Transcript Term Test 1 Click Here      This presentation is completely interactive In order for this presentation to work you MUST follow the indicated tabs on.

Term Test 1
Click Here





This presentation is completely interactive
In order for this presentation to work you MUST
follow the indicated tabs on each slide
Answer the question on a separate piece of paper
and compare with the slides
This presentations purpose is to try and find what
you haven’t understood or what you haven’t
attempted
Follow it properly and you will succeed!
Next Slide
Phases and Phases Diagrams
When dealing with matter, Chemists have noticed that certain
substances at certain pressures and temperatures tend to
change in appearance and property. These changes are called
Phase Changes and usually consists of molecules breaking or
making bonds with its self or other molecules. These bonds can
be covalent bonds, ionic bonds, or even intermolecular forces.
Next Slide
Phases and Phases Diagrams
Here you see the FREEZING of
water when exposed to
temperatures around -40ᵒC. This
shows a substance changing
from LIQUID to SOLID. The
substance is loosing heat and
releasing pressure, thus
EXOTHERMIC.
Note: Helium-3 and Helium has
a negative enthalpy of fusion.
Thus, at certain pressures, heat
must be added in order to
freeze.
Next Slide
Phases and Phases Diagrams
Here you see the FUSION or MELTING of metal when exposed to
concentrated solar heat. This shows a substance changing from SOLID
to LIQUID. The substance is gaining heat and gaining pressure, thus
ENDOTHERMIC.
Next Slide
Phases and Phases Diagrams
Here you see the
CONDENSATION of warm humid
air when in contact with the cold
icy surface. This shows a
substance changing from GAS to
LIQUID.
Next Slide
Phases and Phases Diagrams
Here you see the EVAPORATION of liquid as the pressure of the system
decreases. It seems as if the pressure is increasing, but once the valve
is released, the pressure decreases changing the LIQUID to a GAS.
This process is endothermic because it takes energy to overcome the
intermolecular forces of the liquid.
Next Slide
Phases and Phases Diagrams
Here you see the SUBLIMATION of solid iodine when combined with
aqueous zinc. This reaction can also occur if iodine is heated. Another
popular sublimation reaction is dry ice, which causes SOLID carbon
dioxide to form carbon dioxide GAS. This process is endothermic
because it takes energy to overcome the intermolecular forces of the
solid.
Next Slide
Phases and Phases Diagrams
Here you see the
accumulation of snow.
Snow is formed in subfreezing air which
allows water vapour to
change directly to ice.
This is an example of
DEPOSITION
involving a substance
changing from a GAS
to SOLID.
Next Slide
Phases and Phases Diagrams
•
•
Gas particles are widely separated from one another and are not
strongly intermolecularly bonded to the same degree as liquids
or solids.
Solids are usually arranged in regular, repeating patterns. These
types of solids are referred to as Crystals. A diamond is an
example of a solid who consists of one crystal, thus one regular,
repeating pattern.
Next Slide
Phases and Phases Diagrams
QUESTION 1
A substance that contains regular, repeating patterns undergoes a phase
change. This new phase exhibits random movement and large
intermolecular separations. What phase change has occurred? Is this an
endothermic process?
Answer
Phases and Phases Diagrams
QUESTION 1 ANSWER
This phase change is SUBLIMATION involving the change of a SOLID to
a GAS. Because it requires energy to distort a solid to a gas, this process
is ENDOTHERMIC.
SUBLIMATION
TRUE
Next
Question
Next
Section
Phases and Phases Diagrams
QUESTION 2
An extensive understanding of intermolecular forces is essential to
understand phase changes. If these essential forces didn’t occur, what
would all substances behave as?
Answer
Phases and Phases Diagrams
QUESTION 2 ANSWER
If intermolecular forces didn’t occur, molecules would behave like
particles that have no ability to interact. Particles that lack the ability to
attract electrons to itself. Thus particles with no electronegativity.
Therefore all particles would behave as ideal gases.
