Chemistry Module
Subject:
Chemistry/IPC
Grade Level:
9-12
TEKS:
112.42 IPC 1A, 2B-D, 3C-E, 6H, 7C-D
TAKS:
Objective 1 IPC 1a, 2c and 3a
Concepts:
Crystal Structure of Metals
Particle Model of Metals
Metallic Properties of Metals
Authors:
Jamie Adams
Laura M. Rodriguez
Project Partners:
Texas A&M University
College of Engineering
Mechanical Engineering Dept.
School Districts:
Spring Branch ISD/ Houston, TX
United ISD/ Laredo, TX
Texas A&M University /College of Engineering
E3 Summer Research Project Summer 2004
NSF Funded
Chemistry Module
Objectives
 Identify basic crystal structures that metal atoms form.
 Examine basic particle models for metals
 Demonstrate the effect of cold working (strain hardening) and annealing on the
ability of wires of the same metal to support a load.
 Introduce students to the field of nanotechnology.
 Introduce students to the field of materials science.
Materials
 Aluminum bar
 26 Styrofoam balls, about 1.5”diameter
 16 round toothpicks
 Plastic Petri Dish
 Bb’s
 Hammer, Bunsen burner, tongs, 16 or 18 gauge solid wire of Cu or Al
 16 or 18 gauge solid wire of other metals, high carbon steel wire or bobby pins
Exploration
o Hand a female student the aluminum bar and asker her to bend it as much
as she can. Hand it to another student and ask him to unbend it. Then ask
the strongest student to bend it once more. The strongest student will find
it very difficult to bend the bar again. Why is this so?. Have students
discuss possible reasons why this happens.
Concept Introduction
o Solids can be classified as amorphous or crystalline. Amorphous solids
lose their shapes readily with small changes in pressure and temperature.
Metals are crystalline structures with geometrical repeating patterns. The
physical and chemical properties depend on the arrangement of particles in
atoms. As technology improves more is known about how the internal
structure of matter affects its properties. Atoms in metals are closely
packed together. Metal structures, however can be altered by processing
treatments to make them more useful in various applications.
Concept Application/Assessment
o Do Experiment 1 Crystal Packin’ Mama
Crystal Packin’ Mama
Purpose: To learn more about the basic crystal structures that metal atoms form.
Application: The properties of metals are very dependent on their crystal structures.
By processing treatments metals can have more useful applications.
Time: 50 minutes
Materials and Supplies: 26 Styrofoam balls about 1.5” diameter, 16 round
toothpicks and water colors
Procedure:
1. Each of the Styrofoam balls will represent an atom and the toothpicks will represent
bonds. Attach 10 of the balls together with toothpicks to form a triangle with four
balls at the base. This will form the first layer of the packing model. Draw a
diagram of the arrangement of the atoms in the space below labeled models.
2. Attach 6 of the balls together with toothpicks to form a triangle with 3 balls at the
base. This will form the second layer of the packing model. Draw a diagram of the
arrangement of the atoms in the corresponding space below.
3. Form another triangle of Styrofoam balls like the one in procedure 1 with the
remaining 10 balls.
4. Place the second layer on top of the first one with “atoms” of the second layer
nesting in the hollows between the “atoms” of the first layer. This creates the
closest possible packing of atoms.
5. The third layer can be placed on top of the second layer in one of two positions. It
can be placed so that its “atoms” are directly over those in layer one. This gives the
ABABAB arrangement, which corresponds to hexagonal closest packing (HCP).
The third layer can also be placed on top of the second layer so that its “atoms” are
not directly over those in the first layer. This gives the ABCABC arrangement
which corresponds to face centered cubic (FCC). Try both arrangements with your
layers. Draw both arrangements.
