State of Matter
Solids
There are four types of solids
1. Molecular Solids – formed from molecules
2. Covalent network solids – formed from atoms
3. Ionic solids – formed from ions
4. Metallic solids- formed from metal atoms
There physical properties relate closely to the
intermolecular forces that hold them together.
Crystal
Type
Forces
holding
units
together
Examples
Melting
Point
Hardness
Electrical
Conductivity
Ionic
Electrostati
c Attraction
LiF
NaCl
High
Hard,
Brittle
Only molten
(liquefied)
aqueous
solution
Covalent
(Network)
Shared
Electrons
C
(diamond)
SiC
Si02
(quarts)
Very High
Very Hard
None
Molecular
H-bonding,
dipoledipole,
dispersion
forces
H20
HCl
He
Low
Soft
None
Water only
Metallic
Electrostati
c attraction
between
cations and
a sea of
Na
Fe
Cu
Etc.
Variable
Malleable
Ductile
High
Able to be
hammered
Crystalline Solids
• Arranged in fixed geometric patterns or
lattices.
• Examples:
– Ice and sodium chloride
– They have an ordered arrangement of units
maximizing the space they occupy , and are
practically incompressible
Crystalline Solids
Crystalline solid: is a wellordered, definite
arrangements of molecules, atoms or ions.
• Crystals have an ordered structure, which repeats
itself.
• The smallest repeating unit in a crystal is a unit
cell.
• The unit cell is the smallest unit. It has the same
symmetry as the entire crystal.
• Threedimensional packing of unit cells produces
the crystal lattice.
Metallic Crystals
• Composed of positively charged ions in a field
of freely moving electrons
• More than 90% of naturally occurring and
artificially prepared solids are crystalline.
Minerals, sand, clay, limestone, metals, alloys,
carbon (diamond and graphite), salts ( NaCl,
KCl etc.) , all have crystalline structures.
Amorphous Solids
• Have a random orientation of particles
– Examples of amorphous solids are glass and
plastic
– They are considered super-cooled liquids in which
the molecules are arranged in a random manner
similar to the liquid state
Difference between crystals and
amorphous solids
• Another difference between solids in a crystalline
versus amorphous state is their behavior when they
are heated
• Crystals become liquids at a specific temperature, Tm
(the melting point). At this temperature physical
properties of the crystalline solids change sharply.
• Amorphous solids soften gradually when they are
heated.
• There tends to be a relatively wide temperature range
for the melting point, a zone between the solid and the
liquid state where physical properties of the substance
change gradually.
Allotropes
• Two or more distinct physical forms of a
chemical element in the same physical state
• Allotropes arise because of differing
arrangements of an element’s atoms within its
molecules or crystals.
• Allotropes are in the same phase but have
vastly different chemical and physical
properties.
Allotropes
• One of the bestknown examples of allotropy is
carbon , which has multiple distinct allotropes
including graphite and diamond.
• Carbon atoms in diamond form a rigid, threedimensional structure, with each carbon atom
bonded to four other carbon atoms.
• In graphite the carbon atoms form stacks of
flat honeycomb layers with only weak
intermolecular forces between layers.
Allotropes
• Elements exhibiting allotropy include arsenic, antimony,
iron, oxygen, phosphorus, selenium, sulfur, and tin.
• C(s) 3 forms O(g) 2 forms
• Because of their different internal structures, allotropic
forms of an element may exhibit greatly differing values for
such physical properties as color, luster, density , hardness,
odor, and electrical and thermal conductivity.
• For example, diamond is extremely hard and does not
conduct electricity, while graphite is much softer and does
conduct electricity.
Allotropes
• Allotropes may also differ in chemical reactivity.
• Oxygen, another allotropic element, normally
exists as an odorless gas necessary for life, each
of whose molecules contains two atoms of
oxygen.
• Sometimes, however, it exists as ozone, a highly
reactive, poisonous gas with a sharp, pungent
odor, each of whose molecules contains three
atoms of oxygen.
Hydrated Crystals
• Hydrated crystal is a crystal that contains
water as part of its chemical formula and
structure. It may or may not absorb water
vapor from the atmosphere.
• CuSO4 . 5H2O Means water is added.
• The water is not really part of the compound
(you can remove them by heating the
crystals).
Anhydrous Crystal
• If the water of crystallization is removed from
blue crystals of copper (II) sulfate, a white
powder (anhydrous copper (II) sulfate) is
formed.
• The formula for anhydration of pentahydrate
copper (II) sulfate (CuSO4· 5H2O) is as follows:
• CuSO4·5H2O + heat → CuSO4 + 5H2O
Liquids
• Liquids and solids are often referred to as
condensed phases because the particles are
very close together.
• Liquids and gases are called fluids because
they can be made to flow, or move. In any
fluid, the molecules themselves are in
constant, random motion, colliding with each
other and with the walls of any container.
Cohesion
• Forces at work that hold the liquid molecules
together.
Evaporation
• Evaporation is all about the energy in individual
molecules, not about the average energy of a system.
The average energy can be low and the evaporation
still continues.
