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Landmark Lesson Plan:
Joseph Priestley, Discoverer of Oxygen
Grades: 9-12
Subject areas: Chemistry and History
Based on “Joseph Priestley House,” a National Historic Chemical Landmark
The following inquiry-based student activities are designed for use in high school lesson planning. The handout and
activities will help students understand how chemistry was practiced during Joseph Priestley’s time (1733-1804),
developments leading to the discovery of oxygen, the historical context of scientific discoveries made at this time, and
related developments in chemistry that took place during the late 1700s and early 1800s.
The activities are designed as a ready-to-go lesson, easily implemented by a teacher or his/her substitute to
supplement a unit of study. In chemistry, the activities relate to identifying physical and chemical properties,
nomenclature, and the scientific process. In history, the themes are the chronology of scientific discoveries and the
relationships between England, France and America in the late 1700s.
All resources are available online at www.acs.org/landmarks/lessonplans
.
While these activities are thematically linked, each is designed to stand alone as an accompaniment for the handout.
Teachers may choose activities based on curricular needs and time considerations.
Take a few minutes to introduce the lesson with a few conversation starters. What historical events were
occurring between 1750 and 1800? Who are some major scientists in history, and what did they discover (Isaac
Newton’s Law of Universal Gravitation; Nicolaus Copernicus’ demonstration of the sun as center of the solar
system; Marie Curie’s theory of radioactivity and discovery of radium and polonium)? How have science and
society evolved in the last 10, 50, 100, 250 years?
Distribute the Activities selected for the class.
Have students read the handout on Joseph Priestley, Discoverer of Oxygen.
After class use the Answer Guide for student feedback and discussion.
Student Activities with Objectives
Anticipation Guide for Handout on “Joseph Priestley, Discoverer of Oxygen” (10-20 min.)
• Students read the handout and explore their own ideas about chemical discoveries
made in the 1700s that are fundamental to the modern chemical sciences.
History Exercise: Chronology of the Discovery of Gases (10-15 min.)
• Students chronologically order events in the reading.
• Students recognize the different names and properties of common gases when they
were first being examined in the 1700s.
Exploring the Scientific Process (25-30 min.)
• Students analyze information from the reading and relate it to scientific processes.
Properties of Oxygen Gas (15-20 min.)
• Students categorize properties of oxygen gas as chemical or physical.
• Students determine the importance of the properties of oxygen gas in identifying it as
an element.
Nomenclature Exercise (10-15 min.)
• Students use inductive reasoning to discover a rule for naming compounds that
contain oxygen.
American Chemical Society | National Historic Chemical Landmarks
Discover more stories and activities about chemistry’s history at www.acs.org/landmarks.
Joseph Priestley, Discoverer of Oxygen
Some 2,500 years ago, the ancient Greeks identified air—along with earth, fire and water—as one of
the four elemental components of creation. That notion may seem charmingly primitive now, but it
made excellent sense at the time. The idea persisted until the 1700s and might have endured even
longer had it not been for a free-thinking English chemist and maverick theologian named Joseph
Priestley, who discovered the gas we now know as oxygen in 1774.
Early Beliefs about Air
In the mid-1700s—the time of
the Industrial Revolution—the
concept of an element was still
evolving. Scientists had
distinguished no more than two
dozen or so elements.
However, it wasn't clear how air
fit into that system. Nobody knew
what air was.
The most pressing issue in
chemistry and physics at this
time was to determine what
exactly happens when
something burns. The prevailing
theory was that flammable
materials contained a substance
called “phlogiston” (from the
Greek word for “burn”) that was
released during combustion.
For example, the theory held that
when a candle burned,
phlogiston was transferred from
it to the surrounding air. When
the air became saturated with
phlogiston and could contain no
more, the flame went out.
Breathing, too, was a way to
remove phlogiston from a body.
A typical test for the presence of
phlogiston was to place a mouse
in a container and measure how
long it lived. When the air in the
container could accept no more
phlogiston, the mouse would die.
