February 2013 Teacher's Guide
Table of Contents
About the Guide ............................................................................................................ 3
Student Questions (from the articles) ........................................................................ 4
Answers to Student Questions (from the articles) .................................................... 6
ChemMatters Puzzle: Su-Chem-Du............................................................................ 10
Answers to the ChemMatters Puzzle ......................................................................... 12
NSES Correlation ........................................................................................................ 13
Anticipation Guides .................................................................................................... 14
Fighting Cancer with Lasers .................................................................................................................... 15
Brand-Name vs. Generic Drugs: What’s the Difference? ........................................................................ 16
Sniffing Out Cancer ................................................................................................................................. 17
Drivers, Start Your Electric Engines! ....................................................................................................... 18
Is Your Car a Living Thing? ..................................................................................................................... 19
Reading Strategies ...................................................................................................... 20
Fighting Cancer with Lasers .................................................................................................................... 21
Brand-Name vs. Generic Drugs: What’s the Difference? ........................................................................ 22
Sniffing Out Cancer ................................................................................................................................. 23
Drivers, Start Your Electric Engines! ....................................................................................................... 24
Is Your Car a Living Thing? ..................................................................................................................... 25
Fighting Cancer with Lasers ...................................................................................... 26
Background Information (teacher information) ....................................................................................... 26
Connections to Chemistry Concepts (for correlation to course curriculum) ........................................... 43
Possible Student Misconceptions (to aid teacher in addressing misconceptions) ................................. 43
Anticipating Student Questions (answers to questions students might ask in class).............................. 44
In-class Activities (lesson ideas, including labs & demonstrations) ....................................................... 46
Out-of-class Activities and Projects (student research, class projects) ................................................. 47
References (non-Web-based information sources) ............................................................................... 48
Web sites for Additional Information (Web-based information sources) ................................................ 50
Brand-Name vs. Generic Drugs: What’s The Difference? ....................................... 53
Background Information (teacher information) ....................................................................................... 53
Connections to Chemistry Concepts (for correlation to course curriculum) ........................................... 63
Possible Student Misconceptions (to aid teacher in addressing misconceptions) ................................. 64
Anticipating Student Questions (answers to questions students might ask in class)............................. 64
In-class Activities (lesson ideas, including labs & demonstrations) ....................................................... 64
Out-of-class Activities and Projects (student research, class projects) ................................................. 65
References (non-Web-based information sources) ............................................................................... 66
Web sites for Additional Information (Web-based information sources) ................................................ 67
More Web sites on Teacher Information and Lesson Plans (sites geared specifically to teachers) ...... 68
Sniffing Out Cancer..................................................................................................... 70
Background Information (teacher information) ....................................................................................... 70
Connections to Chemistry Concepts (for correlation to course curriculum) ........................................... 77
Possible Student Misconceptions (to aid teacher in addressing misconceptions) ................................. 78
Anticipating Student Questions (answers to questions students might ask in class)............................. 78
1
In-class Activities (lesson ideas, including labs & demonstrations) ....................................................... 80
Out-of-class Activities and Projects (student research, class projects) ................................................. 81
References (non-Web-based information sources) ............................................................................... 81
Web sites for Additional Information (Web-based information sources) ................................................ 82
Drivers, Start Your Electric Engines!......................................................................... 86
Background Information (teacher information) ....................................................................................... 86
Connections to Chemistry Concepts (for correlation to course curriculum) ........................................... 99
Possible Student Misconceptions (to aid teacher in addressing misconceptions) ............................... 100
Anticipating Student Questions (answers to questions students might ask in class)............................ 100
In-class Activities (lesson ideas, including labs & demonstrations) ..................................................... 102
Out-of-class Activities and Projects (student research, class projects) ............................................... 104
References (non-Web-based information sources) ............................................................................. 105
Web sites for Additional Information (Web-based information sources) .............................................. 107
More Web sites on Teacher Information and Lesson Plans ................................................................. 110
Is Your Car a Living Thing? ...................................................................................... 111
Background Information (teacher information) ...................................................................................... 111
Connections to Chemistry Concepts (for correlation to course curriculum) ......................................... 122
Possible Student Misconceptions (to aid teacher in addressing misconceptions) ............................... 122
Anticipating Student Questions (answers to questions students might ask in class)........................... 123
In-class Activities (lesson ideas, including labs & demonstrations) ..................................................... 123
Out-of-class Activities and Projects (student research, class projects) ............................................... 124
References (non-Web-based information sources) ............................................................................. 125
Web sites for Additional Information (Web-based information sources) .............................................. 126
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About the Guide
Teacher’s Guide editors William Bleam, Donald McKinney, Ronald Tempest, and Erica K.
Jacobsen created the Teacher’s Guide article material. E-mail: bbleam@verizon.net
Susan Cooper prepared the national science education content, anticipation guides, and
reading guides.
David Olney created the puzzle. E-mail: djolney@verizon.net
Patrice Pages, ChemMatters editor, coordinated production and prepared the Microsoft Word
and PDF versions of the Teacher’s Guide. E-mail: chemmatters@acs.org
Articles from past issues of ChemMatters can be accessed from a CD that is available from the
American Chemical Society for $30. The CD contains all ChemMatters issues from February
1983 to April 2008.
The ChemMatters CD includes an Index that covers all issues from February 1983 to April
2008.
The ChemMatters CD can be purchased by calling 1-800-227-5558.
Purchase information can be found online at www.acs.org/chemmatters
3
Student Questions
(from the articles)
Fighting Cancer with Lasers
1. What medical tool did doctors use to determine the problem causing Chris’s pain?
2. What is the name of the type of tumor found in his thigh?
3. Was the tumor cancerous?
4. What two medical tools do doctors use to treat the tumor?
5. What role does the needle play in destroying the tumor?
6. Was the operation difficult or complicated?
7. What is the meaning of the acronym LASER?
8. Name three properties of laser light.
9. Name the two processes involved in generating laser light. Explain each.
10. Name two advantages and two disadvantages of using lasers for treating cancers.
Brand-Name vs. Generic Drugs: What’s the Difference?
1. By law, what must be the same for a brand-name drug and its generic equivalent? What can
be different?
2. What is the role of the active ingredients in a drug?
3. What can affect the solubility of a drug, or the way it dissolves in the body?
4. Explain why a hot solvent dissolves a solid faster.
5. What does a concentration–time graph (or blood concentration curve) of a drug show?
6. What is the U.S. Food and Drug Administration rule regarding the concentration–time
graphs for a brand-name drug and its generic equivalent?
Sniffing Out Cancer
11. What is a Volatile Organic Compound (VOC)?
12. For people with tumors, what body products can carry or contain VOCs?
13. Volatility of an organic compound depends on its vapor pressure. What is meant by vapor
pressure?
14. Describe the chemical properties of reactive oxygen species and how they are related to
cancer.
15. What is the relationship between VOCs and reactive oxygen species?
16. Give two advantages when choosing dogs over chemical instrumentation for cancer
detection?
17. What types of cancer are dogs capable of detecting?
18. What two biological products of the body are sniffed by dogs in detecting cancer?
4
Drivers, Start Your Electric Engines!
1.
2.
3.
4.
5.
Name two advantages for the electric car.
For what use is the electric car primarily designed?
What helps to minimize “range anxiety”?
True or false: The first electric car was the Nissan Leaf. Explain your answer.
What is the chemical term for the process that happens at the lead plate in a lead-acid
battery? Describe this process.
6. What happens when a lead-acid battery recharges?
7. What type of battery is used in today’s electric cars?
8. Describe the composition of the two electrodes in a lithium-ion battery.
9. List four advantages that lithium-ion batteries have over lead-acid batteries.
10. List three disadvantages of using electric cars.
Is Your Car a Living Thing?
1. Name three chemical compounds mentioned in the article that are broken down in either a
car or a human.
2. Name and describe the process that separates the components of petroleum (crude oil).
3. What is the difference between hydrocarbons and carbohydrates?
4. What chemicals in the body are responsible for much of the breakdown of food in the
digestive process?
5. What are the common products of both cellular respiration and combustion?
6. Where in human cells is energy produced?
7. In what part of a car is the majority of the energy produced?
8. Name the three chemical elements that are used as catalysts in the catalytic converters of
automobiles.
5
Answers to Student Questions
(from the articles)
Fighting Cancer with Lasers
1. What medical tool did doctors use to determine the problem causing Chris’s pain?
The medical tool used by doctors to determine the origin of Chris’s pain was the computed
tomography scan, or CT scan.
2. What is the name of the type of tumor found in his thigh?
The tumor in Chris’s thigh was an osteoid osteoma.
3. Was the tumor cancerous?
Luckily, Chris’s tumor was not cancerous; it was benign.
4. What two medical tools do doctors use to treat the tumor?
Doctors typically use radio waves of lasers to treat tumors of this type.
5. What role does the needle play in destroying the tumor?
Doctors insert the needle into the center of the tumor; then they insert an optic fiber into the
needle. The fiber is used to direct the intense light/heat of the laser to the center of the tumor.
6. Was the operation difficult or complicated?
Although Chris needed general anesthesia, the operation itself only took an hour, and Chris
“... went home the same day and, within a short period of time, he was able to walk and
resume his daily activities.” In short, the operation seemed pretty easy (although it’s still
surgery and it’s still scary).
7. What is the meaning of the acronym LASER?
The acronym LASER means “Light Amplification by Stimulated Emission of Radiation”.
8. Name three properties of laser light.
Laser light:
a. is focused in a narrow beam,
b. has one specific wavelength,
c. is very intense.
9. Name the two processes involved in generating laser light. Explain each.
The two processes in generating laser light are stimulated emission and light amplification.
a. Stimulated emission involves incoming light causing atoms within the laser to emit light
on their own. These atoms are bombarded with flashes of light or electrical discharges.
This causes electrons within the atoms to absorb energy and jump to higher energy
states (excited states). When these electrons from excited states return to their original
ground states, they release photons of light. These photons then stimulate other
electrons in excited states to jump back down to their ground state, thereby emitting
more photons, all of which travel in the same direction.
b. Light amplification occurs when the photons of light travel back and forth within the laser
medium reflecting off the two mirrors. As they bounce back and forth between the
mirrors, they stimulate more and more excited electrons to return to their ground states,
thus emitting even more photons. Eventually the light wave leaves the laser medium
through the partially-coated mirror, creating the laser beam.
10. Name two advantages and two disadvantages of using lasers for treating cancers.
Two advantages of using laser for treating tumors are:
a. The laser can be used to repair small parts or surfaces of the body, much like a scalpel,
b. The heat from laser light actually helps to sterilize wounds.
The disadvantages of using laser light for tumor treatment are:
6
a. their high price,
b. the bulkiness of the equipment to generate the laser beams,
c. the need for training and precautions for medical staff using the laser.
Brand-Name vs. Generic Drugs: What’s the Difference?
1. By law, what must be the same for a brand-name drug and its generic equivalent?
What can be different?
By law, a brand-name drug and its generic equivalent must have the same active
ingredients. The inactive ingredients, such as pigments, flavoring, and binders can differ.
2. What is the role of the active ingredients in a drug?
Active ingredients are the ingredients that cause a drug’s effect, such as pain relief or antinausea.
3. What can affect the solubility of a drug, or the way it dissolves in the body?
Inactive ingredients in a drug can affect the way a drug dissolves in the body. Temperature
also affects solubility. Pharmaceutical companies adjust their drugs so they dissolve at body
temperature.
4. Explain why a hot solvent dissolves a solid faster.
Hot solvents dissolve solids faster because their molecules move faster than cold ones.
Increased molecular motion competes with the attraction between the molecules in the
solute and tends to make them come apart more easily. Increased molecular motion also
causes more solvent molecules to interact with solute molecules and pull on them with more
force, which makes them dissolve more.
5. What does a concentration–time graph (or blood concentration curve) of a drug
show?
A concentration–time graph of a drug shows the concentration of a drug in the bloodstream
at regular time intervals.
6. What is the U.S. Food and Drug Administration rule regarding the concentration–time
graphs for a brand-name drug and its generic equivalent?
The U.S. Food and Drug Administration rule states that when the concentration–time graphs
for a brand-name drug and its generic equivalent are compared, the difference between
them should not be larger than 20% of the brand-name drug’s curve.
Sniffing Out Cancer
1. What is a Volatile Organic Compound (VOC)?
A volatile organic compound is a molecule that evaporates or sublimates from a liquid or
solid phase of the same substance.
2. For people with tumors, what body products can carry or contain VOCs?
Some of the body products containing VOCs include exhaled breath, urine, and stool,
among others.
3. Volatility of an organic compound depends on its vapor pressure. What is meant by
vapor pressure?
“Vapor pressure is the pressure at which vaporized molecules reach equilibrium with the
solid or liquid phase of the same substance in a closed system.”
4. Describe the chemical properties of reactive oxygen species and how they are related
to cancer.
Reactive oxygen species are molecules with unpaired valence electrons that make them
highly reactive with surrounding biological materials. If reactive oxygen species are in
7
5.
6.
7.
8.
excess, perhaps because of a deficiency of antioxidant molecules that keep reactive oxygen
species in check, then they can damage DNA and healthy cell tissue. This damaging
process is known as oxidative stress and is known to be a precursor of cancer.
What is the relationship between VOCs and reactive oxygen species?
Under oxidative stress as outlined in answer #4, “reactive oxygen species oxidize fats in cell
membranes, resulting in increased emissions of VOCs ..”. Dozens of specific VOCs have
been linked to various types of cancer. Tumors produce changes in not just one type of
VOC, but many.
Give two advantages when choosing dogs over chemical instrumentation for cancer
detection?
A dog’s nose is a highly efficient chemical sensor, ready-made to sniff cancer VOCs.
Second, a dog can detect a cancer through smelling VOCs without needing to know the
specific chemical or chemicals present in the vapor. A chemical instrument can only be
designed when a specific chemical to be detected is known.
What types of cancer are dogs capable of detecting?
Dogs that are trained can detect skin, breast, lung, prostate, colon, bladder, and ovarian
cancer.
What two biological products of the body are sniffed by dogs in detecting cancer?
The two biological products sniffed for cancer-produced VOCs are urine and exhaled air.
Drivers, Start Your Electric Engines!
1. Name two advantages for the electric car.
Advantages of the electric car are:
a. Fewer moving parts, so less maintenance is required,
b. Brakes, part of the energy-recovery system, last much longer than ordinary car brakes.
2. For what use is the electric car primarily designed?
City driving is the main use for which electric cars are designed. This includes commuting,
running local errands and trips around town.
3. What helps to minimize “range anxiety”?
Onboard computers in electric cars indicate level of charge and remaining range of travel,
making it less likely that you will allow the battery to run down, minimizing “range anxiety”.
4. True or false: The first electric car was the Nissan Leaf. Explain your answer.
This statement is false. Electric cars were built as early as 1828, and had become prevalent
in the 1900s, until improvements in the gasoline-powered car gave it dominance.
5. What is the chemical term for the process that happens at the lead plate in a lead-acid
battery? Describe this process.
Oxidation occurs at the lead plate in the lead-acid battery. This process involves the loss of
electrons from the lead plate as it reacts to form lead(II) sulfate.
6. What happens when a lead-acid battery recharges?
Recharging a lead-acid battery involves pumping electrons into the battery from an outside
source. This causes the oxidation of lead(II) to lead(IV), releasing two electrons in the
process.
7. What type of battery is used in today’s electric cars?
Today’s electric cars (unlike those of the 1900s, which used lead-acid batteries) use lithiumion batteries.
8. Describe the composition of the two electrodes in a lithium-ion battery.
The cathode (the positive terminal) is made of “a type of layered lithium oxide, such as
lithium cobalt oxide (LiCoO2)”, while the “negative electrode, or anode, is made of graphite—
a form of pure carbon.
8
9. List four advantages that lithium-ion batteries have over lead-acid batteries.
Four advantages of lithium-ion batteries over lead-acid batteries:
a. They’re much lighter (think atomic weights: Li, 7; Pb, 207)
b. Lithium is much more reactive than lead, providing a higher charge density, 6:1 over
lead.
c. Lithium-ion batteries hold a charge much longer than lead-acid batteries. They only lose
5% of their charge per month.
d. They have no “memory effect”, so they can be recharged at any level of charge.
10. List three disadvantages of using electric cars.
Three disadvantages of electric cars:
a. Their relatively short range of travel
b. Their high price
c. Their contribution to pollution, since the electricity they use for recharging is generated
by burning coal.
Is Your Car a Living Thing?
1. Name three chemical compounds mentioned in the article that are broken down in
either a car or a human.
There are multiple possible answers here, but the most obvious are the hydrocarbons that
make up gasoline or the basic food nutrients—fats, carbohydrates or proteins. Other
compounds mentioned include glucose, adenosine diphosphate or adenosine triphosphate.
2. Name and describe the process that separates the components of petroleum (crude
oil).
The process to separate crude oil is called fractional distillation, a physical process that
depends on the fact that each hydrocarbon component in crude oil has a unique (or nearly
unique) boiling point. The petroleum is heated and each component vaporizes at its own
temperature and is then condensed into liquid form. The liquid components are then
remixed in desired proportions to form fuels like gasoline.
3. What is the difference between hydrocarbons and carbohydrates?
Both are considered organic compounds, but hydrocarbons are made up only hydrogen and
oxygen while carbohydrates contain carbon, hydrogen and oxygen.
4. What chemicals in the body are responsible for much of the breakdown of food in the
digestive process?
The article points to enzymes as the chemicals responsible for breaking down food into
nutrients that can be used by the body
5. What are the common products of both cellular respiration and combustion?
In both processes oxygen is combined with a food or fuel to produce carbon dioxide and
water.
6. Where in human cells is energy produced?
Cells have organelles called mitochondria. Energy is produced in these mitochondria.
7. In what part of a car is the majority of the energy produced?
In the cylinders of a car, gasoline vapor and oxygen are mixed and the mixture is ignited by
a spark from the spark plug. The combustion of the fuel creates energy to move the car.
8. Name the three chemical elements that are used as catalysts in the catalytic
converters of automobiles
The three elements used for catalytic converters listed in the article are platinum, palladium
and rhodium.
9
ChemMatters Puzzle: Su-Chem-Du
Here’s a variation of a SUDOKU puzzle that needs some chemical knowledge as well as logic
to solve.
1. Instead of numbers, we’re using nine letters in the grid: alphabetically they are C D E I N O R
T and U.
Note that five of those letters are one-letter symbols of an element, namely C,I,N,O, and U,.
2. The more letters in the grid at the start, the easier its solution. We’re providing several of the
letters
directly and 14 more can come from clues below. Any box in the grid with a number has as
its letter one
of our five elements. The clue should help you zero in on the proper one.
3. Once you’ve answered as many clues as you can, proceed to solve the Sudoku grid.
Remember that any
given letter must appear exactly ONCE in each row, column, and 3x3 square.
At any time you can go back to identify any remaining clues.
4. When finished, the letters in the top row complete this phrase: “In REDOX, the gaining of
electrons is…”
D
U
T
5
N
O
C
8
1
C
I
N
O
10
T
4
N
E
2
U
T
9
R
U
O
I
E
O
C
C
U
3
N
13
U
T
D
C
11
7
D
I
O
12
I
N
U
E
14
C
6
10
THE CLUES
1. Makes up about 36% by weight in laughing gas.
2. Makes up about 64% by weight in laughing gas.
3. A commercial source of this element is kelp in sea water.
4. Its 235 isotope is fissionable.
5. The key element in organic chemistry.
6. DNA has less of it than comparable RNA does.
7. In organic chemistry “amine” denotes the presence of this element, along with hydrogen.
8. Its 131 isotope is sometimes used in thyroid medical treatments.
9. The heaviest of the naturally occurring elements.
10. Its four outermost half-filled sp3 orbitals can fuse with like atoms to form a DIAMOND
crystal.
11. It has the next-to- highest electronegativity of all the elements.
12. Of all the atoms in Earth’s atmosphere, about 4/5th of them are of this element.
13. It dissolves in non-polar solvents, making a beautiful violet color.
14. Alpha decay of its most common isotope produces Th-234.
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Answers to the ChemMatters Puzzle
R
E
D
U
T
N
O
I
8
C
N
D
O
T
I
D
C
5
E
R
O
1
C
N
2
U
I
U
9
N
O
R
E
D
T
R
I
C
10
U
4
D
T
E
O
U
E
T
N
O
C
I
R
3
N
D
T
C
R
I
13
E
U
U
O
11
T
E
D
C
N
7
R
I
C
D
R
I
T
N
12
O
U
14
E
E
I
N
O
6
R
U
D
T
C
THE CLUES
1.
2.
3.
4.
5.
6.
Makes up about 36% by weight in laughing gas.
Makes up about 64% by weight in laughing gas.
A commercial source of this element is kelp in sea water.
Its 235 isotope is fissionable.
The key element in organic chemistry.
DNA has less of it than comparable RNA does.
O
N
I
U
C
O
7. In organic chem., “amine” denotes the presence of this element, along with hydrogen
N
8. Its 131 isotope is sometimes used in thyroid medical treatments.
9. The heaviest of the naturally occurring elements.
10. Its four outermost half-filled sp3 orbitals can fuse with like atoms to form a DIAMOND.
11. It has the next-to- highest electronegativity of all the elements.
12. Of all the atoms in Earth’s atmosphere, about 4/5th of them are of this element
13. It dissolves in non-polar solvents, making a beautiful violet color.
14. Alpha decay of its most common isotope produces Th-234.
I
U
C
O
N
I
U
12
NSES Correlation
National Science Education
Content Standard Addressed
As a result of activities in
grades 9-12, all students
should develop understanding
Physical Science Standard
A: necessary to do scientific
inquiry.
Physical Science Standard
A: about scientific inquiry.
Physical Science Standard B:
of the structure and properties
of matter.
Physical Science Standard B:
of chemical reactions.
Life Science Standard C: of
matter, energy, and
organization in living systems.
Science and Technology
Standard E: about science
and technology.
Science in Personal and
Social Perspectives Standard
F: of personal and community
health.
Science in Personal and
Social Perspectives Standard
F: of science and technology
in local, national, and global
challenges.
History and Nature of
Science Standard G: of
science as a human endeavor.
History and Nature of
Science Standard G: of the
nature of scientific knowledge
History and Nature of
Science Standard G: of
historical perspectives.
Fighting
Cancer with
Lasers
Sniffing
Out
Cancer
Electric
Car
Is Your
Car a
Living
Thing?
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
Brand-Name
vs. Generic
Drugs
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
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13
Anticipation Guides
Anticipation guides help engage students by activating prior knowledge and stimulating student
interest before reading. If class time permits, discuss students’ responses to each statement
before reading each article. As they read, students should look for evidence supporting or
refuting their initial responses.
Directions for all Anticipation Guides: Before reading, in the first column, write “A” or “D”
indicating your agreement or disagreement with each statement. As you read, compare your
opinions with information from the article. In the space under each statement, cite information
from the article that supports or refutes your original ideas.
14
Fighting Cancer with Lasers
Directions: Before reading, in the first column, write “A” or “D” indicating your agreement or
disagreement with each statement. As you read, compare your opinions with information from
the article. In the space under each statement, cite information from the article that supports or
refutes your original ideas.
Me
Text
Statement
1. Tumors smaller than a marble can cause severe, sharp pain.
2. Laser surgery involves aiming a laser beam at the tumor to destroy it.
3. The term LASER is an acronym.
4. Light from a laser has many wavelengths.
5. Lasers have mirrors inside.
6. Electrons emit photons of light when they become excited.
7. Lasers are already used to treat harmful cancers such as liver cancer.
8. Laser surgery has less risk of infection and less pain.
15
Brand-Name vs. Generic Drugs: What’s the Difference?
Directions: Before reading, in the first column, write “A” or “D” indicating your agreement or
disagreement with each statement. As you read, compare your opinions with information from
the article. In the space under each statement, cite information from the article that supports or
refutes your original ideas.
Me
Text
Statement
1. The U.S. FDA must regulate generic drugs.
2. Some people react better to generic drugs than to brand-name drugs.
3. By law, generic drugs and brand-name drugs must have exactly the same
ingredients.
4. Both your stomach and your small intestine have acidic environments.
5. One significant way generics may differ from brand-name drugs is the
amount of time it takes to dissolve in the body.
6. Switching from a brand-name to a generic drug is more risky than switching
from one generic drug to another generic drug.
7. No matter what the drug, all generic and brand-name drugs must be within
20% of each other on the concentration-time graph for the drug product.
8. By far, generic drugs are more dangerous than brand-name drugs.
9. If one epileptic patient has a seizure after taking a drug, that drug cannot be
sold any more.
16
Sniffing Out Cancer
Directions: Before reading, in the first column, write “A” or “D” indicating your agreement or
disagreement with each statement. As you read, compare your opinions with information from
the article. In the space under each statement, cite information from the article that supports or
refutes your original ideas.
Me
Text
Statement
1. A report of a dog alerting his owner to a malignant melanoma was first
published in 2002.
2. Vapor pressure depends on intermolecular forces.
3. Cancerous cells produce different concentrations of volatile organic
compounds (VOCs) than healthy cells do.
4. A dog’s sense of smell is up to 100,000 times better than a human’s sense of
smell.
5. Cigarette smoke interferes with a dog’s ability to detect lung cancer in a
patient’s breath.
6. Researchers need to know what chemical they are looking for before they can
train dogs to detect cancer-related smells.
7. Artificial noses are being developed that will eventually take over the work of
dogs in detecting cancer in human patients.
8. All VOCs in our environment are harmful to human beings.
17
Drivers, Start Your Electric Engines!
Directions: Before reading, in the first column, write “A” or “D” indicating your agreement or
disagreement with each statement. As you read, compare your opinions with information from
the article. In the space under each statement, cite information from the article that supports or
refutes your original ideas.
Me
Text
Statement
1. Electric cars require much less maintenance than cars with internal
combustion engines.
2. Electric cars in use today require 220-volt charging stations.
3. Today’s electric cars can travel about 400 miles before being recharged.
4. Electric cars were available in the early 20th century.
5. Lead-acid batteries can be recharged indefinitely.
6. Lead-acid batteries are found in today’s golf carts and gasoline-fueled cars.
7. Lithium batteries were not developed until the late 20th century.
8. Lithium-ion batteries are much lighter than lead-acid batteries, and they can
store much more energy per kilogram than lead-acid batteries.
18
Is Your Car a Living Thing?
Directions: Before reading, in the first column, write “A” or “D” indicating your agreement or
disagreement with each statement. As you read, compare your opinions with information from
the article. In the space under each statement, cite information from the article that supports or
refutes your original ideas.
Me
Text
Statement
1. The only similarity between a car and a living organism is that a car uses
energy.
2. The most common internal combustion engine has two steps that occur in
each cylinder.
3. On average, between 10 and 20 mitochondria are found in each cell of a
human body.
4. Mitochondria convert sugar to energy in four steps.
5. A person releases energy much faster than a car.
6. Catalytic converters have a large surface area and a catalyst, both of which
speed up reaction rates.
7. Before entering the catalytic converter, the main pollutants in automobile
exhaust are carbon monoxide, unburned hydrocarbons, and nitrogen oxides.
8. Charles’s Law describes how the heat produced in a car engine makes the
gases expand very rapidly.
19
Reading Strategies
These matrices and organizers are provided to help students locate and analyze information from
the articles. Student understanding will be enhanced when they explore and evaluate the
information themselves, with input from the teacher if students are struggling. Encourage
students to use their own words and avoid copying entire sentences from the articles. The use of
bullets helps them do this. If you use these reading strategies to evaluate student performance,
you may want to develop a grading rubric such as the one below.
Score
Description
4
Excellent
3
Good
2
Fair
1
Poor
0
Not
acceptable
Evidence
Complete; details provided; demonstrates deep
understanding.
Complete; few details provided; demonstrates
some understanding.
Incomplete; few details provided; some
misconceptions evident.
Very incomplete; no details provided; many
misconceptions evident.
So incomplete that no judgment can be made
about student understanding
Teaching Strategies:
1. Links to Common Core State Standards: There are several opportunities to compare
alternatives in this issue of ChemMatters. For example, you might ask students to take
sides and find support for one of the following:
a. Using brand-name vs. generic drugs
b. Driving electric cars vs. cars with internal combustion engines
2. To help students engage with the text, ask students what questions they still have about
the articles.
3. Vocabulary that may be new to students:
a. VOCs
b. Internal combustion engine
4. Important chemistry concepts that will be reinforced in this issue:
a. Reaction rate
b. Oxidation and reduction
20
Fighting Cancer with Lasers
Directions: As you read the article, describe how tumors are treated with lasers.
Detection
Locating tumor
during surgery
Directing laser into
tumor
Laser energy
production
Future uses of
lasers in removing
tumors
Advantages of laser
surgery
Disadvantages of
laser surgery
21
Brand-Name vs. Generic Drugs: What’s the Difference?
Directions: As you read, compare brand-name and generic drugs using the chart below.
Brand-Name Drugs
Generic Drugs
Similarities
22
Sniffing Out Cancer
Directions: As you read, describe they VOCs produced in cancer cells, then compare how dogs
and machines can detect cancer in humans.
What are they?
How are VOCs produced by cancer
cells different from those produced by
normal cells?
VOCs
Dogs
Artificial Noses
Advantages
Cancer
detection
Future use in
cancer
detection
23
Drivers, Start Your Electric Engines!
Directions: As you read, compare lead-acid and lithium-ion batteries using the chart below.
Lead-Acid Battery
Lithium-ion Battery
When were they
developed?
What chemicals
are involved?
How do they
work?
What are the
electrodes made
of?
Where are they
used?
Compare the
reactivity of the
metals involved.
24
Is Your Car a Living Thing?
Directions: As you read, compare the chemical processes in you and a car.
Process
You
A car
Digestion
Energy generation
Cleaning
25
Fighting Cancer with Lasers
Background Information
(teacher information)
More on the history of lasers
The concept of the laser was first brought forth by Albert Einstein in 1917. His work
seemed to always focus on light (no pun intended), and the idea of the laser was just a small
piece of his studies. He theorized about stimulated emission of radiation, saying that if there
were a large number of energized atoms each ready to emit a photon at a random time in a
random direction, and if a stray photon happened to pass by, the energized atoms would be
stimulated by its presence to emit their photons early. These new photons, he said, would have
the same direction and same frequency as the original “trigger” photon. Repeating this process
with more and more “stray” photons with each pass would result in laser light.
Of course, Einstein never actually built a laser; he was, after all, a theorist, not an
engineer. Building a laser would have to wait until 1960, when Theodore Maiman and coresearchers actually built the first working laser. But prior to the first laser, a slightly different
version of the same concept had been designed. In 1954 Charles Townes (Columbia University)
and James Gordon (Bell Labs) in the U.S. and Nikolai Basov and Alexander Prokhorov of the
Lebedev Institute of Physics, Moscow, developed the first maser, microwave amplification by
stimulated emission of radiation. This instrument showed the feasibility of building a laser and it
set many scientists; e.g., Arthur Schawlow and Charles Townes, to speculate about using
visible light to achieve the same goal. Their research led them to construct an optical cavity that
contained two highly reflecting mirrors with the amplifying medium between them. On the basis
of this work they thereafter applied for the first patent for an “optical maser”.
Gordon Gould, a graduate student working with Townes worked to build a visible light
instrument similar to the optical maser, but he called it a laser. He was the first person to coin
the term. He began work on his laser in 1958, but he failed to file a patent until 1959. His patent
was denied in favor of Townes’ and Schawlow’s patent. In 1987, Gould was finally granted
patent rights for a gas-discharge laser, following a protracted 30-year legal battle.
26
Theodore Maiman of the
Hughes Research
Laboratories actually built the
first laser, using a synthetic
ruby crystal as the lasing
medium. The ruby was
silvered on both ends, one
end completely and the other
one partially. It was
stimulated using flashes of
intense light from a xenon
flashtube. The first
demonstration of laser light
occurred on May 16, 1960.
This laser is referred to as a
pulsed laser, meaning that
the laser light emanated in a
series of pulses.
(National Ignition Facility
https://lasers.llnl.gov/education/how_lasers_work.php)
The first continuous laser using helium and neon gases was developed at Bell Labs by
Ali Javan, William Bennett and Donald Herriot. It was demonstrated on December 12, 1960, just
months after Maiman’s laser debuted. The He-Ne laser was the first to be stimulated by an
electric current rather than a light pulse. He-Ne lasers were the first lasers to be mass-produced
and they found widespread commercial use, from store UPC barcode scanners to video disc
players and medical technologies and laser printers. Today they have largely been replaced by
diode-pumped solid state lasers and laser diodes.
In 1961, the first neodymium glass (Nd-glass) laser was demonstrated. This type of
laser, much refined, is what is used in the National Ignition Facility’s 102-laser device (see
“More on national security”, below).
Nineteen sixty-two saw many advancements on the laser front. In that year the first
gallium-arsenide (Ga-As) laser was developed. This was a semi-conductor device that
converted electrical energy into IR light; it needed to be cooled to operate. Also developed in
1962 was the gallium arsenide phosphide (GaAsP) “visible red” laser diode. It was the precursor
to today’s red LED used in CD and DVD players. The first yttrium aluminum garnet (YAG) laser
was also developed in 1962.
Carbon dioxide lasers were developed in the early 1960s (Kumar Patel at Bell Labs in
1964 made the first). It is still one of the most useful of all types, due in no small part to the
persistent efforts by Patel to find new uses for his device.
In industry, the CO2 laser is used for welding, drilling and cutting, even at the
microscopic level. In medicine it is used in laser surgery, as well as noninvasive procedures. In
science, it is used to analyze the composition of the upper atmosphere, even detecting
pollutants down to parts per trillion (ppt). In military applications, the CO2 laser was used in
Ronald Reagan’s “Star Wars” laser defense system.
Nineteen sixty-six saw a breakthrough involving fiber optics. It was discovered that pure
glass fibers could be used to transmit light over 100 km. Telecommunications via fiber optics
was born. (http://www.photonics.com/Article.aspx?AID=42279)
27
In 1970 another new type of laser was developed, called an excimer laser—short for
excited dimer laser. The first excimer laser (1970) produced a xenon dimer (Xe2), excited by an
electron beam. It underwent stimulated emission at the 172 nm wavelength. These excimers
can only exist in an energized state, and they generally produce laser light in the ultraviolet
range of the electromagnetic spectrum.
Within five years an improved version, an exciplex, had been developed. These lasers
used a noble gas—argon, krypton or xenon—and a reactive halogen gas (fluorine or chlorine)
as the laser medium. At high pressure and electric stimulation, the two gases form a pseudomolecule, an exciplex, an excited complex. Like excimers, exciplexes only exist in the excited
state and they also produce light in the UV range. Today, most excimer lasers are really
exciplex lasers, since they use two different gases, while a dimer is a diatomic molecule of only
one gas. The term exciplex, however, has not caught on.
Over the years, laser discoveries have been mixed with new uses for those developed
lasers. The new laser discoveries typically became more complex, but they also became more
“user-friendly” as lasers were miniaturized and became part of everyday life. Uses of lasers are
discussed later in this Teacher’s Guide.
More on laser science and chemistry
A series of short (1–2 page) articles in past ChemMatters issues called “Question from
the Classroom:” dealt with questions posed by students themselves and answered by Bob
Becker. One such article appearing in the April 2003 issue was “How do lasers work and what
is so special about laser light?”
Here’s Bob’s response:
The answers can be found in one very excited group of electrons!
You may recall that an atom’s electrons can only exist in very specific, discrete
energy levels. When they absorb energy, they can become excited from their ground
state up to a higher level. Being unstable there, however, they immediately drop back to
a lower level, and when they do, they emit a photon of light.
The energy of this photon depends on the specific electron drop that occurred.
For example, in a hydrogen atom, an electron dropping from level 3 to level 2 emits light
with a wavelength of precisely 656 nm—a red band in the visible spectrum.
In a similar way, fluorescent lights make indirect use of gaseous mercury atoms
whose electrons are excited by electrical current. Because the ground state is more
stable, only a small fraction of the mercury atoms are in the excited state at any point in
time. When an emitted photon strikes another mercury atom, it will most likely be in the
ground state, so it will probably absorb the photon, only to reemit it immediately
afterward.
The UV light emitted as the electrons fall back to their ground states is invisible—
not exactly what you want in a light bulb. Then how do fluorescent bulbs light up your
classroom? Visible light results when ultraviolet light emitted by the mercury strikes the
phosphor coating on the inside of the bulb.
28
Laser devices also involve excited electrons, but there is an important difference.
The sample inside the device is being constantly pumped with a steady stream of
sufficiently high energy.
Under this condition, a population Inversion can occur. This means that there are
more electrons in the excited state than there are in the ground state at any point in time.
In this high-energy environment, a remarkable chain of events can occur:
1. In an “inverted population” an emitted photon from one atom
approaches another atom in which there is an excited electron.
Dropping
electron
Emitted
photon
Excited electron
of neighboring
atom
2. The approaching photon stimulates the excited electron of
the neighboring atom to drop. The second emitted photon
heads off in the same direction—matching the first one
crest for crest. The wavelengths match perfectly!
Coherent
light
Should this pair of photons happen to approach yet another excited atom, a third
photon will join their ranks, and so on. These synchronized photons are known as
coherent light, for they do not tend to spread apart the way regular light does as it travels
along.
Thus, the laser device simply consists of some medium to be excited (which can
vary from a gas mixture to a dye molecule to a ruby crystal) and an “energy pump”
pumping fast enough to cause a population inversion in that medium.
But there is one more important feature: a pair of mirrors facing one another on
either end of the excited medium. It is important to remember that when the sample of
atoms is excited and starts emitting light, the photons are emitted randomly in all different
directions. In the laser device, most of these photons are lost as they get absorbed into
the sidewalls. A small fraction, however, will just happen to emit their photons precisely
perpendicular to one of the two mirrors. This beam of photons will effectively have an
infinite path through the medium. Try positioning yourself between two perfectly parallel
mirrors, and you’ll witness this infinite pathway.
And as the photons bounce back and forth between the two mirrors, they
stimulate more and more excited electrons to drop and recruit more and more coherent
photons, amplifying the beam with each passage.
29
This light amplification by the stimulated emission of radiation goes by the
familiar acronym “LASER”. But this laser beam would be trapped inside the tube,
bouncing back and forth forever, if it were not for the fact that one of the two mirrors is
only partially reflective, allowing some of the coherent light to escape as a narrow beam.
Because this beam does not tend to spread apart, its energy can be focused in ways that
regular light cannot. This makes lasers much more powerful—and dangerous—than
ordinary light.
From guided missiles to supermarket bar-code scanners, from CD players to
fiber-optic phone connections, from tattoo removal to delicate eye surgery, there is no
question that our world would be quite different if it were not for lasers. But without
question, laser pointers should never be treated as toys. It’s very likely your school
district has banned them for non-classroom use.
(Becker, R. Question from the Classroom. ChemMatters 2003, 21 (2), pp 2–3,
http://portal.acs.org/portal/PublicWebSite/education/resources/highschool/chemmatters/a
rchive/CNBP_028409)
And here is an excerpt from the Teacher’s Guide that accompanied the issue containing
the Becker article, above.
The article nicely explains the nature of laser light and how it is created. A
concise answer to the question about how laser light differs from ordinary light has three
points:
(1) Laser light is monochromatic. It consists of only one specific wavelength,
although this wavelength will be different for different types of lasers. It is possible to
have regular non-laser light that is monochromatic. But we don’t often encounter this in
our everyday world. One possible exception is that of certain yellow street lights. These
are sodium vapor lights and are nearly monochromatic.
The specific wavelength of light emitted by a laser simply depends on the
magnitude of the energy difference between the two energy levels in the atoms that emit
the laser light. The greater this energy difference, the higher the frequency, the shorter
the wavelength, and the more energy carried by each photon of the light.
(2) Laser light is coherent. This is one of the key differences between it and
normal light. In laser light all the waves are moving in unison. In regular light the waves
move independently. Laser light is more organized. You might think of a highly trained
army marching along “in step,” vs. a bunch of people just casually walking across a field.
(3) Laser light is directional. The beam is very tight and concentrated. All the light
moves in the same direction, as opposed, for example, to the light emitted from a
flashlight or an incandescent bulb, which moves off in all different directions.
(Teacher’s Guide to Becker, R. Question from the Classroom. ChemMatters 2003, 21 (2),
pp 2–3)
The helium-neon (He-Ne) laser is the one most frequently used in high school physics
labs because it is relatively inexpensive and relatively safe. It is classified as a neutral gas laser.
The energy transitions for this laser are fairly easy to understand. The gas mixture (~5–10:1,
He:Ne) inside the laser cavity is first zapped (pumped, in laser terms) with approximately 1000
volts of electricity.
30
The laser process in a HeNe laser starts with collision of electrons from the
electrical discharge with the helium atoms in the gas. This excites helium from the ground
state to the 23S1 and 21S0 long-lived, metastable excited states. [See diagram.] Collision
of the excited helium atoms with the ground-state neon atoms results in transfer of
energy to the neon atoms, exciting them into the 2s and 3s states. This is due to a
coincidence of energy levels between the helium and neon atoms.
This process is given by the reaction equation:
He* + Ne → He + Ne* + ΔE
where (*) represents an excited state, and ΔE is the small energy difference
between the energy states of the two atoms, of the order of 0.05 eV.
The number of neon
atoms entering the excited
states builds up as further
collisions between helium and
neon atoms occur, causing a
population inversion between
the neon 3s and 2s, and 3p
and 2p states. Spontaneous
emission between the 3s and
2p states results in emission
of 632.8 nm wavelength light,
the typical operating
wavelength of a HeNe laser.
After this, fast
radiative decay occurs from
the 2p to the 1s energy levels,
which then decay to the
ground state via collisions of
the neon atoms with the
container walls. Because of
The energy level diagram for helium and neon in a He-Ne laser
this last required step, the
(http://www.chemistrydaily.com/chemistry/Image:Hene-2.png)
bore size of the laser cannot
be made very large and the
HeNe laser is limited in size and power.
(http://www.chemistrydaily.com/chemistry/Helium-neon_laser)
And we would be remiss if we did not mention safe use and potential hazards involved in the
use of lasers. Here is another excerpt from the April 2003 ChemMatters Teacher’s Guide, this
one dealing with the biological classifications of lasers.
There are four broad categories of lasers with a couple of sub-categories that
relate to their potential for causing biological damage. All lasers should be labeled as to
their biological classifications.
Class I—These are the least harmful. They cannot emit radiation at any known
harmful level. They are typically found in devices like laser printers, CD players, CD ROM
devices and laboratory analytical equipment. There are no safety requirements governing
their use.
31
Class IA—This classification applies only to lasers that are “not intended for
viewing.” The upper limit to the power output of these kinds of lasers is set at 4.0 mW, or
4.0 mill joules per second.
Class II—These are considered to be low-power lasers, but more powerful than
Class I. Their upper limit is 1 mW. Although a laser of this power can cause eye damage,
it is assumed that this is not likely to occur because of the human tendency to quickly blink
or in some other way divert their eyes when they are exposed to a bright light. Some laser
safety Web sites state that you would have to look at one of these lasers for an extended
period of time, perhaps as long as 15 minutes in order to sustain eye damage. Some laser
pointers fall into this category.
Class IIIA—These are considered to be of intermediate power, between 1-5 mW.
Most pen-like pointing lasers fall into this category. These are considered to be more
hazardous than Class II lasers and are never to be viewed directly. A Class IIIA laser
should never be pointed at a person’s eyes nor should the light ever be viewed with a
telescopic device.
Class IIIB—These are considered to be of intermediate power, between 5-500
mW. These are often used in spectrometry devices and entertainment light shows. These
are considered to be quite hazardous. They should never be viewed directly. Even diffuse
reflections can be dangerous.
Class IV—These are very high-powered lasers, up to 500 mW. They are used in
surgery, research, drilling, cutting and welding. These are very dangerous, not only to the
eyes, but to the skin as well. They can also constitute a fire hazard.
(Teacher’s Guide to Becker, R. Question from the Classroom. ChemMatters 2003, 21 (2),
pp 2–3)
More on uses of lasers
Excimer lasers
The wavelength of an excimer laser depends on the molecules used as the lasing
medium, and is usually in the ultraviolet region of the electromagnetic spectrum:
Excimer Wavelength
Relative Power
mW
Ar2*
126 nm
Kr2*
146 nm
Xe2*
172 & 175 nm
ArF
193 nm
60
100
KrF
248 nm
XeBr
282 nm
XeCl
308 nm
50
XeF
351 nm
45
KrCl
222 nm
25
(http://en.wikipedia.org/wiki/Excimer_laser)
32
These shorter wavelength lasers
produce energy that is absorbed by biological
material as well as organic compounds. The
effect is not burning or cutting, but rather a
disruption of chemical bonds at the surface
material. This effectively disintegrates into the
air in a process known as photoablation. This
results in removal of very thin layers of the
Microphotograph of cuts made in a human hair
surface material with almost no heat and no
by an excimer laser (a demonstration of the
subsequent damage to underlying material.
precision attainable using this technique)
These characteristics make excimer lasers
(http://www.defence.gov.au/health/infocentre/
very useful in delicate surface surgery, as in
journals/ADFHJ_sep03/images/84-92_6.jpg)
dermatology and especially in eye surgery. It
is also useful for precisely “micro-machining” organic materials, including some polymers and
plastics.
Eye surgery
LASIK® surgery and some other types of eye surgery use laser technology. (LASIK is an
acronym for Laser-Assisted in Situ Keratomileusis). The lasers used for LASIK are excimer
lasers, which generate laser light at 193 nm. An incision is made across the corneal surface to
create a flap, which can then be folded back to allow access to the tissue inside the cornea. The
instrument used to create this flap is a microkeratome, a metal scalpel of sorts. The excimer
laser is then used to cut away some of the underlying corneal tissue to resculpt the cornea to
improve vision.
Today, more advanced LASIK facilities use two different lasers for “bladeless” eye
surgery. A new device, the femtosecond laser, is used to cut the corneal flap, exposing the rest
of the cornea for surgery by the excimer laser. The femtosecond laser produces bursts of laser
light at 1053 nm (in the infrared region of the electromagnetic spectrum), a much longer
wavelength and therefore lower energy light than the excimer laser. The cornea is transparent
to the femtosecond pulses and is not damaged by them. The shorter wavelength excimer laser
light will destroy corneal tissue, but only very tiny amounts at a time, in order to reshape the
cornea. The process of removing corneal tissue is known as photoablation. It is not really a
burning of tissue, but rather a vaporizing of the tissue as it breaks carbon-carbon bonds.
The femtosecond laser is a vast improvement over the metal blade, as it results in much
more accurate cuts and far fewer post-operative complications.
(http://www.ehow.com/about_5188350_kind-used-laser-eye-surgery_.html)
The femtosecond laser procedure was developed at the University of Michigan in 2003.
(http://www.lasereyesurgery.com/a-kindler-gentler-cut-for-lasik.html)
Skin surgery
Excimer lasers are also used for other types of surgeries, including dermatological
applications and even angioplasty. The only major disadvantage to excimer lasers is their rather
large size, which makes them less desirable for their medical applications. Future development
may decrease their size.
Photolithography—making computer chips
33
Other uses include photolithography, manufacturing microelectronic devices like
semiconductor integrated circuits. A newer version of excimer laser involves the use of KrF and
ArF dimer lasers that produce even smaller wavelength UV light called deep UV. Use of deep
UV lithography has miniaturized electronic chip manufacture to the 22-nm level, allowing the
continuance of Moore’s law for at least another decade. (Moore’s law states that the number of
transistors on integrated circuits doubles approximately every two years.)
Newer developments in excimer laser use




