Transcript i. the composition of the universe

Ch. 2 – The Chemistry of Life
02
I. THE COMPOSITION OF THE
UNIVERSE
A. Everything in the universe is made of up atoms.
B. An element is a pure substance that cannot be
broken down chemically into other matter.
1. Examples of elements: Oxygen, Carbon,
Hydrogen, Nitrogen, Phosphorous
2. More than 100 elements have been
identified, but less than 24 are important
to living things.
I. THE COMPOSITION OF THE
UNIVERSE
3. Periodic Table of Elements:
I. THE COMPOSITION OF THE
UNIVERSE
4. The simplest part of an element is an
atom.
5. Parts of an atom (a.k.a. sub-atomic particles):
a. The “Central Core” or nucleus is made
up of:
protons (+ charge)
neutrons (neutral)
I. THE COMPOSITION OF THE
UNIVERSE
6. The electron energy levels move around the
nucleus at a high speed in every levels.
a. Electron (- charge) – located outside the
atomic nucleus
b. The number of electrons is equal to the
number of protons an atom has.
c. Electrons are tiny! Only 1/1840th of the
mass of a proton.
I. THE COMPOSITION OF THE
UNIVERSE
7. How do you determine the Atomic
Number? Atomic Mass?
a. Atomic Number = Number of
protons
b. Atomic Mass = Sum of
protons and neutrons
I. THE COMPOSITION OF THE
UNIVERSE
C. Building More Complex Substances
1. Most elements combine with other elements in
nature.
2. A pure substance that is made up of a fixed number
of atoms of two or more elements is called a
compound.
a. Examples of compounds: NaCl, H2O, CO2,
C6H12O6
b. The properties of a compound are different
than those of the elements that create it!
I. THE COMPOSITION OF THE
UNIVERSE
3. All atoms “want” to be stable; if their
outermost energy level is not filled, then they
will tend to undergo chemical reactions to
find stability.
a. Bonds are then formed!
I. THE COMPOSITION OF THE
UNIVERSE
b. Two Important Biological Bonds:
1. Covalent Bonds – share
electrons
Example: Water, Ammonia
** Covalent Bonds are usually
found between non-metals
and non-metals. **
I. THE COMPOSITION OF THE
UNIVERSE
I. THE COMPOSITION OF THE
UNIVERSE
2. Ionic Bonds – “Opposites”
attract; “steal” or transfer
electrons; Because of this, they
have a charge.
An atom or molecule with a charge
is an ion.
Example: NaCl
** Ionic Bonds are usually
found between metals
and non-metals. **
I. THE COMPOSITION OF THE
UNIVERSE
I. THE COMPOSITION OF THE
UNIVERSE
4. A molecule is the simplest form of a
compound; when two or more atoms join.
a. Example of molecule:
I. THE COMPOSITION OF THE
UNIVERSE
5. van der Waals forces: slight attractions that
form when oppositely charged regions of a
molecule are near each other.
a. Not as strong as ionic or covalent
bonds!
b. Can help to keep larger molecules
together.
I. THE COMPOSITION OF THE
UNIVERSE
Bond Review: Ionic or Covalent Bond?
a. CCl4 –
b. Li2O –
II. MIXING IT UP….Solutions!
A. A mixture is a material composed of two or
more elements or compounds that are
physically mixed together but not chemically
combined.
II. MIXING IT UP….Solutions!
B. A solution is a mixture in which one or more substances
are evenly distributed in another substance.
1. Two major components:
a. Solute – substances dissolved into the
solution
b. Solvent – substance in which the solute is
dissolved (the dissolver)
Examples of Solvent:
Chocolate Milk – Solvent is the milk
Ocean water- Solvent is the water
II. MIXING IT UP….Solutions!
2. How do we analyze the strength of a solution?
Concentration – amount of solute dissolved in solution
III. Biology is “Burning” Up . . . (Acids,
Bases, and pH)!
A. The acidity or basicity of a solution can be
measured using the pH scale.
1. Range of the scale: 0-14
III. Biology is “Burning” Up . . . (Acids,
Bases, and pH)!
2. An acid has a pH of less than 7. It is a
larger number of hydrogen (H+) ions than
hydroxide (OH-) ions.
a. Example of acid: Milk – pH is 6.5,
Stomach Acid – pH is 1.5
III. Biology is “Burning” Up . . . (Acids,
Bases, and pH)!
3. A base has a pH of greater than 7. It
has a larger number of hydroxide (OH-) ions
than hydrogen (H+) ions.
a. Example of base: Blood – pH is 7.4,
Ammonia – pH is 11.5
III. Biology is “Burning” Up . . . (Acids,
Bases, and pH)!
4. Neutral pH = 7
a. Example of neutral: WATER!
5. Buffers neutralize acids or bases!
IV. The Chemistry of Water
A. The Polarity of Water
1. Remember . . . covalent bonds join the
hydrogen atom and oxygen atom that
make up water!
2. Though the electrons are shared, they
are not shared equally.
a. Oxygen has 8 protons/positive
charges to attract electrons.
b. Hydrogen only has 1 proton/positive
charge.
IV. The Chemistry of Water
c. Because of its greater positive charge,
the nucleus of the oxygen atom pulls
the shared electron towards its own
nucleus and away from the hydrogen.
d. This makes the region of the water
molecule where the oxygen is slightly
negative (-) and the region where the
hydrogen is slightly positive (+).
IV. The Chemistry of Water
e. This is why water is called a polar
compound  it has an uneven pattern
in charge!
f. A polar compound is good at
dissolving other polar (sugar, proteins)
substances and ionic compounds.
V. Hydrogen Bonding
A. The polarity of water causes water molecules
to attract to each other or be “sticky”.
1. Hydrogen bond – attraction holding two
(+) water molecules together
2. The region of one water molecule
positive (H+) is attracted to the negative
(O-) region of another.
3. These are weak bonds and can be
broken easily.
V. Hydrogen Bonding
B. Why is hydrogen bonding important to life and
biology?
1. Creates cohesion of particles.
a. Cohesion – an attraction between
molecules of the same substance.
b. Example of cohesion: Water “sitcks”
allowing striders to move across
water.
V. Hydrogen Bonding
c. Surface tension is created by cohesion.
d. Surface tension is a force existing on the
surface of a liquid, preventing the layer from
being broken.
V. Hydrogen Bonding
2. Creates adhesion of particles.
a. Adhesion – an attraction between
molecules of different substances.
b. Example of adhesion: Meniscus of a
test tube.
V. Hydrogen Bonding
3. Adhesion + cohesion work together to create a
property of water known as capillary action.
a. This allows water molecules to move upward
through narrow tubes against the force of
gravity.
b. Example of capillary action: Water out of the
roots of a plant and up the stem to leaves.
V. Hydrogen Bonding
4. Moderate temperature.
a. Water must gain or lose large
amount of energy (heat) to break/form
the hydrogen bonds for any
temperature change.
b. Why is this important?
1. Helps organisms maintain
homeostasis.
2. Helps moderate
climate/ocean water
temperature.