Emerging Understanding
British chemists were especially
prolific in studying air. In 1754,
Joseph Black identified what he
called "fixed air" (now known as
carbon dioxide) because it could
be returned, or fixed, into the sort
of solids from which it was
produced. In 1766, Henry
Cavendish produced “flammable
air,” a gas which Lavoisier would
name hydrogen, from the Greek
words for "water maker."
In 1772, Daniel Rutherford found
that when he burned material in
a bell jar, then absorbed all the
"fixed air” by soaking it up with a
substance called potash, a gas
remained. Rutherford dubbed it
"noxious air" because it
asphyxiated mice placed in it.
Today, we call it nitrogen.
Priestley’s Investigations
The next major discovery came
from Joseph Priestley.
Priestley systematically analyzed
the properties of different "airs"
using the favored apparatus of
the day: an inverted container on
a raised platform that could
capture the gases produced by
various experiments below it.
The container could also be
placed in a pool of water or
mercury, effectively sealing it.
Within the container further tests
could be done to determine if a
gas would sustain a flame or
support life.
In the course of these
experiments, Priestley made an
enormously important
observation: A flame would
extinguish itself and a mouse
would suffocate when placed in
the sealed jar. However, putting
a green plant in the jar and
exposing it to sunlight would
"refresh" the air, permitting the
flame to burn and the mouse to
breathe. Perhaps, Priestley
wrote, "the injury which is
continually done by such a large
number of animals is, in part at
least, repaired by the vegetable
creation." Thus he observed that
plants release oxygen into the
air—the process known to us as
photosynthesis.
Laboratory equipment used
by Priestley in the 1700s.
American Chemical Society | National Historic Chemical Landmarks
Discover more stories and activities about chemistry’s history at www.acs.org/landmarks.
Discovery of Oxygen
On August 1, 1774, Priestley
conducted his most famous
experiment. Using a 12-inch-
wide glass lens, he focused
sunlight on a lump of mercuric
oxide in an inverted glass
container placed in a pool of
mercury. The colorless, odorless,
and tasteless gas emitted from
the lump caused a flame to burn
intensely and kept a mouse alive
about four times as long as a
similar quantity of air.
Priestley called his discovery
"dephlogisticated air" on the
theory that it supported
combustion so well because it
had no phlogiston in it. Hence it
could absorb the maximum
amount during burning.
Whatever the gas was called, its
effects were remarkable. "The
feeling of it in my lungs,"
Priestley wrote, "was not
sensibly different from that of
common air, but I fancied that
my breast felt peculiarly light and
easy for some time afterwards.
Who can tell but that in time, this
pure air may become a
fashionable article in luxury.
Hitherto only two mice and
myself have had the privilege of
breathing it."
The Chemical Revolution
Shortly after his discovery,
Priestley visited France and met
Antoine Lavoisier, another
scientist investigating gases.
It turned out that
“dephlogisticated air” was the
clue Lavoisier needed to develop
his theory of chemical
reactions—the "revolution" in
chemistry that would finally
dispel the phlogiston theory.
Burning substances, Lavoisier
argued, did not give off
phlogiston; they took on
Priestley’s gas. Lavoisier called
the gas "oxygen" from the Greek
word for acid-maker, because it
combines with non-metals to
produce acids.
Joseph Priestley
Joseph Priestley was born in
Yorkshire, England, in 1733.
Around the age of 19, he was
encouraged to study for the
ministry. And study, as it turned
out, was something Joseph
Priestley did very well.
Aside from what he learned in
the local schools, he taught
himself Latin, Greek, French,
Italian, German and a smattering
of Middle Eastern languages,
along with mathematics and
philosophy. This preparation
would have been ideal for study
at Oxford or Cambridge, but as a
Dissenter (someone who was
not a member of the Church of
England) Priestley was barred
from England's great universities.
