Transcript chemical reaction

In-Basic Chem PreviewUse a periodic table to complete
Name
Carbon
Hydrogen
Nitrogen
Oxygen
Phosphorus
Symbol
Atomic #
Atomic
Mass
# Proton
#
electron
Avg #
Neutron
Electron
Configuration
Thru 9/14
Basic Chemistry
Chapter 2
Reductionist Approach
 A scientific approach based on the idea that the whole


can best be understood by the examination of its parts.
Only by reducing organisms to their smallest parts have
biologists been able to understand the complex
structures and functions of life.
The “whole” is the sum of its parts.
Elements
 The
basic chemical units that cannot be
broken apart by chemical processes.
 92 naturally occurring, chemically
individual atoms. (“atom” is the term we
use for a single elemental unit)
 25 are required by living organisms
 “The Big 4”- Oxygen, Carbon, hydrogen,
Nitrogen (96.3% of the human substance)
“Trace” Doesn’t mean
Unimportant
Deficiency
Iodine
Iron
Fluoride
Condition
Goiters due to malfunction of
the thyroid
Anemia that causes fatigue
and malaise
Tooth decay and
osteoporosis
Goiter Due to Iodine Deficiency
Compounds
 Two
or more atoms in a fixed ratio
 Different combinations of atoms determine
properties
Examples of compounds:
NaCl
H 2O
H 2O 2
C40H30O
The Parts of an Atom
Protons - occupy the central region
(nucleus), have a + charge.
Neutrons - occupy the central region
(nucleus), have no charge.
Electrons – occupy outer region, have a
negative charge.
Atomic
Number
6
= the
number of
protons in
the nucleus
Atomic Mass
12.0107
= number of
Protons +
average
number of
Neutrons in the
nucleus
Isotopes
 Atoms
with the same atomic number,
different atomic mass
 What must be different, protons, neutrons
or electrons?
Ex: Carbon 12,13, and 14
Carbon Isotopes
Protons
C12
6
C13
6
C14
6
Neutrons
6
7
8
Electrons
6
6
6
Electron Arrangement
 Electrons
orbit the nucleus in electron
shells.
 Atoms may have one or more electron
shells, depending on the number of
electrons
 The chemical individuality of an atom
depends on the number of electrons in the
valence (outer) shell
Stability
•
In order for an atom to be stable, its outermost
orbital must be full or have eight electrons!
• All elements before Carbon must get rid of
their electrons
• Note: The first orbital holds only 2 electrons
Electron Configurations
Draw the electron shells of the BIG 4
Types of Bonding
Ionic Bonding

Electron transfer between atoms

Causes each atom to have a charge
Negative = Anions
Positive = Cations

Atoms are attracted to each other due to
opposite charge

Resulting compound is neutral. Crystalline
solid at room temp.
Example: NaCl Draw it!
Ionic Bonding of NaCl
Covalent Bonding
Covalent Bonding

Electrons are shared between atoms

Valence shells overlap

Every two electrons = 1 single bond

4 shared electrons = double bond
Example: CH4 Draw it!
Covalent Bonding - Methane
Common Ground
In each of the bond types, two rules are
satisfied:
1.) The resulting compound is electrically
neutral
2.) Outer electron orbits (shells) are filled
What does bonding have to do with
life?
Molecules play many roles in living organisms:
 Energy storage and transfer
 Structural Molecules
 Communication
 Information Storage
and Retrieval
Check Out 09/14-Structural
Formulas
1.
2.
3.
4.
5.
6.
C3H8
C4H6
C3H4
C2H6O
C2H2O
CH5N
2.9-2.15
The Properties of Water
In – Water 9/28
Draw the molecular formula, electron
configuration, and structural formula of
water
Thru-The properties of Water
Water is a polar molecule
Polar  one end of the molecule is negative, the
other is positive. This happens when electrons
are not equally shared by the atoms involved in
the covalent bond.
Oxygen “pulls” the electrons away from the H
atoms.
Oxygen has a higher level of
electronegativity
Nonpolar Molecules
Why are these molecules nonpolar?
H2, O2, CH4
Evenly distributed electronegativity
The Benefits of Polarity:
#1 Hydrogen Bonding




Polarity of water leads to
hydrogen bonding between
water molecules
Negative oxygens are
attracted to positive
hydrogens
Important in organic
molecules like DNA and
proteins.
Allows water to have
properties different than any
other compound on earth
#2 Cohesion and Adhesion
The tendency of water molecules to stick
together (cohesion) and to other things
(adhesion)

allows water to form drops

allows capillary action needed for
transport through plants and circulatory
system
 Creates surface tension
Cohesion
#3 Temperature Moderation