Excimer lasers are being used in these developmental areas as well:
Silicon annealing and recrystallization—used in flat-screen technology
Micromachining of plastic parts—used in inkjet nozzle drilling in inkjet printers
Surface modification—used in greener automobile manufacturing; e.g., Audi cars
Pulsed Laser Deposition (PLD)—used in making superconducting tape
(http://photonics.com/Article.aspx?AID=25164)
The excimer laser has become an indispensible tool of our technological world, so much
so that President Barack Obama awarded Samuel Blum, Rangaswamy Srinivasan and James
Wynne, all from IBM, and co-inventors of the ultraviolet excimer laser, a National Medal of
Technology and Innovation. Gholam Peyman, the retina surgeon credited with invention of the
Lasik eye surgery procedure (which uses the excimer laser), from Arizona Retinal Specialists,
was also awarded one of these prestigious medals.
More on national security
The U.S. National Ignition Facility (NIF), headquartered at the Lawrence Livermore
National Laboratory, is charged with three missions:
 National Security: How do we ensure the nation’s security without nuclear weapons
testing?
 Energy for the Future: Where will the world’s energy come from when all the fossil fuels
are gone? and How can we produce the energy we need without causing catastrophic
climate change?
 Understanding the Universe: How did the universe come into being? How did the stars
and planets form? What happens in supernovas and black holes?
One of the facility’s primary goals has been to develop conditions which could initiate a
fusion reaction. To reach this goal, the program has built a huge building (think ten stories high,
the size of three football fields) to contain an experiment that uses192 very powerful lasers all
aimed at a tiny target in the target chamber in the center of the building. The incident ultraviolet
light energy will be approximately 2 million joules of energy, all impacting the central target
simultaneously. This energy will create “conditions similar to those that exist only in the cores of
stars and giant planets and inside a nuclear weapon. The resulting fusion reaction will release
many times more energy than the laser energy required to initiate the reaction.”
(https://lasers.llnl.gov/about/nif/)
In order to ensure that the output of the 192 beamlines is uniform, the initial light is
generated from a single source—a low-power flash of 1053 nm infrared light. This is generated
by an ytterbium-doped solid state optical fiber laser. The flash from this driver laser is then split
34
and sent into 48 preamplifier modules which amplify the beams. The partially-amplified light
goes into the system of 192 flashlamp-pumped neodymium-doped phosphate glass lasers to be
greatly amplified before entering the target chamber. A much more detailed account of the
generation process can found at http://en.wikipedia.org/wiki/National_Ignition_Facility, or at the
NIF Web site:
The light emitted from these 192 lasers is infrared light, which is later converted to
ultraviolet light just before impacting the target. The 2 million Joules of laser energy slamming
into “millimeter-sized targets ... can generate unprecedented temperatures and pressures in the
target materials—temperatures of more than 100 million degrees and pressures more than 100
billion times Earth’s atmosphere.” (https://lasers.llnl.gov/about/nif/about.php) Initiating the fusion
reaction will simultaneously further the goals of the three missions discussed above. As of the
writing of this Teacher’s Guide, experiments called “shots” have already produced 1.89 MJ of
energy inside the NIF—very close to the 2 million MJ expected to be required for fusion
initiation.
But fusion initiation is not the only experiment being done in NIF. Other laser shots will
help scientists better understand properties of material under extreme conditions and
hydrodynamics, “the behavior of fluids of unequal density as they mix”. Extremely high-speed
cameras (a billion frames a second!) inside the target chamber can be used to diagnose the
results of the experiments.
This video clip describes how the NIF laser-induced fusion reaction will work:
https://lasers.llnl.gov/multimedia/video_gallery/how_nif_works.php. If this is unavailable, you can
also access it on YouTube at
http://www.youtube.com/watch?v=yixhyPN0r3g&NR=1&feature=endscreen.
35
Selected other uses for lasers
Consumer
 Laser pointers
 Gunsights and targeting systems
 CD and DVD players
 Leveling devices
 Fiber optics for data and
telecommunications
 Supermarket barcode scanners
 Laser printers
 Holograms
Research
 Spectroscopy
 UV-Vis
 IR
 Fluorescence
 Raman
 Non-linear
 Laser-induced Breakdown (of
molecules)
 Laser-induced chemical reactions
 Monitoring of chemical intermediates
in reactions
 Detection of pollutants in air, in
wastewater
 Creating extremely low temperatures
at the atomic level
Industry
 Transfer energy to different materials
very quickly (cooling and heating)
 Welding
 Cutting
 Drilling
 Marking
 Scribing
 Soldering
 Micro-machining
 Heat treating
 Metal deposition
 Paint stripping and surface removal
 Measuring
 Distances–remote sensing
 Concentrations
 Cylindricity of ball bearings
 Thickness by shadow
 Speed (LIDAR, like radar,
only with laser)
Medicine
 Precision surgery
 Tumor removal/ablation
 Cosmetic surgery
 Dermatology
 Dentistry
 Laser acupuncture
More on osteoid osteoma
This excerpt from a Web-published medical report from the Royal Belgian Society of Radiology
affirms claims made about osteoid osteoma in the ChemMatters article. The report concerns a
32-year old man complaining of recurrent pain in the upper thigh.
Radiological diagnosis
Clinical data and imaging findings are strongly suggestive for a subperiosteal
osteoid osteoma of the right acetabulum. Patient underwent a percutaneous CT guided
thermocoagulation [needle through the skin and laser heating, tissue destruction of the
lesion and had no more pain after this procedure. Biopsy confirmed the diagnosis.
[Editor’s note: This means the CT scan tells where the tumor is; the needle is
inserted there through the skin (percutaneous); the laser does the thermo-ablation and
heats the tumor to oblivion; the patient is all better, just like the ChemMatters article said.]
Discussion
Osteoid osteoma is a well known benign osteoblastic tumor, most commonly
found in the cortical bone of the long bone shaft and spine. Fusiform sclerosis and a
36
central nidus [place of origin] are seen on radiographs, CT and MRI. The nidus is “hot” on
scintigraphy.
Subperiosteal extra-osseous lesions are rare and arise adjacent to bone, usually
in the femoral neck, talar neck, hand and foot. Patients are young, usually between 5-40
years. Male/female ratio is 2-3:1. Pain is almost invariably the presenting complaint. Pain
relief is accomplished with acetylsalicylic acid. Surgical excision or percutaneous CT
guided thermo-ablation are curative and will bring dramatic relief of symptoms.
(http://www.rbrs.org/dbfiles/journalarticle_0357.pdf)
More on laser treatment of tumors
The laser used in the treatment of Chris’ osteoid osteoma may well have been a
neodymium-doped yttrium-arsenic-garnet (Nd:YAG) laser. “Nd:YAG lasers emitting light at 1064
nm have been the most widely used laser for laser-induced thermotherapy, in which benign or
malignant lesions in various organs are ablated by the beam.”
(http://en.wikipedia.org/wiki/Nd:YAG_laser)
The National Cancer Institute Web page on laser treatment of cancer provides this information:
Key Points

Laser light can be used to remove cancer or precancerous growths or to relieve
symptoms of cancer. It is used most often to treat cancers on the surface of the
body or the lining of internal organs.

Laser therapy is often given through a thin tube called an endoscope, which can
be inserted in openings in the body to treat cancer or precancerous growths
inside the trachea (windpipe), esophagus, stomach, or colon.

Laser therapy causes less bleeding and damage to normal tissue than standard
surgical tools do, and there is a lower risk of infection.

However, the effects of laser surgery may not be permanent, so the surgery may
have to be repeated.
1. What is laser light? [We already know the answer to this one.]
The term “laser” stands for light amplification by stimulated emission of radiation.
Ordinary light, such as that from a light bulb, has many wavelengths and spreads in
all directions. Laser light, on the other hand, has a specific wavelength. It is focused
in a narrow beam and creates a very high-intensity light. This powerful beam of light
may be used to cut through steel or to shape diamonds. Because lasers can focus
very accurately on tiny areas, they can also be used for very precise surgical work or
for cutting through tissue (in place of a scalpel).
2. What is laser therapy, and how is it used in cancer treatment?
Laser therapy uses high-intensity light to treat cancer and other illnesses. Lasers can
be used to shrink or destroy tumors or precancerous growths. Lasers are most
commonly used to treat superficial cancers (cancers on the surface of the body or the
lining of internal organs) such as basal cell skin cancer and the very early stages of
some cancers, such as cervical, penile, vaginal, vulvar, and non-small cell lung
cancer.
37
Lasers also may be used to relieve certain symptoms of cancer, such as bleeding or
obstruction. For example, lasers can be used to shrink or destroy a tumor that is
blocking a patient’s trachea (windpipe) or esophagus. Lasers also can be used to
remove colon polyps or tumors that are blocking the colon or stomach.
Laser therapy can be used alone, but most often it is combined with other treatments,
such as surgery, chemotherapy, or radiation therapy. In addition, lasers can seal
nerve endings to reduce pain after surgery and seal lymph vessels to reduce swelling
and limit the spread of tumor cells.
3. How is laser therapy given to the patient?
Laser therapy is often given through a flexible endoscope (a thin, lighted tube used to
look at tissues inside the body). The endoscope is fitted with optical fibers (thin fibers
that transmit light). It is inserted through an opening in the body, such as the mouth,
nose, anus, or vagina. Laser light is then precisely aimed to cut or destroy a tumor.
Laser-induced interstitial thermotherapy (LITT), or interstitial laser photocoagulation,
also uses lasers to treat some cancers. LITT is similar to a cancer treatment called
hyperthermia, which uses heat to shrink tumors by damaging or killing cancer cells.
(More information about hyperthermia is available in the NCI fact sheet Hyperthermia
in Cancer Treatment.) During LITT, an optical fiber is inserted into a tumor. Laser
light at the tip of the fiber raises the temperature of the tumor cells and damages or
destroys them. LITT is sometimes used to shrink tumors in the liver.
Photodynamic therapy (PDT) is another type of cancer treatment that uses lasers. In
PDT, a certain drug, called a photosensitizer or photosensitizing agent, is injected
into a patient and absorbed by cells all over the patient’s body. After a couple of
days, the agent is found mostly in cancer cells. Laser light is then used to activate the
agent and destroy cancer cells. Because the photosensitizer makes the skin and
eyes sensitive to light afterwards, patients are advised to avoid direct sunlight and
bright indoor light during that time. (More information about PDT is available in the
NCI fact sheet Photodynamic Therapy for Cancer.)
4. What types of lasers are used in cancer treatment?
Three types of lasers are used to treat cancer: carbon dioxide (CO 2) lasers, argon
lasers, and neodymium:yttrium-aluminum-garnet (Nd:YAG) lasers. Each of these can
shrink or destroy tumors and can be used with endoscopes.
CO2 and argon lasers can cut the skin’s surface without going into deeper layers.
Thus, they can be used to remove superficial cancers, such as skin cancer. In
contrast, the Nd:YAG laser is more commonly applied through an endoscope to treat
internal organs, such as the uterus, esophagus, and colon.
Nd:YAG laser light can also travel through optical fibers into specific areas of the
body during LITT. Argon lasers are often used to activate the drugs used in PDT.
5. What are the advantages of laser therapy?
Lasers are more precise than standard surgical tools (scalpels), so they do less
damage to normal tissues. As a result, patients usually have less pain, bleeding,
swelling, and scarring. With laser therapy, operations are usually shorter. In fact,
laser therapy can often be done on an outpatient basis. It takes less time for patients
to heal after laser surgery, and they are less likely to get infections. Patients should
38
consult with their health care provider about whether laser therapy is appropriate for
them.
6. What are the disadvantages of laser therapy?
Laser therapy also has several limitations. Surgeons must have specialized training
before they can do laser therapy, and strict safety precautions must be followed.
Laser therapy is expensive and requires bulky equipment. In addition, the effects of
laser therapy may not last long, so doctors may have to repeat the treatment for a
patient to get the full benefit.
7. What does the future hold for laser therapy?
In clinical trials (research studies), doctors are using lasers to treat cancers of the
brain and prostate, among others. To learn more about clinical trials, call NCI’s
Cancer Information Service at 1–800–4–CANCER or visit the clinical trials page of
NCI’s Web site.
(http://www.cancer.gov/cancertopics/factsheet/Therapy/lasers)
Laser treatment of tumors is not the only game in town, either; treatment of tumors by
thermal ablation can be done using many different moieties. “Thermal tumor ablation modalities
either freeze or heat tumors to lethal temperatures. These include cryoablation, radiofrequency
(RF), microwave, laser and high-intensity focused ultrasound (HIFU).”
(http://www.cancernews.com/search/fulltext.asp?cat=26&aid=504&Type=all&SearchStr=laser&
Archives=on)
Especially for liver tumors, invasive surgery is often not the answer, as liver cancer is
often discovered in late stages of development, potentially with many tumors spread throughout
the liver. Image-guided tumor ablation then becomes the best choice for treatment for these
types of cancers.
More on the effect of heat on tumors
Local hyperthermia (ablation) is the process of heating tumors to the point of extinction.
The effect of increased temperature on tumor cells is to desiccate the cells, thereby destroying
them and the tumor, coagulating nearby proteins and destroying blood vessels that had
supplied blood to the tumor. In effect, the cells are “cooked”. The hoped-for outcome is total
destruction of the tumor, or at least diminishing its size and slowing its growth. As mentioned
previously, thermal ablation can use any of the following sources of energy. Here is a short
video clip from the University of Wisconsin-Madison that describes thermal ablation:
 Radio frequency ablation (RFA)
 Ultrasound ablation (HIFU—high intensity focused ultrasound)
 Laser ablation
 Microwave ablation
 Electric current
The method the doctor finally chooses to use depends on many factors; e.g., size of the tumor,
its location, the number of tumors, proximity to other body parts, degree of comfort/familiarity of
doctor with using method, cost, past efficacy, etc.
39
Here is a short (7:16) video clip from the University of Wisconsin-Madison that describes
thermal ablation and discusses one patient’s treatment, from observations and diagnosis right
through to the actual operation and follow-up: http://www.jove.com/video/2596/thermal-ablationfor-the-treatment-of-abdominal-tumors. (The video uses very detailed medical terminology, but
students may actually like the video because of this.)
More on other modes of treatment
The use of lasers in the treatment of cancer is a relatively new development. Here are a
few other modalities—other than surgery, radiation and chemotherapy—that have been in use
for some time, and a few new ones that are getting attention as well.
From the ChemMatters Teacher’s Guide for October 2007, one article of which dealt
with the life and research of Percy Julian, a specialist in developing useful products from the soy
bean and the yam, comes the following:
Anticancer Drugs—There are a number of drugs used to treat cancer which are derived
from plants. Among them are:

Rosy periwinkle (Catharanthus roseus)—used to treat leukemia and Hodgkin’s
Disease

Mayapple—This plant contains podophyllotoxin, which is the starting material for
producing the antitumor agent etoposide, used for the treatment of lung and
testicular cancer.