Name:___________________________
Date:______________
Drawings:
Table 1:
First Layer
Second Layer
Table 2:
FCC Arrangement
HCP Arrangement
Questions:
1. Which packing arrangement, FCC or HCP, is denser?
2. What is the difference in FCC and HCP arrangement?
3. About how small would an atom have to be to fit in an interstitial hole
in an FCC or HCP crystal structure?
Teacher Notes:
 It would be beneficial for the teacher to have a completed model
constructed with the layers painted different colors to help the
students visualize the two types of packing arrangements.
 To paint the Styrofoam balls use water based paint diluted slightly and
add a small amount of detergent.
 Below are the arrangements for the triangles the students are to
construct.
First Layer
ABABAB (HCP)
second layer
ABCABC (FCC)
Answers to Questions:
1.
2.
3.
Actually, FCC and HCP packing arrangement have the same
atomic density. They each have approximately 26% empty
space.
FCC has an ABC arrangement while HCP has a ABABAB
arrangement
Depending on the type of hole, an interstitial atom should be
approximately one third the size of the atom, which makes
up the crystal structure in order to “fit” well.
Lesson 2
Scientific Principle:
As in all atoms the valence electrons are responsible for the bonding that takes
place in all substances. Metallic bonds however have loosely held valence
electrons that are shared by all the atoms in the crystal. This loosely held bonding
is called the electron sea model. This characteristic of metallic bonds allows for
imperfections in the metallic crystals. Sometimes, there are empty spaces,
vacancies, where an atom should be. There are also mismatches, dislocations, in
the rows of atoms, and these are found in all metals. Defects in the crystal
structure of metals control many of the properties including hardness and
ductility. The (FCC) Face centered cubic arrangement, and the (HCP) hexagonal
closest packing arrangement are responsible for many of the metallic and physical
properties of these metals.
Demonstration:
Place a plastic Petri dish on an overhead projector. Fill the Petri dish about
3/4 full with copper Bb’s. As you perform the steps in the demo allow
students to write answers to the questions in complete ideas to increase
understanding. Pass out student handout to be done as demo is performed.
1. The Bb’s represent the atoms in a metal.
2. If you move the Petri dish back and forth very slowly you can get an
idea of how atoms move. When atoms are heated the kinetic energy of
the atoms increases allowing the atoms to vibrate about is equilibrium
point. The more heat the larger the vibration becomes. Move the Petri
dish quicker to simulate this motion. This simulates the atoms in a metal
when it is heated. As heat is removed the particles begin to slow down
allowing for the formation of crystals.
3. Move the dish back and forth again and try to get the atoms arranged as
neatly as possible. A) Ask students to sketch the Bb’s in the proper
space on their handout. They don’t have to sketch all the Bb’s. Slowing
the motion of the dish and gradually stopping it simulates the formation
of a crystal. Move the Petri dish so that the Bb’s are arranged around an
empty space. B) Have students sketch the Bb’s showing this empty
space arrangement. Explain to the students that when this happens in
the metal it is called a vacancy, or dislocation.
4. Show video clip http://matse1.mse.uiuc.edu/~tw/metals/b.html
Name:____________________________
Date:_____________________
Bb’s Demo Answer Sheet
Drawing:
Step 3: A
Step 3: B
Questions: Answer the questions in complete ideas so to show understanding of the
subject.
1. Describe the bonding between the atoms in a metal.
2. What type of energy do “moving” atoms possess?
3. How do the atoms in a crystal move?
4. Describe the arrangement of the Bb’s. Are there any empty spaces, i.e., places
where a Bb is missing?
5. Are the Bb’s arranged perfectly? Would you expect atoms to be perfectly
arranged?
6. Do more or less defects exist in the metal when heated, and why?
Teacher Notes: Answer Key
Drawing:
Step 3: A
Step 3: B
Questions: Answer the questions in complete ideas so to show understanding of the
subject.
1. Describe the bonding between the atoms in a metal.
The valence electrons of a metal atom are loosely held and considered to be
shared by all the atoms of the crystal, as described in the electron sea model.