IDEAL/NOBLE GASES
Next
Question
Next
Section
Phases and Phases Diagrams
QUESTION 3
In order, list the following phase changes:
1)
Gas to Liquid
2)
Liquid to Solid
3)
Solid to Gas
4)
Gas to Solid
5)
Liquid to Gas
6)
Solid to Liquid
Answer
Phases and Phases Diagrams
QUESTION 3 ANSWER
1)
2)
3)
4)
5)
6)
Condensation
Freezing
Sublimation
Deposition
Vaporization
Fusion
Next
Question
Next
Section
Phases and Phases Diagrams
QUESTION 4
Phase Changes are due to what external forces?
Answer
Phases and Phases Diagrams
QUESTION 4 ANSWER
Temperature and Pressure
Next
Section
Phases and Phases Diagrams
A PHASE DIAGRAM is a
representation of a substances
phases at all possible pressures
and temperatures. The y-axis is
the PRESSURE of the
substance while the x-axis is the
TEMPERATURE of the
substance.
Next Slide
Phases and Phases Diagrams
A PHASE DIAGRAM has three distinct lines:
•
S-L line, usually a slightly positive slope, deals with the temperatures
and pressures that allow a SOLID ↔ LIQUID equilibrium. In water, the
S-L line is negative.
•
L-G line deals with the temperatures and pressures that allow a
LIQUID ↔ GAS equilibrium. At the end of the L-G line exists a
CRITCAL point in which after this point, transitions between gas and
liquid aren’t noticeable.
•
S-G line deals with the temperatures and pressures that allow a
SOLID ↔ GAS equilibrium. This line eventually reaches an end. This
point is referred to as absolute zero, -273.15ᵒC.
•
At the triple point, all three phases are in a stable equilibrium.
Next Slide
Phases and Phases Diagrams
When a substances
temperature and pressure are
high enough, a special fluid is
created. This fluid is called
SUPERCRITICAL FLUID and
shows no distinction when a
substance changes from gas to
liquid or liquid to solid. In this
video you see the transition of
Benzene as it decrease
temperature above the
supercritical point
Next Slide
Phases and Phases Diagrams
QUESTION 5
Given the following Phase Diagram,
what does A, B and C represent?
Answer
Phases and Phases Diagrams
QUESTION 5 ANSWER
A) Gas
B) Liquid
C) Solid
Next
Question
Next
Section
Phases and Phases Diagrams
QUESTION 6
Density is the relationship of mass over volume. When a vertical line is
drawn on a phase diagram such that 2 lines come in contact with this
vertical line, the phase in which the top of the line touches is considered
to be more Dense than all other substances. A phase diagram with a
positive S-L line is being studied. Which substance is more dense, Liquid
or Solid?
Answer
Phases and Phases Diagrams
QUESTION 6 ANSWER
Because the Solid phase is the phase in which the top of the line is in
contact with, Solids will be more Dense than liquids.
NOTE: to remember this relationship think of water! We all know that ice
floats on liquid water, in other words, liquid is heavier (more dense) than
the ice. Water has a negative S-L line. Thus any phase diagram with a
negative S-L line (like water) causes liquids to be more dense than solids
and vice versa for a phase diagram with a positive S-L line.
Next
Question
Next
Section
Phases and Phases Diagrams
QUESTION 7
Given the following Phase Diagram,
what phase change(s) will occur
when the substance decreases in
temperature from 50ᵒC to -105ᵒC at a
constant pressure of 30atm?
Answer
Phases and Phases Diagrams
QUESTION 7 ANSWER
The substance will change from Gas to
To Liquid (Condensation) and from Liquid
To Solid (Freezing).
CONDENSATION
FREEZING
Next
Question
Next
Section
Phases and Phases Diagrams
QUESTION 8
Given the following phase diagram,
what phase(s) exist at 6 atm and 15ᵒC.
Answer
Phases and Phases Diagrams
QUESTION 8 ANSWER
This is the Triple Point, thus a
solid, liquid and gas form of the
substance coexists in stable
conditions.
Next
Question
Next
Section
Phases and Phases Diagrams
QUESTION 9
A particular substances phase diagram has a negatively sloped S-L
line. Given that a substance increases greatly in pressure before
and below the triple point, what phase(s) could occur?
Answer
Phases and Phases Diagrams
QUESTION 9 ANSWER
DEPOSITION and possibly FUSION
Next
Section
Liquids and Liquid Properties
A phase in particular that has many properties is liquid. Some
of these properties are VAPOR PRESSURE, NORMAL
BOILING POINT, SURFACE TENSION and VISOCISTY. In
addition to liquids properties, we also achieve an equation
(Clausius - Clapeyron) when dealing with the Liquid to Gas Line
on Phase Diagrams.
