SHPE Jr. Chapter January 2015 STEM Activity
Instructor resource
Pencils, Diamond, Graphene
Students learn about nano materials and explore the electrical properties of
graphite. They learn about different allotropes of carbon and how differing
arrangements of atoms in a substance can alter its electrical and physical
properties. They propose uses for nanoscale graphene
Learning objectives
• Understand what nanotechnology is
• Learn about graphene as a nanoscale material
• Understand the concept of allotropes
• Learn about the electrical properties of carbon allotropes
• Learn about circuits and conductors
• Consider how nanoscale engineering can address societal issues
Engineering/STEM areas:
Materials science, nanoscale science
Materials
• Student Resource Sheets (in lesson)
• For each pair or team:
• A sharpened pencil or mechanical pencil
• Paper
• Small LED bulb
• 330 Ohm resistor
• Insulated alligator clip connectors
• 9-volt battery
(The LED bulb, resistor, and clips can be purchased at Radio Shack)
Optional: A pencil or leads from a mechanical pencil, and diamond-like jewelry
(or photos of these things).
Instructions for building the graphite circuit are in the Student Worksheet.
Time required
45 - 60 mins
Suggested group size:
2-3, depending on budget and number of students
Preparation
1. Read through both the student and instructor resources so you have the
background information
2. Gather all the necessary materials. Assemble sets of materials for each
group
3. Make enough copies of the Student Resource so that each student has
one, plus a few extras
4. Make your own setup of a simple circuit to use as a demo
Procedure
1. This lesson will involve more explaining and discussion on your part,
almost a mini-lecture. But first you’ll have the students do an activity to
pique their interest. Begin the lesson by asking them what a diamond and
a pencil have in common and how they’re different. If possible, have a
picture of a pencil and a diamond, or even bring a pencil and some
diamond-like jewelry.
2. Explain that both diamond and pencil “lead” are made of carbon
(therefore, the “lead” isn’t actually lead. It’s a compound called graphite.),
and solicit explanations of why they are so different if they are made of the
same thing.
3. Explain allotropes, and cite diamond and graphite as examples.
4. Tell students that graphite and diamond differ in an invisible way that is
very important to engineers. Explain that they’re going to do an activity
where they demonstrate for themselves an important property of graphite.
It will involved making a circuit.
5. If necessary, go over the introduction to the Student Resource (the
paragraphs about circuits) and make sure students understand what a
circuit is.
6. Make sure each group has a set of materials required for making the
graphite circuit. Go over the first page of the Student Resource, explaining
what a circuit is. Ask what students think will happen. Then circulate
among student groups as they’re doing their setup. Have your circuit
ready to show them as an example (but either don’t put any graphite on
yours or don’t close the circuit). Make sure all students manage to get
their light bulbs lit.
7. Explain that the conductivity of graphite makes it very useful, and that only
a single atom layer of carbon is needed to conduct electricity. In fact,
engineers have been developing new materials using a single layer of
graphite, which they call graphene, Graphene is a very efficient conductor,
and is one of the strongest materials known.
8. Go over the information in the Student Resource. Make sure students
understand:
o Nanoscale materials
o The relationship between graphene and graphite
o Special nanoscale properties of graphene
o Potential applications that engineers can consider
9. Have each group work together to come up with applications for graphene
and describe them in their student resource. Students then share their
ideas with the larger group.
Assessments
•
Have student groups devise a new application of graphene and describe it
to the whole group. Their description should include:
• A description of what the application looks like on a nanoscale (and
a macroscale, if appropriate)
• An explanation of how the special properties of graphene make this
device possible
• An explanation of how the special properties of graphene make this
device an improvement over what already exists and/or how this
device could contribute to solving a problem.
Extensions
• Have students research some current applications of nanoscale carbon
technologies and describe the science behind how they work.
• Introduce students to the types of microscopes used to visualize
nanoscale materials.
• Discuss the use and benefits of allotropes of elements other than carbon.
For example, different allotropes of phosphorus have different industrial
applications based on their conductivity and whether or not they’re
flammable.