Instead, he enrolled at Daventry
Academy, a celebrated school
for Dissenters. After graduation,
he supported himself, as he
would for the rest of his life, by
teaching, tutoring and preaching.
In 1773, the Earl of Shelburne
asked Priestley to serve as a sort
of intellectual companion, tutor
for the earl's offspring, and
librarian for his estate. The
position provided access to
social and political circles
Priestley could never have
gained on his own, while leaving
ample free time for the research
that would earn him a permanent
place in scientific history.
Despite his scientific successes,
Priestley still suffered for his
religious beliefs. In 1780 he was
asked to leave the estate.
Priestley’s unorthodox religious
writings and support for the
American and French revolutions
so enraged his countrymen that
he and his wife were forced to
flee England.
Joseph and Mary set sail for
America on April 8, 1794. They
built a house in the town of
Northumberland, Pennsylvania,
to be near their sons.
There Priestley continued his
research, isolating carbon
monoxide (which he called
"heavy inflammable air") and
founding the Unitarian Church in
the United States. For the most
part, he led a quiet and reflective
life—especially after his friend
Thomas Jefferson was elected
president in 1800.
On February 3, 1804, Priestley
began an experiment, but found
himself too weak to continue. He
went to his bed in his library,
never again to emerge. On
February 6, he summoned one
of his sons and an assistant. He
dictated some changes in a
manuscript.
When he was satisfied with the
revisions, he said "That is right. I
have now done." Minutes later
he died painlessly, ending what
Jefferson called "one of the few
lives precious to mankind."
Joseph Priestley, 1783.
Student Name: ________________________________________ Date: _______________ Period: ______
Anticipation Guide for Handout on Joseph Priestley, Discoverer of Oxygen
Before reading the handout, consider the statements below. In the first column, write “A” or “D” to indicate your
agreement or disagreement with each statement.
As you read the handout, compare your thoughts with information from the article, writing “T” or “F” to indicate whether
the statement is true or false. Write notes from the reading that support or refute the statement in the spaces below.
Me Text Statement
In the early 1700s, scientists understood the composition of air.
In the early 1700s, scientists understood why things burn.
Oxygen was discovered before 1800.
Priestley gave his discovery the name oxygen.
Priestley understood the chemical changes involved when things burn.
Priestley was a devout member of the Church of England.
Priestley discovered carbon monoxide.
Priestley moved to America seeking religious and political freedom.
Priestley founded the Unitarian church in the United States.
Priestley was primarily a scientist.
Student Name: ________________________________________ Date: _______________ Period: ______
History Exercise: Chronology of the Discovery of Gases
1. Using the handout provided, put the following historical events in chronological order, from earliest to latest. Provide
the year of the event, if known.
Order Year Event
a. Priestley discovers oxygen gas.
b. Priestley visits Antoine Lavoisier in France.
c. Priestley discovers carbon monoxide.
d. Priestley attends Daventry Academy.
e. Priestley begins working for the Earl of Shelburne.
f. Priestley flees England for the United States.
2. Using the handout provided and other resources, answer the following questions.
a. What period in modern history was happening in Europe and America at the time of Priestley’s discoveries?
b. What was the relationship between the United States and England at the time of Priestley’s discoveries?
c. How does Priestley’s work relate to the French Revolution?
3. Use information from the reading to complete the table below.
Name of gas today Year of discovery
Common name at the time
of discovery
Carbon dioxide
Hydrogen
Oxygen
Nitrogen
Carbon monoxide
Student Name: ________________________________________ Date: _______________ Period: ______
Exploring the Scientific Process
Refer to the reading about the discovery of oxygen by Joseph Priestley. As with all scientific information, especially new
discoveries, you should think about:
• What do we know? How do we know it? What is the evidence? Why should we care?