Next Slide
Liquids and Liquid Properties
When in a closed container, we can
calculate the pressure of vapour
that forms above the liquid. This
pressure is greater when
intermolecular attractions are lower.
This is because at low
intermolecular forces, the ease for
a substance to change into a gas is
higher than when the substance
has high intermolecular forces, thus
because it is easier, the substance
readily changes into a gas and thus
the pressure of the gas above the
liquid is greater!
Next Slide
Liquids and Liquid Properties
The Normal boiling point is the
temperature at which the vapour
pressure of the liquid equals 1
atm. The pressure is simply the
pressure of the surroundings,
since it is normal for us to have a
pressure of 1 atm, the normal
boiling point is calculated at 1
atm. When intermolecular forces
are high, the normal boiling point
is high because it takes more
energy to aggregate the
molecules. In the video you see
steel boiling at approximately
1616ᵒC!
Next Slide
Liquids and Liquid Properties
Surface Tension is a property of a
liquid that allows the surface of
the liquid to resist an external
force. In the picture, the liquid is
resisting the gravitational force of
the water spider. This force can
also be represented as a quantity
of energy, and thus surface
tension is also the energy
required to increase the surface
area of a liquid. Thus, if a liquid
have higher intermolecular forces,
the liquids surface tension is
higher because if takes more
energy to increase its surface
area!
Next Slide
Liquids and Liquid Properties
Viscosity is the measure of the
resistance of a fluid. In the video,
the substance on the far left has
the highest viscosity, the
substance on the far right has the
lowest viscosity. So, in general
terms, higher viscosity means a
liquids rate is slower and a lower
viscosity means a liquids rate is
faster. Thus the measure of
viscosity and the rate of a liquid is
inversely proportional. Finally, as
intermolecular forces increase,
viscosity also increases.
Next Slide
Liquids and Liquid Properties
The Clausius-Clapeyron Equation deals with the phase transition between
two phases of matter. We know that for every phase, there is an associated
Pressure and Temperature for that phase. Thus given two phases, we can
use this information with the Clausius-Clapeyron Equation to determine
unknowns that we care to find. It is important to note that when dealing with
the Clausius-Clapeyron Equation, some information may be hidden. If in a
question you are given that the normal boiling point of a substance is 78ᵒC,
you are also given that the pressure for that substance is 1atm, because the
definition of normal boiling point gives us this value!
Next Slide
Liquids and Liquid Properties
QUESTION 10
If the normal boiling point of water is 100.0ᵒC, determine an estimate
for this substances standard enthalpy of vaporization given that the
vapour pressure of water is 217.75atm at 373.99ᵒC.
Answer
Liquids and Liquid Properties
QUESTION 10 ANSWER
Water’s actual enthalpy of
vaporization is
40.68KJ/mol
Next
Question
Next
Section
Liquids and Liquid Properties
QUESTION 11
Yes/No
Do Liquids have more kinetic energy than solids?
Answer
Liquids and Liquid Properties
QUESTION 11 ANSWER
Yes, liquids have more kinetic energy than solids because liquids are
more readily able to move and kinetic energy is the energy of
movement.
Next
Question
Next
Section
Liquids and Liquid Properties
QUESTION 12
When a substance is in the presence of high temperature and low
pressure. Which phase is most stable?
When a substance is in the presence of low temperature and high
pressure. Which phase is most stable?
Answer
Liquids and Liquid Properties
QUESTION 12 ANSWER
A) Gas
B) Solid
Next
Question
Next
Section
Liquids and Liquid Properties
QUESTION 13
True/False
A solid block of ice is dropped into a cup full of a specific liquid that
causes the block to drop to the bottom extremely slow. The liquid
doesn’t exhibit much movement. The property of liquid exhibited is
surface tension?
Answer
Liquids and Liquid Properties
QUESTION 13 ANSWER
FALSE
The property is viscosity, and this liquid has
a high viscosity.
Next
Section
Intermolecular Forces
Intermolecular Forces are forces of attraction or repulsion
which act between NEIGHBORING PARTICLES. Not the same
molecule! These forces have many different levels and types.