2. What type of energy do “moving” atoms possess?
All atoms have potential and kinetic energy. As atoms move the potential energy
decreases and the kinetic energy increases. The more heat added the more kinetic
energy it has.
3. How do the atoms in a crystal move?
The atoms when heated begin to vibrate about an equilibrium position.
4. Describe the arrangement of the Bb’s. Are there any empty spaces, i.e., places
where a Bb is missing?
Students descriptions should vary and depend on the attention placed to detail,
however their answer should include both neatly order arrangement and empty
space arrangement.
5. Are the Bb’s arranged perfectly? Would you expect atoms to be perfectly
arranged?
It is unlikely that the atoms are perfectly arranged. Some disorder is expected.
6. Do more or less defects exist in the metal when heated, and why?
More defects exist at higher temperatures because the forces holding the atom
together cannot control the atoms vibrations.
Lesson 3
Introduction: Metals are very important elements because they have so many
useful applications. Throughout history man has been researching how some
metals can become more useful to man. Most metals were found on earth as ores
father then pure metals. Man learned how to extract the metal from its ore and
realized that different properties exist for different substances. As time passed
and man learned more about the atomic structure of metals he experimented with
changes in the structure and what affects it had on the properties of the metals.
Application: It is known that processing can alter the properties of metals.
Since the properties of a material dependent upon its structure on the atomic level,
altering its structure should alter its properties. Common treatments include
quenching, cold-working, tempering, and annealing (heat treating).
Scientific Principles: Because plastic deformation results from the movement
of dislocations, preventing this motion can strengthen metals. When a metal is
deformed, new dislocations are produced. As dislocations are generated and
move, the metal can be bent and shaped without cracking. As the number of
dislocations in the crystal increase, they will get tangled or pinned and will not be
able to move. This will strengthen the metal, making it harder to deform. When
this done at or near room temperature, the process is known as cold-working.
When cold-worked metals are annealed (heated gently), new grains form from the
cold-worked structure and grow until they are replaced with new, soft crystals.
Steels (alloys of iron with up to 1% carbon) can also be hardened by heating and
quenching. At high temperatures (red hot) iron has a FCC structure, which can
dissolve carbon. At low temperatures, the iron changes to a BCC structure, which
cannot dissolve carbon, so it precipitates as an iron-carbon compound, if
quenched, this compound does not have time to form, the carbon is trapped and
distorts the BCC crystal structure to create a new, hard and brittle structure called
Martensite. It Martensite is gently heated; the carbon can precipitate giving a
strong, tough structure.
Materials per group:
Hammer, Bunsen burner, tongs, beaker, 16 or18 gauge non insulated Cu wire,
16 or 18 gauge solid wire of other metal depending on availability, 7 four inch
pieces of high carbon steel wire or bobby pins, and wire gauze
General Safety Guidelines:
Remind students to:
 Take precautions to avoid burns when using the Bunsen burner to heat
metals. Wear heat resistant gloves if available.
 Make sure all fingers are out of the way when hammering the wires.
Name:__________________________
Date:___________________
Lab: Making Metals Strong
Objective:
The objective of this lab is to demonstrate the effect of cold working (strainhardening) and annealing on the ability of wires of the same metal to support a
load.
Materials and supplies: Hammer, Bunsen burner, tongs, beaker, 16 or18 gauge
non insulated Cu wire, 16 or 18 gauge solid wire of other metal depending on
availability, 7 four inch pieces of high carbon steel wire or bobby pins, and wire
gauze
Procedure (Part I):
1. Hammer one of the pieces of copper wire until it is about half of its original
thickness.
2. Bend it back and forth several times. Observe ease of bending.
3. Heat the flattened (work hardened) piece of copper in the burner until red hot.
4. Let it cool slowly on the wire gauze.
5. Once the wire is cool to the touch bend it back and forth again noticing any
changes in the ease or difficulty of bending.
