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States of Matter
Solids Liquids Gases
2
Solid vs. Liquid vs. GasDepends on
Kinetic
Energy of
particles
Attractions
between
particles
vs
only two things: What?
3
Intermolecular Forces
(Molecular Attractions)
Covalent molecules are attracted to
each other by “intermolecular forces”.
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are what “stick” one molecule to
other molecules (not the
bonds within one molecule)
are responsible for the solid
and liquid states for molecules
Intermolecular Forces
(Molecular Attractions)
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Dipole-dipole force
(dipole force)
Dispersion force
Hydrogen bond force
(a special dipole force)
van der
Waals
forces
3 Types:
Intermolecular Forces
(Molecular Attractions)
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1. Dipole-Dipole Force “Electrostatic” attraction
of polar molecules.
+ - + - + -
- + - + - +
+ - + - + -
For example: HF and H2O
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Dipole-Dipole
charged rod
Buret with
water
(+) (-)(-)
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Review: Polar Molecules
A molecule with only two atoms is
polar if the atoms have different
electronegativities.
H-Cl
polar
Br-Br
nonpolar
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Review: Polar Molecules
If more than 2 atoms in molecule:
•Draw dot structure
•If outside atoms are the same
and central atom has
no nonbonding electrons,
the molecule is nonpolar.
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Are These Polar(do they have a dipole force)?
CH4
H2
NH3
CH3Cl
SO2
NaCl
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2. Dispersion Force
All molecules have “instantaneous”
polarity due to the random motion
of the e- around the nucleus.
+ -
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Attractive force resulting
from the temporary dipoles
2. Dispersion Force
Responsible for condensation
of nonpolar gases
Is stronger the larger the
molecule (molar mass)
+ - + -
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The States of Halogens
At room temperature:
F2 and Cl2 :gases
Br2: liquid.
I2: solid.
Increased
molar mass
so
larger
dispersion force
All are nonpolar and have
only dispersion forces.
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3. Hydrogen Bond ForceA strong dipole-dipole attraction
between molecules when hydrogen
is bonded to N, O, or F
d- d+strong
H-bond force
……
Why?
F—H F—Hd- d+strong
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Hydrogen Bond
H—O H—O
H H
electronegative
F, O, or N atom
H-bond
from H to
lone pair
on O
H atom on
different
molecule
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Strength of Molecular
Attractions1. Dispersion Force
(weakest unless molecule is large)
2. Dipole Force
3. H-Bond Force (strongest)
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Name the Type of
Molecular Attractions
N2 NH3
CH4 H2O
HCl SO2
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Gases (KE >> attractions)
“Kinetic Molecular Theory”
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Gases: KMT
1.Gas “particles” (atoms
or molecules) are: Hard spheres
Insignificant volume
(compared to container)
Far apart
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Gases: KMT
Random motion
Straight line paths
until collision
Fill container
2. Gas “particles” are in
constant motion
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Gases: KMT
3. Gas particles have no
attractive forces between them.
(not 100% true!)
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Gases: KMT
4. Collisions are perfectly “elastic”
no energy lost
during collisions
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Gas
Mostly Empty SpaceCompare volumes in liters of:1 mole water vapor (gas)
vs.1 mole liquid water
Gas is >1000 times volume of liquid
22.4 L
0.018 L
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Gas Speed
Speed of O2 at 20 oC is
~1660 km/hr. WOW !!!
Why don’t you smell
perfume as soon as
someone enters a room?
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What keeps the walls of an
inflated balloon pushed out?
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Gas Pressure
Pressure = force /area
Gas molecules exert
pressure on the
walls of a container
due to collisions.
More molecules more pressure
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VacuumIf there are no gas
molecules, pressure is zero.
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What Will Happen?
plastic sheet
water
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Atmospheric Pressure
Collision of air molecules with
objects results in atm. pressure.
1.00 atm = ave. pressure at sea level
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Atmospheric PressureIs pressure higher or lower than
1 atm on top of Mt. Everest?
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Measuring Pressure
Vacuum
atm P760 mm Hg
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Measuring Pressure
1 atm = 760 mm Hg = 101.3 kPa
What is pressure in
atm. and kPa during
a hurricane if
P = 720 mm Hg?
(Table A)
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Gas Temperature
Molecules speed up
“Average kinetic energy”
(energy of motion) increases.
Temperature (K) increases
What happens when a gas
is heated?
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Kinetic Energy Distribution
low T (K)
high T (K)
NO!!!
kinetic energy
% m
ole
cu
les
100%
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Liquids
A “condensed” state of matter.