Such types are Dipole-Dipole Forces, London Dispersion
Forces, and even Hydrogen Bonding.
Next Slide
Intermolecular Forces
Dipole-Dipole Forces are the
intermolecular forces that deal with force
vectors and electronegativty differences.
The molecule on the left is highly
symmetrical, but, the electronegativity
difference between C-F is much different
between C-H. The electronegativity
difference is higher. Thus, this molecule,
is highly polar, due to the dipole formed
on the C-F bond. When looking for
dipole-dipole forces, first check if the
molecule is symmetrical, then check if
the atoms situated on the molecule are
the same. If any of the two points aren’t
true, the molecules most likely has a
dipole moment.
Next Slide
Intermolecular Forces
Van der Waals Forces or London
Dispersion Forces, are the
intermolecular forces due to
electrons. Because electrons are
always moving, it is possible that
more electrons at a given moment
could be situated more on one
side of a molecule. This
positioning of electrons causes
the molecule to have a partial
charge which attracts other
molecules. From the video, you
see that these electrons are
sometimes on the same end of
the molecule.
Next Slide
Intermolecular Forces
When discussing Van der Waals Forces, it is often the case that the
POLARIZABILITY of a molecule is important. The polarizability is the measure
of the change in a molecules' electron distribution in response to an applied
electric field or other molecule charges. The larger the molecule, the larger the
polarizability because a molecule with more mass must have more electrons.
All molecules (except for H⁺ and He²⁺) have Van der Waals Forces because all
molecules have electrons.
FACT
The Gecko lizard has the
ability to walk on glass. This
ability is due to the London
Dispersion Forces between
the Geckos Lipid enriched
footpads and the glass!
Next Slide
Intermolecular Forces
The Final Intermolecular force is Hydrogen
Bonding. Hydrogen Bonding are the forces
of attraction between molecules involving
H-N , H-F and H-O bonds. The hydrogen
bond that is covalently bonded to N, F and
O is also attracted to the negative lone pair
of other molecules. Hydrogen Bonding also
exists in INTRAMOLECULAR forces
(forces within a molecule) when lone pairs
exists on that molecule. Hydrogen is the
STRONGEST of intermolecular forces. In
the picture on the left, you see hydrogen
bonding between two molecules. The
dashed lines indicate such bonding. Other
examples of hydrogen bonding is in DNA
(between nitrogenous bases) and water.
Next Slide
Intermolecular Forces
•
To sum up:
HYDROGEN BONDING are the strongest intermolecular forces dealing
with hydrogen covalently bonded to O, F and N and negative lone pairs
situtated on other or the same molecule.
•
DIPOLE-DIPOLE FORCES are the second highest intermolecular
forces and deals with a net charge “dipole” on a molecule due to
symmetry and different atoms situated on the molecule.
•
VAN DER WAALS FORCES are the weakest intermolecular forces that
deal with the movement of electrons and the possibility of more
electrons being on one side of a molecule.
Next Slide
Intermolecular Forces
QUESTION 14
Given the following three molecules, order the molecules from least
to greatest according vapor pressure. H₂ , H₂O and H₂O₂ .
Answer
Intermolecular Forces
QUESTION 14 ANSWER
Strongest
intermolecular Forces
- Hydrogen bonding
- Dipole-Dipole forces
- Van der Waals
Next
Question
Weakest
intermolecular Forces
- Hydrogen bonding
- Van der Waals
- Dipole-Dipole forces
- Van der Waals
H₂ > H₂O > H₂O₂ for Vapour Pressure!!!
Next
Section
Intermolecular Forces
QUESTION 15
A bent molecule that has different atoms situated on the ends is
being studied. What intermolecular forces could be present in this
atom?
Answer
Intermolecular Forces
QUESTION 15 ANSWER
Dipole – Dipole Forces , London Dispersion Forces, and hydrogen
bonding.
Next
Question
Next
Section
Intermolecular Forces
QUESTION 16
An extremely large molecule has very high intermolecular forces.
What intermolecular forces are the cause assuming the molecule is
non-polar?
Answer
Intermolecular Forces
QUESTION 16 ANSWER
Because the molecule is large, this implies a large amount of
electrons, since the molecule is non-polar, there are no dipole-dipole
moments and most likely no hydrogen bonding. Thus we can
conclude this high intermolecular force due to Van Der Waals
Forces.