Pacific Yew(taxus brevifolia)—contains the compound taxol, used in the
treatment of ovarian and breast cancer.
And the following excerpt is from the ChemMatters Teacher’s Guide for December 2001.
The article for which the material was researched is “Trolling the Seas for New Medicines”:
One of the most exciting and promising of new anti-cancer drugs may be a
compound called ecteinascidin (pronounced ed-TIN-aside-in) and a simpler, easier to
make form called phthalascidin (pronounced THAL-aside-in). This has been described as
“the most complicated molecule ever to be made on a commercial scale” by Elias, J.
Corey, who won the 1990 Nobel Prize in chemistry. The two primary researchers are
Corey, and one of his graduate students, Eduardo Martinez. The drug is approximately
100-500 times stronger than Taxol in inhibiting tumor cell growth, and in general is
estimated to be hundreds to thousands of times more potent than most current cancer
drugs. Researchers estimate that eleven pounds of the drug would be sufficient to satisfy
the needs of the entire world for a year. So promising is this drug that it is being rushed
through clinical trials and it is hoped that it may be available some time in 2002.
At the present time, ecteinascidin is being tested on terminally ill patients afflicted
with cancers of the blood vessels, tendons, muscles, and other soft tissues. According to
Corey, “There hasn’t been effective chemotherapy for such cancers.”
The drug was first discovered by Ken Rinehart of the University of Illinois in the
1980s. Rinehart obtained the original samples of the drug from sea squirts (Ecteinascidia
turbinate) he collected from reefs in the West Indies.
The drug provides an excellent illustration of the difficulties often encountered in
trying to isolate a drug from a marine organism. Ten pounds of sea squirts only yielded a
few millionths of an ounce of ecteinascidin. Attempts to “farm” sea squirts achieved very
40
limited success. Clearly what was needed was a way to synthesize the drug rather than
obtaining it from sea squirts. Following a two-year effort, David Gin, a post-doctoral
student at Harvard University, achieved the synthesis in 1996. Even then, the synthesis
was tedious. A more efficient process was developed by Eduardo Martinez.
Ecteinascidin evidently works by interacting with DNA and an unknown protein
contained in cancer cells. Unlike standard chemotherapy treatments, which kill cancer
cells—and healthy cells as well—the drug doesn’t actually kill cells. Instead, it prevents
treated cells from reproducing and growing.
When tested on drug-resistant colon, lung, melanoma, and prostate tumor cells
grown in Petri dishes, the drug inhibited cell growth in all cases. If it works as well on
patients, this will prove to be one of the most important anti-cancer drugs ever developed.
(Teacher’s Guide for Black, H. Trolling the Seas for New Medicines. ChemMatters 2001, 19 (4),
pp 6–7).
But the oceans aren’t the only source of cancer-fighting substances. One Web
page on the PBS site is called “Venom’s Healing Bite” by Kate Becker. This page
focuses on six venomous animals, the fluids from whose bites or stings are being
researched as potential cures for various diseases/symptoms. Three of the six studies
focus on cancer treatment.
Targeting cancer
The sting of the "death stalker" scorpion, Leiurus quinuestriatus, contains
neurotoxins that can paralyze and kill. But one component of this scorpion's venom,
chlorotoxin, could one day save lives, too, because it is drawn to cancer cells like a
magnet to iron. By combining a synthetic chlorotoxin with a radioactive form of iodine,
researchers can deliver radiation directly to cancer cells. Nanoparticle-spiked chlorotoxin
may also slow the spread of cancer and could help deliver gene therapy to cancer cells.
Because chlorotoxin can cross the blood-brain barrier, scientists are particularly
interested in using it to treat brain cancers like glioma. Chlorotoxin can also help doctors
spot cancer cells by selectively "painting" them with a fluorescent beacon.
Keeping tumors in check
The bite of the southern copperhead Agkistrodon contortrix, a pit viper common
in the eastern United States, is rarely fatal to humans, but it delivers a painful dose of
venom. One component of the venom, a protein named contortrostatin, could stop the
spread of cancer cells. Contortrostatin doesn't kill cancer cells; instead it holds them in
check by interfering with surface proteins and blocking other mechanisms the cells need
to move around the body. Contortrostatin also starves out tumors by staunching the
growth of blood vessels that deliver nutrients to the malignant cells. Contortrostatin has
been tested on breast, ovarian, prostate, melanoma, and brain cancers in mice, and
researchers hope to start human clinical trials soon.
Killing cancer cells
The sharp pain of a honeybee sting is caused in part by a peptide called melittin,
which kills cells by piercing holes in their membranes. To turn this indiscriminate killer into
a fine-tuned cancer drug, researchers have combined it with nanoparticles and cancertargeting agents that allow the melittin to "sting" cancer cells without harming healthy
cells. Though the treatment has not yet been tested on human patients, it has shown
41
promise on mice. Researchers also hope to harness melittin's cell-killing power to knock
out other diseases, including bacterial and fungal infections and arthritis.
(http://www.pbs.org/wgbh/nova/body/venoms-healing-bite.html)
From the October 14, 2010 edition of Science Daily comes this report of doctors at Mayo
Clinic’s Florida campus successfully using laser ablation for kidney and liver tumors. Laser
ablation has been used extensively for brain tumors, but until now (2010) it had not been used
in the U.S. for soft tissue.
Physicians at Mayo Clinic's Florida campus are among the first in the nation to
use a technique known as MRI-guided laser ablation to heat up and destroy kidney and
liver tumors. So far, five patients have been successfully treated -- meaning no visible
tumors remained after the procedure.
They join their colleagues at Mayo Clinic's site in Rochester, Minn., who were the
first to use laser ablation on patients with recurrent prostate tumors.
Although the treatment techniques are in the development stage, the physicians
say the treatment is potentially beneficial against most tumors in the body -- either
primary or metastatic …
"Laser ablation offers us a way to precisely target and kill tumors without harming
the rest of an organ. We believe there are a lot of potential uses of this technique -- which
is quite exciting," says Eric Walser, M.D., an interventional radiologist who has pioneered
the technique at Mayo Clinic, Florida.
In the United States, laser ablation is primarily used to treat brain, spine and
prostate tumors, but is cleared by the U.S. Food and Drug Administration (FDA) for any
soft tissue tumor. Only a few centers have adapted the technique to tumors outside of the
brain ...
The outpatient procedure is performed inside an MRI machine [similarly for CT
scan machine], which can precisely monitor temperature inside tumors. A special
nonmetal needle is inserted directly into a tumor, and the laser is turned on to deliver light
energy. Physicians can watch the temperature gradient as it rises, and they can see
exactly in the organ where the heat is. When the tumor and a bit of tissue that surrounds
it (which may harbor cancer cells) is heated to the point of destruction -- which can be
clearly seen on monitors -- the laser is turned off. In larger tumors, several needles are
inserted simultaneously.
Patients are given anesthesia because, during the 2.5-minute procedure they
should not move, Dr. Walser says.
Dr. Walser adds that laser ablation is a much more precise technology than
similar methods that use probes, such as radiofrequency ablation, which also raises a
tumor's temperature, and cryotherapy, which freezes tumors.
David Woodrum, M.D., Ph.D., from Mayo Clinic, Rochester, has also reported
success using the new technique.
At the March meeting of the Society of Interventional Radiology, Dr. Woodrum,
presented results from the first known cases of using MRI-guided laser ablation to treat
prostate tumors. He said then that the safe completion of four clinical cases using the
42
technique to treat prostate cancer in patients who had failed surgery "demonstrates this
technology's potential."
Dr. Woodrum has now treated seven patients, including a patient with melanoma
whose cancer had spread to his liver.
"MRI-guided ablation may prove to be a promising new treatment for prostate
cancer recurrences," he says. "It tailors treatment modality (imaging) and duration to
lesion size and location and provides a less invasive and minimally traumatic alternative
for men."
(http://www.sciencedaily.com/releases/2010/10/101014131923.htm)
Connections to Chemistry Concepts
(for correlation to course curriculum)
1. Electromagnetic spectrum—Wavelengths and frequency for laser light can be calculated,
just as for “normal” light.
2. Properties of light—Light behaves both as a particle and as a wave, and both can be used
to discuss how a laser works and what its output is. Frequencies, wavelengths and energies
of photons are all related to the speed of light via Einstein’s equation, E = mC2. These
properties of laser light are identical to those of “normal” light. The only difference is that the
green (for example) laser light is much more intense and has much more energy associated
with it only because there are so many photons in the beam of laser light. The energy per
photon of green light is the same for laser light and normal light.
3. Atomic theory—From Bohr’s model of the atom and spectral lines to the quantum theory,
and the wave/particle duality of light, lasers fit right in.
4. Electrons and energy levels—excited and ground states—All the reactions discussed
with the lead-acid and lithium-ion batteries involve oxidation and reduction reactions.
5. Periodic Table—Elements on the periodic table are arranged according to physical and
chemical properties. Students may be able to see a correlation between some of the
elements that are useful in lasers with their positioning on the table.
6. Chemical and physical properties—These properties make specific elements or
compounds useful for specific types of lasers.
Possible Student Misconceptions
(to aid teacher in addressing misconceptions)
1. “Laser pointers are harmless; everybody has them.” Although “everybody” may have
them, that doesn’t make them harmless. They are relatively safe as long as one makes sure
NOT to point them directly at someone else’s (or their own) eyes. And if you watch the
news, you may occasionally see that someone has been arrested for shining a green laser
at a low-flying airplane or helicopter. These lasers are powerful enough to do retinal damage
if they are shined into one’s eyes—even at fairly long distances. A pilot can be blinded by
the light if it shines directly into his eyes, and this could cause him to crash the airplane.
2. “Lasers are just very bright lights.” While it’s true that they’re bright lights, there’s more to
them than just that. They are also monochromatic (having only one wavelength), and the
photons of light emitted are all in phase (“traveling in the same direction”, according to the
43
article), and the photons are very focused into a narrow beam. This makes laser light much
more intense—and dangerous—than “normal” light.
3. “If lasers can surgically remove tumors, then they can be used to cut out all types of
cancers within the body.” Whoa, not so fast! Laser light can be used effectively to
surgically remove lumps of cancerous tissue—tumors—which are concentrated in one part
of the body. Using laser light to cut out many small tumors throughout the body (when the
cancer has metastasized, for instance) would be almost impossible, as doctors would be
unable to insert a needle into each one of these small cancerous blobs to destroy them. And
the more cancerous cells there are, the more likely that some of the laser light might miss its
intended target and hit (and destroy) healthy tissue.
4. “Everybody should have a CT scan to make sure they don’t have any tumors.” CT
scans are actually X-rays that pass through the body. The CT scan uses more radiation than
a normal X-ray, and exposes the body to radiation that could damage DNA in cells that
could actually produce cancerous cells, rather than just detect them. Doctors must
determine if the benefits of detecting tumors with the CT scan outweigh the risks of causing
cancers with the CT scan. Costs of CT scans must also be taken into consideration when
doctors weigh benefits and risks. And some tumors that are discovered may be benign and
cause no problems for the patient, but he/she might still demand that the tumors be
removed at great cost to society, for little real benefit.
5. “It should be easy for a doctor to cut that thin layer of skin with a laser. After all, the
laser beam makes a bright, straight line right to the target so it’s easy to see the
beam, just like in all the ‘Star Wars’ movies.” Actually, those laser beams shining through
the vacuum of space so you can see where they’re going is really just science fiction, not
science fact. You can’t generally see a laser beam until it hits its target, whatever that might
be. Remember that the beam is photons all traveling in the same direction, so they can’t be
seen from the sides of the photon path, unless there’s dust in the air that might deflect some
of the photons. (In the case of higher energy green or blue laser light pointers, you might be
able to see their beam due to Rayleigh scattering on individual molecules in the air.)
Anticipating Student Questions
(answers to questions students might ask in class)
1. “Who discovered the laser?” See “More on the history of the laser”, above.
2. “What’s the difference between sunlight and laser light?” Several differences exist
between sunlight and laser light:
Sunlight
Laser light
a. Broad spectrum light—made of
a. Monochromatic, or almost so—made of only
many wavelengths of light
one, or very few wavelengths of light
b. Incoherent—spreads out as it
b. Coherent—disperses very little as it travels,
travels
all photons are in phase
c. Non-directional and not focused— c. Directional and focused—nearly parallel beam
light is generated in all directions
of photons (when collimated)
from source
3. “What is an excited state? A ground state? How electrons get from one to the other?
And how does that make laser light?” Let’s start with the ground state. Electrons are
usually in the ground state, their lowest energy state within the atom. When they are zapped
with electricity or light, electrons absorb this energy and jump to higher energy states; these
are the excited states. In most cases, excited states are very transient—electrons are more
stable in the ground state, so they almost instantaneously jump back down (in energy terms)
44
to the ground state and release that extra energy they absorbed when they became excited
And that is “normal” light. But in some cases, the excited state is just a tad more stable than
normal—a metastable state. In this state, the electrons can maintain their higher energy for
a brief time. If sufficient numbers of ground-state electrons reach this metastable excited
state, they can form a population inversion wherein more metastable excited electrons exist
than stable ground-state electrons. At this point, it another high-energy photon or electron
(probably from pumping) comes along, it will induce a metastable excited electron to jump to
the ground state, thereby emitting a photon, which can induce another excited electron to do
likewise, etc. All the electrons jumping to the ground state en masse generate all the
photons that become the laser beam.
4. “What do they use to make a laser?” Scientists can use a lot of different things to make
lasers because there are a lot of different types of lasers: gas lasers, solid state lasers,
semiconductor lasers, metal-vapor lasers dye lasers, and free-electron lasers, just to name
a few. A laser can contain any one, two, or more of these elements (and perhaps others):
He
N2
O
Ne
Ar
Ti
Cr
Cu
Se
Kr
Y
Cd
I
Xe
Ce
Pr
Sm
Nd
Ho
Er
Tm
Yb
Au
Hg
U
They can also contain HF, CO, CO2, C2H4, CaF2, ArF, KrF, XeCl, XeF, various organic dyes,
some minerals (chrysoberyl, garnet and sapphire, for example), and some semiconductors,
such as GaN, AlxGa1-xAs and YAG (yttrium aluminum garnet).
5. What is the ‘laser medium’ the article talks about?” The “medium” is the substance that
undergoes pumping, absorbing electrical or photonic energy that sends some of the
medium’s electrons to higher, usually metastable energy levels to provide the population
inversion required to initiate the generation of laser light. The materials above are all
potential laser “mediums”.
6. “What’s the difference between the commonly available red lasers used for laser
pointers and the less common green laser used for the same purpose?” Well, one’s
red and one’s green … OK, sorry, here we go. The red lasers that are prevalent today, used
for laser pointers, emit light in the 630–700 nm region of the spectrum, with the most
common wavelengths being 635 [ruby red], 655 [red-orange] and 671 nm. The green laser
emits between 490 and 560 nm, with the most common being 532 nm [emerald green]. Red
lasers can simply use a red laser diode and a lens to generate the laser beam; however, no
similar diode exists for the green region of the spectrum, so the green laser uses a diode
that emits in the 808 nm region of the spectrum (in the infrared).A crystal then converts the
808 nm to 1064 nm and a second, polarized crystal doubles the frequency, halving the
wavelength to the green 532 nm light. This makes the green laser pointer much more
expensive than its simpler red counterpart.
Another difference between the two lasers is visibility. The human eye is much more
sensitive to green light than to red light. This is why the green laser beam seems so much
brighter than the red (from 10-50 times brighter). (http://ezinearticles.com/?What-is-theDifference-Between-Green-and-Red-Lasers?&id=1815249) The green laser pointer is most
likely a DPSS (diode pumped solid state) laser or a DPSSFD (diode pumped solid state
frequency-doubled) laser. An announcement was made in 2009 that a direct green laser that
does not require doubling the frequency had been developed. This could open (has opened)
the door for a laser-based RGB laser projector, since red and blue laser diodes already
exist. (http://en.wikipedia.org/wiki/Green_laser_pointer#Green) This source shows cutaway
schematics of both laser pointers for comparison: http://searchwarp.com/swa141478.htm.
Yet another difference between the two lasers is that the red beam is usually not visible until
it hits its target, while the green beam is visible all the way to its target, due to Rayleigh
45
scattering. This makes it useful for astronomers to point out specific stars or constellations in
the night sky.
7. “What makes the green laser pointer more dangerous than the red pointer?” First, a
green laser light photon has a shorter wavelength than one of red light. That means it has a
higher frequency and therefore a higher energy. More energy means more potential damage
to the eye (assuming that’s the danger you’re referring to), so this may be at least part of the
reason it is potentially more dangerous. But there are two other factors to consider. 1) The
total energy of the beam is also dependent on the number of photons; one green photon
doesn’t have as much energy as, say, a hundred red photons. So if the green laser pointer
actually is brighter or more intense (more dangerous), it may be because it has a higher
wattage rating (say, 10 mW vs. 5 mW for a red pointer) that delivers more photons per
second than does the red laser light. 2) The sensitivity of the eye to each wavelength/color
of light. We’ve already said above that the human eye is more sensitive to green light than
to red. That means that green light of equal intensity to red would appear to us to be brighter
(maybe more destructive to eye tissue), even though that may not be the case.
8. “Why is general anesthesia needed for this laser surgery?” The patient is given a
general anesthesia because the laser must be focused exactly on the tumor and that
requires that the patient remain completely still so the laser doesn’t go roaming about killing
innocent nearby tissue. Being unconscious leaves you pretty still, eh? Also, I imagine the
placement of the needle—through the skin—doesn’t tickle, either.
9. “How do radio waves and lasers differ in cancer treatment?” Radio frequency ablation
is effective, but in addition to heating up the tumor tissue, it also raises the temperature of
nearby tissue (it is less focused); laser ablation only heats up the tissue at which it is
aimed—the tumor (laser light is more focused, remember?). Laser ablation is also much
quicker—perhaps as much as five or more times faster—than radio frequency ablation. This
results in fewer complications and quicker surgery.
10. “What other uses are there for lasers?” Lasers are used widely in many different
applications across a variety of industries. See “More on uses of lasers” above for more
information.
In-class Activities
(lesson ideas, including labs & demonstrations)
1. The National Ignition Facility at the Lawrence Livermore National Laboratory in California
offers a video or audio clip (you choose) dealing with their “Super Laser at the NIF”. It comes
complete with California Science Standards, a glossary of science terms, background
information for the student, a “Segment Summary Student Sheet” and a “Personal
Response Student Sheet”. It also includes specific questions the teacher can ask students
to answer through their viewing of the video. Download the pdf file at
http://science.kqed.org/quest/files/imp/download/44/203a_SuperLaseratNIF.pdf. The video
and/or audio clips are also available at this same site.
2. An experiment from Middlebury College to build a He-Ne laser from “readily available optical
components is described here:
http://ixnovi.people.wm.edu/phys251/web_manuals/HeNelaser.pdf. Although the lab itself
may be more than you want to or can do, it does contain an energy level diagram of the
energy levels and jumps of electrons from helium and neon responsible for the laser effect.
3. You can definitely connect the energy transitions of some laser action; e.g., the He-Ne laser,
to electron energy positions and transitions within atoms. (See 2, above.)
4. Experiments with lasers:
46
a. There are two experiments students can do using lasers to a) measure the wavelength
of laser light and b) determine the amount of data on a CD. Both are discussed in this lab
procedure from Harvard: http://isites.harvard.edu/fs/docs/icb.topic150831.files/Lab10.pdf.
Note that these are really physics labs, rather than chemistry labs.
b. Another series of experiments with lasers is found here:
http://bigbro.biophys.cornell.edu/~toombes/Science_Education/Laser_Diffraction/Diffraction_
Lesson.pdf. Although the source is Cornell, the intro addresses what seem to be high school
standards. This pdf contains photos and teacher materials to help with set-up of the
experiments.
5. If you want to discuss the science behind the laser, International Fiber Optics, the maker of
Metrologic lasers, has an old version of their experiment book, “Experiments Using a
Helium-Neon Laser” available online. The early part of this pdf document (pp 12–16)
contains good coverage of the entire process of laser light generation, including pumping,
population inversion and electron energy levels. (http://www.i-fiberoptics.com/pdf/45-700manual.pdf)
6. Semiconductor laser diodes involve the use of various semiconductors. When discussing
the periodic table, you can show how elements in column 14 and its two neighbor columns
on either side can become conductive. You can illustrate the effect of adding dopants to
these elements making them electrical conductive by using an analogy. Pure water doesn’t
conduct electricity (and you can show this with a conductivity tester. Yet when we add just a
pinch of salt to the pure water, it conducts extremely well. The same is true of adding dopant
to an element of the aforementioned columns of the periodic table.
(http://edonline.ua.edu/aeep/lessons/conductors.pdf)
7. Here is a YouTube video (NSF?) that simulates normal light vs. laser light using students
moving, either randomly or in sync: http://www.youtube.com/watch?v=fhiOQSc5n90.
8. A two-part YouTube video lecture (~29 minutes total) (in the format of the Kahn Academy
videos, with a black screen and colored writing developing with the lecture) shows how the
He-Ne laser works. It discusses the electron energy level jumps and population inversion.
(http://www.youtube.com/watch?v=O4dwOCwKfzk and
http://www.youtube.com/watch?v=LSS9EUy6vg8&NR=1&feature=endscreen)
9. It might be interesting to show students a LED bulb by itself and light it with a 9-volt battery.
You can purchase single LEDs very inexpensively at Radio Shack stores. You can
demonstrate to students that the LED will light when the leads are connected to the battery
terminals, but when you reverse the leads, the LED won’t light (hence, semi-conductor).
10. You can show students that laser beams are invisible in ordinary air by shining a laser
across the room. They will see it as it hits the wall or whiteboard, but not its path to get
there. Make sure they are looking perpendicular to the beam’s path. If you create smoke or
dust in its path, the laser beam then becomes visible as the particles in its path deflect some
of the photons in the beam. The same effect can be seen by shining the laser through pure
water or a clear solution. They won’t see the beam’s path. Then add something that will
make a colloid, like a few drops of milk or a bit of fine powder. The beam will now be visible
through the liquid as the particles again deflect the beam. Both the dust in the air and the
particles that make the water a tad cloudy are examples of colloids, and the visible beams
are examples of the Tyndall effect.
Out-of-class Activities and Projects
(student research, class projects)
47
1. Progress in developing a new technology often is inhibited by the need for supporting
science and technology that does not yet exist. Students might want to research the history
of lasers in light (no pun intended) of this statement and share that knowledge with their
classmates.
2. If you don’t have much class time for the study of lasers, you might want to assign students
to visit this Web site to learn on their own about lasers:
http://www.colorado.edu/physics/2000/lasers/. It provides a dialogue between a student and
teacher, and it has animations along the way to help students understand the science
behind the content. In fact, if you go back to the table of contents for this site,
http://www.colorado.edu/physics/2000/index.pl?Type=TOC, you’ll find a lot of interactive
information pages about atoms, electrons and light.
3. Students can research the various types of lasers and their applications, and try to
determine what properties of that specific laser make it useful for that particular purpose.
4. Research is now being conducted on the medical applications of laser diodes. They have
both advantages and disadvantages compared to the use of genuine laser beams. Students
might research and report on some of these medical applications, as well as the advantages
and disadvantages of using laser diodes (sometimes called super luminescent light-emitting
diodes) as opposed to classical lasers. (Teacher’s Guide for April 2001 ChemMatters,
Graham, T. Light-Emitting Diodes—Tune in to the Blues. ChemMatters 2001, 19 (2), pp 4–5)
References
(non-Web-based information sources)
The references below can be found on the ChemMatters
25-year CD (which includes all articles published during the years
1983 through 2008). The CD is available from ACS for $30 (or a
site/school license is available for $105) at this site:
http://www.acs.org/chemmatters. (At the right of the screen,
click on the ChemMatters CD image like the one at the right.)
Selected articles and the complete set of Teacher’s Guides
for all issues from the past three years are also available free online
at this same site. (Full ChemMatters articles and Teacher’s Guides are
available on the 25-year CD for all past issues, up to 2008.)
Some of the more recent articles (2002 forward) may also be available online at the URL
listed above. Simply click on the “Past Issues” button directly below the “M” in the ChemMatters
logo at the top of the page. If the article is available online, you will find it there.
The ChemMatters article “Fireworks in the Smokestack” discusses laser spark
spectroscopy and how lasers help scientists detect various metal pollutants as they leave
smokestacks of modern incinerators, both municipal and industrial. Author Scott draws an
analogy between the colors and spectra of fireworks, which are due primarily to the metal
atoms’ electron excitations and the similar effects caused by laser impact. (Scott, D. Fireworks
in the Smokestack. ChemMatters 1996, 14 (1), pp 8–9)
48
This article describes the chemistry behind light emitting diodes—some of the main
lasing mediums in semiconductor diode lasers: Graham, T. Light-Emitting Diodes—Tune in to
the Blues. ChemMatters 2001, 19 (2), pp 4–5.
The ChemMatters Teacher’s Guide to the April 2001 issue includes background
information for teachers concerning p and n type semiconductors and the p-n junction. It also
describes how to create a laser using a light-emitting diode, and the probability that LED lights
will eventually replace incandescent light bulbs (which they already are doing).
This issue of ChemMatters contains a good article on the chemistry of tattoos, including
mention of removal by laser surgery: Rohrig, B. Tattoo Chemistry Goes Skin Deep.
ChemMatters 2001, 19 (3), pp 6–7).
The ChemMatters Teacher’s Guide to the October 2001 issue includes a little more
detail about what is involved in removal of tattoos, from the early days of sanding away surface
layers of skin to dermabrasion to laser removal. Interestingly, the ChemMatters issue contains
two articles that contain references to lasers and the Teacher’s Guide to this issue contains
three articles that have references to lasers.
“Trolling the Seas for New Medicines” describes the search by pharmaceutical
companies to find new medicines from aquatic life. Cancer is obviously a disease they’d like to
focus on when finding new plant/animal life for drugs. (Black, H. Trolling the Seas for New
Medicines. ChemMatters 2001, 19 (4), pp 6–7)
The ChemMatters Teacher’s Guide for the December 2001 issue (above) includes
background information for teachers concerning two “new” anti-cancer drugs being developed
from marine life—sea squirts to be precise.
Check out the “Question from the Classroom” in the December 2002 issue of
ChemMatters. In this feature author Becker discusses how CD players and burners work,
including the role the semiconductor diode laser plays in playing the music. (pun intended).
(Becker, R. “Question from the Classroom”, How Do CD Players Work? ChemMatters 2002, 20
(4), p 2)
In “Nanotechnology: World of the Super Small” the author discusses what nano means,
and applications of nanotechnology, including “cooking up a new drug delivery system with viral
capsids that just might be able to carry potent anti-cancer drugs directly to the tumor site.
(Rosenthal, A. Nanotechnology: World of the Super Small. ChemMatters 2002, 20 (4), pp 9–13)
In this “Question from the Classroom” in the April 2003 issue of ChemMatters, Bob
Becker discusses how lasers work and why they’re “special”. (Becker, R. “Question from the
Classroom”, How do lasers work and what is so special about laser light? ChemMatters 2003,
21 (2), pp 2–3,
http://portal.acs.org/portal/PublicWebSite/education/resources/highschool/chemmatters/archive/
CNBP_028409)
The April, 2003 ChemMatters Teacher’s Guide includes useful background information
for teachers about lasers.
Author Rohrig discusses cryogenics in this ChemMatters article. Among other uses for
cryogenics, scientists have applied it to cryosurgery to battle cancer, both on the skin and within
49
the body. (Rohrig, B. Cryogenics: Extremely Cold Chemistry. ChemMatters 2004, 22 (1), pp 14–
16,
http://portal.acs.org/portal/PublicWebSite/education/resources/highschool/chemmatters/CTP_00
5370)
In the “ChemSumer” section of this issue of ChemMatters “Battling Zits” tells the story of
teenage angst. But it includes a little bit about laser surgery, including wavelengths of laser
emission and what laser beams do to acne. (Baxter, R. “ChemSumer”, Battling Zits.