1. Beginning Ideas: What was Priestley trying to find out?
2. Tests: How did he try to find out? What did he do?
3. Observations: How did Priestley know that what he discovered was different from ordinary air?
4. Claims: What did Priestley claim?
5. Evidence: What evidence was there to support his claim?
6. More Evidence: How did Priestley’s work come to be accepted by the scientific community? What other scientists
replicated his work? How did they help interpret Priestley’s work?
7. Reflection: Did Priestley’s discovery overturn some popular theories of the day? Please explain.
8. Your Reflection: Why was Priestley’s discovery important? Why should we care about Priestley’s discovery today?
Student Name: ________________________________________ Date: _______________ Period: ______
Properties of Oxygen Gas
Use the handout provided to list chemical and physical properties of oxygen gas in the chart below. Think about how
the properties were useful in isolating oxygen gas and determining its importance.
Physical Properties Importance or Significance in Priestley’s Discovery
Chemical Properties Importance or Significance in Priestley’s Discovery
Student Name: ________________________________________ Date: _______________ Period: ______
Nomenclature Exercise
Use the hints provided to study the formulas and names of oxygen-containing compounds below. Mark your
observations in the column provided. Hints:
• How many elements are in each compound?
• Do all of the names contain “ox” or “oxi”?
• What is similar about the suffixes?
Compound Name Observations
MgO Magnesium oxide
MgSO
4
Magnesium sulfate
MgSO
3
Magnesium sulfite
K
2
O Potassium oxide
KClO
4
Potassium perchlorate
KClO
3
Potassium chlorate
KClO
2
Potassium chlorite
KClO Potassium hypochlorite
Na
2
SO
4
Sodium sulfate
Na
2
SO
3
Sodium sulfite
Now, using your observations, try to formulate a “rule” for how to name compounds containing oxygen.
Joseph Priestley, Discoverer of Oxygen Answer Guide
Anticipation Guide
Me Text Statement
(answers
will vary)
F
In the early 1700s, scientists understood the composition of air.
F
In the early 1700s, scientists understood why things burn.
T
Oxygen was discovered before 1800.
F
Priestley gave his discovery the name oxygen.
F
Priestley understood the chemical changes involved when things
burn.
F
Priestley was a devout member of the Church of England.
T
Priestley discovered carbon monoxide.
T
Priestley moved to America seeking religious and political freedom.
T
Priestley founded the Unitarian church in the United States.
F
Priestley was primarily a scientist.
Joseph Priestley, Discoverer of Oxygen Answer Guide
History Exercise: Chronology of the Discovery of Gases
1. Using the handout provided, put the following historical events in chronological order, from earliest to latest. Provide
list the year of the event, if known.
Order Year Event
a. 3 1774
Priestley discovers oxygen gas.
b. 4 no date Priestley visits Antoine Lavoisier in France.
c. 6 no date Priestley discovers carbon monoxide.
d. 1 no date Priestley attends Daventry Academy.
e. 2 1773 Priestley begins working for the Earl of Shelburne.
f. 5 1794 Priestley flees England for the United States.
2. Using the handout provided and other resources, answer the following questions.
a. What major events in history were happening in Europe and America at the time of Priestley’s discoveries?
The Industrial Revolution (circa 1750-1850), the American Revolution (1774-1783), and the French
Revolution (1789-1799).
b. What was the relationship between the United States and England at the time of Priestley’s discoveries?
Priestley’s discovery of oxygen in 1774 took place during the beginning of the American Revolution,
when colonists separated from England and founded the United States of America.
c. How does Priestley’s work relate to the French Revolution?
Priestley visited Lavoisier in France following his discovery of oxygen in 1774. Priestley supported the
French Revolution.
3. Use information from the reading to complete the table below.
Name of gas
today
Year of discovery
Common name at the time
of discovery
Person who first isolated
the gas
Carbon dioxide
1754 Fixed air Joseph Black
Hydrogen
1766 Flammable air Henry Cavendish
Oxygen
1774 Dephlogisticated air Joseph Priestley
Nitrogen
1772 Noxious air Daniel Rutherford
Carbon
monoxide
Between 1794
and 1804
Heavy inflammable air Joseph Priestley
Joseph Priestley, Discoverer of Oxygen Answer Guide
Exploring the Scientific Process
Refer to the reading about the discovery of oxygen by Joseph Priestley. As with all scientific information, especially new
discoveries, you should think about:
1. Beginning Ideas: What was Priestley trying to find out?
He was examining different “airs.”