6. Repeat procedure 1-5 for the other wires.
7. Make sure you record all observations before heating.
8. Label and save the wires for later.
Procedure (Part II):
1. Obtain 4 samples each of high carbon steel wire (bobby-pins or piano wire)
and other metals.
2. Bend one of the wires until it breaks. Count and record the number of bends
needed to break the wire.
3. Heat the second steel wire in the middle until it is red hot. Let it cool slowly
in air.
4. When the wire is cool. Bend it back and forth as before. Count and record the
number of bends needed to break this heat-treated wire.
5. Fill a beaker with cold water.
6. Heat the third wire in the flame until it’s red hot and immediately plunge it
into the water in the beaker.
7. When the wire is cool, bend it as before and record the number of bends
needed to break it.
8. Heat and quench the last wire as in Procedure 6, but cool it slowly in air. This
process is called tempering. As before note the properties of the tempered
wire and record your observations.
9. Repeat step 1-8 for the other metal wires.
Observation Table:
Part I
Hammered Wire:
Type of Wire
# of Bends
Observations
Hammered and Heated Wire:
Type of Wire
# of Bends
Observations
Part II:
Type of Wire: __________________________________
Step #
# Bends
Observations
Type of Wire: __________________________________
Step #
# Bends
Observations
Type of Wire: __________________________________
Step #
# Bends
Observations
Type of Wire: __________________________________
Step #
# Bends
Observations
Type of Wire: __________________________________
Step #
# Bends
Observations
Type of Wire: __________________________________
Step #
# Bends
Observations
Questions:
1. What is the hammering in Part I procedure 1 called?
2. In Part I, procedure 2, what generalizations can you make regarding the ease of
bending after treatment, and why do you think this happened?
3. For Part II, procedure 2, how many bends were required to break the wire? Did it
break easily? Describe the mechanical properties for this sample.
4. What term describes the heat treatment method used in Part II, procedure 3
(heating, slow cooling)?
5. In Part II, procedure 4, how many bends were required to break the wire? Did it
break easily? Describe the mechanical properties for this sample.
6. What is cooling the hot metal rapidly as in Part II, procedure 6 called?
7. In Part II, procedure 7, how many bends were required to break the wire? Did it
break easily? Describe the mechanical properties for this sample.
7. In Part II, procedure 8, what were the properties of the tempered wire?
Teacher Notes:
 The answers for the tables will vary depending on the lab technique of the
students in each group. You might want to grade them on clarity of observations,
neatness and completeness.
 There might be more tables than needed it depends on how many different types
of wire you will compare. Three different types may are sufficient for 1:30 hours.

Make sure you secure all materials before lab and remind students of safety
issues.
Answers to Questions:
1. Cold-working
2. The hammered wire was harder to bend, but broke more easily. The hammering
produced many dislocations, which became tangled, inhibiting the sliding of
planes of atoms.
3. Answers will vary. The unworked wires should be easier to bend and bend more
times before breaking.
4. Annealing
5. Annealing the wires should soften the metal allowing it to bend more easily, and
more times before breaking than the previous two procedures.
6. Quenching
7. The quenched wires should be harder and bend fewer times before breaking.
8.
The tempered wire should bend more times than the quenched wire did before
breaking.
Enrichment:
Ask students to compare and contrast the four processes in essay form.
LESSON 4
Introduction:
Ask students if they know what a nanocrystal is and where it can be found? The majority
of your students might not know the answer. Therefore begin your lesson by explaining
that the prefix nano means 10-9. Nanotechnology is building and using things between 1100 nanometers. A nanometer is one-billionth of a meter. Nanotechnology is changing
the way we live. In order to learn more about nanotechnology students will research a
topic in nanotechnolgy.
Group students according to the number of internet excess computers you might have.