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Liquids
similarKinetic
Energy of
particles
Attractions
between
particlesvs
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Molecules in Liquid
in constant motion
not much affected by pressure
“touching”
held together by intermolecular
forces
can glide past each other (flow)
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Evaporation
Not
magic!
What happens to a glass of
water left overnight?
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Evaporation
kinetic energy
% m
ole
cule
s Energy to
break
intermolecular
forces
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EvaporationAfter some liquid evaporates, the
remaining liquid is cooler.
Why ?
The liquid warms again.
Why ?
Then more evaporates.
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Evaporation in
Closed ContainerVapor pressure:Pressure due to
evap. gas in closed
container.
open closedDepends on 2 things
Kinetic
Energy of
particles
Attractions
between
particlesvs
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“Dynamic Equilibrium”(closed container)
Liquid Vapor (gas)
At equilibrium:
rate evap. = rate cond.
evaporation
condensation
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Vapor Pressure
As T increases, vapor
pressure increases
(more KE)
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Table H: Vapor Pressure
VP depends only on:
substancetemperature
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Vapor PressureUsing Regents Table H:
What is VP of ethanol at 60oC?
At what T does VP of water
equal 50 kPa?
Which substance has greater
molecular attractions:
ethanol or water?
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Boiling Point (BP)
The temperature at which vapor
pressure equals external pressure.
“normal boiling point”
(BP at 1 atm.)
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Boiling
How do you know when
something is boiling?
What’s in the bubble?
What’s P in bubble?
Add heat energy to over-
come molecular attractions
(T doesn’t change!)
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What is Boiling Point of H2O:
in Endwell
where P = 1.0 atm?
in Denver
where P = 86 kPa?
on Mt. Everest
where P = 35 kPa?
Table H is also BP vs. Pressure!
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Boiling Point
Would it take longer or shorter
time to boil at egg in Denver
than in Endwell?
50
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Solids
Particles arranged in
regular, repeating
pattern called crystal
lattice.
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Comparison of K.E. to
Molecular Attractions
Gas: KE >> I.M. forces
Liquid: KE ~ I.M. forces
Solids: KE << I.M. forces
(only vibrations are possible)
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Melting
Solid Liquidmelting
freezing
Ionic compounds: high M.P.
NaCl: 801 oCNa+ Cl-
Molecular compounds: low M.P.
HCl: -112 oCHCl HCl
Break ionic bond
Break IM force
diamond graphite “bucky-ball”54
Allotropes Different forms of the same state
of an element or compound.
Example: carbon
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Allotropes
Other examples:
Sulfur
O2 and O3
Red &
white phosphorous
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Amorphous Solids
Solids with no crystal structure
Examples:
plastic & rubber
asphalt
glass
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solid
Phase Diagram for H2O
Triple point
Temperature (oC)
Pre
ssure
(atm
)
liquid vapor
1
Normal
M.P.
Normal
B.P.
0 100
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Sublimation Substance passes from
solid directly to vapor.
See phase diagram below
“Triple Point”. examples:
dry ice (CO2)
iodine (I2) (demo)
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Lab 12 Analysis
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CuCl2 + Fe Cu + FeCl2vs.
3CuCl2 + 2Fe 3Cu + 2FeCl3DATA TABLE
Mass empty dry beaker_________
Mass iron nails (before rxn)______
Mass iron nails (after rxn)_______
Mass beaker & dry product______
Warm-up
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What is an “intermolecular force”?
List the three types of IM forces
Warm-up
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List the three types of
molecular attractions.
What causes the “dispersion
force”? Which molecules have
this force?
Warm-up
63
Predict the shape of PCl3.
Is it polar?
What forces hold molecules of PCl3together?
What are the 4 assumptions of KMT?
Warm-up
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Predict the shape of SCl2. Is it polar?
What forces hold molecules of SCl2together in the liquid state?
What is meant by
“kinetic energy distribution”?
What is pressure?
What is vapor pressure?
What is VP of H2O at 80oC? At 100oC?
Warm-up
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Predict the shape of SCl2.Is it polar?
What forces hold molecules of SCl2together in the liquid state?
What is pressure?
Use KMT to explain why a
balloon gets smaller when cold.
Warm-up
66
What is “STP” ?
What molecular attractions hold ammonia
molecules (NH3) together?
What temp. will water boil at
if P = 620 mm Hg?
How can liquid water in underground
geysers be hotter than 100oC?
What is meant by “kinetic energy
distribution”?
