposite charge
H2O
H+
hydrogen ion
and
OH-
hydroxide ion
Acids and
? Bases
Acids- Bases
• ACID:
Any substance that increases the
concentration of hydrogen ions when added to a
water solution. (< 7 on the pH scale)
– # H+ ions is greater than the number of OH- ions, the
solution is an acid
• BASE:
Any substance that increases the
concentration of hydroxide ions when added to a
water solution
– # OH- ions is greater than the number of H+ ions, the
solution is a base
Definition of acids and bases
pH = Powers of Hydrogen Scale 0-14
Concentration of free floating H+ determines
the pH (acidity) of the solution
0-14 Acid Base Scale- A Logarithmic Scale
ONE pH unit is a
tenfold change in
acidity or
alkalinity.
A solution with a
pH of 4 has 10
times more H+
ions than a
solution with a
pH of 5, and 100
times more H+
ions than a
solution with a
pH of 6
Dissociation of Acids and Bases
Strong acids (HCl) and
bases (NaOH)
completely dissociate;
irreversible
Weak acids and
bases do not
H2CO3
Carbonic acid
*A reversible reaction
Dissociation of a Water Molecule:
Breaking apart into two ions of
opposite charge
H2O
H+ = 1 X 10-3 pH = ?
H+
hydrogen ion
and
OH-
hydroxide ion
Acids and Bases
Dissociation of Acids and Bases
Strong acids (HCl) and
bases (NaOH)
completely dissociate;
irreversible
Weak acids and
bases do not
H2CO3
*A reversible reaction
Buffers
• Any substance
that resists
changes in pH
when an acid
or base is
added
• Maintain
dynamic
equilibrium
Carbonic Acid Buffer System in Blood
Respiratory Acidosis/Alkalosis
1.
2.
3.
4.
Metabolic Acidosis/Alkalosis
Excessive Protein dieting/Prolonged exercise-muscle overuse
Impaired lung function/narcotics use (abuse)
Excess diuretics (Decr. blood volume)/vomiting (loss of stomach acids)
Hyperventilating
Right or Left Shift to fix?
Alkalosis vs Acidosis
THE PROBLEM:
• Excessive Protein dieting/Prolonged exercise-muscle
breakdown or overuse
• XS diuretic use (Decr. blood volume)/vomiting (loss of
stomach acids)
• Impaired lung function(emphysema, pneumonia)/narcotics
• Hyperventilating
Effect of [CO2] on Shell Growth Rate
• Chemical energy = energy
stored in bonds.
• Some bonds require more
energy to form than others.
• When these high energy
bonds break, new lower
energy molecules are
formed.
• In a redox reaction,
the energy
difference
is released.
Oxidation
I s *Supplies energy
Loss of electrons (H)
Reduction
Is
*For this reaction
Gain of electrons (H)
OxidationReduction
(Redox)
Reactions
“OIL RIG”
EXERGONIC vs ENDERGONIC