ChemMatters 2005, 23 (2), pp 4–6,
http://portal.acs.org/portal/PublicWebSite/education/resources/highschool/chemmatters/CTP_00
5380)
In this article about digital photography and printing, author Rohrig discusses the roles
semiconductors and lasers play in both devices. (Rohrig, B. The Chemistry of Digital
Photography and Printing. ChemMatters 2006, 24 (1), pp 4–7,
http://portal.acs.org/portal/PublicWebSite/education/resources/highschool/chemmatters/archive/
CNBP_025144)
Web sites for Additional Information
(Web-based information sources)
More sites on the history of the laser
The Laserfest Web site, a celebration of 50 years of laser development (1960–2010),
contains a timeline of laser science milestones at http://laserfest.org/lasers/history/timeline.cfm.
You can drag the cursor across the screen to view discoveries that happened at various times,
from 1900 to 2009. Clicking on any of the discoveries provides more information about that
event.
Here’s another slide-the-cursor timeline from Photonics Media:
http://www.photonics.com/linearcharts/default.aspx?ChartID=2. This timeline begins at 1950.
The Nobel Prize Web site contains a Laser Challenge game for kids (middle school,
maybe) that asks them to answer questions about uses and history of lasers. They can get
points in a game format: http://www.nobelprize.org/educational/physics/laser/challenge.html.
More sites on laser science
For more information about lasers—how they work, how they were developed, types of
lasers and their uses, as well as a list of links to other laser sites, see the EnglishInfo! (yeah, I
know sounds improbable) Web site at http://english.turkcebilgi.com/Lasers.
For detailed information on lasers visit the RP Photonics Web site, “Encyclopedia of
Laser Physics and Technology” at http://www.rp-photonics.com/encyclopedia_p.html An
alphabet at the top allows you to search for an item by clicking on the first letter of the item.
Here is a detailed discussion of how excimer lasers work, from Photonics Handbook:
http://photonics.com/Article.aspx?AID=25164, It includes diagrams and microphotographs.
50
Laser Fundamentals provides more detail about how a laser works and gives
descriptions of several different types of lasers:http://www.fas.org/man/dod101/navy/docs/laser/fundamentals.htm.
Wikipedia has a good Web page on the He-Ne laser at
http://en.wikipedia.org/wiki/Helium%E2%80%93neon_laser.
More sites on uses of lasers
The Optics.org Web site contains this page about LG’s new (2013) 100-inch laser
projected television about to go on display: http://optics.org/news/3/12/37. Dubbed the “hectolaser” TV, it can be ceiling-mounted only 22 inches from the screen/wall. (Hecto is the prefix for
100.)
These videos show commercial television stations covering the progress of the U.S.
National Ignition Facility (NIF):
CBS Sunday Morning News, which did not view NIF in a very favorable light:
http://www.cbsnews.com/video/watch/?id=7403916n&tag=contentMain;contentBody, and
BBC’s segment (<12 minutes) of “Horizon” about the National Ignition Facility’s attempt to
create a star on earth: http://www.youtube.com/watch?v=DyB7Ho_W9RE.
You can view a list of the videos available from the NIF here:
https://lasers.llnl.gov/multimedia/video_gallery/ They include “How NIF Works” and “Take a Ride
on a Beamline”, which shows in animation the path of the laser beams shot into the hohlraum,
the fusion target .
Here is a July 2012 NIF press release reporting on the 500 terawatt and 1.89 MJ shot
from their bank of 192 lasers: https://www.llnl.gov/news/newsreleases/2012/Jul/NR-12-0701.html.
This Web page from the Chemistry Daily site contains a table of types of lasers, their
lasing medium, their operating wavelength and applications for each:
http://www.chemistrydaily.com/chemistry/List_of_laser_types#Other_types_of_lasers.
More sites on semiconductors
If you want to learn a bit more about semiconductors and their composition, visit
http://ece.utep.edu/courses/ee3329/ee3329/Studyguide/ToC/Fundamentals/Materials/structure.
html.
More sites on cancer
PBS’s NOVA series contains one entitled “Cancer Warrior”. This 54:32 video focuses on
the life of Judah Folkman, originator of the term angiogenesis, and his 40-year search for clues
to how cancer grows, and eventually for a cure for cancer.
(http://www.pbs.org/wgbh/nova/body/cancer-warrior.html)
More sites on cancer treatment
51
This Cancer News page is a technical overview of image-guided tumor ablation:
http://www.cancernews.com/data/Article/454.asp. Although it does not discuss laser ablation, it
yields similar results as the other methods highlighted. Before-and after ablation CT scans show
its effectiveness.
This Web page report from the American Journal of Neuroradiology describes in
(medical) detail the process of actually performing interstitial photodynamic therapy (IPDT)
needle laser ablation on a brain tumor. CT scans are included in the report.
(http://www.ajnr.org/content/26/5/1193.full)
And here from MedScape is an April 20, 2011 interview with Dr. Walser, the doctor
referenced in the Mayo Clinic article about laser ablation in the “More on modes of treatment”,
above, about his pilot study: http://www.medscape.com/viewarticle/741178.
And here is a video clip interview with Dr. Walser from Visualase, the company that
makes the lasers: “Mayo Clinic Finds Early Success with Laser that (Ablates) Tumors with
Heat”: http://www.visualaseinc.com/2011/mayo-clinic-laser-destroys-tumors/. Another video clip
that appears on the same site, after viewing the Walser clip, is one from a patient of Dr.
Walser’s who was very ill and who was successfully operated upon by Dr.Walser: “A Hot
Treatment to Kill Cancer: Laser Ablation”.
This study from Radiology reports on more than 100 patients who had osteoid osteomas and
who had interstitial laser ablation (ILA) as did Chris in the ChemMatters article. The outcome
was successful in 113 of the 114 patients treated.
(http://radiology.rsna.org/content/242/1/293.full)
Not all cancer treatments are equal. This 2005 document from Australia rejects one
doctor’s findings about the use of microwaves in treating cancer:
http://www.cancertreatmentwatch.org/reports/holt.shtml. Note that this doesn’t necessarily mean
all microwave treatment of cancers is bad—just this microwave treatment, and we don’t know
the details of this treatment. Microwave ablation seems to be an up-and-coming treatment for
larger tumors (see below).
This article from Science Daily discusses the use of and success rate with microwave
ablation treatment for lung cancers:
http://www.sciencedaily.com/releases/2007/11/071129183821.htm. Microwave treatment seems
to work best for larger tumors, where laser treatment would take longer because the laser heats
such small areas (but intensely) at one time, while the microwaves are not so focused.
This site has a brief video animation clip that shows how ablation works on a patient and
his tumor. They don’t use laser ablation, but the process would be similar, except for the lack of
focus on the area of the tumor to be ablated. A laser would be more focused, obviously.
(http://www.cancerablation.com/index.html)
52
Brand-Name vs. Generic Drugs: What’s The Difference?
Background Information
(teacher information)
More on the U.S. Food and Drug Administration (FDA)
The approval of drugs, brand-name and generic, prescription and over-the-counter
(OTC), for sale in the U.S. market is under the regulatory umbrella of the U.S. Food and Drug
Administration (FDA). The FDA’s Center for Drug Evaluation and Research (CDER) performs
this role for human drugs, along with other drug-related monitoring. This extends beyond our
idea of drugs as pills and injections; the FDA Web site states, “This work covers more than just
medicines. For example, fluoride toothpaste, antiperspirants, dandruff shampoos and
sunscreens are all considered ‘drugs.’”
(http://www.fda.gov/AboutFDA/CentersOffices/OfficeofMedicalProductsandTobacco/CDER/defa
ult.htm) Students may also be interested to learn that a separate group within the FDA performs
similar functions, but for drugs developed for use with animals.
(http://www.fda.gov/AnimalVeterinary/default.htm)
The CDER’s responsibilities are summarized in the publication “Center for Drug
Evaluation and Research 2007 Update: Improving Public Health through Human Drugs”:
Reviewing drugs before marketing. FDA does not conduct the clinical studies that
support marketing. A drug company seeking to sell a drug in the United States must
conduct the studies intended to demonstrate effectiveness and defining the drug’s risks.
We monitor clinical research to ensure that people who volunteer for studies are
protected and that the quality and integrity of scientific data are maintained. The company
then sends us the evidence from these tests to prove the drug is safe and effective for its
intended use. We assemble a team of physicians, statisticians, chemists,
pharmacologists and other scientists to review the company’s data and proposed use for
the drug. If the drug is effective and we are convinced its health benefits outweigh its
known risks, we approve it for sale. … We also review drugs that you can buy over the
counter without a prescription and generic versions of over-the-counter and prescription
drugs.
Watching for drug problems. … We monitor the use of marketed drugs for
unexpected health risks. If new, unanticipated risks are detected after approval, we take
steps to inform the public and change how a drug is used or even remove it from the
market. We monitor changes in manufacturing to ensure they will not adversely affect
safety or efficacy. We evaluate reports about suspected problems from manufacturers,
health-care professionals and consumers. We try to make sure an adequate supply of
needed drugs is always available to patients who depend on them.
Monitoring drug information and advertising. Accurate and complete information
is vital to the safe use of drugs. In the past, drug companies promoted their products
almost entirely to physicians. More frequently now, they are advertising directly to
consumers. We oversee advertising of prescription drugs, whether to physicians or
consumers. We pay particular attention to broadcast ads that can be seen by many
consumers. The Federal Trade Commission regulates advertising of over-the-counter
53
drugs. Advertisements for a drug must contain a truthful summary of information about its
effectiveness, side effects and circumstances when its use should be avoided.
Scientific research. We conduct and collaborate on focused laboratory research
and testing. This maintains and strengthens the scientific base of our regulatory policymaking and decision-making. We focus on drug quality, safety and performance;
improved technologies; new approaches to drug development and review; and regulatory
standards and consistency.
Protecting drug quality. In addition to setting standards for safety and
effectiveness testing, we also set standards for drug quality and manufacturing
processes. We work closely with manufacturers to see where streamlining can cut red
tape without compromising drug quality. To ensure a safe and effective drug supply, we
enforce federal requirements for drug approval, manufacturing and labeling. When
necessary, we take legal action to stop distribution of products in violation of these
requirements. As the pharmaceutical industry has become increasingly global, we are
involved in international negotiations with other nations to harmonize standards for drug
quality and the data needed to approve a new drug. This harmonization will go a long
way toward reducing the number of redundant tests manufacturers do and help ensure
drug quality for consumers at home and abroad.
(http://www.fda.gov/downloads/AboutFDA/CentersOffices/OfficeofMedicalProductsandTo
bacco/CDER/WhatWeDo/UCM121704.pdf)
A major responsibility is to evaluate new drug applications. The FDA states,
Since 1938, every new drug has been the subject of an approved NDA [New
Drug Application] before U.S. commercialization. The NDA application is the vehicle
through which drug sponsors formally propose that the FDA approve a new
pharmaceutical for sale and marketing in the U.S. The data gathered during the animal
studies and human clinical trials of an Investigational New Drug (IND) become part of the
NDA. … The documentation required in an NDA is supposed to tell the drug's whole
story, including what happened during the clinical tests, what the ingredients of the drug
are, the results of the animal studies, how the drug behaves in the body, and how it is
manufactured, processed and packaged.
(http://www.fda.gov/Drugs/DevelopmentApprovalProcess/HowDrugsareDevelopedandAp
proved/ApprovalApplications/NewDrugApplicationNDA/default.htm)
The information contained in an NDA allows the FDA to determine the following information:
whether the drug is safe and effective in its proposed use(s), whether the benefits of the drug
outweigh the risks, whether the drug's proposed labeling is appropriate, what the labeling
should contain, and whether the methods used in manufacturing the drug and the controls used
to maintain the drug's quality are adequate to preserve the drug's identity, strength, quality, and
purity.
(http://www.fda.gov/Drugs/DevelopmentApprovalProcess/HowDrugsareDevelopedandApproved
/ApprovalApplications/NewDrugApplicationNDA/default.htm)
Even after a drug is approved by the FDA, monitoring of the drug does not stop. As
stated above, the FDA continues to examine any new data and reports that arise, in particular,
regarding side effects and risks of a specific drug that may not have come to light earlier. Even
though we may view some drugs as “completely safe” either because they are widely used,
have been used for a long time, or have never given us trouble when we’ve taken them, all
drugs have a balance of risks and benefits. The FDA presents information to help consumers
make decisions about medications:
54
Although medicines can make you feel better and help you get well, it's important
to know that all medicines, both prescription and over-the-counter, have risks as well as
benefits.
The benefits of medicines are the helpful effects you get when you use them,
such as lowering blood pressure, curing infection, or relieving pain. The risks of
medicines are the chances that something unwanted or unexpected could happen to you
when you use them. Risks could be less serious things, such as an upset stomach, or
more serious things, such as liver damage. …
When a medicine's benefits outweigh its known risks, the FDA considers it safe
enough to approve. But before using any medicine—as with many things that you do
every day—you should think through the benefits and the risks in order to make the best
choice for you.
There are several types of risks from medicine use:
 The possibility of a harmful interaction between the medicine and a
food, beverage, dietary supplement (including vitamins and herbals),
or another medicine. Combinations of any of these products could
increase the chance that there may be interactions.
 The chance that the medicine may not work as expected.
 The possibility that the medicine may cause additional problems.
(http://www.fda.gov/drugs/resourcesforyou/consumers/ucm143558.htm)
If problems with a drug do come to light after its approval, different actions can be taken,
such as adding new advisory information to the label about a potential side effect, or even up to
the level of recalling, or removing, the drug from the market. There are several options for
recalls, described by the FDA: “Recalls may be conducted on a firm’s own initiative, by FDA
request, or by FDA order under statutory authority. Class I recall: a situation in which there is a
reasonable probability that the use of or exposure to a violative product will cause serious
adverse health consequences or death.
Class II recall: a situation in which use of or exposure
to a violative product may cause temporary or medically reversible adverse health
consequences or where the probability of serious adverse health consequences is
remote.
Class III recall: a situation in which use of or exposure to a violative product is not likely
to cause adverse health consequences.” (http://www.fda.gov/Safety/Recalls/ucm165546.htm)
One example of this that has received a lot of press over the past decade or so is Vioxx,
an anti-inflammatory drug produced by the pharmaceutical/healthcare company Merck. It was a
prescription medication used mainly for arthritis pain. The drug was approved by the FDA in
1999 after an expedited review. The FDA explains, “Vioxx received a six-month priority review
because the drug potentially provided a significant therapeutic advantage over existing
approved drugs due to fewer gastrointestinal side effects, including bleeding. A product
undergoing a priority review is held to the same rigorous standards for safety, efficacy, and
quality that FDA expects from all drugs submitted for approval.”
(http://www.fda.gov/Drugs/DrugSafety/PostmarketDrugSafetyInformationforPatientsandProvider
s/ucm106290.htm) While the drug studies did show less gastrointestinal bleeding for the drug,
further study revealed an increased risk of cardiovascular problems such as heart attack or
stroke. Merck eventually announced a voluntary worldwide withdrawal of the drug. Many news
sources on the internet chronicle this story, with various accusations; a student research project
is suggested in the Out-of-class Activities and Projects section below.
55
Another interesting research project could involve direct-to-consumer marketing
regarding prescription drugs. You can often find pharmaceutical advertising simply by leafing
through a magazine or watching television. In the year 2009 alone, 4.5 billion dollars were spent
on direct-to-consumer advertising. (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3278148/) The
FDA is responsible for regulating advertising for prescription drugs. Companies are not required
to submit advertisements to the FDA before they are released to the public, but the FDA does
monitor ads to confirm that they adhere to regulations. The FDA site describes the information
such advertisements are required to share: at least one approved use for the drug, the generic
name of the drug (approved brand-name drugs have an associated common scientific name,
called its generic name, even if no generic version of the drug is being manufactured at that
point), and all the risks of using the drug.
(http://www.fda.gov/Drugs/ResourcesForYou/Consumers/PrescriptionDrugAdvertising/UCM076
768.htm)
Depending on the type of advertisement, certain information can be shortened or left out.
The advertisements are not required to tell you certain information: cost, whether there is a
generic version of the drug, if there is a similar drug with fewer or different risks that can treat
the condition, if changes in your behavior could help your condition (such as diet and exercise),
how many people have the condition the drug treats, how the drug works, how quickly the drug
works (although if the ad claims it works quickly, the ad must explain what that means), and how
many people who take the drug will be helped by it.
(http://www.fda.gov/Drugs/ResourcesForYou/Consumers/PrescriptionDrugAdvertising/UCM076
768.htm) Several pages on the FDA site help to educate consumers on how to be aware of this
advertising and what sorts of questions to ask when viewing an ad. For example, an FDA page
shows three different types of advertisements, along with two examples of each, one that
follows regulations and one that doesn’t.
(http://www.fda.gov/Drugs/ResourcesForYou/Consumers/PrescriptionDrugAdvertising/default.ht
m) Another page lists questions to consider when you see an ad, such as “What condition does
this drug treat?”, “Why do I think that I might have this condition?”, “How will this drug affect
other drugs I am taking?”, “Is there a less costly drug I could use to treat my condition?”
(http://www.fda.gov/Drugs/ResourcesForYou/Consumers/PrescriptionDrugAdvertising/ucm0719
15.htm)
There are various arguments for and against such advertising. For example, some argue
that it “informs, educates, and empowers patients,” “promotes patient dialogue with health care
providers,” and “removes the stigma associated with certain diseases.”
(http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3278148/) Others believe that it “promotes new
drugs before safety profiles are fully known,” “leads to inappropriate prescribing,” and “strains
relationships with health care providers.”
(http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3278148/) The topic provides a good opportunity
to discuss how to make informed choices as a consumer.
More on brand-name drugs
The basics of brand-name compared to generic drugs are succinctly summarized:
A brand name drug is a medicine that’s discovered, developed and marketed by
a pharmaceutical company. Once a new drug is discovered, the company files for a
patent to protect against other companies making copies and selling the drug. At this
point the drug has two names: a generic name that’s the drug’s common scientific name
and a brand name to make it stand out in the marketplace. This is true of prescription
56
drugs as well as over-the-counter drugs. An example is the pain reliever Tylenol®. The
brand name is Tylenol® and the generic name is acetaminophen.
Generic drugs have the same active ingredients as brand name drugs already
approved by the Food and Drug Administration (FDA). Generics only become available
after the patent expires on a brand name drug. Patent periods may last up to 20 years on
some drugs. The same company that makes the brand name drug may also produce the
generic version. Or, a different company might produce it.
(http://www.dbsalliance.org/pdfs/GenericRx.pdf)
The general path that a potential new drug takes is described in a December 13, 2004,
Scientific American article:
The development of any new pharmaceutical is a complex and expensive
project. In many instances, the research divisions within pharmaceutical companies
spend years studying aspects of the biology and biochemistry of the disease in question
(malaria, cancer or bacterial infections, for example) in an effort to develop an approach
to attack the disease. Once the biology of the disease is understood and an assay or
animal model is in place, medicinal chemists begin to prepare potential chemical
inhibitors. From initial results in the biological system, the chemists then prepare new,
and hopefully improved, lead compounds. This sort of teamwork between the chemists
and biologists often takes years before a final group of lead compounds is ready for more
significant evaluation. At this point, a candidate drug is evaluated for toxicity, efficacy and
other properties in an animal model (rats or dogs, for instance). This evaluation process
may last years. Assuming that the drug candidate is successful in these tests, it then
enters into Phase 1, Phase 2 and, finally, Phase 3 clinical trials in humans. The FDA
establishes the number of patients required for each phase of the clinical trials according
to guidelines based on the disease being treated. For example, a drug candidate for a
disease that afflicts only 10,000 people would have a smaller number of patients in its
trials than would a potential drug to fight a disease that afflicts millions such as high blood
pressure. At the end of the clinical trials the company presents its data to the FDA, which
then decides whether or not to approve the drug for sale to the public.
(http://www.scientificamerican.com/article.cfm?id=whats-the-difference-betw-2004-1213&page=2)
The three phases of human clinical trials have different types and numbers of subjects:
In phase I, a small number of usually healthy volunteers are tested to establish
safe dosages and to gather information on the absorption, distribution, metabolic effects,
excretion, and toxicity of the compound. To conduct clinical testing in the United States, a
manufacturer must first file an investigational new drug application (IND) with the FDA.
However, initiation of human testing can, and often does, occur first outside the United
States.
Phase II trials are conducted with subjects who have the targeted disease or
condition and are designed to obtain evidence on safety and preliminary data on efficacy.
The number of subjects tested in this phase is larger than in phase I and may number in
the hundreds.
The final pre-approval clinical testing phase, phase III, typically consists of a
number of large-scale (often multi-center) trials that are designed to firmly establish
efficacy and to uncover side-effects that occur infrequently. The number of subjects in
phase III trials for a compound can total in the thousands.
57
Once drug developers believe that they have enough evidence of safety and
efficacy, they will compile the results of their testing in an application to regulatory
authorities for marketing approval. In the United States, manufacturers submit a new drug
application (NDA) or a biological license application (BLA) to the FDA for review and
approval.
(http://moglen.law.columbia.edu/twiki/pub/LawNetSoc/BahradSokhansanjFirstPaper/22J
HealthEcon151_drug_development_costs_2003.pdf)
A poster showing the top 200 pharmaceutical products based on the amounts of retail
sales in the United States in 2011 shows some of the major players and top drug names you
may have heard of in the brand-name drug market.
(http://cbc.arizona.edu/njardarson/group/sites/default/files/Top 200 Pharmaceutical Products by
US Retail Sales in 2011_small.pdf) The top 10 brand-name drugs were:
Brand name of drug Company
Type of drug
Amount spent
Lipitor
Pfizer
Cholest. & trigly. regulator
$7,688 million
Plavix
Bristol-Myers Squibb Platelet aggr. inhibitors
$6,711 million
Nexium
AstraZeneca
Antiulcerants
$6,156 million
Abilify
Otsuka
Antipsychotics
$5,194 million
Advair Diskus
GlaxoSmithKline
Corticoids
$4,637 million
Seroquel
AstraZeneca
Antipsychotics
$4,637 million
Singulair
Merck
Antileuk. antiasthmatics
$4,593 million
Crestor
AstraZeneca
Cholest. & trigly. regulator
$4,404 million
Cymbalta
Lilly
Antidepress. & mood stab. $3,666 million
Humira
Abbott
Spec. antirheumatic agent
$3,531 million
(http://cbc.arizona.edu/njardarson/group/sites/default/files/Top 200 Pharmaceutical Products by
US Retail Sales in 2011_small.pdf.)
The top pharmaceutical companies for 2012 are summarized on the CNN Money site.
(http://money.cnn.com/magazines/fortune/fortune500/2012/industries/21/) The top company
was Pfizer, with a Fortune 500 ranking of 40, revenues of $67,932 million, and profits of $10,009
million; rounding out the top five were Johnson & Johnson, Merck, Abbott Laboratories, and Eli
Lilly. Pharmaceutical companies are big business, with large amounts of money spent annually
on their products by consumers. However, the time and money spent on average to get just one
drug to market is also large. Different numbers have been thrown around. For example, a 2009
article in Canadian Medical Association Journal suggests an “estimated cost to develop test,
and bring one drug to market—$1.3 to $1.7 billion [U.S. dollars]”.
(http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2630351/) A 2012 Forbes article mentions similar
numbers that have been reported, but makes a case to suggest that they may be even higher.
Forbes … took Munos’ count of drug approvals for the major pharmas and
combined it with their research and development spending as reported in annual
earnings filings going back fifteen years, pulled from a Thomson Reuters database using
FactSet. We adjusted all the figures for inflation. Using both drug approvals and research
budgets since 1997 keeps the estimates being skewed by short-term periods when R&D
budgets or drug approvals changed dramatically.
The range of money spent is stunning. AstraZeneca has spent $12 billion in
research money for every new drug approved, as much as the top-selling medicine ever
generated in annual sales; Amgen spent just $3.7 billion. At $12 billion per drug,
58
inventing medicines is a pretty unsustainable business. At $3.7 billion, you might just be
able to make money (a new medicine can probably keep generating revenue for ten
years; invent one a year at that rate and you’ll do well).
There are lots of expenses here. A single clinical trial can cost $100 million at the
high end, and the combined cost of manufacturing and clinical testing for some drugs has
added up to $1 billion. But the main expense is failure. AstraZeneca does badly by this
measure because it has had so few new drugs hit the market. Eli Lilly spent roughly the
same amount on R&D, but got twice as many new medicines approved over that 15 year
period, ad so spent just $4.5 billion per drug.
(http://www.forbes.com/sites/matthewherper/2012/02/10/the-truly-staggering-cost-ofinventing-new-drugs/)
As mentioned above, the cost of developing a new drug goes beyond the cost of running
clinical trials and supporting researchers’ salaries. It also includes drug research by a company
that doesn’t result in a new product being offered on the market. For example, an article in The
Wall Street Journal states,
Currently, bringing one new drug to market takes roughly 14 years, at a cost of
about $1.3 billion. For every drug that makes it to market, more than 50 other research
programs fail. After all that, only two of every 10 newly approved drugs will be profitable.
Those profits must fund not only all the research programs that failed, but also all the
drugs that are launched but lose money.
When the industry was producing a steady stream of blockbuster drugs, as it did
beginning in the 1990s (for example, all the AIDS drugs), the math worked in its favor.
But in recent years the numbers have turned against the drug industry, for several
reasons.
For one, the Food and Drug Administration has become more risk-averse in the
wake of the 2004 Vioxx debacle. Drug makers are now required to conduct more studies
with many more subjects. That adds to costs and stretches out development times. And
every year spent in clinical trials equals one year of lost patent coverage.
In 1968, when development time was much shorter than today, most drugs had
an effective patent life of about 17 years. Now companies usually have only about 11
years of market exclusivity for their drugs. And this number is expected to continue
dropping as development times grow even longer—approaching a point where the costs
and risks of development outweigh the rewards and research will stop
(http://online.wsj.com/article/SB10001424052970204542404577156993191655000.html)
Another cost is described: “… the financial cost of tying up investment capital in multiyear drug
development projects, earning no return until and unless a project succeeds. That “opportunity
cost” of capital reflects forgone interest or earnings from alternative uses of the capital.
(Opportunity costs are common to all innovative industries, but they are particularly large for
pharmaceutical firms because of the relatively long time that is often required to develop a new
drug.)” (http://www.cbo.gov/sites/default/files/cbofiles/ftpdocs/76xx/doc7615/10-02-drugr-d.pdf)
The number of applications to the FDA for approval of new drugs, called “new molecular
entities (NMEs)” has been on a decline based on data from 1996 to current.
(http://www.fda.gov/downloads/AboutFDA/Transparency/Basics/UCM247465.pdf) The same
site summarizes the number of NMEs approved each year over the past decade:
59
Year
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
NMEs approved
24
17
21
36
20
22
18
24
26
21
(http://www.fda.gov/downloads/AboutFDA/Transparency/Basics/UCM247465.pdf)
Often drug applications to the FDA are not for new compounds, but rather for slightly modified
forms, or new uses for drugs that are already on the market.
More on Generic Drugs
The use of generic drugs has been on the rise for the past several years. Statistics
show: “In 2010, generic medicines accounted for more than three-quarters of the prescriptions
dispensed by retail drugstores and long-term care facilities. The exact figure is 78 percent, a
historic high, that was up four percentage points from 2009. Generic use has climbed steadily
from 63 percent of dispensed prescriptions in 2006.”
(http://www.npr.org/blogs/health/2011/05/16/135538006/3-in-4-prescriptions-are-now-forgeneric-drugs)
As stated in the Washam article, users of generic drugs can expect that a generic
substitute for a brand-name drug will contain the same active ingredient(s), but likely not
identical inactive ingredients. The similarities and differences between generic and brand-name
drugs are summarized in a document from the Depression and Bipolar Support Alliance:
The Similarities
According to the FDA, to substitute a generic for a brand name drug:

It must contain the same active ingredients (the chemical substance that makes the
drug work).

It must have the same dosage strength (the amount of active ingredients, for
example 20 mg or 40 mg).

It must be the same dosage form (that is, it needs to be available in the same form as
the original—for example, as a liquid, pill, etc.).

It must have the same route of administration (the way the medication is introduced
into the body).

It must deliver similar amounts of the drug to the bloodstream (that is, it needs to
deliver a comparable amount of the drug into the bloodstream within a similar time
period as the brand name drug).
The Differences
Here’s how generics and brand name drugs differ:
60

They look different. (Federal law requires this.)
 They could have different sizes, shapes, colors or markings.
 They have different names.

They might have different inactive ingredients.
 Drugs are made up of both active and inactive ingredients. Some people may be
sensitive to inactive ingredients. For example, some people have reactions to
certain dyes used in some drugs.

The generic costs less than the brand name drug.
 The cash price and insurance co-pay is usually lower. Generics can cost
between 20 and 80 percent less, but keep in mind that cost is only one factor
when considering the right medication for your condition.

Generics vary by manufacturer, which means you could receive different versions
based on where you purchase your medications and what type of generic they
dispense.
 Different pharmacies carry different generics.
 Even the same pharmacy may change generic suppliers.
(http://www.dbsalliance.org/pdfs/GenericRx.pdf)
In the U.S., a generic version of a brand-name drug may be marketed by a manufacturer
only after the patent on the brand-name drug expires, and after the manufacturer has completed
a successful application to the FDA to offer the generic. Typically the length of a drug patent is
20 years. The patent is meant to offer protection to the company who first developed a particular
innovative drug, giving them exclusive rights to market and sell that particular drug for the length
of the patent. This allows them to somewhat recoup the extensive costs of development and
bringing a drug to market. However, in reality, this does not mean that the manufacturer is able
to exclusively offer the drug on the market for 20 years. A manufacturer will usually apply for the
patent while the drug is still in development. It can take over a decade for a drug to be
completely developed, tested, and approved for the market by the FDA, leaving a much smaller
fraction of the 20 years left for exclusive sales.
After the patent expiration, a brand-name drug can be made into a generic drug. The
manufacturer of a generic drug could be the same company that makes the brand-name drug,
or an entirely different company, such as one that specializes in offering generic drugs (e.g.
Teva Pharmaceuticals, http://www.tevagenerics.com/). In order to offer a generic drug on the
U.S. market, the manufacturer must submit an application to the FDA, much like the
manufacturer of a brand-name drug. However, a major difference is that an application for a
generic drug does not need to redo clinical testing of the drug, which is one reason that generic
drugs can be offered at a lower cost than brand-name drugs.
The FDA Web site briefly summarizes the application process for a generic drug:
Drug companies must submit an abbreviated new drug application (ANDA) for
approval to market a generic product. The Drug Price Competition and Patent Term
Restoration Act of 1984, more commonly known as the Hatch-Waxman Act, made
ANDAs possible by creating a compromise in the drug industry. Generic drug companies
gained greater access to the market for prescription drugs, and innovator companies
gained restoration of patent life of their products lost during FDA's approval process.
The ANDA process does not require the drug sponsor to repeat costly animal
and clinical research on ingredients or dosage forms already approved for safety and
effectiveness. This applies to drugs first marketed after 1962.
61
Health professionals and consumers can be assured that FDA approved generic
drugs have met the same rigid standards as the innovator drug. To gain FDA approval, a
generic drug must:
•
contain the same active ingredients as the innovator drug (inactive
ingredients may vary)
•
be identical in strength, dosage form, and route of administration
•
have the same use indications
•
be bioequivalent
•
meet the same batch requirements for identity, strength, purity, and
quality
•
be manufactured under the same strict standards of FDA's good
manufacturing practice regulations required for innovator products
(http://www.fda.gov/Drugs/ResourcesForYou/Consumers/QuestionsAnswers/uc
m100100.htm)
The FDA defines bioequivalence as: “The absence of a significant difference in the rate
and extent to which the active ingredient or active moiety in pharmaceutical equivalents or
pharmaceutical alternatives becomes available at the site of drug action when administered at
the same molar dose under similar conditions in an appropriately designed study.”
(http://www.fda.gov/downloads/Drugs/.../Guidances/ucm070124.pdf) A December 13, 2004,
Scientific American article provided this brief summary: “The major difference between a brandname pharmaceutical and its generic counterpart is neither chemistry nor quality, but whether
the drug is still under patent protection by the company that initially developed it.”
(http://www.scientificamerican.com/article.cfm?id=whats-the-difference-betw-2004-12-13)
The Washam article discusses problems that can arise when a patient switches from
one drug to another, whether it be from brand-name to generic, vice versa, or a generic to
another generic. The FDA site presents data that may help to dispel the idea consumers may
have that there can be a very large difference between generic and brand-name drugs. It states:
FACT: FDA does not allow a 45 percent difference in the effectiveness of
the generic drug product.
FDA recently evaluated 2,070 human studies conducted between 1996 and
2007. These studies compared the absorption of brand name and generic drugs into a
person’s body. These studies were submitted to FDA to support approval of generics.
The average difference in absorption into the body between the generic and the brand
name was 3.5 percent [Davit et al. Comparing generic and innovator drugs: a review of
12 years of bioequivalence data from the United States Food and Drug Administration.
Ann Pharmacother. 2009; 43(10):1583-97.]. Some generics were absorbed slightly more,
some slightly less. This amount of difference would be expected and acceptable, whether
for one batch of brand name drug tested against another batch of the same brand, or for
a generic tested against a brand name drug. In fact, there have been studies in which
brand name drugs were compared with themselves as well as with a generic. As a rule,
the difference for the generic-to-brand comparison was about the same as the brand-tobrand comparison.
Any generic drug modeled after a single, brand name drug must perform
approximately the same in the body as the brand name drug. There will always be a
slight, but not medically important, level of natural variability – just as there is for one
batch of brand name drug compared to the next batch of brand name product.
62
(http://www.fda.gov/drugs/resourcesforyou/consumers/buyingusingmedicinesafel
y/understandinggenericdrugs/ucm167991.htm)
Each year, the patents of certain brand-name drugs expire, making them fair game for
generic manufacturers. A name students might recognize is Lipitor, a drug used to treat high
cholesterol, that was eligible for generic manufacturing in late 2011. The FDA approved the first
generic version, atorvastatin calcium tablets, on November 30, 2011.
(http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm281817.htm) Certain
drugs may have more than one manufacturer producing a generic version; the competition
between generic companies can serve to drive down the cost of generic drugs even further. A
2012 article describes a “patent cliff” (a take on the term “financial cliff” often tossed around in
the news at the end of 2012) for generic drug manufacturers. Compared to the number of
brand-name drugs whose patent expired in 2012, the number in 2013 will be much lower,
resulting in fewer possibilities to add to the lineup of generic drug moneymakers for a company.
The continued decline in the number of “new molecular entities”, or new drugs, mentioned
above, will have a similar effect in the future, leaving manufacturers looking for new options.
This year [2012], more than 40 brand-name drugs — valued at $35 billion in
annual sales — lost their patent protection, meaning that generic companies were
permitted to make their own lower-priced versions of well-known drugs like Plavix,
Lexapro and Seroquel — and share in the profits that had exclusively belonged to the
brands.
Next year, the value of drugs scheduled to lose their patents and be sold as
generics is expected to decline by more than half, to about $17 billion, according to an
analysis by Crédit Agricole Securities.“The patent cliff is over,” said Kim Vukhac, an
analyst for Crédit Agricole. “That’s great for large pharma, but that also means the
opportunities theoretically have dried up for generics.”
In response, many generic drug makers are scrambling to redefine themselves,
whether by specializing in hard-to-make drugs, selling branded products or making large
acquisitions. The large generics company Watson acquired a European competitor,
Actavis, in October, vaulting it from the fifth- to the third-largest generic drug maker
worldwide.
(http://www.nytimes.com/2012/12/04/business/generic-drug-makers-facing-squeeze-onrevenue.html?pagewanted=all&_r=0)
Connections to Chemistry Concepts
(for correlation to course curriculum)
1. Solubility—The solubility of drugs is mentioned in the article, including where and when a
drug dissolves, such as in the stomach or the small intestine, and the adjustment of a drug
to dissolve at body temperature. It also describes the effect temperature has on solubility.
2. Concentration—The concentration of drugs in the bloodstream and the typical units used
for their reporting can be discussed. The article includes a concentration–time graph (blood
concentration curve) for two drugs; instructors can emphasize the reasons for the shape of
the curve.
3. Organic/Biochemistry—Although the structures of drug molecules are fairly complex,
students can compare and contrast structures for various functional groups.
63
Possible Student Misconceptions
(to aid teacher in addressing misconceptions)
1. “It doesn’t matter if you take a brand-name or generic form of a particular
medication.” In many cases, it does not matter, but sometimes a patient reacts better to
either the generic or the brand-name drug. Switching between two generic types of the
same drug can also trigger a problem in some patients.
2. “The brand-name and generic forms of a particular drug are identical.” By law, the
brand-name and generic forms of a particular drug must have the same active ingredients,
but the inactive ingredients, such as pigments, flavoring, and binders often differ. In addition,
the typical concentration of a drug in the bloodstream over time is allowed to slightly differ
between a brand-name drug and its generic equivalent.
3. “Every brand-name drug has a generic drug.” New brand-name drugs are protected by
patents for approximately 15–20 years, which means that other manufacturers may not
make and sell a generic version of the drug. Even when patent protection expires, other
manufacturers need to submit an application to the FDA to be able to sell the generic drug,
or manufacturers may not be interested in pursuing a generic version.
Anticipating Student Questions
(answers to questions students might ask in class)
1. “Why is a generic drug so much cheaper than the brand-name?” Companies with
brand-name products have spent substantial amounts of money to initially develop and test
the drugs, which generic manufacturers do not have to do. These companies also tend to
spend much more money on marketing and advertising than would a generic manufacturer.
2. “If generic drugs are so much cheaper, why would anyone choose to use a brandname instead?” As discussed in the article, even though the active ingredients of a brandname vs. generic drug must be identical, a patient’s response to a particular drug can
actually vary. A brand-name drug might work better for someone, or one particular generic.
Or, someone may simply prefer one over the other for other reasons; for example, the
author usually purchases the brand-name Advil instead of generic ibuprofen because of her
preference for the slightly-flavored smooth coating on the pill.
In-class Activities
(lesson ideas, including labs & demonstrations)
1. Students can investigate the effect different variables have on how fast sugar dissolves in
water. For example, students could vary the temperature of the water, whether they stir the
solution or not, and the form of the sugar (cubes, regular, superfine). Two such experiments
available online are http://atlantis.coe.uh.edu/texasipc/units/solution/sugar.pdf and
http://www.mrsec.psu.edu/education/nano-activities/nanosilver/oh_sugar_sugar/oh_sugar_sugar.pdf. The second is designed for younger students.
2. The December 2001 ChemMatters Teacher’s Guide offered the suggested activity:
You could hold a “Can you discover the winning drug?” contest. Let’s say that
only one in 100 (or choose whatever number you like) organisms offers the promise of
containing a potentially useful drug. Then let’s say that only 1 in 100 (or choose another
number) compounds that are isolated prove to be effective. Then let’s say that only one
64
in 50 make it through Phase 1 trials, one in 10 through Phase 2 trials, and one in 10
through Phase 3 trials. Present students with a piece of paper on which 100 (or the
number you choose) boxes are drawn. Only you know which box contains the organism
that holds the “potentially useful” drug. Have students select a box. If any students select
correctly, present them with another piece of paper containing another 100 (or whatever)
boxes, only one of which contains an “effective” compound. Continue this. Will any
student EVER actually end up selecting correctly all the time until he/she gets to the one
drug that makes it to the marketplace? While this may not be a completely realistic
exercise, it should allow students to see to what extent the search for effective, safe new
drugs is the proverbial “needle in a haystack” exercise. (p 6)
3. A collection of downloadable pharmaceutical posters created by a research group at the
University of Arizona graphically summarizes the top brand-name and generic drugs by
sales and by total U.S. prescriptions for various years. The posters could be used to
highlight similarities and differences between different drug structures, the huge array of
available pharmaceuticals, and the large amount of money spent each year on drugs.
(http://cbc.arizona.edu/njardarson/group/top-pharmaceuticals-poster) The posters were
described with sample questions to ask higher level students in the Journal of Chemical
Education (JCE) article “A Graphical Journey of Innovative Organic Architectures That Have
Improved Our Lives” (McGrath, N. A.; Brichacek, M.; Njardarson, J. T. J. Chem. Educ. 2010,
87 (12), pp 1348–1349, http://pubs.acs.org/doi/abs/10.1021/ed1003806). The article is
available to JCE subscribers.
4. The author of the JCE article “The Analysis of a Drug Circular as a First-Day Assignment for
Freshman Chemistry” gives freshman-level college students an advertisement for a drug on
the first day of class, asking them to return the next day with answers to questions such as
“What is the generic name for the active ingredient?”, “What is the chemical name? “How
does it work?”, “Who manufactures it?” “Are there any drugs that should not be taken with
it?”. The article is available to JCE subscribers. (Millevolte, A. J. J. Chem. Educ. 1995, 72
(12), p 1085, http://pubs.acs.org/doi/abs/10.1021/ed072p1085)
5. The JCE activity “What’s the Diagnosis? An Inquiry-Based Activity Focusing on Mole–Mass
Conversions” presents two brief descriptions of medical cases and blood concentration data
for various minerals in units of moles per deciliter. Students must determine how to convert
the data to match the units of normal concentration ranges reported in the literature to
“diagnose” the problem. The article and supporting handouts are available to JCE
subscribers. (Bruck, L. B.; Towns, M. H. J. Chem. Educ. 2011, 88 (4), pp 440–442,
http://pubs.acs.org/doi/abs/10.1021/ed100466j)
Out-of-class Activities and Projects
(student research, class projects)
1. As described above in the section “More on the FDA”, the approval and recall of the drug
Vioxx has garnered a lot of press over the years. Students could research the timeline and
story and evaluate reports of wrongdoing of both the FDA and Merck. For example, a few
internet sources are a timeline of events on the National Public Radio site
(http://www.npr.org/templates/story/story.php?storyId=5470430), Congressional testimony
by the FDA (http://www.fda.gov/NewsEvents/Testimony/ucm113235.htm), a 2011 article
from The New York Times reporting on a settlement by Merck
(http://www.nytimes.com/2011/11/23/business/merck-agrees-to-pay-950-million-in-vioxxcase.html), and a Harvard Law student paper summarizing the story
(http://leda.law.harvard.edu/leda/data/783/Mancinelli06.pdf).
65
2. The February 2004 ChemMatters Teacher’s Guide described a project on investigating the
way different pain relievers are marketed. Students could also research how brand-name
drugs are now marketed to consumers instead of just physicians through magazine ads and
television commercials.
The number of different over-the-counter pain relievers being sold is staggering.
Currently there are about 150 different brand names to choose from, even though the
actual number of “different” choices is rather limited. As might be expected,
manufacturers go to great lengths to try and market their product in such a way that
consumers will select it from all the other available choices. A good project, or even a
class activity, would be to have students go their local drugstore, examine the choices
available, write down and compare the actual ingredients, and then evaluate how
“different” the different products actually are. What were the actual differences in the
contained ingredients? How were the products presented—what kinds of words and
phrases are being used to “sell” the product? What were the differences in cost per
dosage? Did it appear that the cost differences were justified? (p 32)
References
(non-Web-based information sources)
The references below can be found on the ChemMatters
25-year CD (which includes all articles published during the years
1983 through 2008). The CD is available from ACS for $30 (or a
site/school license is available for $105) at this site:
http://www.acs.org/chemmatters. (At the right of the screen,
click on the ChemMatters CD image like the one at the right.)
Selected articles and the complete set of Teacher’s Guides
for all issues from the past three years are also available free online
at this same site. (Full ChemMatters articles and Teacher’s Guides are
available on the 25-year CD for all past issues, up to 2008.)
Some of the more recent articles (2002 forward) may also be available online at the URL
listed above. Simply click on the “Past Issues” button directly below the “M” in the ChemMatters
logo at the top of the page. If the article is available online, you will find it there.
The ChemMatters article “Trolling the Seas for New Medicines” discusses the ocean as
a source of chemical compounds that could be potential medicines. (Black, H. Trolling the Seas
for New Medicines. ChemMatters 2001, 19 (4), pp 6–7)
“The Aspirin Effect: Pain Relief and More” describes how nonsteroidal anti-inflammatory
drugs such as aspirin and ibuprofen work in the body. (Kimbrough, D. R. The Aspirin Effect:
Pain Relief and More. ChemMatters 2004, 22 (1), pp 7–9,
http://portal.acs.org/portal/PublicWebSite/education/resources/highschool/chemmatters/CTP_00
5370)
Students can learn more about a different method of drug delivery—the transdermal
patch—here: Herlocker, H. The Transdermal Patch: Driving Drugs Skin Deep. ChemMatters
2004, 22 (4), pp 17–19.
66
(http://portal.acs.org/portal/PublicWebSite/education/resources/highschool/chemmatters/CTP_0
05402)
A related topic is the appropriate disposal of pharmaceuticals and how traces of drugs
can enter the water supply. (Washam, C. Drugs Down the Drain: The Drugs You Swallow, the
Water You Drink. ChemMatters 2011, 29 (1), pp 11–13,
http://portal.acs.org/portal/PublicWebSite/education/resources/highschool/chemmatters/CNBP_
026576)
Web sites for Additional Information
(Web-based information sources)
More sites on the U.S. Food and Drug Administration (FDA)
The FDA’s Center for Drug Evaluation and Research offers several educational tutorials
designed for health care professionals as well as consumers. These include the 90-minute
course “The Past, Present, and Future of FDA Human Drug Regulation” and “Medicines in My
Home—An Interactive Home,” to help consumers from adolescence to adulthood understand
how to use a drug facts label. (http://www.fda.gov/training/forhealthprofessionals/default.htm)
Part of the FDA’s job is to regulate what is called “direct-to-consumer pharmaceutical
advertising.” A 2011 paper in Pharmacy & Therapeutics discusses these regulations and
presents arguments for and against such advertisements.
(http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3278148/)
An online database of drugs approved the FDA can be searched or browsed online at
http://www.accessdata.fda.gov/scripts/cder/drugsatfda/index.cfm?fuseaction=Search.Search_Dr
ug_Name.
More sites on Brand-Name Drugs
The National Library of Medicine has a “drug information portal” of over 36,000 drugs
that can be searched in different ways. (http://druginfo.nlm.nih.gov/drugportal/drugportal.jsp)
The National Institutes of Health offers this page with personal stories from clinical trial
volunteers and researchers. Additional links on the left side of the page take the user to
additional information on clinical trials. (http://www.nih.gov/health/clinicaltrials/stories/index.htm)
A January 23, 2012 The Wall Street Journal article presented two opposite viewpoints to
the title question, “Should Patents on Pharmaceuticals Be Extended to Encourage Innovation?”
(http://online.wsj.com/article/SB10001424052970204542404577156993191655000.html)
A November 28, 2012 The New York Times article discusses the recent increase in price
in brand-name drugs and decrease in price of generic drugs.
(http://www.nytimes.com/2012/11/29/business/cost-of-brand-name-prescription-medicinessoaring.html)
67
A report highlights work done by a high school student to help develop an anti-obesity
drug. (http://news.vanderbilt.edu/2012/07/high-school-student-speeds-anti-obesity-research-atvu/)
An HHMI “Ask a Scientist” column answers the question “Why do medicines expire after
a certain period of time?” It states that an FDA drug application must include evidence of a
drug’s shelf life. (http://www.hhmi.org/bulletin/aug2007/pdf/ask_scientist.pdf)
More sites on Generic Drugs
A short column on the Mayo Clinic Web site answers the question: “Brand-name vs.
Generic Drugs: Is One Better than the Other?” (http://www.mayoclinic.org/medical-edgenewspaper-2012/feb-03b.html)
The U.S. Food and Drug Administration site lists generic drug approvals by month and
year, from 2001 through the current year (2012).
(http://www.fda.gov/Drugs/DevelopmentApprovalProcess/HowDrugsareDevelopedandApproved
/DrugandBiologicApprovalReports/ANDAGenericDrugApprovals/default.htm)
A U.S. Food and Drug Administration page includes a discussion of “Facts about
Generic Drugs” with an accompanying infographic.
(http://www.fda.gov/drugs/resourcesforyou/consumers/buyingusingmedicinesafely/understandin
ggenericdrugs/ucm167991.htm)
A collection of educational resources for educators, health care professionals, and
consumers, such as brochures, posters, and multimedia presentations about generic drugs are
available from the FDA for download.
(http://www.fda.gov/Drugs/ResourcesForYou/Consumers/BuyingUsingMedicineSafely/Understa
ndingGenericDrugs/ucm169209.htm)
A description of how to find the generic equivalent to a brand-name drug is described,
along with a link to the “Electronic Orange Book” that lists drug products approved by the FDA.
(http://answers.usa.gov/system/selfservice.controller?CONFIGURATION=1000&PARTITION_ID
=1&CMD=VIEW_ARTICLE&ARTICLE_ID=10966&USERTYPE=1&LANGUAGE=en&COUNTRY
=US)
More Web sites on Teacher Information and Lesson Plans
(sites geared specifically to teachers)
Drs. Elizabeth M. Vogel Taylor and Catherine L. Drennan from the Massachusetts
Institute of Technology present a short article “Redox chemistry and hydrogen bonding in drug
design: Using human health examples to inspire your high school chemistry students”, using the
examples of brand-name drugs Cipro (antibiotic), Paxil (antidepressant), and Januvia (antidiabetic). (http://educationgroup.mit.edu/HHMIEducationGroup/wpcontent/uploads/2011/10/Drennan2.pdf)
A document describes the “Pharmacology Education Partnership” (PEP) project,
curriculum modules designed for high school biology and chemistry teachers and students. It
68
also contains a link to the PEP Web site (http://www.thepepproject.net) where the modules can
be found. (http://www.iuphar.org/sections/teaching/docs/ASPET_PEP_Schwartz-Bloom.pdf)
69
Sniffing Out Cancer
Background Information
(teacher information)
More on Volatile Organic Compounds
Volatile organic compounds (VOCs) are found in a wide range of compounds that are
found in everyday products: paints, adhesives, fuels, sol-vents, coatings, permanent marker
pens, polish remover, dry cleaning agents, feedstocks, refrigerants, aerosol sprays, and moth
repellents among others. Some of the worst VOCs in terms of health problems include benzene,
methylene chloride and perchloroethylene. When you experience a strong chemical smell you
are most likely smelling a VOC. Some manufacturers of VOC-containing products label them as
“low VOC” or “VOC free”. There is no international standard for defining VOCs.
VOC exposure can cause asthma and allergies. Exposure to certain VOCs has been
shown to cause cancer in test animals and is widely suspected to do the same for people.
Benzene, the VOC found in cigarette smoke is definitely carcinogenic. Another VOC that can
cause allergies in children and respiratory problems in adults is formaldehyde. This VOC is
found in adhesives, furniture varnishes and plywood. Alternatives to formaldehyde-containing
glues and adhesives include soy-based adhesives. The chemical behavior of this glue is similar
to the abyssal threads used by mussels to cling to rocks!
From one study, it is difficult to determine to what degree VOCs are responsible for
causing cancer. The study estimates that only about 2% of cases are due to air borne volatile
organic chemicals. Tracking the precise exposure of a large number of individuals to specific air
toxicants in the different and unique environments to which they subject themselves presents a
formidable task.
More on the sense of smell
Our sense of smell comes about because of specialized nerves in our nose in a
specialized area known as the olfactory bulb. Supposedly we are able to distinguish over
10,000 different odor molecules. Inhaled air through the nose passes over a bony plate
that contains millions of olfactory receptor neurons in an epithelial cover. These olfactory
nerves have cilia extending out into a mucosal lining that is exposed to the atmosphere.
The cilia contain olfactory receptors which are specialized proteins that bind low
molecular weight molecules (odorants). Each receptor has a pocket (binding site) that
has a particular shape that will match either a specific molecule or a group of structurally
similar molecules.
Research done by Linda Buck and Richard Axel (joint recipients of the 2004
Nobel Prize in Physiology) suggests some 1,000 genes that encode the olfactory
receptors for a particular type of odorant molecule. The interaction of the right molecule
with the right receptor causes the receptor to change its shape (called its structural
conformation). The conformational change generates an electrical signal that goes to the
olfactory bulb and then to the areas of the brain where any one nerve impulse is
“interpreted” as a particular smell. Within the olfactory bulb it is thought that groups of
olfactory receptors produce spatial patterns of olfactory bulb activity that are
70
characteristic for a given odorant molecule or a blend of odorant molecules. These spatial
patterns of activity create the information that leads to the recognition of odor quality and
intensity between odors. The information is processed at higher levels of the olfactory
system and in the brain to produce the perception of smell.
(http://www.senseofsmell.org/smell101detail.php?id=1&lesson=How%20Does%20the%20Sense%20of%20Smell%20Work)
(http://www.nobelprize.org/nobel_prizes/medicine/laureates/2004/illpres/images/olfactory.jpg)
Buck and Axel studied a type of cell found in the nose called olfactory receptor
cells, and a family of proteins called receptor proteins found in those cells. By studying
mouse olfactory receptor cells, they found that each such cell contained only one type of
receptor protein. In mice there are over 1,000 different kinds of receptor proteins,
although humans may possess only about 350. … A relatively large part of the genome
of any given mammal is devoted to coding for receptor proteins. With so many different
kinds of receptor proteins, as much as 3% of a mammal’s gene codes for the proteins
involved in odor reception.
Proteins are long chain-like molecules, made by joining together many amino
acid molecules. Receptor proteins are found at the surfaces of receptor cells, and the
proteins snake in and out of the cell membrane, crossing it seven times. In the process,
receptor proteins are twisted and bent into different shapes, creating cavities of different
shapes and sizes. Each receptor protein has a different cavity shape. Odorant molecules
can dock with these cavities in the receptor proteins. The shape of the cavity of a
particular receptor protein is shaped to allow only members of specific families of
molecules to dock with it, in the familiar lock-and-key manner of protein-substrate
chemistry. This means that each kind of receptor protein responds to only a specific
family of compounds. While a human may only have 350 or so different kinds of receptor
cells, many odors are made of combinations of substances. Humans can discern as
many as 10,000 different odors, that is, 10,000 different combinations of substances. In
addition, within a chemical family, different members may not bind to the same receptor
protein, allowing additional levels of nuance in the smell that is perceived.
71
(ChemMatters Teacher’s Guide (pp. 10–11), for Ebach, C. What’s That Smell?
ChemMatters 2012, 30 (4), pp 12–14,
http://portal.acs.org/portal/acs/corg/content?_nfpb=true&_pageLabel=PP_MULTICOLUM
N_T2_66&node_id=1090&use_sec=false&sec_url_var=region1&__uuid=9e5db572-7ab143f8-94b9-f3d848308aee)
The original paper by Buck and Axel with all the experimental details and data (including
the nucleotide sequences) can be found at
http://www.columbia.edu/~col8/BuckAxel_ORcloning_Cell91.pdf.
A complete description of the work by Buck and Axel from the Nobel Prize committee is
found at http://www.nobelprize.org/nobel_prizes/medicine/laureates/2004/press.html.
More on specialized smell in dogs
When it comes to detecting odors, dogs have a very highly developed sense of
smell, in part because a larger portion of their brain is designed for neural activity from
their nasal passages. A comparison of humans with different dog breeds and their neural
capacity is shown below:
Table: Scent-Detecting Cells in People and Dog Breeds
Species
Number
of Scent
Receptors
(millions)
Humans
5
Dachshund
Fox Terrier
Beagle
German Shepherd
Bloodhound
125
147
225
225
300
(Teacher’s Guide for Ebach, C. What’s That Smell? ChemMatters 2012,
30 (4), pp 12–14,
http://portal.acs.org/portal/acs/corg/content?_nfpb=true&_pageLabel=PP
_MULTICOLUMN_T2_66&node_id=1090&use_sec=false&sec_url_var=r
egion1&__uuid=9e5db572-7ab1-43f8-94b9-f3d848308aee)
Inside the nose, receptor cells are attached to a tissue called the olfactory
epithelium. In humans, the olfactory epithelium is rather small, and only covers a small
part of the surface of the inside of the nasal cavity near the cavity’s roof. In dogs,
however, the olfactory epithelium covers nearly the entire surface of the interior of the
nasal cavity. On top of this, a long-snouted tracking dog like a bloodhound or a basset
hound may have a considerably larger nasal cavity than a human. All in all, the olfactory
epithelium of a dog may have up to fifty times the surface area as that of a human. While
a human may have around 3 cm 2 of olfactory epithelium, a dog might have up to 150
cm2.
A dog’s wet nose also helps it smell more acutely, as odorants are captured as
they dissolve in the moisture. The shape of the interior of a dog’s nasal cavity also allows
odors to be trapped inside during inhalation, without being expelled during exhalation.
72
This allows odorants to concentrate inside the dog’s nose for easier detection. When
dogs exhale, the spent air exits through the slits in the sides of their noses. The manner
in which exhaled air swirls out actually helps usher new odors into the dog’s nose. This
also allows the dog to sniff more or less continuously. And they smell stereophonically,
that is, they can determine the direction of the odorant molecules depending on which
nostril detects the odor. A dramatic result of all of these adaptations is that dogs can
smell certain substances at concentration up to 100 million (1 x 108) times lower than
humans can.
(Sniffing Landmines. ChemMatters 2008. 28 (2),
http://portal.acs.org/portal/PublicWebSite/education/resources/highschool/chemmatters/a
rchive/WPCP_008628; Teacher’s Guide access at
http://portal.acs.org/portal/PublicWebSite/education/resources/highschool/chemmatters/a
rchive/WPCP_012145.
A 3-D model of a dog’s nasal passage and neural connections:
The canine nasal airway: (a) Three-dimensional model of the left canine nasal airway,
reconstructed from high-resolution MRI scans. (b) The olfactory recess is located in the rear of the
nasal cavity and contains scroll-like ethmoturbinates, which are lined with olfactory epithelium.
The olfactory (yellowish-brown) and respiratory (pink) regions shown here correspond to the
approximate locations of sensory (olfactory) and non-sensory (squamous, transitional and
respiratory) epithelium, respectively (Craven et al. 2007).
(http://rsif.royalsocietypublishing.org/content/early/2009/12/09/rsif.2009.0490/F1.expansion.ht
ml)
(Teacher’s Guide (pp 12–15), for Ebach, C. What’s That Smell? ChemMatters)
Beagles, bloodhounds, and basset hounds have been bred to have especially
keen senses of smell, even for dogs. They can be trained to discriminate between
various chemical odors, sniffing out land mines, bombs in luggage, drugs at border
crossings—and now they are being used in medical diagnosis (cancer in particular).
Dogs are trained to detect odors, too faint for humans to smell, that indicate a diabetic
patient might be about to go into insulin shock, a condition that results when blood sugar
levels drop dangerously low, and can lead to coma and even death. When the dog smells
insulin shock on the way, it can alert the patient to take preventive measures, like eating
something sweet. If the insulin shock comes while the patient is asleep, a barking dog
can be a lifesaver.
73
(Sniffing Landmines. ChemMatters 2008, 28 (2), Teacher’s Guide; access at
http://portal.acs.org/portal/PublicWebSite/education/resources/highschool/chemmatters/a
rchive/WPCP_012145)
In the future, dogs may also be used to smell cancers while still too small to be
detected by conventional means. Some studies that have been done with what are called
sniffer dogs are able to detect some of the chemicals being exhaled by patients with lung
cancer. In some well controlled experiments, dogs were able to detect lung cancer from
exhaled breath in 71 of 100 test cases and determined that 372 of 400 other patients did
not have lung cancer. In addition, the dogs could discern lung cancer from other lung
problems such as chronic obstructive pulmonary disease, even sniffing accurately
through the exhaled breath of patients that just smoked a cigarette. The dogs are
detecting volatile organic compounds being emitted from cancerous cells in the very early
stages, which other medical tests or diagnostic technologies are not able to do. Other
studies have shown that urine of cancer patients contain volatiles that are detectable by
dogs. The ideal would be to identify the particular marker molecules after which an
electronic detector might be developed.
(ChemMatters Teacher’s Guide (p 14), for Ebach, C. What’s That Smell? ChemMatters)
More on pheromones
Chemical senses are the oldest of senses, shared by all organisms including
bacteria. Very recently, it has been determined that several species of bacteria can
detect very specific chemicals. Several species of soil bacteria have their own “noses” for
detecting airborne ammonia, an important nitrogen source for the bacteria’s protein
metabolism. Most animal olfactory systems have a large range of relatively non-specific
olfactory receptors, which means that almost any chemical in the rich chemical world of
animals will stimulate some olfactory sensory neurons and can potentially evolve into a
pheromone. A pheromone is a molecule used for communication between animals of the
same species. [The word pheromone comes from the Greek, pherein, to carry or
transfer and hormon, to excite or stimulate.] Across the animal kingdom, more
interactions are mediated by pheromones than by any other kind of signal. There is a
certain commonality between vertebrates and invertebrates in terms of the pheromones
produced and in the range of behaviors that pheromones influence.
Insects such as ants use pheromones to direct their “colleagues” to a food
source and find their way back to the colony. They also have other pheromones to
 mark the way to new nest sites during emigration
 aggregate
 mark territories
 recognize nest mates.
Mating activities of moths depend upon the male detecting the odors emitted by
the female of the species. Chemical knowledge of this “mating” pheromone or sex
attractant has been used to lure male moths into traps to limit reproduction of moths that
are destructive to plants, such as the Gypsy moth. But other animals as large as the
elephant make use of pheromones, primarily for reproductive purposes (sexual
signaling). An interesting note is the fact that the pheromone used by elephants is the
same molecule used by 140 species of moth! Yet there is no interaction between the two
groups of animals because the receptors and the signals produced are different! Dogs
like many other mammals (except humans) respond to pheromones meant to indicate
mating readiness and other sexual details. Since we were talking previously about the
74
highly sensitive olfactory system in the dog, it turns out that the dog possesses a special
olfactory structure in its nose for detecting pheromones in the mix of chemicals that come
through its nasal channels. This structure is called Jacobson’s organ; it is located in the
bottom of the dog’s nasal passage. ”The pheromone molecules that the organ detects—
and their analysis by the brain—do not get mixed up with odor molecules or their
analysis, because the organ has its own nerves leading to a part of the brain devoted
entirely to interpreting its signals. It's as if Jacobson's organ had its own dedicated
computer server. (http://www.pbs.org/wgbh/nova/nature/dogs-sense-of-smell.html)
Some known pheromone molecular structures are shown here.
Chemical composition of certain pheromones: (1) sex attractant of female of
Asiatic silkworm, (2) marking substance of certain bumblebees, (3) aphrodisiac of male
of Danaidae butterfly, (4) attractant of female of gypsy moth, (5) component of marking
secretion of a rodent (clawed jird), (6a, 6b, 6c) three components of clustering
pheromone of Scolytus bark beetle, (7) anxiety pheromone of Lasius ant
(http://encyclopedia2.thefreedictionary.com/Pheromone)
There are defined criteria for a pheromone. “The general size of pheromone
molecules is limited to about 5 to 20 carbons and a molecular weight between 80 and
300. This is because below 5 carbons and a molecular weight of 80, very few kinds of
molecules can be manufactured and stored by glandular tissue. Above 5 carbons and a
molecular weight of 80, the molecular diversity increases rapidly and so does the
olfactory efficiency. Once you get above 20 carbons and a molecular weight of 300, the
diversity becomes so great and the molecules are so big that they no longer are
advantageous. They are also more expensive to make and transport and are less
volatile. In general, most sex pheromones are larger than other pheromones. In insects,
they have a molecular weight between 200 and 300 and most alarm substances are
between 100 and 200.” (Sociobiology: The Abridged Edition, 1980, 114)
(http://www.angelfire.com/ny5/pheromones5/structure.html)
Besides the category of pheromone associated with sexual signaling, there are
alarm pheromones that are released to promote fight and flight reactions in receivers.
Many ant species release the same pheromones to repel an opponent and an alarm to
recruit fellow ants for assistance in a battle with the invaders. In other animals, alarm
pheromones are used to make flesh unpalatable or toxic to a predator. These substances
would be released by an injured animal. There are a variety of sea organisms that use
this technique.
75
(ChemMatters Teacher’s Guide (pp 15–16), for Ebach, C. What’s That Smell?
ChemMatters)
More on specialized smell in fish
The function of smell in non-humans is more than just imbibing on pleasant (or unpleasant)
odors.
Being able to smell particular chemicals serves a most interesting purpose for
salmon—their ability to return to their place of birth several years later to repeat the
reproductive cycle. Classic experiments done by Arthur D. Hasler in the 1950s clearly
demonstrated that salmon can smell particular chemicals in a stream that are associated
with the migration route that the salmon takes after hatching to return to the ocean. If
their nostrils are blocked, the salmon are unable to follow a particular stream of water that
contains the chemical clues. The memory of those smells serves the salmon several
years later when they begin the migration from the sea back to the fresh water stream, a
distance of 800 to 900 miles away where they developed in and hatched from eggs. It is
not known just exactly how the mature salmon find their way along the coastline (Pacific
and Atlantic) to zero in on a particular fresh water river that empties into the ocean. There
are ideas that for the ocean portion of the return trip, salmon use some navigational tools
in the open water that include day length, the sun’s position and the polarization of the
light that results from the angle in the sky, the earth’s magnetic field, water salinity and
temperature gradients. Whatever the combination of tools, the salmon are able to find
where their natal waters discharge into the ocean.
Young salmon (smolts) are particularly sensitive to the unique chemical odors of
their locale when they begin their downstream migration to the sea. Odors that the smolts
experience during this time of heightened sensitivity are stored in the brain and become
important direction-finding cues years later, when adults attempt to return to their home
streams. In one early experiment, salmon that were reared in one stream and then
moved to a hatchery during the smolt stage returned to the hatchery, demonstrating the
crucial role of imprinting during the transformative period of the fish’s life. Recent work
has suggested young salmon may go through several periods of imprinting, including
during hatching and while emerging from their gravel nest. (A good reference on studying
olfaction in salmon in detail is found at
http://fish.washington.edu/research/publications/ms_phd/Havey_M_MS_Sp08.pdf.
(ChemMatters Teacher’s Guide (p 12), for Ebach, C. What’s That Smell? ChemMatters)
More on olfactory fatigue
One of the interesting neural responses of our olfactory system is a
disappearance of the recognition or registration of a particular smell in the air being
inhaled, over a short period of time. The neural receptors for smell eventually stop
sending signals to our brain for interpretation of a particular smell. This is known as
olfactory fatigue.
Have you ever noticed a particular scent upon entering a room, and then not
noticed it ten minutes later? This is due to olfactory fatigue. The olfactory sense is unique
because it relies on mass, not energy to trigger action potentials. Your ears do not "stop"
hearing a sound after a certain period of time, nor do your eyes stop seeing something
you may be staring at. This is because both the ears and the eyes rely on energy to
trigger them, not mass. In the nose, once a molecule has triggered a response, it must be
disposed of and this takes time. If a molecule comes along too quickly, there is no place
76
for it on the olfactory hairs, so it cannot be perceived. To avoid olfactory fatigue, rabbits
have flaps of skin that open and close within the nostrils. This allows for short, quick
sniffs and lets the rabbit "keep in close odor contact with its environment." When we wish
to fully perceive a scent, we humans also smell in quick, short sniffs, often moving the
source of the smell in front of one nostril then the other. This behavior also prevents odor
fatigue. (Stoddard & Whitfield, 1984)
(http://www.macalester.edu/academics/psychology/whathap/ubnrp/smell/odor.html)
An interesting trick or technique to counter olfactory fatigue in perfume shoppers
is to have containers of coffee beans on the store counter which tend to
‘reset’ olfaction. Anosmia is the permanent loss of the sense of smell, and is different
from olfactory fatigue. (Wikipedia, http://en.wikipedia.org/wiki/Olfactory_fatigue)
(ChemMatters Teacher’s Guide (pp16–17), for Ebach, C. What’s That Smell?)
Connections to Chemistry Concepts
(for correlation to course curriculum)
1. Organic compound—Any chemical that contains carbon (except carbon monoxide, carbon
dioxide and metal carbonates) is considered an organic compound. Because of the bonding
based on the carbon atom, organic compounds have an almost infinite number of
configurations with important “functional” groups attached. The size of the molecules of
organic compounds is wide-ranging. It is thought that a truck tire of synthetic or natural
rubber, an organic polymer, is a single molecule!
2. Kinetic molecular theory of gases—Because gas molecules are constantly in motion,
volatile substances can reach our nose from a source at some distance from us.
3. Phase change—Although a volatile organic compound can exist in a biological solution, it
can only be detected by a dog’s nose if the compound undergoes a phase change from
liquid to a gas (evaporation). But to be detected in the nose, the gas has to then go into
solution.
4. Reactive Oxygen Species (ROS)—These molecules that are considered chemical radicals
(meaning they have unpaired electrons within a molecule) are considered to be highly
reactive and can cause damage to cells and tissues, including DNA structures. This in turn
can potentially alter the behavior of a functioning cell because of changes in the formation of
specific enzymes that are under DNA control. Alteration of enzymes affects biochemical
reactions.
5. Antioxidant—This category of chemical, found within cells as well as in the intercellular
fluid, can latch on to reactive oxygen species and prevent them from damaging important
biological molecules such as enzymes and other proteins. There are both water-soluble as
well as lipid soluble types. Vitamin E and C are considered to be the most abundant and
effective of the antioxidants.
6. Volatile Organic Compounds (VOC) —There are many volatile organic compounds that
are not necessarily connected to biological situations, including the cancer state. Commonly
occurring VOCs include formaldehyde, benzene, methylene chloride, perchloroethylene,
methyl tert-butyl ether (MBTE), methane (often separately classified), chlorofluorocarbons,
styrene and limonene. These compounds have to have high vapor pressure which in turn
suggests they have weaker intermolecular bonds than non-volatile compounds. The lack of
strong intermolecular bonds is determined by the molecular structure itself.
7. Polar, nonpolar—Volatility of compounds (the ease which liquids vaporize) is dependent on
the types of intermolecular bonds that exist. These bonds in turn depend on intramolecular
77
bonds, some of which can produce polar or nonpolar molecules. Nonpolar molecules will
have lower boiling points and higher vapor pressures compared with polar molecules of
similar molecular weight.
Possible Student Misconceptions
(to aid teacher in addressing misconceptions)
1. “Taking anti-oxidants, such as vitamins, will prevent developing cancer.” Although
some investigators suggest a link between excessive reactive oxygen species and
damage to DNA which in turn might cause cancer, there is no definitive connection. In
fact, it is known that DNA can repair itself. Taking anti-oxidants such a vitamin E or C
could reduce the number of reactive oxygen species. It does not mean we have
eliminated a known cause of cancer, however.
2. “We have a limited number of odors that we can detect.” OK, this isn’t really a
misconception, but it comes close; it seems as if our olfactory system can detect up to
10,000 different odorants, which seems to be quite extensive!
3. “Liquids evaporate or vaporize only at high temperatures, as in the boiling of
water.” The temperature at which a liquid evaporates, whether at the boiling point or
not, is dependent on the molecular structure of the molecule which in turn determines
the type of intermolecular bond. If you compare the rate at which water evaporates at
room temperature and an organic compound such as carbon tetrachloride (CCl4), you
find that carbon tetrachloride will evaporate much quicker than water because the
intermolecular bonds between the carbon tetrachloride molecules are much weaker than
those between water molecules. The type of intermolecular bond results from the
bonding within the molecules. The water molecule ends up being a polar molecule which
means it possesses slight electrical charges of plus and minus on opposite ends of the
structure (dipoles). This allows for attractive forces between water molecules (plus to
minus). The carbon tetrachloride molecules are the exact opposite or non-polar. The
intermolecular bonds are much weaker than that of water. So it takes less kinetic energy
for separation of carbon tetrachloride molecules in the evaporative process. The
molecules do not have to reach the boiling point in order to evaporate because some of
the molecules have enough kinetic energy to break intermolecular bonds and become
gaseous. Non-polar molecules create a higher vapor pressure (from more gaseous
molecules) at a given temperature than polar molecules because of their weaker