Each group must pick a topic to research on the internet from the following list:
Nanostrands
Nanocrystals
Nanobeads
Carbon Nanotubes
Nanofibers
Each group will prepare an 8-10 slide, power point presentation about their chosen topic.
Each group will present their topic to the class.
Assign each group one of the following internet articles dealing with nano-crystals.
Students need to read the article and prepare a critique of it. The critique should be in the
form of not more than one page summary, single spaced, 12 point font, one inch margins.
Each group will then be required to present their article to the rest of the class.
Discovery could bring widespread uses for “nanocrystal”
http://news.purdue.edu/UNS/html4ever/020816.Chandrasekar.nano.html
Nanocrystals: The Shapes of Things to come
http://www.lbl.gov/ScienceArticles/ResearchReview/Magazine/2001/Fall/features/02Nanocrystals.html
Nanocrystals from Machining Waste Suitable for the Production High Performance
Nanostructured Materials
http://www.azom.com/details.asp?ArticleD=1811
Assessment:
You can grade the power point presentation, and the critique using a rubric. You can
combine the two parts for one project grade.
Name:____________________ Date:________________
Grading Rubric for Nanotechnology
#
Criteria
points
1
Number of slides 8-10 slides (10 points)
less than 4 slides (0 points)
2.
Spelling and Mechanics. No mistakes 10 points
Up to 3 mistakes 5points. 4 or more mistakes 0 points
3.
Does presentation define and clearly explain topic.
Yes (10 points) No ( 0 points)
4.
Are slides relevant to the content.
All (10 points) More than half (5 points), less than half (0 points)
5.
Creativity to include color, scheme, and animation if appropriate
Yes ( 10 points) Not really (5 points)
6.
Understanding of Nanotechnology article as witnessed through
oral presentation (10 points)
7.
Did group use visual aids to explain topic (10 points)
8.
Were margins, spacing, and correct font size used in critique (10 points)
9.
Punctuation and grammar usage (10 points)
10.
Team work apparent as evaluated by other team members (10 points)
4-7 slides (4 point)
Total grade
Lesson 5
Introduce students to the field of Material Science/Material Engineering at
A&M.
Use power point presentation prepared during E3 summer research project.
References:
Materials processing by simple shear: V.M. Segal
www.mengr.tamu.edu/Research/ecae/subject.htm
The Equal Channel Angular Extrusion Process for Materials Processing: L.R. Cornwell,
K.T. Hartwig, R.E. Goforth,and S.L. Semiatin.
www.mengr.tamu.edu/Research/ecae/subject.htm
Microstructure Evolution and Mechanical Behavior of Bulk Copper Obtained by
Consolidation of Micro- and Nanopowders Using Equal-Channel Angular Extrusion:
M.Haouaoui, I.Karaman, H.J. Maier, and K.T. Hartwig
www.mengr.tamu.edu/Research/ecae/subject.htm
Discovery could bring widespread uses for “nanocrystal”
http://news.purdue.edu/UNS/html4ever/020816.Chandrasekar.nano.html
Nanocrystals: The Shapes of Things to come
http://www.lbl.gov/Science-Articles/ResearchReview/Magazine/2001/Fall/features/02Nanocrystals.html
AAP Saint Mary’s The Savings are in the Chips
http://www.eere.energy.gov/industry/financial/case_studies3.html
Nanocrystals from Machining Waste Suitable for the Production High Performance
Nanostructured Materials
http://www.azom.com/details.asp?ArticleD=1811
Equal Channel Angular Pressing (ECAP)
http://www.oeaw.ac.at/esi/english/research/facilities/spd/ECAP.html
Crystal Packin’ Mama
http://matse1.mse.uiuc.edu/~tw/metals/a.html
Atomic Bb’s
http://matse1.mse.uiuc.edu/~tw/metals/b.html
Making Metals Strong
http://matse1.mse.uiuc.edu/~tw/metals/c.html
Engineering Design Concept: Feb 2004
http://www.techdirections.com