Water must absorb a large amount of heat in order to
evaporate b/c the H bonds hold the molecules in place
When water is cooled, more H bonds form, releasing
more heat energy and slowing down the cooling process
• Water vaporizes less quickly.
• Water cools slower
How might these qualities affect life?
Bodies of water can store heat
evaporative cooling, etc
#4 The density of Ice is less that of
Liquid Water
1.Hydrogen Bonds in ice result in a
stable, three dimensional structure
2.A given volume of ice has fewer
water molecules than an equal
volume of liquid water and is
therefore less dense
#5 Water is a Versatile Solvent
 Because
water is polar, it readily forms
solutions with a wide variety of other
covalently bonded, polar compounds and
with the charged ions of ionically bonded
compounds.
Mixtures –The four S’s
Solvent  dissolving agent (water)
Solute  Substance being dissolved (solid or
liquid)
Solution  a liquid that is a homogenous mixture
of two or more substances
Suspension a heterogeneous mixture of two or
more solids
Negative end
of water
attracted to
cation
Positive end of
water attracted
to anion
Identify the property associated
with the following phenomena…
1. Sea Ice Floats!
2. Aquatic Insects can walk on water
3. Not all oceans and ponds are frozen solid.
4. Plants get water from a root system
5. The ocean is salty
Life is sensitive to acidic and
basic conditions
A
few water molecules can break apart into
ions
–
–
Some are hydrogen ions (H+)
Some are hydroxide ions (OH–)
– Both are extremely reactive
– A balance between the two is critical for chemical
processes to occur in a living organism
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Life is sensitive to acidic and
basic conditions
 Chemicals
other than water can contribute
H+ to a solution
–
–
They are called acids
An example is hydrochloric acid (HCl)
– This is the acid in your stomach that aids in digestion
 An
acidic solution has a higher
concentration of H+ than OH–
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Life is sensitive to acidic and
basic conditions
 Some
chemicals accept hydrogen ions and
remove them from solution
–
–
–
These chemicals are called bases
For example, sodium hydroxide (NaOH)
provides OH– that combines with H+ to produce
H2O (water)
This reduces the H+ concentration
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Life is sensitive to acidic and
basic conditions
A
pH scale (pH = potential of hydrogen) is
used to describe whether a solution is acidic
or basic
–
–
pH ranges from 0 (most acidic) to 14 (most
basic)
A solution that is neither acidic or basic is
neutral
(pH = 7)
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pH scale
0
1
Acidic solution
Increasingly ACIDIC
(Higher concentration of H+)
Battery acid
2 Lemon juice, gastric juice
3 Grapefruit juice, soft drink,
vinegar, beer
4 Tomato juice
5
Rain water
6 Human urine
Saliva
NEUTRAL
[H+]=OH–]
7 Pure water
Human blood,
tears
8
Seawater
Increasingly BASIC
(Lower concentration of H+)
Neutral solution
9
10
Milk of magnesia
11
Household ammonia
12
Household bleach
13
Oven cleaner
Basic solution
14
Acidic solution
Neutral solution
Basic solution
Acid precipitation and ocean
acidification threaten the
environment
 When
we burn fossil fuels (gasoline and
heating oil), air-polluting compounds and
CO2 are released into the atmosphere
–
Sulfur and nitrous oxides react with water in the
air to form acids
– These fall to Earth as acid precipitation, which is
rain, snow, or fog with a pH lower than 5.6
–
Additional CO2 in the atmosphere contributes to
the “greenhouse” effect and alters ocean
chemistry
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Chemical Reactions
 You
learned that the structure of atoms and
molecules determines the way they behave

–
–
Chemical reactions make and break bonds, changing
the composition of matter
Remember that atoms combine to form
molecules
Hydrogen and oxygen can react to form water
2H2 + O2
2H2O
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Chemical Reactions
 The
formation of water from hydrogen and
oxygen is an example of a chemical
reaction
 The reactants (H2 and O2) are converted to
H2O, the product
–
–
Organisms do not make water, but they do carry
out a large number of chemical reactions that
rearrange matter
Photosynthesis is an example where plants
drive a sequence of chemical reactions that
produce glucose
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2 H2
O2
2 H2O
Atoms
Check Out/10/6 Chemistry Concept Map
have positively
charged
have neutral
have negatively
charged
(b)
(a)
number present
equals
(c)
number may
differ in
atomic number of
each element
number in outer
shell determines
formation of
(d)
Chemical
Bonds
electron transfer
between atoms
creates
ions
(e)
unequal
sharing creates
attraction between
ions creates
(g)
(f)
example is
water
electron sharing
between atoms
creates
has important
qualities due
to polarity and
equal
sharing creates
nonpolar
covalent bonds
can lead to
(h)
Atoms
have positively
charged
(a)
number present
equals
atomic number of
each element
have neutral
(b)
number may
differ in
(d)
have negatively
charged
(c)
number in outer
shell determines
formation of
Chemical
Bonds
electron transfer
between atoms
creates
ions
(e)
unequal
sharing creates
attraction between
ions creates
(g)
(f)
example is
water
electron sharing
between atoms
creates
has important
qualities due
to polarity and
equal
sharing creates
nonpolar
covalent bonds
can lead to
(h)