intermolecular bonds. NOTE: Vapor pressure relies on the existence of three distinct
types of intermolecular forces- London forces (temporary dipoles), present in all
molecules, dipole-dipole interactions, which are the result of polarized structure, and
hydrogen bonds, which are the result of a hydrogen atom covalently bonded to a highly
electronegative atom (such as oxygen) in a polarized structure.)
Anticipating Student Questions
(answers to questions students might ask in class)
1. Is smell different than taste? Do fish ‘smell’ food or do they ‘taste’ the food?”
Depending on the type of animal, there can be separate locations for taste detection
(e.g., taste buds or receptors) and smell detection (e.g., olfactory receptors). In the
case of fish, there are olfactory receptors in their nasal passages for the detection of
various types of molecules in the water including those that identify the type of water
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(related to homing instincts in salmon) or the presence of another fish of the same
species. So fish smell food. But they are also able to taste with taste buds on their
lips and on the roof of their mouths as well as on the gills. They do not have taste
buds on their tongue as is true for humans. For humans, we taste as well as smell
food with olfactory receptors in the nose and taste buds on the tongue as well as in
the back of the throat. The taste buds detect certain “tastes”—salt, sweet, bitter, sour
and umami (“deliciousness”). Smell comes in multiple categories creating a complex
of “odors”. Sometimes smell and taste work in conjunction with each other to produce
a particular “taste”. If your taste buds are blocked, as in a cold, some flavors of food
are not detected. Chocolate’s flavor depends on smell as much as taste. If you block
out smell, the only components of the chocolate flavor will be sweetness and
bitterness (from the taste buds).
2. Why does the initial odor of a substance such as a deodorant disappear even
though the person is still in the room?” The molecules responsible for the odor of
the deodorant are still in the air and reaching a person’s nose. But the person’s
nervous system has reached what is known as olfactory fatigue. If the person who no
longer smells the odor were to leave the area of the perfume, then return, that person
would again smell the perfume for another period of time before sensory fatigue sets
in.
3. How do the molecules of an odor become a sensation of smell?” When the
molecules associated with an odor reach the nerve endings of the olfactory sensors
in the nose, they must first go into solution (the mucosa).
(http://www.senseofsmell.org/smell101detail.php?id=1&lesson=How%20Does%20the%20Sense%20of%20Smell%20Work)
This solution bathes cilia that are part of nerve endings (olfactory nerve endings)
which are an extension of what is known as the olfactory bulb. Within the olfactory
bulb are nerve endings that connect to the cilia-olfactory nerve endings, carrying a
nerve impulse to the brain. The stimulation of the nerve endings is accomplished
through specialized proteins in the cilia that bind low molecular weight molecules
(odorants). The binding of the odorant molecules to the specialized proteins causes a
change in the structure of the specialized proteins which in turn sets off an electrical
signal that passes into the olfactory bulb and on to the brain for interpretation as a
particular smell.
4. “Why are dogs more sensitive to smell than humans?” If you look at the sensory
area for smell in a dog’s brain, it is apparent that it is much more extensive than in
our brains. It is estimated that a dog has some 20 to 40 times as many receptors as
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humans. If you test a dog’s ability to smell the particularly odoriferous molecule
hydrogen sulfide, it is found that the lowest concentration of hydrogen sulfide in air
that is detected is 10-13 % (0.00000000000001%, or 1000 ppt). The lowest
concentration of hydrogen sulfide detected by humans is 10-6 % (0.0000001% or 100
ppm). Note that the MSDS for hydrogen sulfide lists the short term exposure limit (10
minutes) at 15 ppm, which means we can’t even detect it at its toxic level—but dogs
can.
(Above questions originally printed in the Teacher’s Guide (pp 18–19) for Ebach, C.
What’s That Smell? ChemMatters 2012, 30 (4), pp 12–14)
In-class Activities
(lesson ideas, including labs & demonstrations)
1. Several class lab exercises on olfactory fatigue can be found at the following Web sites:
a. http://www.sciencebuddies.org/science-fairprojects/project_ideas/HumBio_p031.shtml#materials
b. http://academic.evergreen.edu/curricular/perception/Lab1006.htm. This latter Web site
has very good questions for the students to think about with regard to the topic of
olfactory fatigue.
c. Another Web site on olfactory fatigue activity is found at
http://faculty.washington.edu/chudler/chems.html.). The teacher’s guide for this activity is
found at http://faculty.washington.edu/chudler/pdf/chemstg.pdf.
2. Another student lab exercise involves the synthesis of esters, which are normally used as
flavoring in foods, but for this exercise would simply be the production of pleasantly smelling
compounds that they can recognize. Ester synthesis involves the use of concentrated
sulfuric acid. But if done in small quantities it presents less of a lab safety issue. Or the
teacher can add the acid for the students at the correct step in the procedure. Refer to the
following Web site for a complete lab exercise in ester synthesis:
http://www.nuffieldfoundation.org/practical-chemistry/making-esters-alcohols-and-acids.
3. Although this ChemMatters article deals with smell, students could map their tongue for the
locations of the principle tastes of salt, bitter, sweet and sour (acidic). A printable outline of
the tongue with the locations on the tongue for the different categories of taste is found at
http://www.teachervision.fen.com/tv/printables/orange/SL-27.pdf. A Web site for the lab
procedure can be found at http://faculty.washington.edu/chudler/chtaste.html. You can also
actually see the taste buds on the tongue and compare the number for different people. See
the following Web site for the simple instructions:
http://www.bbc.co.uk/science/humanbody/body/articles/senses/tongue_experiment.shtml.
Additional background information and discussion about the integral role of smell with taste
and touch for the sensations of what some people would call the flavor of foods is found at
http://www.tastescience.com/default.html. Smell is often involved with a particular taste. This
exercise would also point out to students the specificity of neural receptors. Most biology lab
manuals contain the exercise procedure.
4. Instructions for doing vapor pressure lab exercises follow:
a. one based on Vernier’s “LabQuest 10: Vapor Pressure of Liquids Lab” is found at
http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CEIQFjAA
&url=http%3A%2F%2Fwww.myexperiment.org%2Ffiles%2F187%2Fdownload&ei=OEvb
UKiHO4a50QH68YFY&usg=AFQjCNEsXwKXUXpXiWo9tiPzcGXXOFMg6g&bvm=bv.13
55534169,d.dmQ. The reference for the Vernier Lab Quest experiment with a list of
Vernier equipment needed is found at
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http://www.vernier.com/experiments/cwv/10/vapor_pressure_of_liquids/ The most recent
listing of Vernier publications that include the chemistry experiments can be found at
http://www.vernier.com/products/books/cwv/. Finally, the basics of using Vernier Lab
Quest programs are found at
http://www.esf.edu/outreach/k12/solar/2009/Labs/Vernier%20LabQuest%20basics.pdf.
b. A second experimental procedure for measuring vapor pressure is found at
http://www.macalester.edu/~kuwata/Classes/200102/Chem%2011/Vapor%20Pressure%20Lab.pdf.
c. Another experiment to determine vapor pressure as well as heat of vaporization for more
capable students (the technique is interesting and non-electronic) is found at
http://books.google.com/books?id=Z9f3CrD38bwC&pg=PA105&lpg=PA105&dq=measuri
ng+vapor+pressure+lab&source=bl&ots=0Q4K6ovobG&sig=Kbhx2prRRUR4I0bQCOQ1
2g63DNI&hl=en&sa=X&ei=OEvbUKiHO4a50QH68YFY&ved=0CHgQ6AEwCQ#v=onepa
ge&q=measuring%20vapor%20pressure%20lab&f=false.
Out-of-class Activities and Projects
(student research, class projects)
1. There are many interesting biological/biochemical aspects to smell in living organisms, from
bacteria to humans. How does a chemical in the air become a nerve impulse and a detected
sensation in the brain? What chemistry is involved? What is common to different animals
and their sense of smell? What is different- what types of odor molecules are detected by
what animals?
2. Students could research the connection, if any, (what research evidence?) between
antioxidants and cancer prevention. A useful reference to start is found at
http://well.blogs.nytimes.com/2012/10/22/curbing-the-enthusiasm-on-daily-multivitamins/
3. The issue of the effectiveness of vitamins and other supplements in terms of using
antioxidant properties to prevent cancer needs to be investigated by students. A starting
point is http://blogs.scientificamerican.com/observations/2010/04/20/antioxidants-may-notbe-worth-their-salt-in-preventing-cancer/. A related study on the effectiveness of a specific
naturally occurring compound, alpha-carotene, is found at
http://blogs.scientificamerican.com/observations/2010/12/30/alpha-carotene-from-veggieslinked-to-longer-life/ . A research team found an especially strong correlation between
higher alpha-carotene levels and lower risk of death from diabetes, upper respiratory tract
and upper digestive tract cancers, as well as lower respiratory disease.
4. There are all kinds of ideas, with various degrees of supporting evidence as to the
effectiveness of antioxidants against aging, that can be researched, starting with
http://www.scientificamerican.com/article.cfm?id=free-radical-shift
5. An additional reference that students could use in their research is a government site that
presents a balanced view about antioxidants and the research evidence supporting or not
supporting the effectiveness of this special class of chemicals. Refer to
http://www.cancer.gov/cancertopics/factsheet/prevention/antioxidants.
References
(non-Web-based information sources)
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The references below can be found on the ChemMatters
25-year CD (which includes all articles published during the years
1983 through 2008). The CD is available from ACS for $30 (or a
site/school license is available for $105) at this site:
http://www.acs.org/chemmatters. (At the right of the screen,
click on the ChemMatters CD image like the one at the right.)
Selected articles and the complete set of Teacher’s Guides
for all issues from the past three years are also available free online
at this same site. (Full ChemMatters articles and Teacher’s Guides are
available on the 25-year CD for all past issues, up to 2008.)
Some of the more recent articles (2002 forward) may also be available online at the URL
listed above. Simply click on the “Past Issues” button directly below the “M” in the ChemMatters
logo at the top of the page. If the article is available online, you will find it there.
Although the title suggests this article is only about pheromones, the content is about
aromas in general. The suggestion about human pheromones is not supported by scientific
evidence to date. (Kimball, A. Human Pheromones: The Nose Knows. ChemMatters 1997, 15
(2), pp 8–10)
This article may appeal to students because it explores those bodily odors that do not
qualify as attractive perfumes. It explores the origins of the typical teenager odors! (Kimbrough,
D. How We Smell and Why We Stink. ChemMatters 2001, 19 (4), pp 8–10)
This article discusses how dogs are able to detect landmines through training to
recognize specific volatile chemicals that emanate from the buried explosive device. (Vos, S.
Sniffing Landmines. ChemMatters 2008. 28 (2), pp 7–9,
http://portal.acs.org/portal/PublicWebSite/education/resources/highschool/chemmatters/archive/
WPCP_008628)
A recent ChemMatters article related to smell is Ebach, C. What’s That Smell?
ChemMatters 2012, 30 (4), pp 12–14.
Web sites for Additional Information
(Web-based information sources)
More sites on a dog’s sense of smell
“This is a Nova Web site about dogs and their use in tracking things:
http://www.pbs.org/wgbh/nova/nature/dogs-sense-of-smell.html. It includes an extensive set of
references that are Web-accessible.”
(Teacher’s Guide (p 2) for Ebach, C. What’s That Smell? ChemMatters)
A series of references on dogs about their sense of smell plus training is found at the
PBS Kids Web site for Scientific American Frontiers at http://www.pbs.org/saf/1201/index.html.
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Additional uses of dogs for odor detection are described in The NY Times article found
at
http://www.nytimes.com/2006/06/13/nyregion/13dogs.html?pagewanted=1&_r=1&ei=5094&en=
1098a4ffbdf88db&hp&ex=1150257600&partner=homepage.
A newspaper article that describes the work of a cancer-research station, Pine Street
Foundation, which also utilizes dogs for cancer detection (and how they are trained) is found at
http://pinestreetfoundation.org/can-dogs-detect-cancer/. A short video of a dog in action is
available at http://pinestreetfoundation.org/can-dogs-detect-cancer/.
A more extensive video on the training techniques for cancer-sniffing dogs is found at
http://www.youtube.com/watch?v=IZA9R0uSGWc .
Videos on dogs detecting bedbugs and alerting diabetic conditions for a patient are
available at http://www.youtube.com/watch?v=EJ-6gvPJUI8 (bedbugs),
http://www.youtube.com/watch?v=Y-bi2FEsK4o (diabetic) and
http://www.youtube.com/watch?v=tb4WiUTAA5M (diabetic). During the past 10 years, diabetic
alert dogs have been used successfully in the management of Type 1 diabetes.
More sites on pheromones
Current thinking on human pheromones and the role of odors in human
interaction can be found at
http://www.scientificamerican.com/article.cfm?id=pheromones-sex-lives.
Another site that provides a very extensive background on pheromones and their
use by various groups of animals is found at
http://catdir.loc.gov/catdir/samples/cam033/2002024628.pdf.
An example of how scientists go about studying and deciphering ant behavior
that includes using pheromones is found at
http://beheco.oxfordjournals.org/content/18/2/444.full.
A complementary article on studying the behavior of ants, in terms of detecting
scents, is found at http://blogs.scientificamerican.com/thoughtfulanimal/2011/06/23/nosejobs_for_ants/.
A Web site that is all about ants and how they communicate (includes video and
drawings of body parts important to the communication) is found at
http://blog.wildaboutants.com/2010/06/27/questions-about-ant-pheromones/.
A college Web site about pheromones might prove useful to students who adopt
the topic of pheromones for a research project. The Web site is quite extensive and also
readable. The Web address is
http://www.macalester.edu/psychology/whathap/UBNRP/pheromone10/pheromones%20i
ntro.html .
An extensive collection of Web sites from Scientific American dealing with
pheromones can be found at
http://www.scientificamerican.com/search/?q=pheromones&x=0&y=0.
(all from Teacher’s Guide (p 23) for Ebach, C. What’s That Smell? ChemMatters)
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More sites on homing traits of salmon
One site that summarizes current thinking on the ability of salmon to return to
their freshwater site of birth is found at
https://www.novapublishers.com/catalog/product_info.php?products_id=26321&osCsid=1
68c08748e890891d8335a0f23b338ea.
Additional sites that deal with salmon homing instincts are found at
http://fish.washington.edu/research/publications/ms_phd/Havey_M_MS_Sp08.pdf. (a
PhD thesis that discusses the experimental setup for evaluating imprinting on salmon)
For a story about studying the geomagnetic abilities of salmon in homing from
ocean to freshwater see
http://www.pnas.org/content/105/49/19096.full.
A site that shows the role of amino acids in water that salmon use for homing can
be found here:
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0008633.
This site gives a very complete discussion of what is known and not know about
how salmon find their way from ocean to their site of birth in an inland freshwater stream:
http://jeb.biologists.org/content/199/1/83.full.pdf.
(all from Teacher’s Guide (p 23) for Ebach, C. What’s That Smell? ChemMatters)
More sites on using animal sense of smell for medical purposes
This site, http://www.monell.org/news/news_releases/lung_cancer_odors, is from
one of the major research centers on smell, the Monell organization. Their news
information describes the research into detecting cancer through odors in urine using
both animals and electronic chemical sensing. In this case the subjects are mice. Of
course dogs are also known to be able to detect cancer in human patients, both from
sensing volatile organic compounds emitted in a person’s breath as well as sniffing a
patient’s urine, depending on the type of cancer.
Another Web site dealing with cancer detection by dogs is found at
http://www.huffingtonpost.com/organic-authoritycom/dogs-smell-cancer_b_976797.html.
(two sites above from Teacher’s Guide (p 24) for Ebach, C. What’s That Smell?
ChemMatters)
Two recent scientific papers that justify the accuracy of trained dogs in detecting lung
cancer compared with electronic devices are found at
http://erj.ersjournals.com/content/early/2011/08/05/09031936.00051711 and
http://erj.ersjournals.com/content/39/3/511.full.pdf+html.
More sites on electronic smelling devices
Although animals such as dogs are available, if trained, to sniff out a variety of materials
including medical odors, drugs, and explosive devices, there continues to be research into
electronic devices for detecting a whole host of vapors. The basis for some of these devices is
explained at this Web site: http://techno-glitz.blogspot.com/2008/03/electronic-smell.html.
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Another electronic device for detecting cancer uses a nuclear magnetic resonance
scanner that detects specific antibodies (with injected magnetic particles) associated with
cancerous cells. The device is reported to have a 96% accuracy rate, 12% higher than other
standard methods. A “smartphone” can be programmed to read the results based on analysis of
nine protein markers associated with cancer cells. The device is quite small and portable. Refer
to this Web address:
http://phys.org/news/2011-02-smartphone-app-cancer-diagnosis.html.
Another electronic device developed specifically to detect heart failure conditions with an
explanation of how the device works is found at http://news.cnet.com/8301-27083_3-20098835247/could-an-electronic-nose-sniff-out-heart-failure/?part=rss&subj=news&tag=2547-1_3-0-20.
More sites on chemical-based cancer detectors
The Web site http://news.bbc.co.uk/2/hi/health/6387773.stm describes the development
of an inexpensive chemical test to detect VOCs given off from lung cancer patients. Because it
is based on color changes, expert analysis is not required. And the accuracy of the test is about
75% including detection of very early tumors which is very important in the case of lung cancer
which needs very early detection in order to have any success in treatment.
More sites on Reactive Oxygen Species (ROS) and antioxidants
Two Web sites that provide chemical information on reactive oxygen species are
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/R/ROS.html, which may be useful in
class because of the electronic structures of ROSs that are shown, and
http://lpi.oregonstate.edu/f-w97/reactive.html, which is an academic Web site of the Linus
Pauling Institute (LPI). This site discusses the role of ROSs in a biological/biochemical context
along with how certain vitamins, particularly Vitamin C and E, may play a role as antioxidants to
counter the effects of ROSs. Among other things, Linus Pauling discovered several important
properties of bonding that included hybridization and resonance. He also explained the
properties of ionic solids. This Web site of the LPI may prove useful for future classes as it
includes biographical details of Linus Pauling’s life work in chemistry.
An extensive Web site (fact sheets) on antioxidants and cancer is at the National Cancer
Institute and is found at http://www.cancer.gov/cancertopics/factsheet/prevention/antioxidants.
Among other things is scientific information on various research projects (clinical trials) that are
investigating connections between antioxidants, such as vitamins, and the prevention of cancer.
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Drivers, Start Your Electric Engines!
Background Information
(teacher information)
More on the history of electric cars
As mentioned in the article, electric cars were more popular than gasoline powered cars
in the late 1890s and early 1900s. In addition to being easier to start (no manual crank like
gasoline-powered cars) and having no gears to change while driving, they were also quieter and
did not have any smells attached to them, as did gasoline cars. Some electric car and truck
drivers utilized exchangeable batteries, instead of recharging their own. Typical use for electric
cars in those times was for city driving, much like electric cars today (so far). In those days that
was sufficient because most roads were confined to urban areas. Typical drivers were the wellto-do and women, due to ease of operating the electric cars. Taxi companies also used electric
cars.
Popular use of electric cars also occurred because they were more economical to drive
than gasoline cars. But gradually, as mass production (think, Henry Ford and his assembly line)
resulted in cheaper gasoline-powered cars (half the cost of an electric car), other technological
advances like the electric starter were made, improved highways were developed, and a
national gasoline pipeline infrastructure became reality, the internal combustion engine became
the propulsion mechanism of choice and electric car sales declined significantly. By the 1930s,
the electric car was all but gone from US roadways.
Here’s an interesting story from the early days of electric cars involving the use of a car
on a cold night.
Perhaps you have noted that if you have been trying to start the car and you let it
"rest" for a few minutes the battery will have renewed zest. Why?
A Related Anecdote--from the Life of Eddie Rickenbacker
Concerning his trip in a Waverly Electric Car taken without permission from
his employer. He was about 14 years old of the time (1904).
Contributed by Arra Nergararian, Worcester Polytechnic Institute
"After supper I started back to the garage. Mr. Evans would be in next morning. .
. But I hadn't gone one quarter of the way when the little car began to give signs that I
had driven it too much. It slowed down and came to a stop. It was out of juice. The
batteries were dead. Darkness was coming on and I had a mile and a half to go . . . no
wrecker service . . . only the Evans Garage which was going to be minus its one
employee should its irate owner return to find said employee out with a customer's car.
"In discussing electrical energy with me, Evans had observed that frequently a
battery would regain some current if allowed to sit idle for a while . . . I decided to wait an
hour. Never had time dragged so slowly. My Ingersoll dollar watch was in and out of my
pocket a. dozen times . . .I gingerly pushed the control lever, fully expecting nothing to
happen, but . . . the car lurched forward . . . several blocks before it died. Again I sat for
an hour . . . the refreshed batteries took me a few more blocks. As the night wore on, the
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hope became shorter and the waits longer, but finally about 3:00 A.M. I reached the
garage. I hooked up the battery charger and took the streetcar home. . . ."
(J. Chem. Educ., 1970, 47 (5), p 383, DOI: 10.1021/ed047p383.1, also online at
http://pubs.acs.org/doi/abs/10.1021/ed047p383.1—reminder: subscription required to
read content)
In the US, little progress was made in the electric vehicle arena, until the 1990s. The
energy crises of the 1970s and ‘80s renewed interest in electric cars, as potential buyers viewed
them as a way to exert energy independence from oil shortages and crude oil price increases.
General Motors actually produced an electric car in 1994, that proved to be a
commercial bust. Called the EV1, it was a two-seater sports coupe that was simply
battery powered. A total of only 1400 vehicles were sold. One major problem was price.
The EV1 had a cost about 30% higher than comparable traditional vehicles. General
Motors’ states that its own customer research has lead it to believe that the typical
consumer will not pay more for a vehicle just for the “sake of the environment.” Another
problem was that the range of the car was only about 60 miles before recharging was
required. Northern winters posed another problem to EV1 drivers---Run the heater or run
the car, your choice!
(ChemMatters Teacher’s Guide, December 2000)
Yet another problem with the EV1 was that the state of California’s Air Resources Board
(CARB) rescinded its stringent air quality law requiring more energy-efficient, low-emissions
vehicles, eventually moving to zero-emissions vehicles. The eventual rescission of the law was
due to continued pressure from automobile manufacturers and the oil industry. It was this law
that had pushed GM’s research into and production of the EV1 in the first place. This new, lessstringent atmosphere in California law resulted in fewer people interested in purchasing the allelectric vehicle and a subsequent lack of sales. GM eventually recalled all the EV1 electric cars
and demolished them, save for a very few, stripped of their batteries, that were donated to
museums. A 2006 feature-length film that discussed this situation, “Who Killed the Electric
Car?”, appeared at the Sun Dance Film Festival. Apparently it is still available as a DVD,
available on Amazon for $9.52 at the time of the writing of this Teacher’s Guide. It’s also
available on Netflix at
http://movies.netflix.com/WiMovie/Who_Killed_the_Electric_Car/70052424?locale=en-US.
Around the world, many multiple-passenger battery-powered electric vehicles (BEVs)
have been produced and put in trial-use since the mid-1990s. Many bus and shuttle BEVs are in
use today for urban transit that take advantage of the BEV’s lack of emissions. Often these
vehicles have their batteries swapped out for recharge, in order to allow 24-hour operation of
the vehicles. Vans and trucks that operate in urban settings have also been fitted out with
batteries for electric propulsion. (http://en.wikipedia.org/wiki/Battery_electric_vehicle#Vehicles)
In 1910, Seoul, South Korea was the first city to put into use a fleet of five (soon
thereafter to be 14) commercial electric buses, which utilize Li-ion batteries, for part of its transit
system. Recharge times for these batteries is under 30 minutes! Their plan is to have 120,000
electric vehicles in use in the city by 2020.
(http://www.gizmag.com/korea-begins-first-commercial-electric-bus-service/17385/)
More on electric cars and the environment
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Studies have shown that battery-powered electric vehicles (BEVs) are environmentally
friendly, relative to today’s gasoline-powered cars. One such study, “Contribution of LI-Ion
Batteries to the Environmental Impact of Electric Vehicles”, published in the American Chemical
Society journal Environmental Science &Technology, reported the results of tests that compared
the environmental impact of the BEV with that of the internal combustion engine vehicle (ICEV).
Their report on BEVs and ICEVs used four different assessment methods. All four methods
showed that ICEVs had greater negative impact on the environment than BEVs, in one method
by as much as 60%. And these findings were based on a “new efficient gasoline car”. “This
ICEV consumes 5.2 L of gasoline per 100 km.” This is equivalent to 45.2 miles per gallon, so
they are comparing BEVs to a very technologically advanced ICEV, not the typical car on the
road in the U.S. today. (You might want to have students do the conversion for themselves,
using dimensional analysis.)
In analyzing the environmental impact, the study says
There are no differences between ICEV and BEV with respect to the
environmental burden related to road use (infrastructure, maintenance, and disposal) and
the glider [the body of the car, without the propulsion system]. Small differences are
related to the drivetrain, maintenance, and disposal of the car. The main difference is
reflected in the operation phase, which rises far above the impact of the battery.
(Notter, D. et al. Contribution of Li-Ion Batteries to the Environmental Impact of Electric
Vehicles. Environmental Science & Technology, 2010, 44 (17), pp 6550–6556) abstract
here:
http://pubs.acs.org/doi/abs/10.1021/es903729a?prevSearch=Contribution%2Bof%2BLiIon%2Bbatteries&searchHistoryKey=)
Operation of the BEV does not produce air pollutants as does the ICEV. Discussion here
also must take into account the environmental impact of creating the electricity needed to
recharge the batteries in BEVs. The study found that even including the pollution produced from
burning fossil fuels to generate the electricity to recharge the Li-ion batteries, less pollution was
produced by BEVs. Actually, the choice of electricity generation was the major factor in the
environmental impact of BEVs.
…the choice of the electricity generation led to considerable variations in the
results. Propelling a BEV with electricity from an average hard coal power plant increases
the environmental burden by 13.4%. On the other hand, using electricity from an average
hydropower plant decreases environmental burden by 40.2%. This results in a decrease
for the operation from 41.8% to 9.6% when charging the battery with electricity from
hydropower plants.
(Notter, D. 6550-6556)
Of course, if the majority of drivers in the United States changes over to electric cars,
recharging all their batteries will cause a major problem for electricity producers.
The time of day when plug-in electric cars are charged will determine the impact
they will have on the national power grid, says a new study by Oak Ridge National
Laboratory (ORNL).
The Department of Energy lab study assumes that by 2025, one-quarter of U.S.
cars will run on a combination of electric and liquid fuels and will require plug-in charging.
If all cars are charged at 5 PM, when electricity demand is high, some 160 large power
88
plants will be needed nationwide to supply the extra electricity, according to the study.
However, it says, if the charging is done after 10 PM, when demand is minimal, as few as
eight—or possibly no—new power generation facilities will be needed, depending on the
availability of regional electricity.
The study comes at a time when several automakers are exploring plug-in
electric vehicles. Earlier studies, including one by Pacific Northwest National Laboratory,
found that off-peak, idle capacity at existing electric utilities could provide enough power
to fuel 84% of the U.S.'s 220 million cars if all of them were shifted to hybrid plug-in
electric vehicles (C&EN, Dec. 18, 2006, page 40).
"That assumption doesn't necessarily take into account human nature," says
ORNL's Stan Hadley, who led the study. "Consumers' inclination will be to plug in when
convenient, rather than when utilities would prefer.
"Utilities will need to create incentives to encourage people to wait," Hadley
continues. "There are also technologies such as ???smart' chargers that know the price
of power, the demands on the system, and the time when the car will be needed next to
optimize charging for both the owner and the utility. That can help too," he adds.
(Johnson, J. Plug-in Vehicles May Lead To More Power Plants. Chemical & Engineering
News 2008, 86 (12)
More on lithium
Some physical and chemical properties of lithium
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Appearance: soft, silvery-white metal
Member of Group I, the alkali metal
family
Symbol: Li
Atomic Number: 3
Electron configuration: 1s2 2s1
Atomic mass: 6.941 g/mol
Atomic radius: 155 pm
Atomic volume: 13.1 cm3/mol
Covalent radius: 163 pm
Ionic radius: 68 pm (+1 charge)
Density: 0.534 g/cm3
Melting point: 180.54 oC
Boiling point: 1342 oC
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Specific gravity: 0.534 (at 20 oC)
Oxidation state: +1
Specific heat: 3.489 J/g-K
Heat of fusion: 2.89 kJ/mol
Heat of vaporization: 148 kJ/mol
Heat of combustion: -298 kJ/mol
First Ionization energy: 519.9 kJ/mol
Second Ionization energy: 7,298 kJ/mol
Third ionization energy: 11,815 kJ/mol
Pauling electronegativity: 0.98
Lattice structure: Body-centered Cubic
(BCC)
Electrical resistivity: 92.8 nΩ-m
Thermal conductivity: 84.8 W/m-K
Mohs hardness: 0.6
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Lithium is the lightest (lowest density) of all the metals. It has the highest specific heat of any
metal.
90
Sources of lithium
Although
lithium
is
widely
distributed on Earth, it does not naturally
occur in elemental form due to its high
reactivity. The total lithium content of
seawater is very large and is estimated as
230 billion tonnes, where the element
exists
at
a
relatively
constant
concentration of 0.14 to 0.25 parts per
million (ppm), or 25 micromolar; Higher
concentrations approaching 7 ppm are
found near hydrothermal vents.
Lithium mine production (2011) and reserves
in tonnes
Country
Production
Reserves
Argentina
3,200
850,000
Australia
9,260
970,000
Brazil
160
64,000
Canada (2010) 480
180,000
Estimates for crustal content
range from 20 to 70 ppm by weight. In
12,600
7,500,000
keeping with its name, lithium forms a
Chile
minor part of igneous rocks, with the
largest concentrations in granites. Granitic
People's Rep. 5,200
3,500,000
pegmatites also provide the greatest
of China
abundance of lithium-containing minerals,
with spodumene and petalite being the
820
10,000
Portugal
most commercially viable sources.
Another significant mineral of lithium is
Zimbabwe
470
23,000
lepidolite. A newer source for lithium is
hectorite
clay,
the
only
active World total
34,000
13,000,000
development of which is through the
Western Lithium Corporation in the United
(http://en.wikipedia.org/wiki/Lithium)
States. At 20 mg lithium per kg of Earth's
crust, lithium is the 25th most abundant element.
According to the Handbook of Lithium and Natural Calcium, "Lithium is a
comparatively rare element, although it is found in many rocks and some brines, but
always in very low concentrations. There are a fairly large number of both lithium mineral
and brine deposits but only comparatively a few of them are of actual or potential
commercial value. Many are very small, others are too low in grade."
One of the largest reserve base of lithium is in the Salar de Uyuni area of Bolivia,
which has 5.4 million tonnes. US Geological Survey, estimates that in 2010 Chile had the
largest reserves by far (7.5 million tonnes) and the highest annual production (8,800
tonnes). Other major suppliers include Australia, Argentina and China. Other estimates
put Chile's reserve base (7,520 million tonnes) above that of Argentina (6 million).
(http://en.wikipedia.org/wiki/Lithium)
Alkali metals are always found combined with other elements, due to their high chemical
reactivity, and lithium is no exception. Since they are such active metals, no other metal can be
used to replace them from their compounds, as might be done to extract less active metals. So,
to extract the elemental form, electrolysis must be used, which is highly energy intensive. An
advantage of using lithium in Li-ion batteries is that lithium-ion batteries don’t contain elemental
lithium; they use lithium compounds.
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There are two principle methods by which lithium is extracted from ores. The first
involves spodumene, a silicate compound of lithium and aluminum. In order to produce lithium
from this mineral, spodumene must first be ground into a powder and heated to 1100 oC, treated
with sulfuric acid at 250 oC to produce lithium and aluminum sulfates, put into a solvent to
extract the sulfates, put into a separator to extract the aluminum sulfate, and finally the lithium is
precipitated by reaction with soda ash (sodium carbonate) to form lithium carbonate. Until about
1997, this was the principle method for lithium extraction from ores. It is still used for some
specific purposes, such as making certain types of glass and ceramics. But the second method
is much simpler and less energy-intensive—therefore more economical.
Most lithium today is extracted commercially from salt brine that forms underground.
This is a mixture of salts—mostly chlorides—of lithium, sodium, potassium and magnesium
dissolved in water to form a saturated solution. South America has several large deposits in
desert areas in salt flats called salares along the Andes Mountain chain, one in Chile in the
Atacama Desert, one in Argentina in the Salar del Hombre Muerto (Salt Flat of Dead Men) and
the other in Bolivia, in the Salar de Uyuni (Uyuni Salt Flat). Together, these salt flats are
estimated to contain more than two-thirds of all the world’s reserves of lithium.
The salt flats themselves are made of the solid form of some of these compounds (but
not much of lithium salts). When winter snow-melt runs off the mountains in the spring and
summer, the water flows underneath these flats and travels through their porous surface and
dissolves them to form a saturated liquid called brine. The brine is anywhere from 10s of
centimeters to possibly 30 meters below the surface of these desert areas. Any of the salt
(halite or rock salt) below that depth is believed to have undergone complete recrystallization so
that it is no longer porous, and the brine cannot penetrate that. Even though the brine is well
below the surface, wells dug into the salt flat can bring the brine to the surface, where it is
pumped into shallow pools. The sun then evaporates much of the water, until the concentrated
material can be removed and trucked to processing plants.
The solubility of lithium chloride (83 g/100 mL of water) is much greater than the other
alkali metal chlorides (sodium chloride: 35.7 g/100 mL of water, potassium chloride: 34.2 g/100
mL of water, and magnesium chloride: 54.6 g/100 mL of water, all at 20 oC). So, as the sun
evaporates the water from the brine solution, the sodium, potassium and magnesium chlorides
crystallize out first, as solids and fall to the bottom of the pool, leaving the remaining liquid ever
more concentrated in lithium chloride. Eventually, the sun evaporates off all the water, leaving
the lithium chloride solid on the surface of the pool, where it can be scraped off and sent off for
processing into lithium carbonate for shipment to battery manufacturers. (The chloride of lithium
is much easier to convert to the carbonate than is the silicate, from spodumene processing.)
Even though the salt flats are desert areas and there are rarely clouds or rain, this
process of solar evaporation from the pools of brine can still take as long as 6 months to two
years to accomplish. Since the sun is the principal energy source, this is a very inexpensive
source of this lithium salt. Of course, the resulting solid material must still be purified, because it
will still contain a mixture of lithium, sodium, potassium and magnesium salts, but it will be
predominantly lithium chloride.
So, with the anticipated worldwide proliferation of BEVs in the decades to come, and
their demand on lithium resources, should we be worried that we will run out of lithium any time
soon?
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According to a 2011 study conducted at Lawrence Berkeley National Laboratory
and the University of California Berkeley, the currently estimated reserve base of lithium
should not be a limiting factor for large-scale battery production for electric vehicles, as
the study estimated that on the order of 1 billion 40 kWh Li-based batteries could be built
with current reserves. Another 2011 study by researchers from the University of Michigan
and Ford Motor Company found that there are sufficient lithium resources to support
global demand until 2100, including the lithium required for the potential widespread use
of hybrid electric, plug-in hybrid electric and battery electric vehicles. The study estimated
global lithium reserves at 39 million tons, and total demand for lithium during the 90-year
period analyzed at 12–20 million tons, depending on the scenarios regarding economic
growth and recycling rates.
(http://en.wikipedia.org/wiki/Lithium#Production)
Some companies are not so sure the estimated resources are realistic. The Meridian
International Research group, after extensive study of the area, has made the following
conclusions regarding the Salar de Atacama, the Chilean salt flat that has already been mined
for about 20 years.
Since 1984 some 100,000 tonnes of Lithium have been extracted from the
richest grade deposit on the Southern Edge of the Salar.
The most realistic assessment based on the known low porosity of this Southern
Edge is that before production commenced, this southern high grade zone contained
200,000 tonnes of Lithium. The maximum it would have contained was 450,000 tonnes.
There 50% of the highest grade Lithium deposit in the world may already have
been extracted.
While the nucleus may contain 3MT (million tonnes) or more of Lithium in total,
access can only be gained to this by wholesale destruction of the salar by expanding
wells and pipelines over a much greater area of its surface. In reality, the realistic
recoverable reserve is less than 1MT.
Increasing investment and resources will be required to maintain production at
current levels as the Lithium content in the salar continues to fall. Any increase in
production will require accessing lower grade areas of the salar and an exponential
increase in resources per unit production increase.
(http://www.meridian-int-res.com/Projects/Lithium_Microscope.pdf)
And an overall conclusion they reach is that “…maximum sustainable production of
battery grade Lithium Carbonate will only be sufficient for very limited numbers of Electric
Vehicles.” (This very thorough report contains much detailed information about many sources of
lithium—including spodumene and ocean water—around the globe. The study includes
environmental issues as well as economic and political concerns.)
More on “Why lithium in batteries?”
Lithium is the element of choice for use in batteries used for electric cars for many
reasons:
1) Lithium is the lightest of all metals: 6.94 g/mol—compare to lead, 207.2 g/mol, so
batteries weigh less and require less energy to propel in a vehicle
93
2) Lithium offers one of the greatest electrochemical potentials (3.04 Volts) of all elements,
resulting in
a. Higher energy density: Li-ion battery, 150-250 W-h/kg (400 W-h/kg experimental,
February 2012, 500 W-h/kg experimental, October 2012)—compared to lead-acid
battery, 22 W-h/kg
b. Higher specific power (power to mass ratio): 250-1500 W/kg—compare to lead-acid
battery, 180 W/kg
(http://en.wikipedia.org/wiki/Lead_acid and
http://en.wikipedia.org/wiki/Lithium-ion_batteries)
3) Li is reasonably inexpensive and easy to obtain from brine deposits
4) The Li-ion battery requires little maintenance, unlike many other types
5) The Li-ion battery has no memory effect (no need to fully discharge before recharging)
6) It has low self-discharge rate (5-10%/month, compared to 30% for NiMH batteries)
7) It has no required scheduled cycling to prolong battery life
Several disadvantages to the Li-ion battery also exist:
1) Charging produces deposits inside the electrolyte that inhibit movement of ions,
decreasing the cell’s capacity.
2) Maintaining a high charge level increases the rate of capacity loss. (It’s better to store Liion batteries at 40-60% charge level to minimize this loss)
3) High ambient temperature also increases the rate of capacity loss.
More on batteries
Many different types of batteries have been in use over the past 100 years or so. These
include:
Primary batteries: these batteries are “once-and-done” or “throw-aways”. They are not
designed to be rechargeable. The chemicals in these batteries are used up at the end of their
discharge cycle and cannot—or should not—be recharged.
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Zinc-carbon (Zn-C) battery with carbon electrode surrounded by manganese dioxide and
an ammonium chloride (the electrolyte) paste (typical “AAA”, “AA”, “C”, or “D” cells used
since “way back”, and even today, that are not rechargeable)
A newer version of this battery uses zinc chloride instead of the ammonium chloride
electrolyte—these are often marketed as “heavy duty” cells.
Lead-acid battery (car battery—rechargeable)
Mercury oxide (HgO) battery (banned in 1995 in the US)
Silver oxide (Ag2O) battery (chemistry similar to mercury oxide battery)
Alkaline battery (chemistry similar to Zn-carbon battery, but higher energy density—
higher even than the “heavy duty” zinc chloride cell. Most are not rechargeable, a few
are.)
Lithium battery (“button” cells, high charge density, not Li-ion battery and not
rechargeable)
Secondary batteries: these batteries are designed to be rechargeable. At the end of the
discharge cycle, voltage at a slightly higher level than their discharge level is applied to reverse
the chemical reactions inside the battery and “bring it back to life”. (Note that some of the
alkaline batteries mentioned above, may be designed to be rechargeable.)
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Nickel-cadmium (Ni-Cd or “Nicad”) battery (rechargeable battery)
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Nickel metal hydride (Ni-MH) battery (similar to, but higher energy density than
Ni-Cd)
Li-ion battery (one of the highest charge-density batteries on the market today)
More on chemical reactions in batteries
The following information describes the chemical reactions involved in a select few of
these.
Zinc carbon batteries
In a zinc–carbon dry cell, the outer zinc container is the negative terminal. The
zinc is oxidised according to the following half-equation.
Zn(s) → Zn2+(aq) + 2 e− [e° = −1.04 volts]
A graphite rod surrounded by a powder containing manganese(IV) oxide is the
positive terminal. The manganese dioxide is mixed with carbon powder to increase the
electrical conductivity. The reaction is as follows:
2MnO2(s) + 2 e− + 2NH4Cl(aq) → Mn2O3(s) + 2NH3(aq) + H2O(aq) + 2 Cl− [e° ≈ +.5 v]
and the Cl− combines with the Zn2+. In this half-reaction, the manganese is reduced from
an oxidation state of (+4) to (+3).
There are other possible side-reactions, but the overall reaction in a zinc–carbon
cell can be represented as:
Zn(s) + 2MnO2(s) + 2NH4Cl(aq) → Mn2O3(s) + Zn(NH3)2Cl2 (aq) + H2O(l)
(http://en.wikipedia.org/wiki/Zinc%E2%80%93carbon_battery)
Alkaline batteries
The alkaline battery anode is composed of zinc powder. This provides more surface
area than the zinc sheet in the Zn-C battery above. This, in turn, provides a faster chemical
reaction (think reaction kinetics) and results in greater current. The cathode is manganese
dioxide, and the electrolyte is a paste of potassium hydroxide.
Zn(s) + 2OH−(aq)
ZnO(s) + H2O(l) + 2e− [e° = -1.28 V]
2MnO2(s) + H2O(l) + 2e−
Mn2O3(s) + 2OH−(aq) [e° = +0.15 V]
Overall reaction:
Zn(s) + 2 MnO2(s)
Mn2O3(s) + ZnO(s) [eo = 1.43 V]
(http://en.wikipedia.org/wiki/Alkaline_battery#Chemistry)
Lead-acid batteries
In the discharge cycle of the normal operation of lead-acid batteries, the lead “plate”
electrodes are the anode, reacting with HSO41- ions to produce lead sulfate, releasing electrons.
These flow externally through the connecting wires to the lead dioxide electrode, the cathode.
Here they are used up along with PbO2 and HSO41- ions in the production of lead sulfate,
according to the equations on the next page. For both half-reactions, sulfuric acid acts as the
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electrolyte and provides the sulfate ions for the formation of lead sulfate. Lead and lead dioxide
plates are alternated in the battery with a separator material between them to prevent contact
and a resultant short-circuit.
Each lead plate is actually a very thin lead grid that appears waffle-like. The holes in the
grid are filed with a paste of red lead and 33% H2SO4. Red lead is lead(II,IV) oxide; its formula is
Pb3O4 or PbO•PbO2. The paste is pressed into the holes of the grid. This porous paste allows
the acid inside to react with the lead inside the pate, increasing surface area significantly. The
plates must be charged or “formed” before the battery is ready for use. After forming, the
cathodic plates are brown, the color of lead dioxide, and the anodic plates are slate gray, the
color of lead.
In the charge cycle, the reverse electrochemical reaction occurs, and the notations of
anode and cathode are reversed as the lead sulfate in both half-reactions reverts to lead and
lead dioxide, respectively. This charging occurs constantly in the car battery via the alternator
(in the old days, this was a generator) as the engine runs. The alternator provides current to the
battery at a slightly higher voltage—14.4-14.6 volts—(referred to as “overvoltage”) than the
normal voltage of the discharging battery (~12 volts) to drive the normally spontaneous reaction
in the reverse direction. This is a great example of spontaneous and non-spontaneous
reactions, and electrochemical and electrolytic cells. In the spontaneous discharge, it is an
electrochemical cell, and when it is being charged, it is an electrolytic cell.
Problems arise as the lead-acid battery is discharged and charged repeatedly. As the
active materials absorb sulfate from the acid during discharge, they increase in size, and as
they release the sulfate during the charge cycle, they decrease in size. This causes the plates to
gradually “shed” some of the paste. This loose material can short-circuit that cell of the battery if
it builds up enough to touch both anode and cathode plates simultaneously.
(http://en.wikipedia.org/wiki/Leadacid_battery)
Construction of a typical lead-acid battery:
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Pb(s) + HSO4− (aq) → PbSO4(s) + H+(aq) + 2e−
PbO2(s) + HSO4−(aq) + 3H+(aq) + 2e− → PbSO4(s)
+ 2H2O(l)
The total discharge reaction can be written:
Pb(s) + PbO2(s) + 2HSO4− (aq) + 2H+(aq) → 2PbSO4(s) + 2H2O(l) + energy
(http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/leadacid.html#c2)
Lithium-ion batteries
Since lithium is an alkali metal and reacts vigorously with water, a non-aqueous solvent
must be used in the formulation of the electrolyte that connects the anode and cathode in these
batteries. In the lithium-ion battery, lithium ions move through the electrolyte from the negative
electrode to the positive electrode during discharge; they move in the reverse direction during
charging. The ions move into the positive electrode material (usually lithium cobalt oxide,
LiCoO2) by a process known as intercalation, where they are inserted into openings in the
structure of the electrode. They are deintercalated during charging and flow through the
electrolyte once more, this time back to the graphite electrode.
During discharge, at the anode, some of the lithium ions that are intercalated in the
graphite material at that electrode move away from the electrode, and the electrode loses
electrons to the outside circuit leading to the cathode:
LinC