Next
Section
Heating Curves
A heating curve is a graphical
representation of the temperature
variation as heat is added to a
molecule. It also gives us two
important values:
• Enthalpy of Fusion
• Enthalpy of Vaporization
This Section is not on exam!
Next Slide
Heating Curves
QUESTION 17
Determine the enthalpy of vaporization from the following heating curve.
Answer
Heating Curves
QUESTION 17 ANSWER
The enthalpy of vaporization is approximately 500 Calorie/mol and occurs
at approximately 100ᵒC
Next
Section
Introduction to Solids
Solids are characterized by there structural rigidity and there resistance
to changes of shape or volume. It is classified as CRYSTALLINE or
AMORPHOUS. Crystalline solids can be either ionic, network covalent,
molecular or metallic. These structures all exhibit different properties.
Next Slide
Introduction to Solids
Amorphous Solids are identified by their
irregular packing and melt over temperature
range. Examples of Amorphous solids
include Candles, Glass and Cotton Candy.
Next Slide
Introduction to Solids
In Chemistry 123, we focus more on
CRYSTALLINE structures because there regulated
structure can be related among molecules with
similar properties. Crystalline structures are solids
that have regulated patterns. These structures tend
to melt at a specific temperature, unlike amorphous
solids. The CRYSTAL LATTICE of a structure,
deals with the intersections of three sets of parallel
planes. When dealing with three parallel
intersections you achieve 3 dimensional space, and
thus a crystal lattice will deal with the arrangement
of atoms in 3 dimensional space. A special lattice
that deals with all parallel planes at a 90 degree
angle is the Cubic Lattice.
Next Slide
Introduction to Solids
Because we are dealing with structures
that have the same pattern throughout
the molecule, it is much better to
compare a small portion that
represents the entire crystal lattice.
This portion will be the building block of
the crystal lattice. The UNIT CELL,
shown on the right by the shaded cube,
is the smallest portion of a crystal
lattice that can be successfully related
among other crystal lattice unit cells. It
can also be used to make a crystal
lattice by stacking identical unit cells
together. There are many different
types of unit cells due to the vast
differences in crystal lattices. This will
be discussed in more detail later in the
presentation.
Next Slide
Introduction to Solids
IONIC Crystalline Solids have the following properties.
• Cations (+) and Anions (-)
• Strong Ionic bonds
• Electrostatics Attractions
• Hard
• Moderate to high boiling points
• Nonconductors as solids, but good electric
conductors as liquids.
• Soluble in Polar Solvents like water.
*** A good way to remember Ionic Properties is to
think of a the popular substance Salt! Salt is
composed of Na ions and Cl Ions. Salt forms
strong ionic bonds. Salt is a hard substance, and
has a moderate boiling point (800ᵒC). Salt does
not conduct electricity as solid, but when placed
in polar solvent (water) conduct electricity.
Next Slide
Introduction to Solids
NETWORK COVALENT Crystalline Solids have the
following properties.
• Formed by Covalent bonds between Atoms.
• Extremely Hard substances.
• Melt at very high temperatures
• Most are non-conductors of electricity.
*** A good way to remember Network
Covalent Properties is to think of
Diamonds. Diamonds are the hardest
structure known to man kind and melt
at really high temperatures and
pressures. Diamonds do no conduct
electricity and are formed from covalent
bonds between the single Carbon
Atom.
Next Slide
AT 900 degrees, the diamond renders undamaged!
Introduction to Solids
MOLECULAR Crystalline Solids have the
following properties.
• Held together by intermolecular forces,
when compared to other types of solids, are
extremely weak.
• These substances are soft with extremely
low melting points.
• They are also soluble in non-polar solvents.
*** A good way to remember Molecular
Properties is to think of Ice. Ice can be
broken with minimal force, ice melts to
liquid water at a low temperature. Water
experiences intermolecular forces
(hydrogen bonding).
Next Slide
Introduction to Solids
An important fact about METALLIC solids is that
they consist of cations that are stationary with
delocalized electrons that move around the solid
as shown in the picture on the right. Because this
solid isn’t completely still, as are other solids, it
gets different properties. First off, these Solids are
extremely malleable. Second, because of the
“sea of electrons” these solids conduct electricity
really well. There melting points differ from low to
very high and they can also range from soft to
very hard.