• Imagine that one engineer devises a new application for carbon
nanotubes, and another engineer improves upon it. Both the application
and its improvement are included in a new product. Have a debate
addressing how each engineer should be credited and/or compensated for
their inventions.
Resources/Bibliography
The Power of Graphene
http://tryengineering.org/lesson-plans/power-graphene
Exploring Materials: Graphene
http://www.nisenet.org/catalog/programs/exploring_materials__graphene_nanodays_2012
The Nanotechnology Revolution: Graphene
http://www.classroomengineers.org/education/media/nanotechnology-revolutiongraphene-engineer/?ar_a=6
Carbon nanotubes find real world applications:
http://phys.org/news/2014-03-carbon-nanotubes-real-world-applications.html
Allotropes Explained:
http://www.chemistryexplained.com/A-Ar/Allotropes.html
Jan. 2015 SHPE Jr. Chapter STEM Activity
Student Resource and Worksheet
Pencils, Diamonds, Graphene
You’re going to start this lesson by doing an activity and explaining what you see.
Activity Procedure
This activity has four steps:
1) Put together a simple circuit
2) Test your circuit
3) Add graphite to your circuit
4) Test the new circuit
Your instructor should give you the following materials:
 A sharpened pencil or mechanical pencil
 Paper
T h e P o w e r oSmall
f GLED
rap
hene
bulb
 330 Ohm resistor
tudent Resource:
 4 Insulated alligator clip connectors
What is a Simple Circuit?
 9-volt battery
Simple Circuit
simple circuit consists of three minimum elements that are required to complete a
To build
the simple
circuit:
nctioning electric circuit:
a source
of electricity
(battery), a path or conductor on which
A
circuit
is
a
closed
loop
that electrons
candevice
travel that
through.
A simple circuit
ectricity flows (wire) and an electrical resistor (lamp)
which is any
requires
three elements:
anaenergy
sourcecontaining,
(often a battery),
a path for electrons
ectricity to operate.requires
The illustration
below shows
simple circuit
one
attery, two wires, and
a
bulb.
The
flow
of
electricity
is
from
the
high
potential
(+)
to flow along (a conductive material, sometimes a wire), and a device that
rminal of the battery
throughelectricity
the bulb (lighting
it up), and back to the negative (-)
requires
to operate.
rminal, in a continual flow.
Schematic Diagram of a Simple Circuit
In order for a circuit to operate, it has
to be a closed, meaning that there has
to be a continual path for the electrons
to follow. In the illustration here,
electrons flow from the battery through
the wire to the bulb. As electrons pass
through the bulb, they light it up.
Electrons leave the bulb through
another wire that takes them to the
battery. If the wire was disconnected
from either end of the battery, the
electrons wouldn’t be able to flow
through the whole loop, and the circuit
wouldn’t light the bulb.
he following is a schematic diagram of the simple circuit showing the electronic symbols
r the battery, switch, and bulb.
First, put together a simple circuit by making the following connections
between the items you have:
1) Connect on end of a pair of alligator clips to cathode (positive node) of the
battery. Connect the other end of that same alligator clip to one wire of the
resistor.
2) Using second alligator clip, connect the other wire from the resistor to one
wire on the LED bulb.
3) Using a third alligator clip, connect the other wire on the LED bulb to the
anode (negative node) of the battery.
Your LED bulb should light up! If it doesn’t, ask for some help with your circuit.
Now, you’ll add something to your circuit and see what happens.
1) Use your pencil to fill in a space on the edge of the card or paper you’ve
been provided with. The space should be 1 or 2 inches wide and go 1 inch
in from the edge of the paper.
2) Disconnect the alligator clip from the anode of the battery (keep it
connected to the LED bulb. Connect the newly freed end of that alligator
clip to the paper so that the clip is solidly in the space you filled in with the
pencil.
3) Connect one end of your fourth alligator clip to the anode of the battery.
Clip the other end to the paper, also solidly in a space that you filled in
with pencil, but at least a half-inch away from the other alligator clip.
What happened when you connected the last alligator clip? What
explanation can you think of to explain it?