n Li+
+
C
+
n e1-
While at the cathode, the lithium ions already in the electrolyte are attracted to electrons coming
from the anode. They react with the electrons and intercalate into the lithium cobalt oxide on the
cathode.
Li1-nCoO2 + n Li+ + n e1-  LiCoO2
During this process, the cobalt in the lithium cobalt oxide is reduced, from Co(IV) to Co(III).
During charging, the two equations above are reversed.
The equation for the overall electrochemical reaction is:
LinC + Li1-nCoO2  C + LiCoO2
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The movement of intercalated lithium ions out of their structure (deintercalation) at one
electrode and movement into the structure of the other electrode (intercalation) is sometimes
referred to as the “rocking chair” or “swing” effect. The process involves only lithium ions moving
back and forth between electrodes, so that no potentially dangerous elemental lithium atoms
should ever be present in the lithium-ion battery.
This YouTube video from BASF, “The Chemical Company”, shows in animation how a
cell in a Li-ion battery works: http://www.youtube.com/watch?v=2PjyJhe7Q1g.
And this site from Panasonic contains much information about Li-ion batteries. In
particular, it shows a schematic diagram at the molecular level that depicts Li+ ions intercalated
within the graphite and lithium cobalt oxide electrodes: http://industrial.panasonic.com/wwwdata/pdf/ACA4000/ACA4000PE3.pdf.
More on modern batteries
Lithium-ion
Today’s lithium-ion
batteries contain a carbon
cathode and a lithium oxide
anode, with an electrolyte
containing lithium salts. The
specific energy capacity of LIion batteries is typically in the
100–200 watt-hours per
kilogram (Wh/kg) range. The
Nissan Leaf, for example, has a
specific energy capacity of 120
Wh/kg.
Li-ion batteries are
typically only used over 80% of
their capacity, in order to avoid
damaging the recharge capacity
(http://inqu.uprm.edu/upload/blog/32/Imagen1.png)
in future recharge cycles. A
study at Penn State University showed that Li-ion batteries lose as much as 18% of their peak
energy capacity after 5200 recharge cycles, under typical hybrid-electric vehicle conditions.
Lithium-sulfur
Lithium-sulfur batteries are currently being researched. Although they are not yet “ready
for prime time,” they do have several theoretical advantages over lithium-ion batteries. One
version of these batteries, from Oxis Energy, contains a sulfur-based cathode, a lithium metal
anode and a lithium sulfide electrolyte.
The advantages of the lithium sulfide electrolyte are that the electrolyte instantly forms a
film on the metal, reducing or eliminating the risk of explosion of the lithium metal. Even at high
temperatures, this coating, which melts at 938 oC, can protect the lithium. The electrolyte’s high
flash point further protects the battery.
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The current version of the Li-S battery already has a specific energy capacity of 320
Wh/kg, already about twice that of the Li-ion battery. But the theoretical value is as high as 2700
Wh/kg, five times that of the Li-ion battery. Oxis hopes to increase its value to 410 Wh/kg by
2014. Sion, a spin-off from Brookhaven National Laboratories, already has a Li-S battery with a
specific energy capacity of 350 Wh/kg.
Oxis Energy also claims that its Li-S battery weighs only about half that of the equivalent
output Li-ion battery. And since the batteries are a significant portion of the entire weight of the
car, this decreased weight could result in a large increase in energy efficiency for the vehicle,
possibly resulting in a greater range of travel.
Another advantage is that the Oxis Li-S battery can be discharged and recharged to
100% of its capacity over multiple cycles, compared to only 80% in Li-ion batteries. Also, the LiS battery from Oxis is now stable for up to 350 cycles, with the target of 1000 cycles by 2014.
Even though the Li-S battery seems to have theoretical advantages, Li-ion technology
has already been developed and is far ahead of Li-S technology. And many technical
challenges exist that must be overcome before the widespread use of Li-S batteries becomes a
reality. Thus the eventual success of Li-S technology is not ensured over the long term.
(Scott, A. Lithium-Sulfur Battery Boost. Chemical & Engineering News 2012, 90 (43), pp 26–7)
(http://cen.acs.org/articles/90/i43/Lithium-Sulfur-Battery-Boost.html)
Connections to Chemistry Concepts
(for correlation to course curriculum)
1. Oxidation-reduction—All the reactions discussed with the lead-acid and lithium-ion
batteries involve oxidation and reduction reactions.
2. Electronegativity—Metal’s low electronegativity results in their being easily oxidized.
3. Activity Series—This table compares the reactivity of various metals. Lithium is very high
on this table, indicating that it will replace from a compound any metal below it on the table,
making lithium a very good choice for an electrochemical cell.
4. Electromotive Series—This list will tell us which redox reactions are likely to be
spontaneous.
5. Reduction potential—These values allow us to predict voltages and spontaneity (or lack
thereof) in electrochemical reactions.
6. Electrolytes—The sulfuric acid in the lead-acid battery and the polymer gel in the lithiumion battery serve to transfer electrons from anode to cathode.
7. Half-reactions—Oxidation half-reactions occur at the anode and reduction half-reactions
occur at the cathode in all batteries/electrochemical cells.
8. Electrochemical cells—Spontaneous redox reactions happen within electrochemical cells.
Both battery types (primary and secondary) are electrochemical cells.
9. Electrolytic cells—Secondary batteries, when being charged, are electrolytic cells.
10. Chemical and physical properties—Lithium’s chemical and physical properties make it
very useful in batteries. (See “Anticipating Student Questions” #1, below.)
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Possible Student Misconceptions
(to aid teacher in addressing misconceptions)
1. “All batteries are alike.” Nope. Many different types of batteries have been developed over
the years. Each has its own strengths and weaknesses. See “More on Chemical reactions in
batteries”, above.
2. “All batteries are rechargeable.” Actually, this is true—up to a point. Although all batteries
can be recharged by subjecting them to a higher voltage than they typically produce—in
order to drive the chemical reaction in the non-spontaneous direction and rejuvenate the
electrochemical reaction—this sometimes results in the disintegration of one of the
electrodes, rendering the battery useless after any number of discharge-recharge cycles.
This is the case for the old-style Zn-MnO2 battery and the alkaline battery, and even for the
lead-acid battery, after many cycles. It can also be dangerous to recharge one-use
disposable batteries as the recharging may cause the casing to corrode and rupture,
causing the electrolyte paste, which is often very alkaline, to leak out. Heat generated in the
recharging process can also cause containment failure—and even fire!
3. “Lithium ion batteries use lithium metal, which is dangerous, since it reacts with
water.” It is true that lithium does react with water and that could make it dangerous if the
lithium in a battery containing lithium were exposed to water. However, Li-ion batteries use
either lithium oxide (on the anode), or other lithium compounds for the electrolyte. There is
no elemental lithium metal used in a Li-ion battery. There IS, however, lithium metal inside
lithium batteries, such as the button cells and others used in electronic equipment like
cameras.
Anticipating Student Questions
(answers to questions students might ask in class)
1. “How did chemists know lithium would work in a battery?” Using the activity series of
metals, chemists know that lithium is a very active metal, which means a lithium atom will
easily oxidize to its cation in a chemical reaction.
http://www.files.chem.vt.edu/RVGS/ACT/notes/activity_series.html (From the periodic table,
chemists also know that Li is one of the group of elements know as the alkali metals, and
they’re all active metals.) And from the table of reduction potentials, they know that the
lithium half-cell produces 3.04 volts when combined with the hydrogen oxidation half-cell
(0.0 volts). (http://hyperphysics.phy-astr.gsu.edu/hbase/tables/electpot.html#c1) This voltage
(3.04 volts) is one of the highest oxidation potentials of any element, which will result in a
large overall voltage for a lithium battery. From the periodic table, chemists know that lithium
is the lightest of all the metals, meaning that it won’t add much weight when it is used in a
battery (unlike lead, which is one of the heaviest metals). All this makes lithium a prime
candidate for use in batteries. And it is all based on the physical and chemical properties of
lithium—on chemistry.
2. “Are electric cars really environmentally friendly?” Yes, they are. See “More on electric
cars and the environment”, above.
3. “Can I buy an electric car where I live?” Electric cars are probably available anywhere in
the United States as of the writing of this Teacher’s Guide; however, the support structure
needed to keep electric cars running is not presently ubiquitous. Several western states
have gotten federal support to build charging stations and to subsidize the installation of
charging stations in individuals’ homes, to keep their electric cars running. Nine states and
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21 major metropolitan areas are now participating in this federal support. Without this
support, it may be difficult to find places to charge an electric vehicle elsewhere in the US.
This is the “range anxiety” mentioned in the Tinnesand article. (Note: GE sells chargers for
electric cars online on Amazon for $899.)
4. “How can both reactions in a lead-acid battery produce the same substance? I
thought the two half-reactions in an electrochemical reaction always produced
different materials.” The two half-reactions in the lead-acid battery ARE different reactions;
they just produce the same chemical at the end. The anode starts with lead metal reacting
with the sulfuric acid. The lead metal is oxidized to Pb2+ and that ion reacts with the sulfate
ion (SO42-) to produce low-solubility lead*(II) sulfate, while the cathode begins with lead(IV)
oxide reacting with sulfuric acid. At the cathode, the Pb4+ ion in lead(IV) oxide is reduced to
Pb2+ that reacts with the sulfate ion (SO42-) to produce lead*(II) sulfate. So the two halfreactions are different, and one is oxidation while the other is reduction. They just both
coincidentally produce the same chemical substance.
5. “Is it really that easy to recharge a battery—just provide more electrons?” Yes, it is
this easy, if you can provide a voltage higher than the voltage produced by the battery. But
after recharging repeatedly, most batteries get run-down and don’t recharge as efficiently as
they did when they were new. See “Possible Student Misconceptions” #2, above.
6. “Is the voltage produced by the lithium-ion battery the highest voltage chemists can
produce in an electrochemical cell?” No, there are other chemical combinations of
oxidation half-cell and reduction half-cell that can result in a higher voltage. One of the
highest voltages would come from a reaction involving the reduction of fluorine atoms in
acidic solution to produce hydrogen fluoride, and the oxidation of lithium atoms to their ions,
according to the following half-reactions:
F2(g) + 2 H+ + 2 e−
2 Li (s)
+
F2(g) + 2 H + Li(s)
2 HF (aq)
2 Li+ + 2 e−
2 HF(aq) + 2 Li+
Eo = +3.05 V
Eo = +3.04 V
Eo = +6.09 V
The total voltage for this cell is 6 volts. To get higher voltages, as already happens in many,
if not most, applications; e.g., the automobile battery, which is 12 volts, one must connect
multiple electrochemical cells in series with one another. The 12-volt lead-acid car battery is
actually composed of 6 cells, connected in series. Each produces 2+ volts, so combined
they produce 12+ volts. Note also the difference between a “cell” and a “battery”. The cell is
a single electrochemical reaction; a battery is a group of cells connected, usually in one
package, to produce a pre-determined voltage. Besides the lead-acid battery, another
example is the 9-volt battery. This is actually a series of 6 1.5-volt cells connected together
in series and arranged in one small case.
7. “Is a ‘battery’ the same thing as a ‘cell’?” In most cases in normal use, the two terms
mean the same thing, but to a chemist, they are NOT the same. To a chemist, a “cell” really
means an electrochemical cell—a chemical reaction that spontaneously produces an
electric current. A battery is a series of electrochemical cells linked together, either to
produce a higher voltage, or to extend the life of the battery. Thus to a chemist a “D-cell” is
not truly a battery, because it consists of only one chemical reaction inside its casing,
producing 1.5 Volts of electric current from that one chemical reaction. But a 9-Volt “battery”
really IS a battery, because it contains within its casing six individual 1.5-Volt “cells”, each
producing its own 1.5 Volts of electricity. Similarly, “C”, “AA”, and “AAA” cells are really NOT
batteries, while “lantern” batteries (6-Volt batteries,) car and truck batteries (12- and 24Volts, respectively) and BEV batteries truly ARE batteries because they all contain more
than one electrochemical cell.
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In-class Activities
(lesson ideas, including labs & demonstrations)
1. For a series of PowerPoint slides dealing with the lead-acid battery, see this site from the
Department of Electrical, Computer, and Energy Engineering from the University of
Colorado at Boulder: http://ecee.colorado.edu/~ecen4517/materials/Battery.pdf. The first 11
slides contain basic stuff, nicely prepared. The remaining slides become a bit much for firstyear chemistry students.
2. This site provides a series of six questions with pull-down tabs offering multiple choice
answers to what is happening inside the lead-acid battery. It also provides a very simplistic
animation illustrating what happens during discharge and charge cycles inside this battery.
After discussing the half-reactions that occur during both cycles, the author asks students to
write the equation for the overall reaction. This might make a good way to teach students
about the reactions in the lead-acid battery. (Note that the discussion of pH may cloud the
issue somewhat—but you can simply skip this small section without losing any significant
meaning.) The solution to the final question is available right on the site.
(http://www.dynamicscience.com.au/tester/solutions/chemistry/redox/leadacidaccumulator.ht
m)
3. For an AP (possibly Honors) class, you can investigate with students the relationship of
temperature on battery performance, using this article from J Chem Ed: “Chemical Principles
Exemplified”, “Car Won’t Start?” (Plumb, R., suggested by Nash, L. J. Chem. Educ. 1970, 47
(5), pp 382–383) (This article is the source of the quote by Rickenbacker, cited in the
Background section above.)
4. Students can make their own battery or galvanic cell in the lab (or at home) from a variety of
starting materials. Examples include:
a. Instructions for making an aluminum-air battery can be found in a J. Chem. Educ.
“Classroom Activity” (Tamez, M. and Yu, J. JCE Classroom Activity # 93, Aluminum-Air
Battery. J. Chem. Educ. 2007, 84 (12), pp 1936A–1936B). The abstract can be found at
http://pubs.acs.org/doi/abs/10.1021/ed084p1936A?prevSearch=classroom%2Bactivity%
2Baluminum%2Bair&searchHistoryKey=. Subscribers can sign in and access the article.
b. Here’s the link for subscribers to another JCE article using an aluminum beverage can
and copper wire as electrodes:
http://pubs.acs.org/doi/abs/10.1021/ed070p495?prevSearch=aluminum%2Bcan%2Belec
trochemical&searchHistoryKey=. (The aluminum can must be stripped of its outer and
inner coatings, and this set of instructions uses concentrated nitric or sulfuric acid, so
you may want to do the cleaning prior to class.) (Schmidt, N. The Aluminum Can as
Electrochemical Energy Source. J. Chem. Educ. 1993, 70 (6), pp 495-6)
c. This JCE article, “A Lemon Cell Battery for High-Power Applications” (abstract and
subscriber sign-in at http://pubs.acs.org/doi/abs/10.1021/ed084p635) discusses the use
of magnesium and copper as electrodes in cells using lemons as the electrolyte. By
connecting lemon cells in series the authors are able to produce enough current to run
an electric DC motor. (Muske, J, Nigh, C. and Weinstein, R. J. Chem. Educ. 2007, 84
(4), pp 635-8)
d. You might want to have students make their own battery out of a potato and two
dissimilar metals. Here’s a source: http://www.allaboutcircuits.com/vol_6/chpt_3/16.html.
5. If students need information or a refresher on oxidation-reduction reactions and how to write
and balance redox reactions, this is a good source: Kolb, D. “chemical principles revisited”,
The Chemical Equation Part II: Oxidation-Reduction Reactions. J. Chem. Educ. 1978, 55
(5), pp 326–331.
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6. To demonstrate the effect of electricity on a chemical reaction (similar to the recharge cycle
of an electric-car battery), you can show the electrolytic decomposition of water using a
Hoffman’s apparatus or students can do the experiment with simpler set-ups using batteries
and pencil-lead electrodes. Of course, in the electric car battery, the electricity to recharge
the system is provided by a power-generating station, not a battery. In a hydrogen fuel cell,
the hydrogen and oxygen produced as above would be reused to again produce electricity.
7. To show students how to make spontaneous chemical reactions reverse themselves (with
outside help from a battery), you can use these lab activity materials from Cornell Center for
Materials Research:
http://www.ccmr.cornell.edu/education/lendinglibrary/getlessonplan.php?id=26 and
http://www.ccmr.cornell.edu/education/lendinglibrary/getdocument.php?id=77. The first URL
provides the lesson plan for “Making a Copper Nickel” (copper-plating a nickel coin) and
“Making a ‘Silvery’ Penny” (zinc-plating the penny). The lesson plan uses the 5E model of
student inquiry and it provides a simple assessment technique. The second URL is the
student activity sheets that you can photocopy for distribution to students. The site says that
a whole series of entire kits that include the materials for doing the activities is available for
loan via the Cornell Web site at http://www.ccmr.cornell.edu/education/lendinglibrary/.
8. Establish an activity series for selected metals using any/all of these: Cu, Al, Mg, Zn, Fe, Pb,
and Ag, and the nitrate solutions of each metal (see standard lab manual); do this in
microscale using well plates.
a. Here is an example of this type of lab:
http://www.instruction.greenriver.edu/knutsen/chem150/actseres.html. Note that this
includes alkali metals which, it suggests, will be demonstrated by the instructor.
b. Another student experiment, complete with data tables, also asks students to include
halogens, to develop the non-metal activity series, to include reduction of elements, as
well as oxidation. (http://teachers.yourhomework.com/Chemistry/labactivityseriesap.pdf)
c. In this problem-based activity, students are asked to work in teams to complete the
experimental work involving the activity series of metals and then to submit a complete
report to The Information Standard organization. They must first predict the activity
series, then perform the experiments, and finally, generate their report that establishes
the actually series. (http://faculty.coloradomtn.edu/jeschofnig/class/class_jeschof/ch1lb11.htm) Although it is written for a college-level class, it can easily fit into an honors
level first-year high school course.
9. If you don’t want to actually DO the activity series experiment, you can use a virtual lab.
a. The Virtual Chemistry Lab has a nice virtual “activity series” experiment. It uses photos
of various metals placed in test tubes containing solutions of the metals. Students view
these photos of the reactions of metals in solutions and determine an activity series from
the photos. (http://www.harpercollege.edu/tmps/chm/100/dgodambe/thedisk/series/series.htm). The activity takes students through
background information, a pre-lab, the experiment itself, and then a post-lab that asks
students to predict other reactions that do not appear in the photos already viewed, and
they must then write equations for those reactions (based on work they did in the pre-lab
section).
b. Here is another activity series activity using a virtual lab. This activity uses animation to
show the reactions or lack thereof as the student controls which metal goes into which
solution:
http://group.chem.iastate.edu/Greenbowe/sections/projectfolder/flashfiles/redox/home.ht
ml. It also uses animation to show, at the atomic scale, atoms and ions exchanging
electrons as oxidation-reduction occurs (or doesn’t occur) in each reaction.
10. You can discuss with students the similarities and differences between electrochemical cells
(in batteries) and electrolytic cells (as in recharging a battery). The brief, professionally-done
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3-minute video “Understanding Electrolysis” found on YouTube will help explain with photos
and animation.
(http://www.bing.com/videos/search?q=electrolysis+of+metal+working+video&view=detail&
mid=278FA26D4A86686FD5D0278FA26D4A86686FD5D0&first=21)
11. Reactions inside batteries are not the only electrochemical reactions that happen
spontaneously. Another example of a spontaneous electrochemical reaction is corrosion.
Students can investigate in the lab corrosion as well as cathodic protection from corrosion.
This Word document from the University of Manitoba contains a series of 10 stations-based
activities dealing with corrosion and corrosion protection. It includes the Table of Standard
Reduction Potentials and asks students to use it to explain many of the reactions. It also
includes extension activities.
(http://www.umanitoba.ca/outreach/crystal/resources%20for%20teachers/Corrosion%20Acti
vities%20C12-1-12.doc)
This document is the first of the two activity sets alluded to in the activity above:
http://www.umanitoba.ca/outreach/crystal/resources%20for%20teachers/Corrosion%20Inve
stigation%20C12-1-12.doc. It offers teacher background as well as a student activity to
identify what corrosion is and ways to prevent it.
12. This Web site, YTeach.com, offers a lab activity where students titrate battery acid to
determine its concentration. This site has many teacher resources, but it require paid
access.
You can see a preview video of the YTeach.com lab at:
http://yteach.com/index.php/resources/acid_base_titration_water_solution_analytical_metho
d_technique_molarity_page_5.html.
13. You might want to have students make their own battery out of a potato and two dissimilar
metals. Here’s a source: http://www.allaboutcircuits.com/vol_6/chpt_3/16.html.
Out-of-class Activities and Projects
(student research, class projects)
1. Students might want to research powering their own electric car (ok, a model electric car)
using batteries. This 2007 J Chem Ed article might be a good place to start: Muske, K, Nigh,
C. and Weinstein, R. J. Chem. Educ. 2007, 84 (4), pp 635-8 (abstract:
http://pubs.acs.org/doi/abs/10.1021/ed084p635.)http://pubs.acs.org/doi/pdfplus/10.1021/ed0
84p635. It uses a lemon cell battery instead of just a lemon cell (remember that a battery
truly is a series of electrochemical cells) with magnesium and copper electrodes.
2. Students can research the development of present-day battery-powered cars.
3. You could assign students or groups of students to research and report on other important
electrochemical processes, such as aluminum refining, galvanic corrosion protection, the
reactions in rechargeable batteries, photovoltaic cells, etc.
4. Assign each student a different metal (especially those used in batteries—past and present)
and ask them to research and find out the chemical nature of the metal’s ores, where
geographically the ores are found, and how the ores are refined into metal. You may choose
to ask your students to pay special attention to any issues of geopolitics or economics that
relate to their assigned metal. (For example, you may ask the student assigned aluminum to
consider why Jamaica is such a poor country despite producing most of the world’s bauxite
aluminum ore.) You can also include the requirement that they explain how and why their
metal is used in batteries. You may ask your students to present their findings as a written
paper, a class presentation, a poster, or in some other medium.
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5. Students could research some of the ores of the more common metals used in batteries and
the processes, both chemical and physical, involved in extracting the metals from these
ores. (This is a much simplified version of number 4, above.)
6. Students could research the chemistry involved with corrosion, methods to prevent
corrosion, and the development of alloys that resist corrosion.
References
(non-Web-based information sources)
The references below can be found on the ChemMatters
25-year CD (which includes all articles published during the years
1983 through 2008). The CD is available from ACS for $30 (or a
site/school license is available for $105) at this site:
http://www.acs.org/chemmatters. (At the right of the screen,
click on the ChemMatters CD image like the one at the right.)
Selected articles and the complete set of Teacher’s Guides
for all issues from the past three years are also available free online
at this same site. (Full ChemMatters articles and Teacher’s Guides are
available on the 25-year CD for all past issues, up to 2008.)
Some of the more recent articles (2002 forward) may also be available online at the URL
listed above. Simply click on the “Past Issues” button directly below the “M” in the ChemMatters
logo at the top of the page. If the article is available online, you will find it there.
In this article, author Gough discusses the danger of lead poisoning. Although the leadacid battery isn’t specifically addressed in the body of the article, there are two photos showing
the manufacture of these batteries as early as 1914. (Gough, M. Lead Poisoning. ChemMatters
1983, 1 (4), pp 4–7)
Robert Bunsen (yes, of Bunsen burner fame) also worked with crude batteries. Using
them he was able to electrolyze many metals, and eventually discovered cesium and rubidium.
An article about him is in the October 1984 issue of ChemMatters. (Davenport, D. “The Back
Burner”, Robert Bunsen…more than a burner design. ChemMatters 1984, 2 (3), pp 14–15)
The April 1985 issue of ChemMatters contains a good article on the rebuilding of the
Statue of Liberty. Corrosion of supports inside the statue necessitated the repairs. There’s a lot
of corrosion chemistry, including the activity series of metals, in the article. The last page of the
article is a student lab on corrosion. (Burroughs, T. Statue of Liberty. ChemMatters 1985, 3 (2),
pp 8–13)
In the December 1986 issue of ChemMatters Derek Davenport writes of the discovery of
fluorine, a very reactive nonmetal, via electrolysis. Read about it here: Davenport, D. “The Back
Burner”, Going Against the Flow: The Isolation of Fluorine. ChemMatters 1986, 4 (4), pp 13–15.
For a story about sunken ships and electrochemical reactions on silver treasure, read
this ChemMatters article: Robson, D. Sunken Treasure. ChemMatters 1987, 5 (2), pp 4–9.
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“Ernie’s Amazing Journey” is the story of Ernie Electron, residing in zinc. The
story revolves around his trips through a zinc-manganese (zinc-graphite) dry cell. Although lighthearted, it does tell the story of the electrochemistry of the cell. (VanOrden, N. Ernie’s Amazing
Journey. ChemMatters 1990, 8 (1), pp 10–12).
The ChemMatters Classroom Guide to the February 1990 issue focuses on the Ernie
Electron article. It describes several side reactions that occur in the zinc/manganese dioxide
cell.
This early ChemMatters article on electric cars describes the then-current technology of
batteries, including lead-acid, sodium-sulfur and, still-in-the-distant-future, lithium-ion batteries.
Some things haven’t changed much since then. (Holzman, D. Electric Cars. ChemMatters 1993,
11 (2), pp 4–7)
The ChemMatters Classroom Guide that accompanies the April 1993 issue with its
article about electric cars has some teacher material about electric cars, ideas for a student
project, and a photocopyable student experiment to make a Gerber cell.
Silver Lightning is a product sold on television (in 1996) to clean silverware with no
scrubbing. ChemMatters author Shaw investigates the product’s claims in terms of
electrochemistry. (Shaw, D. Silver Lightning. ChemMatters 1996, 14 (4), pp 4–5)
The ChemMatters Classroom Guide to the December 1996 issue containing the Silver
Lightning article contains useful teacher background information, including a description of how
to make an “earth cell” from aluminum and decomposing organic material. The guide also
includes a full-page student experiment on removing tarnish from silver.
Here’s a ChemMatters article about another source of electrical power: bacteria! The
author used the lead-acid battery to make analogies to the electrochemical reactions occurring
with the bacteria. The bacteria oxidize acetate from decaying organic material and oxygen is
reduced to water. Holzman, D. Bacteria Power. ChemMatters 2004, 22 (2), pp 11–13,
http://portal.acs.org/portal/PublicWebSite/education/resources/highschool/chemmatters/CTP_00
5378)
In the “Connections to Chemistry Concepts” section of the ChemMatters Classroom
Guide to the April 2004 issue containing the article on bacteria power contains a very good, very
basic discussion, complete with sketches, on oxidation-reduction in electrochemical cells.
(http://portal.acs.org/portal/PublicWebSite/education/resources/highschool/chemmatters/CTP_0
05414)
This article focuses on corrosion (spontaneous electrochemical processes) of the metal
parts of the automobile: Brownlee, C. Flaking Away. ChemMatters 2006, 24 (1), pp 17–19,
http://portal.acs.org/portal/PublicWebSite/education/resources/highschool/chemmatters/archive/
CNBP_025144.
The ChemMatters Classroom Guide to the February 2006 issue containing the article on
corrosion above contains 14 pages of teacher material on corrosion.
(http://portal.acs.org/portal/PublicWebSite/education/resources/highschool/chemmatters/CTP_0
05410)
106
In the “Open for Discussion” feature of this ChemMatters issue, Barbara and Regis have
a dialogue re: the pros and cons of the lithium-ion battery: Sitzman, B.; Goode, R. Lithium-Ion
Batteries: A Clean Source of Energy? ChemMatters 2011, 29 (3), p 5)
____________________
J. Chem. Educ. offers a discussion of a “new” (circa 1973) development in race car
batteries—the silver/zinc battery. Calculations are provided for (an AP level) discussion of the
advantages of this cell over the lead-acid battery. (Plumb, R., Combs, R., Connelly, J. Racing
Car Batteries. J. Chem. Educ. 1973, 50 (12), p 857) Here’s the abstract:
http://pubs.acs.org/doi/abs/10.1021/ed050p857.
Another J. Chem. Educ. article addresses the fundamentals of batteries. It discusses the
basics of how batteries operate, at the level of beginning chemistry students. (Batteries and
Fuel Cells. J. Chem. Educ. 1978, 55 (6), p 399) (abstract:
http://pubs.acs.org/doi/abs/10.1021/ed055p399) The article also discusses fuel cells, which are
very similar to batteries in that they generate electricity, but they are different in that they use a
fuel and, as long as fuel is provided, they continue to generate electricity; they will not “run
down” as batteries do, and eventually “die”.
This article from J Chem Ed that discusses a student project to power a model electric
car using a series of electrochemical cells made from lemon juice, with magnesium and copper
electrodes. (Muske, K, Nigh, C. and Weinstein, R. J. Chem. Educ. 2007, 84 (4), pp 635-8)
(abstract: http://pubs.acs.org/doi/abs/10.1021/ed084p635.) Remember that you need to
subscribe to read full content.
NSTA’s The Science Teacher had an article in the April 2008 issue on corrosion of steel,
entitled “Corrosion in the Classroom”, which contains two activities for students, one lab-based
and the other a paper-and-pencil activity. It is available free for members and costs $0.99 for
non-members. (Drigel, G. Sarquis, A. D’Agostino, M. Corrosion in the Classroom. The Science
Teacher April, 2008, 75 (4), pp 50–56.) View the abstract for this and other articles in that 2008
issue at
http://learningcenter.nsta.org/browse_journals.aspx?action=issue&thetype=buy&id=10.2505/3/ts
t08_075_04. If you are a member of NSTA, you can copy the article into your own online “NSTA
learning center” for future reference.
Web sites for Additional Information
(Web-based information sources)
More sites on the history of electricity
A vintage (1930) article from J. Chem. Educ. discusses historical developments in our
understanding of electricity, from the Greeks to Faraday and Berzelius:
http://pubs.acs.org/doi/abs/10.1021/ed007p33.
More sites on electric cars
For a “definitive guide” to electric cars, see “Electric Cars: A Definitive Guide” at
http://www.hybridcars.com/electric-car. In its defense, this site does offer information about a
large number of (more than 40) all-electric and hybrid-electric cars.
107
There is a budding infrastructure of charging stations growing across the US (and the
world). View maps and charts of its progress at
http://en.wikipedia.org/wiki/Electric_vehicle_network.
More sites on lithium
Here is a 5-minute 2009 CNN video on the development of the lithium resources in the
Bolivian salt flats: http://www.youtube.com/watch?v=JJmXJdp5iHE. The country is adamant that
outside companies will not “steal” their resources. They want their own company to extract the
lithium, process it, develop the batteries (and maybe even the cars) and sell them for
themselves, so that the country benefits at all stages of development. The early part shows the
salt flats and how they extract the brine.
More sites on batteries and oxidation-reduction
For just about any information you can imagine about batteries, check out Battery
University, a site maintained by Cadex Electronics, at http://batteryuniversity.com/.
The Annenberg/CPB Project’s The World of Chemistry series of ~30-minute videos
contains one entitled “The Busy Electron”. The video discusses oxidation and reduction, the role
of the electron, the effects of redox (e.g., rusting), and uses of redox reactions. The video also
provides lab demonstrations of simple electrochemical and electrolytic cells, and animation
depicting the lead-acid battery and electron transfer at the atomic level. The older version, with
Roald Hoffman, can be viewed (but not downloaded) by video-on-demand at
http://www.learner.org/vod/vod_window.html?pid=807. The “Busy Electron” video is # 15 in the
list of videos. (The entire series of 26 videos can be found here:
http://www.learner.org/resources/series61.html.) The series includes closed captioning.
And here is a series of 10 student questions, with answers, to accompany the video:
http://www.woodrow.org/teachers/chemistry/exchange/topics/WOC/woc15.html.
Here’s an article on a student-made, 3-lemon cell used to power a calculator:
http://www.autopenhosting.org/lemon/p181.pdf.
Free Downloads provides about 50 PowerPoint presentations on the battery:
http://freedownloadb.com/ppt/battery.
The Corrosion Doctors Web site has a wealth of information on corrosion,
electrochemical cells and batteries. Battery Basics, here: http://www.corrosiondoctors.org/Batteries/Batteries.htm, provides a good background on batteries.
The Corrosion Doctors Web site also has a series of experiments on corrosion, available
at http://corrosion-doctors.org/Experiments/Introduction.htm.
This site, Free Downloads, offers a lot of freely downloadable PowerPoint presentations
on corrosion: http://freedownloadb.com/ppt/corrosion-ppt-presentation. And you can search for
other topics, as well.
Here’s a series of visuals from Radio Shack depicting cut-away views of various types of
batteries:
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
Zinc-carbon (zinc chloride) battery:
http://support.radioshack.com/support_tutorials/batteries/Images/carbonzinc.jpg

