Why Study Chemistry in
Biology?
STARCH MOLECULE
GLUCOSE MOLECULES
You can prolong life by keeping bananas in cooler
temperatures.
I. The Atom
A. Definition: smallest particle of an element
B. Composition
Subatomic
Particle
Charge
Mass
Location
Proton
+1
1
Nucleus
Neutron
0
1
Nucleus
Electron
-1
1/1840 the
mass of a
proton
Orbiting
nucleus
Location of Electrons
outermost
electrons
participate in
BONDING
Bohr Atomic Model
•Atoms Space
•Why if atoms have
so much space
can we be solid?
II. Elements
A. Definition: substance that cannot be broken
down into other substances
B. Biologically important elements
i. Major: C H O N P S
(Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, Sulfur)
Radioactive Isotopes
III. Chemical Compounds
A. Compound definition:
a substance containing two or more
elements in a fixed ratio
– Ex: H2O, NaCl, CO2
• Atoms want to fill their outer energy
levels to be
• To do this, they will meet up with other
atoms and either
or
electrons
i. Atoms share electrons
Examples of covalent molecules
ii. Ionic Bonds: gimme’ that electron!
• Atoms transfer electrons, becoming (+) or (-)
charged
• The attraction brings them together
– Ex: Na+ and Cl- = NaCl!
JOKE- Don’t Have to write this.
• A NEUTRON walks into a diner and sits down to
order a meal.
• When the waitress brings the food over the neutron
says “Can you bring the check? I am in a hurry!”
• The waitress replies, “Don’t worry about it, there is
NO CHARGE for you.”
JOKE- Don’t have to write this.
• Two atoms walk down the street and collide.
• One atom says to the other, “Are you okay?”
• The second atom replies, “I think I lost an electron.”
• The first atom says, “Are you sure?”
• The second one says, “Yeah, I’m POSITIVE!”
iii. Molecules definition: two or more atoms held
together by COVALENT bonds
V. WATER
LIFE DEPENDS ON THE UNIQUE
PROPERITIES OF WATER
Questions to think about
• Why do put salt on the roads?
• Why do we add salt to a pot of pasta
water?
• At a higher altitude why must we
cook “boil” something longer?
A. Human Composition:
Cells are 70–90% water
B. Plant Composition
As much as 95%
plants can be made
of water
C. Formula:
H2O
D. Bonds:
i. Hydrogen bonds:
Hydrogens from one
water molecule are
ATTRACTED to the
oxygen of ANOTHER
water molecule: they
develop a weak bond
i. Cohesion
1. Definition: Water
“sticks” to each
other
Ex.: Surface tension=
when cohesion pulls
water molecules at
the surface tightly
together, forming a
film-like boundary
1-inch
papercli
p
over-filled water
3oz Dixie cup
Jesus Christ Lizard
ii. Adhesion
1. Definition: Water
molecules attracted
to other molecules.
2. Ex. In
trees/plants water
goes against gravity
Called capillary action
Water is the a Universal Solvent
Water is able to dissolve other Polar & ionic
compounds when mixed by causing the ions to
break away and surround them.
• Water dissolves Salt (Na+Cl-)
iii. Temperature and Water
Boiling Point: 100 oC / 212 oF
• When you heat
molecules move faster
• When you cool
molecules move
slower
• Water takes more
energy to heat
because energy must
break hydrogen
bonds
Does water boil faster if you add salt to it?
• Water Boils when it has enough energy for the
molecules to leave
Freezing Point
0 oC or 32 oF
• What would happen if
our oceans did not
have salt in them?
• Why do we put salt on
our roads?
• Why at effect does salt
have on FREEZING
POINT?
Why is this important for life?
Water Boiling Point
Ethanol Boiling Point
• Why are higher altitude must we cook “boil”
something longer?
•Why do we need salt
in our ice, when
making ice cream?
Watch Video
LOW DENSITY OF ICE
• Density- amount of
matter in a volume
• In most substances the
solid state is more dense
than the liquid state
• Water is the opposite
ICE IS LESS DENSE
THAN WATER and will
FLOAT
LOW DENSITY OF ICE
• WHY?
• Hydrogen
bonds in ice
(solid) keep
molecules
spaced out
LOW DENSITY OF ICE
• Floats
• Ice insulates the
liquid water below
allowing life to persist