Pencils and diamonds: The same, but different
When you look at a pencil “lead” and a diamond, do you see
much resemblance? One is a clear, sparkling solid, hard
enough to cut glass, and rare among the earth’s gems. The
other is dull gray, soft enough to rub off on your fingers, and
found in abundance. But when it comes right down to it, they’re
made of the same stuff: carbon.
The key is that the atoms that
make up the two substances are
arranged in different patterns. In
the pencil “lead,” (which isn’t lead
at all, but a substance called
graphite), the carbon is arranged in
2-dimensional layers of atoms
bound together in a pattern similar
to chicken wire. In a diamond, the
carbon atoms are arranged in a 3dimensional lattice. Different forms
of a pure element are called
allotropes.
These differing arrangements
affect the properties of the
material—what it looks like, how hard it is, and so on. These differing
arrangements affect the properties of the material—what it looks like, how hard it
is, and so on. One invisible way in which diamonds and graphite differ is in their
ability to conduct electricity. Diamonds are pretty ineffective in this regard, while
graphite is a rather efficient conductor.
In the 1980s, two Russian scientists isolated a single-atom layer of graphite by
using simple adhesive tape to collect graphite from a pencil. They discovered
that even this layer graphite just one atom thick can conduct electricity, and can
do so even more efficiently than graphite. Engineers soon began researching
how to make these layers of carbon “chicken wire,” called graphene, in a cost
effective way, and exploring its properties. In 2010, the scientists won a Nobel
prize for their discovery.
Layers of graphite
Single layer of graphene
Graphene is considered a nanomaterial—that is, a material that is either created
or manipulated on the atomic scale. Most of the materials we deal with in
everyday life—cotton, wood, steel, etc.—are made and worked with on the macro
scale. When engineers work with nanomaterials, they may move single atoms or
small groups of atoms.
“Nano” is a prefix used before measurements, like the prefixes “kilo,” “milli,” and
“centi.” A nanometer is one-billionth, or 10-9 of a meter. A nanometer is smaller
than any visible wavelengths of light, so researchers have to use special
microscopes to visualize nanomaterials.
Engineers have devised ways to
make nanoscale structures out of
graphene. They can roll a layer of
graphene into a carbon
nanotube, which is very light and
strong for its size. Engineers are
experimenting with ways to use
these very strong structures in
machines, cars, and sports
equipment. Because they have a
large surface area, they may make
very effective water filters. Their
electrical conductivity makes them
potentially powerful in batteries
and integrated circuits.
Carbon nanotube
The fact that carbon nanotubes are very
light and strong means an airplane
incorporating them might weigh less and
require less fuel.
A circuit with two electrodes and ten
graphene nanoribbons connecting
them.
(http://www.gtresearchnews.gatech.edu)
While most products that incorporate
nanoscale carbon structures are still in the
research stages, there’s no shortage of
ideas of ways to make use of the special
properties of these carbon allotropes. The
field of nanotechnology will remain a
promising area of engineering and research
for many years. And you may find graphene
or other nanoscale carbon structures in
your phone, computer, or other electronics
in the near future!
Devise another application for graphene, while thinking about the
following questions. You can write a description or make a drawing
in the box on the next page.
How would you describe your application? Can you discuss it on both the
nanoscale and the macroscale?
What properties of graphene make this device possible?
What usual properties of graphene make this device an improvement over what
already exists? How could this device contribute to solving a problem?
Draw or describe your application in this box. You’ll share your idea with others
when you’re done.
Vocabulary
•
Allotrope – Materials made of the same element but with different
bonding arrangements between atoms. Different allotropes have different
physical, chemical, and electrical properties.
•
Circuit – A loop that electrons can travel through.
•
Carbon nanotube – A layer of graphene rolled into a tube. Carbon
nanotubes are very strong.
•
Graphene – A layer of graphite-like carbon that is only one atom thick.
Graphene is a very strong material and a very efficient conductor.
•
Graphite – A common compound that is an allotrope of carbon. Graphite
contains many layers of carbon atoms connected in a chicken-wire type
pattern.
•
Nanoscale – Working with or studying materials at the scale of 10-9 of a
meter.