Alkaline battery:
http://support.radioshack.com/support_tutorials/batteries/images/alkaline.jpg

Lead-acid battery: http://www.bing.com/images/search?q=leadacid+battery+radio+shack&qs=n&form=QBIR&pq=lead-acid+battery+radio+shack&sc=022&sp=1&sk=#view=detail&id=96046632CD3ADAE1DD689D923918A13C2DE09C47&selected
Index=20

Nickel-cadmium battery:
http://support.radioshack.com/support_tutorials/batteries/Images/rchg-cyl.jpg

Lithium button battery:
http://support.radioshack.com/support_tutorials/batteries/Images/rchg-cyl.jpg

Lithium-ion battery:
http://support.radioshack.com/support_tutorials/batteries/images/prism.gif
More sites on lithium-ion batteries
Electropaedia has a Web page on “Rechargeable Lithium Batteries” that provides much
information, including newer variations of the Li-ion battery that don’t use lithium cobalt oxide.
View it at http://www.mpoweruk.com/lithiumS.htm.
How Stuff Works has a series of two diagrams showing the charge/discharge cycle of a
lithium-ion battery at http://electronics.howstuffworks.com/everyday-tech/lithium-ionbattery1.htm.
A YouTube video from BASF, “The Chemical Company”, shows in animation how a cell
in a Li-ion battery works: http://www.youtube.com/watch?v=2PjyJhe7Q1g.
More sites on oxidation-reduction reactions
For a very extensive list of electrode potentials (>250 half-reactions), visit the Wikipedia
site at http://en.wikipedia.org/wiki/Table_of_standard_electrode_potentials.
More sites on lead-acid storage batteries
The Hyperphysics site contains some nice drawings of the lead-acid battery, along with
the chemical reactions occurring therein. View these at http://hyperphysics.phyastr.gsu.edu/Hbase/electric/leadacid.html#c2. Note that current is shown as traveling opposite
the flow of electrons, as is usually the way physicists do it.
The US Department of Energy (US DOE) published a “Primer on Lead-Acid Storage
Batteries”. It contains a few diagrams of the battery as well as the chemical equations
describing the charge/discharge cycles. Internal hyperlinks help you navigate through the
109
document. You can download a pdf of the document here:
http://www.hss.doe.gov/nuclearsafety/techstds/docs/handbook/hdbk1084.pdf.
For a detailed description of the basics of lead-acid batteries, visit this Web site from
“autoshop 101” http://www.autoshop101.com/forms/hweb3.pdf.
UStudy’s Web site provides almost 100 links to other sites related to lead-acid batteries.
(http://www.ustudy.in/node/4306)
Here’s a < 3-minute video that describes the manufacture of lead-acid batteries:
http://www.youtube.com/watch?feature=player_embedded&v=P7tOipB_-38. It was originally
from How Stuff Works, but it is no longer on their Web site.
Here is a 5-minute video on the lead-acid battery that shows the construction of the
battery and how it works, and it discusses engineering difficulties in designing batteries to
replace the lead-acid battery.
(http://www.youtube.com/watch?feature=player_embedded&v=rhIRD5YVNbs)
More Web sites on Teacher Information and Lesson Plans
(sites geared specifically to teachers)
This Word document, geared for middle school (grades 6-9), offers for teachers a
complete two-week curriculum on electrochemistry that includes several lab activities and a
culminating project. It provides teacher materials as well as student material and is replete with
standards, although they are Washington state standards. It uses the 5E approach to
teaching/learning. (http://eerc.wsu.edu/SWEET/modules/docs/2006/Fruit-StudyElectrochemistry.doc)
110
Is Your Car a Living Thing?
Background Information
(teacher information)
The article compares the fuel-engine-exhaust system in an automobile to the digestive
system in humans. The major point of comparison is that in both humans and cars the food and
fuel respectively are made up of larger molecules which are broken down for use in both
systems. Noting that petroleum, the source of fuel for cars, is a mixture that includes larger
molecules, and that foods are made up of large molecules like fats, carbohydrates and proteins,
the article details some of the chemical processes that foods and fuels go through as they are
used.
It should be obvious to students that a car is not a living thing, but it might be worth
reviewing with students the characteristics that identify something as living. They include:
 A level of complexity that includes cells-tissues-organs-organ systems-living organism
 Metabolism that transforms chemicals from the environment into useful substances and
energy
 Ability to respond to stimuli in the environment and to alter behavior based on the stimuli
 Ability to move on its own
 Ability to grow by transforming material from the environment into matter like itself
 Can produce copies of itself in a reproductive process
 Can adapt to external environment and evolve
 Ability to influence living things around it.
So, although cars and people are similar in several ways described in the article, cars are not
living organisms. Nevertheless, the comparisons in the article are interesting. The general
approach in the following sections of this Teacher’s Guide is to provide details on the chemicals
and processes on both sides of the comparison—fuels and foods.
More on gasoline
Much of the material that follows on gasoline has been adapted from the October, 2008,
Teacher’s Guide for the Olympic Flame article.
Petroleum, from which gasoline is produced, is a mixture of hydrocarbon compounds.
The simplest series of hydrocarbon compounds—those made up exclusively of carbon and
hydrogen—is called the alkane series. The carbon and hydrogen atoms in all of the compounds
in this series are bonded with single bonds. Such compounds are known as saturated
compounds (the compound has no double bonds).
Since we know that in covalent bonding each carbon atom has a bonding capacity of
four, the simplest hydrocarbon has a formula of CH4 (methane). If there is one C-C bond, then
the formula will be C2H6 (ethane). The third alkane hydrocarbon has a formula of C3H8
(propane), the fourth, C4H10 (butane) and the fifth, C5H12 (pentane). In general the alkanes fit into
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a general formula of CnH2n+2. Beginning with pentane, the names of the rest of the compounds
in this series add a prefix to the –ane ending: pent-, hex-, hept-, oct-, non-, dec-, etc.
These hydrocarbon compounds are all found in either natural gas or petroleum or both.
The individual compounds are separated from the natural petroleum mixture during the refining
process (see below). The individual hydrocarbon compounds or mixtures of them can be used
as fuels like gasoline, which is a mixture of primarily C5 to C12 alkanes.
Your students will be interested in how this relates to the discussion of petroleum and
gasoline. Gasoline is produced by fractionally distilling petroleum (or crude oil), which is a
mixture of hydrocarbons, and then remixing some of the individual hydrocarbons to make the
gasoline, which is itself a mixture. The chart below shows the range of hydrocarbons that make
up commercial products which are derived from petroleum.
Refining Fraction
Natural gas
Petroleum ether
Gasoline
Kerosene
Fuel Oils
Lubricants
Boiling Point (oC)
less than 20
20-60
40-200
50-260
above 260
above 400
Number of Carbon Atoms
C1 to C4 (methane-butane)
C5 to C6
C5 to C12
C12 to C13
C14 and above
C20 and above
Crude oil—petroleum—cannot be used as a
fuel in its natural state. Remember that crude oil is a
mixture of hydrocarbons, and these are separated
from each other in a refinery like the one pictured at
right. The petroleum mixture is heated in a furnace and
the liquid components boil off according to their boiling
points, lowest first. The vapors are allowed to rise in
the refining tower and condense back to liquid form
and are then drawn off. Each liquid distillate has its
own boiling point, which allows the components to be
separated. The process is called fractional distillation.
The liquids are then remixed to produce the products
(http://www.saveamericafoundation.com)
listed above.
Gasoline is made from petroleum in several steps. Gasoline as such does not exist in
crude oil. Rather, crude oil is mostly made up of larger hydrocarbons, like pentadecane (C15H32)
for example. "Cracking" is a method by which these large hydrocarbon molecules are broken
down into the lighter hydrocarbons that make up gasoline. There are two kinds of cracking,
catalytic and thermal. Catalytic cracking is the preferred method of making gasoline because it
requires lower temperatures (making the method cheaper) and because it produces better
gasoline. Catalytic cracking makes use of zeolite catalysts, which are aluminosilicate materials,
to break down large hydrocarbons at temperatures of around 500ºC and at pressures of around
13 atmospheres. Not only are large hydrocarbon molecules broken down into smaller ones in
this process, but linear alkanes are rearranged into highly branched ones, or into aromatic
molecules like benzene and toluene. By contrast, thermal cracking requires much higher
temperatures (around 700ºC) and produces mostly linear alkanes, which make poorer fuels
than branched alkanes and aromatic hydrocarbons. The source of the large hydrocarbon
molecules is often the naphtha fraction (10-12 carbons) or the gas oil fraction (10-70 carbons)
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from the fractional distillation of crude oil. There are many reactions that occur during cracking,
but below is an example using the hydrocarbon C15H32:
C15H32  2 C2H4 + C3H6 + C8H18
ethene propene octane
In this reaction octane is the desired product and can be mixed with other alkanes to increase
the gasoline yield in the refining process. A simulation of the cracking of hexane is shown here:
http://www.bbc.co.uk/schools/gcsebitesize/science/aqa_pre_2011/oils/polymersrev1.shtml.
According to American Chemical Society’s National Historic Chemical Landmark Web
site,
The first full-scale commercial catalytic cracker for the selective conversion of
crude petroleum to gasoline went on stream at the Marcus Hook Refinery of Sun
Company (now Sunoco, Inc.) in 1937. Pioneered by Eugene Jules Houdry (1892-1962),
the catalytic cracking of petroleum revolutionized the industry. The Houdry process
conserved natural oil by doubling the amount of gasoline produced by other processes. It
also greatly improved the gasoline octane rating, making possible today’s efficient, highcompression automobile engines.
(http://portal.acs.org/portal/acs/corg/content?_nfpb=true&_pageLabel=PP_SUPERARTIC
LE&node_id=711&use_sec=false&sec_url_var=region1&__uuid=1c1b95a5-4146-441d960c-2001317c3992)
To summarize: the fuel for automobiles begins as petroleum, a mixture of compounds,
some of which are too large to be of use in a liquid fuel. So the compounds in the petroleum
mixture are separated from each other via distillation in a refinery, thus isolating the smaller
molecules that can be remixed to form gasoline. In addition, in the refining process some of the
larger molecules are broken apart in the cracking process so that they too can be remixed to
form gasoline. Both of these processes confirm part of the article’s claim that in the automobile it
is important that more complex molecules are broken down into simpler molecules that are
suitable for use as a fuel.
More on food and digestion
The “complex-to-simpler” theme of the article is carried through to digestion in the
human body. The article says that food, like petroleum, has to be processed prior to use. The
article also says that the food that is taken into the body is made up of nutrients which are
complex molecules like carbohydrates, fats and proteins. The next section of the Teacher’s
Guide, then, takes a look at the chemicals involved in digestion. Much of this section has been
adapted from the April, 2006, Teacher’s Guide to the article “The Dog Ate My Homework and
Other Gut-wrenching Tales.”
Digestion in humans takes place in stages and in each stage more complex molecules
are broken down into simpler ones. Digestion begins with chewing. This results in a large
increase in surface area of the food, so that enzymes can be more effective in the actual
chemistry of digestion. In addition to breaking down the food, chewing mixes in saliva, which
helps to lubricate the food. Swallowing moves the lubricated food into the esophagus, on its way
down to the biochemical reactions of the digestion process in the stomach and beyond.
The food ingested by humans consists of many different molecules, but the bulk of them
are huge macromolecules that cannot be absorbed by cells in the body. Here’s a look at the
three main groups of macromolecules involved:
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Proteins are long chains (polymers) of amino acids linked together by peptide bonds.
Generally, proteins must be broken down chemically into individual amino acids in order for
them to be absorbed through the cells in the lining of the stomach. Proteins can be hydrolyzed
into peptides by proteases; peptides can then be further broken down into amino acids by
peptidases. Both enzymes break peptide bonds.
Lipids include fatty acids, neutral fats, waxes and steroids. Most important for this article
are fatty acids, which are the building blocks of many complex lipids. Fatty acids are chains of
carbon atoms, 14–22 carbon atoms long, ending in a carboxylic acid. They usually have even
numbers of carbon atoms. Their differences lie not only in the number of carbon atoms, but also
in the positions of the double bonds that make them unsaturated.
Triglycerides are the most abundant storage form for
fat in animals and plants, and are, therefore, the most
important dietary lipid. A triglyceride molecule is made of
one glycerol molecule (in red at right) attached at each of its
three carbon atoms to different fatty acids through ester
bonds (see structure at right). These triglycerides are very
large molecules that cannot be absorbed. They must be
broken down by the enzyme pancreatic lipase into a
monoglyceride and two separate fatty acids, all three of
which are able to be absorbed by the body. Other lipases
are able to hydrolyze triglyceride into three separate fatty
acids and a glycerol molecule.
(http://www.familyhealthave
nue.com)
Carbohydrates are aldehydes or ketones derived from polyhydric alcohols, primarily
penta- and hexahydric alcohols. Carbohydrates can be broken down into three major groups:
monosaccharides, disaccharides and polysaccharides.
Monosaccharides are the simple sugars, mostly hexoses, like glucose, and fructose, or
pentoses, like ribose. These are typically produced by the breakdown of more complex
carbohydrates, and these are easily absorbed and transported across the wall of the digestive
tract and into the bloodstream.
Disaccharides are simply two monosaccharides that are linked together by a glycosidic
bond. Common disaccharides are sucrose, lactose and maltose.
Polysaccharides are large polymers made up of smaller sugars, primarily glucose.
They are the most abundant carbohydrate food group in most animals. This portion of
carbohydrates can be further subdivided into three main groups: starch, cellulose, and
glycogen.
In order for humans to use these nutrients they must be all broken down into their
simplest form. Carbohydrates are digested most easily. Sugars are the first of the major
nutrients to be digested, beginning in the saliva and continuing in the stomach and small
intestine. Starches, the other major carbohydrate class, are digested in two steps. Enzymes in
saliva and pancreatic juice break starch into maltose, and maltose molecules are broken down
to glucose in the intestines. Digestion of proteins begins in the stomach where they are broken
down into peptide units. These are broken down to amino acids in the intestines. Fats are most
114
difficult to dissolve because they are not water soluble. In the intestines fats are emulsified by
bile acids and broken down by enzymes into fatty acids, glycerol and cholesterol.
More about enzymes
This section on enzymes is included here because enzymes are biological catalysts. The
article has a section on catalytic converters and the liver, and it emphasizes the importance of
the catalyst in processing waste chemicals. Even though the article does not mention catalysts
that are used in the petroleum cracking process, these catalysts are referenced above (see
“More on gasoline”). You can point to these examples to illustrate to students the role that
catalysts play in many types of chemical reactions, including the chemistry of digestion.
The major enzymes involved in digestion are: proteases, lipase and amylase,
hydrolyzing proteins, fats, and starches, respectively. A good Web site to learn more about the
actions of these enzymes can be found at
http://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion/pancreas/exocrine.html. A diagram at
that site shows a visual representation of the breakdown of a protein to peptides by trypsin and
chymotrypsin.
Most chemical digestion of food actually happens in the small intestine, where the above
enzymes are delivered primarily by the pancreas. The liver also plays a pivotal role in digestion
as it secretes material into the small intestine—mainly bile acids. These, however, act primarily
to emulsify and solubilize lipids so that pancreatic enzymes can act on them chemically to
hydrolyze them into fatty acids and monoglycerides, both of which can be absorbed through cell
membranes. Without bile acid emulsification of lipids, the fat globules are too large for enzymes
to efficiently carry out hydrolysis—the enzymes can only reach the lipids that are on the surface,
the outside of the globule. The interior of the globule would never be broken down into usable
fatty acids.
More on energy in cars
The basic principle of an internal combustion engine (ICE) is to combine a chemical
compound in which a relatively large amount of energy is stored with air in a closed cylinder and
ignite the mixture to release the energy that results from the combustion. In the modern
automobile engine there are four operating phases, as illustrated in the diagram in the article
and in the diagram below. Note that the diagram below, as well as the one in the article, shows
one engine cylinder as it would look in the four stages or strokes. In modern cars there are
multiple cylinders—fours, six or eight—operating in concert.)
115
(http://www.edu.dudley.gov.uk/roadsafety/pollution.htm)
Internal combustion takes place inside a metal cylinder which has a piston which moves
up and down inside it. In the first phase at left in the above diagram—a downward piston
stroke—air and fuel are taken in to the cylinder in the induction or intake stroke. The piston
moves upward in the cylinder in the second phase to compress the air-fuel mixture. The third
phase, the power stroke, is initiated by a spark from a spark plug at the top of the cylinder. The
spark provides the activation energy to begin the combustion of the air-fuel mixture. The
combustion is exothermic, and as a result the exploding gas mixture forces the gas mixture to
expand and, in turn, forces the piston downward to complete the third phase. As the piston
moves upward once again in the fourth phase the gaseous products of the combustion are
forced out of the cylinder via a small piston that opens and closes.
You may already have studied types of reactions, including combustion, like the example
below using octane as the fuel:
2 C8H18 + 25 O2 ➙ 16 CO2 + 18 H2O + energy
Recall from earlier in this Teacher’s Guide that gasoline is actually a mixture of hydrocarbons so
the reaction shown for octane is only an example of ICE chemistry. In general the stoichiometry
of the ICE combustion requires an ideal air to fuel ratio of 14:1. At that ratio the engine gives
maximum performance with minimum reaction by-products. It is most important to note that the
reaction is exothermic. The energy produced is the energy needed to move the car, as the
article notes. The heat produced in the explosion, or rapid combustion, causes the gases in the
cylinder to expand and drive the piston downward, turning the driveshaft that is attached.
You might want to note that during two of the four cycles the behavior of the gas mixture
in the cylinder can be described by one or more of the gas laws. In only two of the four
strokes—compression and power—can the piston-cylinder setup be considered a closed
system, therefore containing a fixed amount of gas. Since it is a mixture of gases, Dalton’s Law
of partial pressures applies. During the compression stroke the volume of the gases is greatly
decreased. Boyle’s Law applies here. The pressure of the gas molecules on the piston is now
116
greatly increased. As the spark is produced at the beginning of the power stroke, the gas
mixture undergoes rapid combustion (that is, it explodes) and the heat produced raises the
temperature of the gases. This serves to increase the pressure they exert according to
Amontons’ (Gay-Lussac’s) Law, and this pressure does work on the piston, driving it toward the
crankshaft, delivering power eventually to the wheels of the car.
There are several energy conversions in an ICE. The chemical potential energy of the
fuel is converted to thermal energy and then to the desired mechanical energy to move the car.
However, ICEs are very inefficient. Only about 20 per cent of the energy released by
combustion is actually converted to useful motion. The other 80 per cent is lost as heat, friction
or drag. The chart below shows more detail about energy losses in an ICE.
(http://www.rmi.org/RFGraph-Energy_flow_through_a_typical_internal_combustion_engine_drivetrain)
More on energy in the body, including mitochondria
Energy for the human body is produced primarily by aerobic respiration. As the article
suggests, the chemistry of this process using the carbohydrate glucose as the food nutrient
occurs in multiple steps but in summary looks like this:
C6H12O6 + 6 O2 ➙ 6 CO2 + 6 H2O + energy
Glucose oxygen carbon
water
dioxide
Note first that glucose is already the product of a catabolic chemical process in which a
more complex carbohydrate like sucrose (C12H22O11), a disaccharide composed of glucose and
fructose, has been broken down by enzyme action in the stomach. The article emphasizes the
fact that both in automobiles and humans, larger, more complex molecules are broken down
into simpler molecules. Also note that aerobic respiration, like combustion in an automobile, is
exothermic. The energy produced is the energy needed for humans to function. The major
differences between the two reactions is that cellular respiration takes place at a lower
temperature and occurs in multiple steps, thus producing energy at a much slower rate than in
automobile combustion.
117
As noted above, the breakdown of glucose into carbon dioxide (exhaled with the breath)
and water (eliminated as urine, exhaled water vapor or perspiration) is a multi-step process, and
that process occurs primarily in the mitochondria of human cells. All cells in humans contain
mitochondria (the singular is “mitochondrion”). They are organelles whose primary function is to
generate energy by breaking down glucose or other nutrient molecules and in the process,
storing energy in molecules of adenosine triphosphate (ATP). Different cells have varying
numbers of mitochondria, from just one to several thousand, depending on the specialized cell
function. For example, a nerve cell may have relatively few mitochondria, whereas a muscle cell
with its high energy requirement will have hundreds or thousands. Mitochondria are unique
organelles in that they have two membranes. One covers the outside of the organelle
completely and the other is a highly folded membrane that greatly increases the inner surface
area of the organelle. These folds, called cristae, make up the surface area for the chemical
reactions that are part of cellular respiration. Mitochondria, therefore, are structured so as to do
the maximum chemical work possible. Mitochondria range in size from 0.5 to 1.0 µm. See the
diagram below.
The major respiration
steps that take place begin with
the glycolysis of glucose to
form pyruvic acid,
CH3COCOOH, NADH, a
coenzyme, and adenosine
triphosphate, ATP. This step
takes place outside the
mitochondria in the cell
cytoplasm and yields a limited
amount of energy. The pyruvic
acid anion, referred to as
pyruvate, is passed into the
mitochondria and is the
reactant in the Krebs (or citric
acid) cycle which produces
(http://en.wikipedia.org/wiki/Mitochondria)
high-energy electrons which, as
the article describes, are transported through multiple oxidation-reduction reactions by NADH.
This process produces up to 30 additional ATP molecules, which store energy produced in the
process. The ATP molecules are transferred to sites where energy is needed and are converted
back to adenosine diphosphate, ADP. In the release of one phosphate group from ATP and the
bond-forming step that results in ADP the energy once stored in the ATP is released to
biochemical work in the cell. The ADP/ATP process is reversible, much like a rechargeable
battery. ADP is recycled back into the mitochondria to be used to synthesize more ATP. Also, at
the end of the electron-transfer process some electrons have lower energy and are added to
oxygen which, in turn, forms the water that we recognize as one of the products of cellular
respiration.
Although not directly related to the energy focus of the article, mitochondria are
important for multiple reasons. The United Mitochondrial Disease Foundation says this about
the importance of mitochondria:
The conventional teaching in biology and medicine is that mitochondria function
only as "energy factories" for the cell. This over-simplification is a mistake which has
slowed our progress toward understanding the biology underlying mitochondrial disease.
It takes about 3000 genes to make a mitochondrion. Mitochondrial DNA encodes just 37
118
of these genes; the remaining genes are encoded in the cell nucleus and the resultant
proteins are transported to the mitochondria. Only about 3% of the genes necessary to
make a mitochondrion (100 of the 3000) are allocated for making ATP. More than 95%
(2900 of 3000) are involved with other functions tied to the specialized duties of the
differentiated cell in which it resides. These duties change as we develop from embryo to
adult, and our tissues grow, mature, and adapt to the postnatal environment. These
other, non-ATP-related functions are intimately involved with most of the major metabolic
pathways used by a cell to build, break down, and recycle its molecular building blocks.
Cells cannot even make the RNA and DNA they need to grow and function without
mitochondria. The building blocks of RNA and DNA are purines and pyrimidines.
Mitochondria contain the rate-limiting enzymes for pyrimidine biosynthesis
(dihydroorotate dehydrogenase) and heme synthesis (d-amino levulinic acid synthetase)
required to make hemoglobin. In the liver, mitochondria are specialized to detoxify
ammonia in the urea cycle. Mitochondria are also required for cholesterol metabolism, for
estrogen and testosterone synthesis, for neurotransmitter metabolism, and for free
radical production and detoxification. They do all this in addition to breaking down
(oxidizing) the fat, protein, and carbohydrates we eat and drink.
(http://www.umdf.org/site/c.8qKOJ0MvF7LUG/b.7934627/k.3711/What_is_Mitochondrial_
Disease.htm)
On balance the ChemMatters article compares two variations of a chemical process that
can be summarized as:
Food/Fuel + Oxygen ➙ Carbon dioxide + Water
In the case of a car, the process is designed to occur explosively at high temperatures yielding
large amounts of energy quickly. And in humans the process takes place at body temperature
and in a series of slow steps to produce energy at a rate the body can use.
More on engine waste (include catalytic converter)
In theory, only carbon dioxide and water should emerge from the exhaust system of an
automobile. However, due to actual operating conditions in most cars, other compounds are
also present. Some engines do not burn all of the hydrocarbons in gasoline and so these gases
are part of the waste stream. If the combustion is incomplete due to an insufficient supply of
oxygen to the cylinder, then carbon monoxide is produced in combustion along with carbon
dioxide. High operating temperatures of many modern cars causes nitrogen to react when it
would be unreactive at lower temperatures. As a result oxides of nitrogen are also part of the
exhaust gases.
119
For all of these reasons catalytic
converters were introduced in cars in
1975. The converter is contained in a
stainless steel housing. The converter
itself is made up of either a fine mesh
structure or a honeycomb ceramic
structure whose purpose is to provide
maximum surface area on which the
chemical reactions can take place. The
surfaces of the converter are coated
with an aluminum oxide wash that adds
to the surface area. And on this surface
is embedded one of the typical metal
catalysts—either platinum, palladium or
rhodium. The mass of these metals in a
(http://www.worldmufflers.com/catalytic.htm)
single converter is very small, less than
10 grams. At this writing the price of palladium is $705/oz. (that’s $24.87/g), rhodium is
$1150/oz. and platinum is $1525/oz. so the theft of converters is a chronic problem.
Most modern converters are three-way converters. That is, they oxidize waste carbon
monoxide to carbon dioxide, they reduce oxides of nitrogen to nitrogen and oxygen gases and
they oxidize unburned hydrocarbons to carbon dioxide and water.
The three reactions look like this:
Reduction of nitrogen oxide:
NOx → N2 + O2
Oxidation of carbon monoxide: CO + O2 → CO2
Oxidation of hydrocarbons:
CxH4x + 2x O2 → x CO2 + 2x H2O
In the converter the conversions take place in series. First, platinum and rhodium catalysts
reduce the nitrogen oxides in the waste stream. If we use NO2 as an example, we see that the
oxygen is removed from the NO2. Two single nitrogen atoms combine to produce diatomic
nitrogen along with the diatomic oxygen that is produced. The oxygen that is produced is then
used in the oxidation of unburned hydrocarbons and carbon monoxide. This second step is
catalyzed by a platinum-palladium catalyst. In these processes the atoms involved are actually
held temporarily loosely in place by the catalysts so that the reactions can occur.
Note that all three reactions in stage 1 and 2 are redox reactions, and that the metal catalysts
facilitate the exchange of electrons in these reactions. You may want to review (or preview)
oxidation and reduction reactions with your students, noting to them that oxidation is loss of
electrons and reduction is the gain of electrons. For example, again using NO2 as an example,
we see that the oxidation number of nitrogen in NO2 is +4, where the oxidation number of
nitrogen in N2 is 0. The oxidation number moves in a negative direction (+4 → 0) and so we can
say that the nitrogen has gained electrons; that is, it is reduced. So stage 1 of the converter is a
reduction process. At the same time the oxidation number of the oxygen in NO2 is -2, and in O2
it is 0, moving in a positive direction (-2 → 0), indicating that oxygen has lost electrons (it is
oxidized).
The third phase in a converter is an oxygen sensor which monitors the volume of oxygen
in the waste stream. It can signal the car’s computer to adjust the air to fuel ratio in the
cylinders, keeping it near the 14.7 to 1 ratio mentioned earlier. This also insures that there is
sufficient O2 coming to the converter to oxidize unburned hydrocarbons and carbon monoxide.
120
Catalytic converters were first required following the Clean Air Act of 1970. By 1975, the
EPA had regulated the permitted amount of exhaust pollutants, and in order to meet these new
regulations catalytic converts were required on cars. An added benefit to the advent of
converters was the removal of lead from gasoline since lead would deactivate the catalytic
converters. Current three-way converters came on the scene in 1980–81. The Clean Air Act of
1990 further strengthened control of exhaust emissions. The catalytic converter was invented in
the early 1950s by Eugene Houdry, originally not for cars but for factory smokestacks. (See
“More on gasoline”, above, for additional information on Houdry). Later in the 1950s Houdry
began to research how to adapt the smokestack converter for use in cars. The modern threeway converter was developed by John J. Mooney and Dr. Carl D. Keith working at the
Engelhard Corporation (now a division of BASF Catalysts).
More on body waste (liver)
The article points to the human liver as the organ comparable to the catalytic converter
in cars, and in some ways it is. The liver performs hundreds of functions in the body and
removing toxic substances is just one of them. And, as the article says, enzymes in the liver
catalyze the detoxification processes. Some of the harmful substances are the result of normal
biochemical reactions in the body, but most are brought into the body from the environment.
Examples of external toxins include viruses and bacteria, medications and drugs, food additives
and preservatives, food colorings, artificial sweeteners, insecticides and residue from fertilizers
used in agriculture, volatile organic compounds and air pollutants.
The liver detoxifies the body in three ways. It filters
toxins from the blood, produces bile and breaks down
toxins, chemically using enzymes as catalysts. The liver is
suspended behind the ribs on the upper right side of the
abdomen and spans most of the width of the body over to
the heart. It receives blood directly from the stomach,
pancreas and intestines via the hepatic portal vein. Its
intricate web of specialized cells filters larger toxin
molecules from the blood at a rate of two quarts of blood
per minute. Within its cells are hexagonal arrangements
of veins that funnel blood through a web-like structure that
filters out toxins and drains the purified blood into a
central vein which sends the blood to other parts of the
body (see diagram at right).
(http://www.siumed.edu/~dking2/er
g/liver.htm#cords)
The second way the liver purifies the body is by producing bile. Many of the toxins that
enter the body are fat soluble which means they dissolve only in fatty or oily solutions and not in
compounds. Bile emulsifies fat molecules, thus creating increased surface area for enzymes to
break down the fat molecules quickly to a water-soluble form so that they can be absorbed into
the intestines.
The third purifying process is more involved and extensive. It is the two-step process
described in the article. In phase 1 the liver modifies the toxin molecule either by neutralizing it
completely or by modifying it via oxidation, reduction or hydrolysis so that it is less toxic,
resulting in an intermediate product which will be further modified in phase 2. The second phase
is called the conjugation phase because the intermediates from phase 1 are reacted with
compounds that make the toxin water-soluble so that it can be excreted in urine. These two
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phases take place in liver cells, specifically in the smooth endoplasmic reticulum of the cell,
which is rich in enzymes. One such enzyme is the cytochrome p450 enzyme, which has the
ability to catalyze the oxidation of toxins to make them harmless.
It is interesting to see that both the liver and catalytic converter use catalysts extensively
in the chemical changes that take place in them, and that both also do their work in two phases.
And while there are three catalysts typically used in a car’s converter, the liver employs
hundreds of enzymes to detoxify the range of toxins that enter the blood stream.
Connections to Chemistry Concepts
(for correlation to course curriculum)
1. Distillation—Refineries use this process to separate most major fractions of crude oil from
one another. The focus for chemistry class is boiling point as it relates to intermolecular
forces.
2. Intermolecular attractions—Boiling points of organic molecules relate directly to their size
and surface area in contact with other molecules.
3. Organic chemistry—The chemistry of petroleum and respiration is virtually all organic
chemistry.
4. Catalysis—Cracking of larger hydrocarbons into more useful, smaller molecules is done
primarily through the use of catalysts to lower the boiling point of the mixture. Unification of
smaller molecules into larger ones also involves the use of catalysts.
5. Particle size, surface area and reaction rate—When food is digested, it is broken up into
smaller particles that are then able to react with enzymes to actually undergo chemical
digestion.
6. Structural formulas—Organic chemistry gives us a chance to show students the varied
structures of various hydrocarbon molecules. Also, straight-chain vs. branched-chain
alkanes are pertinent here.
7. Types of reactions—Combustion is one of the 5 major types of reactions students study in
chemistry.
8. Thermochemistry and heats of combustion—One emphasis in the article is how cars and
humans produce energy, mostly in the form of heat.
9. Oxidation-reduction reactions—all of the catalytic converter reactions and some of the
mitochondrial reactions involve oxidation-reduction.
10. Biochemistry—All of the reactions related to the human body are biochemical reactions.
11. Gas Laws—The behavior of gases in a car’s cylinders can be described by the gas laws.
Possible Student Misconceptions
(to aid teacher in addressing misconceptions)
1. “Crude oil is the stuff you buy in a can to put in your car engine.” Crude oil is a
mixture of hundreds of different hydrocarbon molecules. Engine oil is only a small
portion of what’s in crude oil – and a very specific small part at that.
2. “Gasoline is a pure substance—octane.” Gasoline is a complex mixture of
hydrocarbons. Even the performance standard, iso-octane, is only one of many
compounds found in normal gasoline.
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3. “Gasoline is one clean fraction of crude oil that is separated off in fractional
distillation.” No, gasoline is a mixture of hundreds of compounds, mostly hydrocarbons.
Most are derived from crude oil, but they come from a variety of crude oil fractions and
are then mixed in proper proportions to give the properties of gasoline needed for
highest efficiency and power output.
Anticipating Student Questions
(answers to questions students might ask in class)
1. “Why can’t petroleum chemists just change all of the crude oil into gasoline? That
would keep prices down.” For starters, some molecules in crude oil are too large or too
complex to be broken down into gasoline. In addition, we need those other fractions of crude
oil for other purposes; e.g., diesel oil for trucks, buses, trains and boats; home heating oil to
keep us warm in winter; crude bottoms for asphalt for roads; volatile compounds for
solvents; petrochemicals for medicines and plastics; etc.
2. “Why can't liquid gasoline burn?” Combustion is the chemical process of a fuel reacting
with oxygen. Fuels burn when their molecules break down, and the atoms in those
molecules combine chemically with oxygen atoms. Actually, liquid gasoline DOES burn. But
it is a relatively slow process that only burns on the liquid surface because that’s where
oxygen from the air can collide--and react--with gasoline molecules. This reaction is not
nearly rapid enough to be useful in the internal combustion engine. To make the reaction
faster, the fuel injectors in the engine aspirate or atomize the gasoline into very tiny droplets
that have much greater surface area than the liquid pool of gasoline in the tank. These small
droplets with their greater surface area can react almost instantaneously with oxygen
molecules to provide the very rapid reaction—the explosion--mentioned in the “More on
energy in cars” section above.
3. “What’s the difference between the term ‘food’ and the term ‘nutrient’?” Products that
are grown naturally or produced for human consumption are considered food. As most
chemistry students should already know, most foods are complex mixtures of chemical
compounds. Some of the compounds—like carbohydrates, fats and proteins—are able to
provide energy in the body or can be changed into materials that help the body grow and
function. These kinds of compounds are called nutrients. For example, a carrot is a food, but
it contains 10 g of carbohydrate and 1 g of protein. The latter are nutrients.
4. “How do catalysts change the rate of a reaction?” They provide the reaction with a new
path, not available without them, that has a lower activation energy. The old, now-higher,
activation energy is still there, but the preferred path is the reaction with the lower energy.
In-class Activities
(lesson ideas, including labs & demonstrations)
1. On the Royal Society of Chemistry Web site is a video demonstration of catalytic cracking
that comes with a pdf of class notes:
http://www.rsc.org/Education/Teachers/Resources/PracticalChemistry/Videos/hydrogencarbon-dehydrating-ethanol.asp.
2. PBS has a site on the science of oil at http://www.pbs.org/wnet/extremeoil/teachers/lp2.html.
3. Students can do a fractional distillation lab in class.
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a. A simple procedure that should be done as a demonstration can be found here:
http://www.oresomeresources.com/resources_view/resource/experiment_fractional_distil
lation.
b. If you have Vernier software, there is another procedure here:
http://www.vernier.com/experiments/cwv/8/fractional_distillation/.
4. Although the chemical reaction below is not related to any hydrocarbon cracking process,
you can present a catalyzed reaction to students using cobalt(II) chloride, Rochelle’s salt,
and hydrogen peroxide. Find it at the Flinn Scientific site,
http://www.flinnsci.com/Documents/demoPDFs/Chemistry/CF0255.01.pdf.
5. For a NASA unit on combustion see http://astroventure.arc.nasa.gov/teachers/pdf/AVAtmoslesson-5.pdf. You may already have combustion labs in your course’s lab manual.
Students can test for the products of combustion using limewater and cobalt chloride paper,
etc.
6. You can have students compare fuels in a lab activity like this one. This article is primarily
about gasoline, but students should understand how different fuels supply differing amounts
of energy. (http://galileo.phys.virginia.edu/outreach/8thGradeSOL/FuelEnergyFrm.htm)
7. A series of demonstrations and experiments can be found at this part of the NSTA Scope,
Sequence and Coordination Web site, http://dev.nsta.org/ssc/pdf/v4-0969t.pdf. The
demonstrations include genie-in-the-bottle catalysis, digestion of egg proteins (this one’s
actually a student experiment), baking bread and yeast, and the enzymes in the liver. These
are presented as inquiry-based, student-designed experiments.
8. The Chemical Heritage Foundation Web site contains a section on “Enzyme Specificity” in
their “Antibiotics in Action” module. This module contains three experiments that show the
digestion of protein, lipid, and starch, respectively. Student and teacher versions of each
activity can be found at:
http://assets.chemheritage.org/EducationalServices/pharm/antibiot/activity/enzlab.htm
9. This lab provides students experience with various factors such as surface area,
temperature and pH affect the rate of a reaction—in this case, the decomposition of
hydrogen peroxide, first with MnO2 as a catalyst, and then with catalase from beef liver. It’s
called “The Liver Lab”.
(http://www.nsa.gov/academia/_files/collected_learning/high_school/science/liver_lab.pdf)
10. This version “cracker and saliva” lab activity from The Exploratorium suggests that the oftstated procedure will not work and provides background and a fail-safe procedure to
observe the catalytic action of amylase on starch.
(http://www.exploratorium.edu/ti/conf/nsta2009/karen/bogus_biology.pdf)
A variation of this procedure can be found on this University of Georgia site:
http://apps.caes.uga.edu/sbof/main/lessonPlan/enzymeCarb.pdf.
Out-of-class Activities and Projects
(student research, class projects)
1. Students, working singly or in teams, can research each section of the digestive system and
produce a class PowerPoint, larger poster, or video that connects each section correctly.
Other students or teams of students might research important molecules in the digestive
system and include this research into the class production.
2. Students could keep a log of their food intake for a week and then prepare a chart that
categorizes the main class of nutrients in each type of food.
3. Students could research the workings of the internal combustion engine and build a model
of an ICE with extra credit if the model has moving parts.
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4. Student could be assigned the task of interviewing auto mechanics to get their perspectives
on the modern internal combustion engines.
5. Revell sells a kit from which you can build a model engine. This might be a worthwhile
purchase for students who are tactile learners. (http://www.amazon.com/Revell-Metal-BodyFord-Engine/dp/B0006I8QHK/ref=sr_1_fed1_4?ie=UTF8&qid=1356898267&sr=84&keywords=internal+combustion+engine+kit)
References
(non-Web-based information sources)
The references below can be found on the ChemMatters
25-year CD (which includes all articles published during the years
1983 through 2008). The CD is available from ACS for $30 (or a
site/school license is available for $105) at this site:
http://www.acs.org/chemmatters. (At the right of the screen,
click on the ChemMatters CD image like the one at the right.)
Selected articles and the complete set of Teacher’s Guides
for all issues from the past three years are also available free online
at this same site. (Full ChemMatters articles and Teacher’s Guides are
available on the 25-year CD for all past issues, up to 2008.)
Some of the more recent articles (2002 forward) may also be available online at the URL
listed above. Simply click on the “Past Issues” button directly below the “M” in the ChemMatters
logo at the top of the page. If the article is available online, you will find it there.
In this article, author Rohrig focuses on carbohydrates in the diet and how they are
metabolized. (Rohrig, B. Carb Crazy. ChemMatters 2004, 22 (3), p 6)
This article explains the chemistry of digestion and emphasizes the role of enzymes as
catalysts. (Tinnesand, M. The Dog Ate My Homework and Other Gut-Wrenching Tales.
ChemMatters 2006, 24 (2), p 4,
http://portal.acs.org/portal/PublicWebSite/education/resources/highschool/chemmatters/archive/
CNBP_025142)
Author Rohrig describes the internal combustion engine and how fuel is burned. (Rohrig,
B. Chemistry on the Fast Track: The Science of NASCAR. ChemMatters 2007, 25 (1), p 5,
http://portal.acs.org/portal/PublicWebSite/education/resources/highschool/chemmatters/CTP_00
5376)
This is an excellent article that describes how petroleum is formed, how it is refined and
how larger molecules in petroleum are broken down into simpler ones. (Baxter, R. Gold in Your
Tank. ChemMatters 2007, 25 (2) p 8,
http://portal.acs.org/portal/PublicWebSite/education/resources/highschool/chemmatters/CTP_00
5385)
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Web sites for Additional Information
(Web-based information sources)
More sites on petroleum refining
The American Chemical Society has a Web site that details important events in chemical
history. This page is devoted to the Houdry process for cracking petroleum:
http://portal.acs.org/portal/acs/corg/content?_nfpb=true&_pageLabel=PP_SUPERARTICLE&no
de_id=711&use_sec=false&sec_url_var=region1&__uuid=fe05eefb-ad32-45f5-a64083b0df899a96.
This site discusses the energy needed to break bonds in fractional distillation and shows
an illustration of petroleum distillation column:
http://www.elmhurst.edu/~chm/onlcourse/chm110/outlines/distill.html.
This Centers for Disease Control site lists many properties of gasoline:
http://www.atsdr.cdc.gov/toxprofiles/tp72-c3.pdf.
This site presents a rather detailed account of the theory behind the process of fractional
distillation. It is probably for teacher background only. It also allows you to backtrack in the site
to other background pages to help you understand this one. At the end of this page is a diagram
of one small part of the petroleum fractional distillation column in more detail, showing the
openings and bubble caps in the column, and it gives a description of how the column works.
(http://www.chemguide.co.uk/physical/phaseeqia/idealfract.html#top)
More sites on combustion
This site gives a very technical explanation of combustion kinetics:
http://webserver.dmt.upm.es/~isidoro/bk3/c15/Combustion%20kinetics.pdf.
A tutorial on the basic chemistry of combustion is given in the YouTube video
http://www.youtube.com/watch?v=oeQTFpuC5Jc.
More sites on digestion
This site from Colorado State University is a comprehensive look at digestion, enzymes
and other chemical components.
(http://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion/pregastric/index.html)
How Stuff Works has a site on digestion including major nutrients, processes, diseases
and references for further study. (http://science.howstuffworks.com/life/human-biology/digestivesystem4.htm)
This site from Great Britain details each organ of the digestive system and also includes
a video. (http://www.biology-innovation.co.uk/pages/human-biology/the-digestive-system/)
KidsHealth from Nemours also describes each organ in the digestive system in simple
language. (http://kidshealth.org/kid/htbw/digestive_system.html)
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The George Matelja Foundation stresses nutritional and digestive health. Along with a lot
of background information, this site has a simulation, with explanations, of the digestive
process. (http://www.whfoods.com/genpage.php?tname=faq&dbid=16)
This site, from the National Institutes of Health “National Digestive Diseases
Clearinghouse”, gives a complete review of digestion:
http://digestive.niddk.nih.gov/ddiseases/pubs/yrdd/.
More sites on mitochondria
For an excellent animated tutorial on how mitochondria function, see
http://www.johnkyrk.com/mitochondrion.swf.
More is being learned about the functioning of mitochondria and how they are related to
disease. See the Mitochondria Research Society at http://www.mitoresearch.org/ and the United
Mitochondrial Disease Foundation at
http://www.umdf.org/site/c.8qKOJ0MvF7LUG/b.7934627/k.3711/What_is_Mitochondrial_Diseas
e.htm.
The Molecular Expressions site at Florida State University has background information
on mitochondria: http://micro.magnet.fsu.edu/cells/mitochondria/mitochondria.html.
More sites on the automobile
This site has a comprehensive review of the influence of the automobile on America:
http://www.autolife.umd.umich.edu/Environment/E_Overview/E_Overview1.htm.
“How Stuff Works” has a Web site that explains internal combustion:
http://auto.howstuffworks.com/engine1.htm.
Lawrence Livermore National Laboratory has a unit studying energy in the internal
combustion engine: https://www-pls.llnl.gov/?url=science_and_technology-chemistrycombustion.
This University of Southern California site provides background on the internal
combustion engine, including some history:
http://ronney.usc.edu/whyicengines/WhyICEngines.pdf.
The Ford Motor Company Design Team created a video animation on how an internal
combustion engine is built and operates. (http://www.youtube.com/watch?v=OXd1PlGur8M)
This page of animated engines includes the internal combustion engine:
http://www.animatedengines.com/.
Kennesaw State University produced this ChemCase on Fuels and Society:
http://chemcases.com/fuels/index.htm.
More sites on catalysts and enzymes
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This site is the chapter on enzymes from the textbook “The Chemical Basis For Life.”
(http://www.dpcdsb.org/nr/rdonlyres/aa7c3798-2373-463a-af7a43268fad5d4f/56413/b12st1069.pdf)
The University of California at Davis has this Web site explaining catalytic converters:
http://chemwiki.ucdavis.edu/Physical_Chemistry/Kinetics/Case_Studies/Catalytic_Converters.
This lab procedure gives a detailed explanation of how enzymes help to digest
carbohydrates, fats and proteins.
(http://www.indiana.edu/~nimsmsf/P215/p215notes/LabManual/Lab12.pdf)
More sites on the liver
This extensive and detailed Web site explains the biochemistry of the liver.
(http://www.siumed.edu/~dking2/erg/liver.htm)
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