• You might be wondering how that can happen when
the temperature is low. It turns out that all liquids can
evaporate at room temperature and normal air
pressure.
• Evaporation happens when atoms or molecules
escape from the liquid and turn into a vapor.
• Not all of the molecules in a liquid actually have
the same energy.
Evaporation
• Ordinary evaporation is a surface
phenomenon some molecules have enough
kinetic energy to escape. If the container is
closed, an equilibrium is reached where an
equal number of molecules return to the
surface. The pressure of this equilibrium is
called the saturation vapor pressure.
Factors that Effect Evaporation
•
•
•
•
•
•
•
Concentration of substance
Concentration of substances in the air
Flow of air
Temperature of substance
Surface area
Pressure
Intermolecular forces
Evaporation vs. Boiling
• Ordinary evaporation is a surface phenomenon
since the vapor pressure is low and since the
pressure inside the liquid is equal to atmospheric
pressure plus the liquid pressure , bubbles of
water vapor cannot form.
• But at the boiling point, the saturated vapor
pressure is equal to atmospheric pressure,
bubbles form, and the vaporization becomes a
volume phenomena.
Vapor Pressure
• Vapor pressure increases with increasing temperature • At
100°C the vapor pressure of water is 760 torr (1 atm) or
equal to the atmospheric pressure on the liquid (in an open
container)
• • At this temperature, interior bubbles will not collapse and
the water boils
• • At high altitudes (i.e. up in the Mountains) the air
pressure is less than at sea level. Thus, water will boil at
• a lower temperature (the vapor pressure needed to
support a bubble is lower at high altitude). Therefore,
cooking times are longer for things that need to be boiled
(e.g. boiled eggs take longer to cook at high altitudes).
Gases
• Pressure: collision of gas molecules with wall
of container. (need to be able to convert to all
units of pressure)
• Temperature: related to average speed of gas
molecules. (only use Kelvin temperature in gas
law problems.)
• Standard temperature and pressure (STP) is
equal to 0 °C and 1 atm.
Behavior of Gases
• Gas laws describe how gases behave, but they
do not explain why gases behave the way they
do.
• The Kinetic Molecular Theory is a theory that
is used to explain the behavior of gases
Kinetic Molecular Theory
1) Gases contain particles that are in constant,
random, straight-line motion.
2) Gas particles collide with each other and with the
walls of the container. These collisions may result in
a transfer of energy among the particles, but there
is no loss of energy.
3) Gas particles are separated by relatively great
distance. Because of this, the volume occupied by
the particles themselves is negligible and need not
be accounted for.
4) Gas particles do not attract each other.
Relationship of Pressure and Number
of Gas Particles
• The greater the number of air particles, the
greater the pressure.
• Direct proportion
• For example, if you add more air to a bicycle
tire, the pressure is increased.
Relationship of Pressure and Volume
of a Gas
• If the molecules of a gas become more
concentrated and hit the walls of the
container more often the pressure increases,
• Volume and pressure are indirectly, or
inversely, related.
Relationship of Temperature and
Pressure of a Gas
• As temperature rises, the kinetic energy
increases.
• This increase is not due to an increase in the mass
of the particles, but rather to an increase in their
velocity.
• As temperature rises, the velocity of the particles
increases, causing them to hit the walls of their
container more often and with greater force.
• An increase in temperature causes the pressure
to increase (direct relationship)
Relationship of Temperature and
Volume of a Gas
• As temperature increases, the molecules push
harder on walls of the container.
• Thus volume and temperature are directly
related.
Combined Gas Law Equation
• The relationship among pressure,
temperature, and volume can be
mathematically represented by an equation
known as the combined gas law.
Ideal Versus Real Gases
• Gas particles do not attract each other
– When conditions become extreme, these small
forces become important.
– For example, water molecules in the atmosphere
attract each other when temperatures become
cold enough. The water molecules combine to
form snow or rain.
Ideal Versus Real Gases
• Gas particles do not occupy volume
– Although gas particles themselves occupy a small
volume of space under normal conditions, as
pressure increases the volume occupied by the
particles can no longer be ignored.
Ideal Gases
• A gas is said to be ideal if it behaves exactly as
predicted.
• Hydrogen and Helium are nearly ideal in
behavior.
• Gases are most ideal at low pressures and
high temperatures
The Gas Laws
• Boyle’s Law
• Charles’ Law
P1V1 = P2V2
V1 = V2
T1
T2
*Temperature must be converted to Kelvin
The Combined Gas Law
• Rather than having to remember each
individual law, you can memorize just one
formula, and based on the variables needed,
use those and get rid of what’s not needed by
using the combined gas law.
P1V1 = P2V2
T1
T2
Moles
• Dozen is a convenient word to describe 12 of
something.
• This enables you to count by a collective unit,
instead of by individual items.
• 1 dozen = 12 eggs
• 1 mole = 6.023 x 10 23 atoms
Moles
1 dozen = 12 donuts =
1 mole = 6.023 x 10 23 atoms = 22.4 L
*the only thing that differs between samples is
mass