*** A good way to remember Metallic Solids is by
Copper. Copper is found in wires because of its
high electric conducting abilities. It also is able to
form these wires because it is soft and easy to
bend. Finally, copper melts at 1083 degrees, a
moderate temperature.
Next Slide
Introduction to Solids
QUESTION 18
A substance is found to melt at 3200 degrees Celsius and is extremely
hard. What type of Crystalline Solid is this substance most likely?
Answer
Introduction to Solids
QUESTION 18 ANSWER
Because the substance exhibits an extremely high temperature and is
very hard, We have two choices, Network Covalent and Metallic. Both
substances have structures with such properties. Since Metallic structures
also deals with substances that are low in melting point and soft,
probability would tell us that the substance is MOST LIKELY to be
NETWORK COVALENT though a Metallic solid is a possibility.
Next
Question
Next
Section
Introduction to Solids
QUESTION 19
The water that we drink from the tap has a small percentage of dissolved
solids that conduct electricity. These Solids should be classified as what
Crystalline Structure?
Answer
Introduction to Solids
QUESTION 19 ANSWER
Because the substance is soluble in water (a polar substance) as well as
having the ability to conduct electricity. We can assume the Solid must be
IONIC.
Next
Question
Next
Section
Introduction to Solids
QUESTION 20
A mysterious substance when placed in heat melts at 500 degrees
Celsius. At the same pressure it is also found the substance melts at 550
degrees Celsius. What type of Crystalline substance is this substance?
Answer
Introduction to Solids
QUESTION 20 ANSWER
Trick Question!!!
This is not a Crystalline substance because the range of melting points is
to large. Thus it must be an AMORPHOUS solid.
Next
Question
Next
Section
Introduction to Solids
QUESTION 21
A special Crystal Lattice has parallel plane intersections at exactly 90
degrees. What type of Crystal Lattice is this? What is the smallest building
block of any Crystal Lattice?
Answer
Introduction to Solids
QUESTION 21 ANSWER
This Crystal Lattice must be a CUBIC Crystal Lattice because of these
angles.
The UNIT CELL is the smallest building block of Crystal Lattices.
Next
Section
Cubic Packing Arrangements
Because Crystal Lattices are so different, we have specific arrangements
of atoms in a Lattice. The unit cell is commonly discussed when dealing
with packing arrangements. There are three types of Cubic packing
arrangements:
• Simple Cubic Packing
• Body Centered Cubic
• Face-Centered Cubic
Next Slide
Cubic Packing Arrangements
SIMPLE CUBIC PACKING is formed
from a sheet of atoms connected at the
furthest extremity of the Sphere. In other
words, if line segments are taken from
the center of the Sphere, perfect cubes
will form because all Spheres are parallel
to each other. The unit cell has 1 atom
from the combination of an 1/8 of an
atom multiplied by 8 atoms. Another
important point about simple cubic
packing is the number of contact points
with other spheres (coordination
number). This particular type of packing
has 6 contact points, thus the
COORDINATION number is 6. Finally,
the SIDE LENGTH (a) of a Simple Cubic
Packing is 2R (a=2R)
Next Slide
Cubic Packing Arrangements
BODY-CENTRED CUBIC PACKING is
formed from multiple sheets of atoms
placed on top of each other except each
sheet is set in the dimples of the
underlying sheet and pressed down to
separate atoms slightly. This allows for a
unit cell to have a complete atom as well
as 1/8 multiplied by 8 atoms, thus a total
of 2 atoms. The center atom touch 8
other atoms, thus the COORDINATION
number is 8. Finally, the SIDE LENGTH
of the unit cell is equivalent to 4R/√3
(approximately 2.3R).
Next Slide
Cubic Packing Arrangements
FACE-CENTRED CUBIC PACKING
consists of 8 1/8 corner atoms, and 6 ½
face atoms. Thus the total number of
atoms in Face-Centred Cubic packing is
4. The SIDE LENGTH for Face-Centred
Cubic is 2R√2. It is important to note that
no full atom is in the centre. Each atom
touches 12 surrounding atoms, thus the
COORDINATION number is 12. FaceCentred Cubic is the most dense of
packing because it has the most atoms
per volume. It is often considered
Closest-Cubic Packing because of this
property.