2. Tests: How did he try to find out? What did he do?
He used a magnifying lens to focus sunlight on mercuric oxide placed in an inverted glass container (bell
jar) in a pool of water or mercury.
3. Observations: How did Priestley know that what he discovered was different from ordinary air?
The gas caused a flame to burn intensely, and kept a mouse alive about four times longer than ordinary
air. Priestley noticed that he felt different when he breathed it.
4. Claims: What did Priestley claim?
He claimed that the gas had no phlogiston in it.
5. Evidence: What evidence was there to support his claim?
His observations about the flame, mouse, and his own breathing, based on the phlogiston theory.
6. More Evidence: How did Priestley’s work come to be accepted by the scientific community? What other scientists
replicated his work? How did they help interpret Priestley’s work?
Priestley visited Lavoisier in France. Lavoisier realized that when substances burn they combine with
oxygen.
7. Reflection: Did Priestley’s discovery overturn some popular theories of the day? Please explain.
Yes, the phlogiston theory was abandoned after Lavoisier’s explanation of burning.
8. Your Reflection: Why was Priestley’s discovery important? Why should we care about Priestley’s discovery today?
Individual answers will vary.
Joseph Priestley, Discoverer of Oxygen Answer Guide
Properties of Oxygen Gas
Use the handout provided to list chemical and physical properties of oxygen gas in the chart below. Think about how
the properties were useful in isolating oxygen gas and determining its importance.
Physical Properties Importance or Significance in Priestley’s Discovery
Does not dissolve easily in
water or mercury
Priestley collected oxygen gas over water and mercury.
Colorless Made it difficult to detect.
Odorless Made it difficult to detect.
Tasteless Made it difficult to detect.
Chemical Properties Importance or Significance in Priestley’s Discovery
Produced by green plants Priestley observed photosynthesis, but did not explain it.
Permits candles to burn A candle burned longer in oxygen gas than in air.
Can be breathed by animals Priestley and mice breathed oxygen gas without harm.
Combines with non-metals to
produce acids
Lavoisier named oxygen after the Greek word for acid-maker.
Joseph Priestley, Discoverer of Oxygen Answer Guide
Nomenclature Exercise
Use the hints provided to study the formulas and names of oxygen-containing compounds below. Mark your
observations in the column provided. Hints:
• How many elements are in each compound?
• Do all of the names contain “ox” or “oxi”?
• What is similar about the suffixes?
Compound Name
Observations
MgO Magnesium oxide
2 elements; ends in –ide
MgSO
4
Magnesium sulfate
3 elements; ends in –ate
MgSO
3
Magnesium sulfite
3 elements; ends in –ite
K
2
O Potassium oxide
2 elements; ends in –ide
KClO
4
Potassium perchlorate
3 elements; ends in –ate
KClO
3
Potassium chlorate
3 elements; ends in –ate
KClO
2
Potassium chlorite
3 elements; ends in –ite
KClO Potassium hypochlorite
3 elements; ends in –ite
Na
2
SO
4
Sodium sulfate
3 elements; ends in –ate
Na
2
SO
3
Sodium sulfite
3 elements; ends in –ite
Now, using your observations, try to formulate a “rule” for how to name compounds containing oxygen. Possible
answers:
If the name ends in –ide, the compound contains two elements and includes “ox” in the name.
If the name ends in –ite or –ate, the compound contains three elements, including oxygen, and does not
include “ox” in the name.
The difference between –ite endings and –ate endings is difficult to determine, but if you know the –ate
formula, the –ite compound has one less oxygen atom.