Next Slide
Cubic Packing Arrangements
When dealing with the three types of cubic packing's we achieve a formula
that determines how efficient the packing arrangement is. In other words,
which packing arrangements cover most of the volume by atoms leaving the
least amount of empty space. The equation is derived from the number of
atoms in each packing arrangement, the volume of a sphere, and the volume
of the cube in which each packing arrangement is enclosed in.
Next Slide
Cubic Packing Arrangements
QUESTION 22
Determine the packing efficiency of Body-Centred Cubic Packing.
Answer
Cubic Packing Arrangements
QUESTION 22 ANSWER
Next
Question
Next
Section
Cubic Packing Arrangements
QUESTION 23
Determine the packing efficiency of Face-Centred Cubic Packing.
Answer
Cubic Packing Arrangements
QUESTION 23 ANSWER
Next
Question
Next
Section
Cubic Packing Arrangements
QUESTION 24
This type of packing arrangement deals with identical spheres placed
directly on the face other atoms. (i.e. its like placing a sheet of atoms
directly on top of a sheet of atoms).
Answer
Cubic Packing Arrangements
QUESTION 24 ANSWER
This packing arrangement is Simple Cubic Packing
Next
Question
Next
Section
Cubic Packing Arrangements
QUESTION 25
Answer the following questions:
What is the most efficient packing arrangement?
What is the least efficient packing arrangement?
FCC has how many atoms per unit cell?
(True or False) BCC has a radius of 4R/√3
(True or False) CCP has a coordination number of 8
What is the coordination number of SCP?
(True or False) SCP has the smallest cubic volume when dealing with the
same atom in all types of arrangements?
Answer
Cubic Packing Arrangements
QUESTION 25 ANSWER
1)
2)
3)
4)
5)
6)
7)
FCP
SCP
4
False (Side Length)
False (12)
6
True
Next
Section
Closest-Packed Structures
Closest-Packed Structures, deals
with sheets of atoms laying on top
of each other in an efficient manner.
Hexagonal Closest-Packing deals
with a repetition of two sheets. The
first sheet lays underneath the
second but then the third lays on
top the second in a way that makes
it symmetrical to the first sheet.
This type of arrangement is called
ABAB… closest packing. FaceCentred Packing is similar to this
except it is a repetition of 3 sheets,
thus ABCABC… Closest Packing.
Next Slide
Closest Packed Structures
QUESTION 26
ABAB…Closest Packing is also called ________________ and deals with
____ sheets laying on top of each other in a _____________ pattern.
Answer
Closest Packed Structures
QUESTION 26 ANSWER
ABAB…Closest Packing is also called Hexagonal Closest Packing and
deals with two sheets laying on top of each other in a repeating pattern.
Next
Question
Next
Section
Closest Packed Structures
QUESTION 27
ABCABC…Closest Packing is also called ________________ and deals
with ____ sheets laying on top of each other in a _____________ pattern.
Answer
Closest Packed Structures
QUESTION 27 ANSWER
ABCABC…Closest Packing is also called Closest-Cubic Packing and
deals with three sheets laying on top of each other in a repeating pattern.
Next
Section
Density of a Crystalline Solid
We all know that Density is the amount of mass in a specified volume. When
we talk about Crystalline Solids, we deal with mass (Atoms) and volume
(cube), thus a density for each packing arrangement can be calculated. The
following equation is derived from the original density equation.
Next Slide
Ionic Solids and Interstitial Sites
So far, we have dealt with identical atoms
when talking about packing arrangements.
We will now discuss the types of Crystal
Lattices with different atoms. These different
atoms are placed at INTERSTITIAL SITES
on a packing arrangement, otherwise known
as holes situated between the larger atoms.
A common example is NaCl. We all know
that Na is much smaller than Cl, so a normal
packing arrangement can’t occur. We will
discuss three types of Interstitial Sites and
will see these sites in specific examples.
Because we have different Radius sizes, we
will also discuss Radius Ratio’s of ionic
solids between the anion and cation.
Next Slide
Ionic Solids and Interstitial Sites
When you are dealing with a
single sheet of atoms, you
often achieve TRIGONAL
HOLES. These holes are in the
middle of what seems to be a
triangle. Recall coordination
number which is the number of
spheres (atoms) around a
particular atom. The trigonal
hole would have a coordination
number of 3.
Next Slide
Ionic Solids and Interstitial Sites
TETRAHEDRAL HOLES are
the holes that are formed from
a tetrahedron. The tiny space
between the 4 atoms is found
in FCC arrangements. Because
of the 4 atoms, the tiny atoms
has a coordination number of
4.
Next Slide
Ionic Solids and Interstitial Sites
OCTAHEDRAL HOLES are
the holes that are formed from
a octahedron. The tiny space
between the 6 atoms is only
found in FCC arrangements.
Because of the 6 atoms, the
tiny atoms has a coordination
number of 6.
Next Slide
Ionic Solids and Interstitial Sites
The following are Hole radius sizes for each of the interstitial holes. The
derivation for how these values are obtained are found in the course
notes in section 9. The derivation was chosen not to be shown because
these values can be found in your data sheet, thus just a understanding
of which value for which hole is important.
TETRAHEDRAL
.225R
OCTAHEDRAL
.414R
CUBIC
.732R
*** Cubic holes come from simple cubic packing, involving a tiny atom
in the center. The coordination number is 8 because the center atom is
in contact with 8 other atoms. Once this structure it is formed, it is
classified as BCC.
Next Slide
Ionic Solids and Interstitial Sites
When discussing Radius Ratios we must have some sort of reference
for which radius we are talking about. For simplicity we will only discuss
Ionic Crystals because we can distinctly reference the anion (R⁻) and
the cation (R⁺). We can use radius ratios to determine what type of
hole is present in the crystalline structure. Here are the following ratios:
.225
< R⁺/ R⁻ < .414 Tetrahedral Site
.414
< R⁺/ R⁻ < .732 Octahedral Site
.732
< R⁺/ R⁻
Cubic Site
*** Tips, if you are good at picturing 3D structures you will know that the
atom in the tetrahedral Site is the smallest, than comes the atom in the
Octahedral Site and finally the atom in the Cubic Site. All you need to
remember is what is smallest and what is largest and than use your
data sheet for the values. Ratio Solved!
Next Slide
Ionic Solids and Interstitial Sites
Sodium Chloride Structures are FCC Lattices which occupy 100% of
the octahedral holes.
Next Slide
Ionic Solids and Interstitial Sites
Cesium Chloride Structure are SC lattice’s with cesium ions occupying
Cubic Holes.
NO VIDEO
Next Slide
Ionic Solids and Interstitial Sites
Zinc Blende Structure are FCC lattice’s where zinc (2+) ions occupy
half of the tetrahedral holes.
Next Slide
Ionic Solids and Interstitial Sites
Fluorite Structure are FCC lattice’s where fluorine ions occupy all
tetrahedral holes.
Next Slide
Ionic Solids and Interstitial Sites
QUESTION 28
Which specific ionic structures exhibits only half of the tetrahedral holes
occupied?
Answer
Ionic Solids and Interstitial Sites
QUESTION 28 ANSWER
Zinc Blende
Answer
Ionic Solids and Interstitial Sites
QUESTION 29
The radius of a cation and an anion were measured. What type of
interstitial holes are present in the structure if the radius of the anion was
4.5 units and the radius of the cation was 1.3 units?
Answer
Ionic Solids and Interstitial Sites
QUESTION 29 ANSWER
The ratio is .288, thus this falls between .225 and .414, thus these are
TETRAHEDRAL SITES
Answer
Ionic Solids and Interstitial Sites
QUESTION 30
Lets say that you have two sheet of atoms separated from each other.
When they join, they form Cubic holes. What type of lattice was the
structure before and after the combination?
Answer
Ionic Solids and Interstitial Sites
QUESTION 30 ANSWER
Before the combination, the sheet of atoms would be considered a SC
structure, but after the combination, the stacked sheets of atoms are BCC.
Answer
Ionic Solids and Interstitial Sites
QUESTION 31
Answer the following Questions
What is the coordination number of tetrahedral holes?
What is the coordination number of cubic holes?
What is the coordination number of octahedral holes?
What is the coordination number of trigonal holes?
Answer
Ionic Solids and Interstitial Sites
QUESTION 31 ANSWER
Answer the following Questions
1)
2)
3)
4)
4
8
6
3
Answer
The Born-Haber Cycle
Next Slide