The AtmosphereWhat Is It?
Name: ___________________________________________________
Section: __ Date: _________
Introduction
It would be among the most profound discoveries in the history of our species
if we could detect life on other planets circling other stars in the galaxy. Whether
the life turns out to be intelligent, technological, or simply microbial, such a
discovery would provide evidence that we are not alone, that life (in one form or
another) is widespread in a universe that suddenly seems less stark and empty.
How might we detect such distant life? Not likely with fleets of starships. The
energies required for star travel (barring a science-fiction style warp drive) are
simply too great and travel times too long. Instead, sophisticated ground and
space-based telescopes are being used to detect planets of nearby star systems.
How planets block the light of their star as detected from Earth can reveal the
chemical composition of the
planet's atmosphere. Some
scientists believe that the
chemical composition of the
planet's atmosphere will provide
evidence of the presence of life.
How is this possible? How can
simple gases tell us about the
presence or absence of life as we
know it? To answer that, we must
look at our own planet.
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Earth has a radius of some 6400 km.
Ninety-nine percent of the earth's
atmosphere is contained within a layer
approximately 50 km thick. Life on
earth inhabits a layer no more than 9
km thick, extending from a bare few
kilometers above sea level (airborne
organisms and life on mountains) to a
few kilometers below (deep ocean basin
creatures and subterranean microbial
communities).
The biosphere is the portion of earth in which all known life forms exist. It
occupies a thin layer of air (atmosphere), water (hydrosphere), and land
(lithosphere).
Cycles
Just as we earthly organisms require a source of energy, water, and the
chemical components of our bodies, so too does the entire global biosphere. These
services are provided to the biosphere by global energy and chemical cycles.
Most people are familiar with the concepts of cycles—that certain substances
move endlessly throughout the
earth's biosphere, hydrosphere,
atmosphere, and lithosphere,
existing in different forms and
being used by different
organisms at different times,
but always moving, always
circulating. Most of your
students are probably familiar
with the water cycle. Water, in its different forms, cycles continuously through
the lithosphere, hydrosphere, atmosphere, and biosphere.
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Water evaporates into the atmosphere from the land and the sea. Plants and
animals use and reuse water and release water vapor into the air. Once in the air,
water vapor circulates and can condense to form clouds and precipitation, which
fall back to earth. At one time or another, all of the water molecules on earth have
been in an ocean, a river, a plant, an animal, a cloud, a raindrop, a snowflake, or a
glacier!
In addition to water, many other substances such as nitrogen, oxygen, and
carbon cycle through the earth and atmosphere. These cycles are important to
individual animals and plants and even to entire ecosystems. But we're less familiar
with the notion that these cycles fundamentally influence the planet as a whole,
dramatically and unmistakably altering the earth's atmosphere. When you think
about it, this influence only makes sense. The atmosphere is the greatest, fastest,
and most reliable global transport system we
have.
Inject almost any stable gaseous material
into the atmosphere and before long it is
spread worldwide. For example, the graphic
below shows how the smoke and ash plume from
the eruption of Mt. Spurr in Alaska spread and
moved over a 4-day period, as detected by satellite imagery. During that time, the
original plume was carried rapidly eastward from Alaska and spread over an area
many times its original size.
Because cycles require the movement of
substances, what better conveyor belt to use than
the atmosphere? To explain what we mean, let's look
at several important components of the earth's
atmosphere and see how they are influenced by
these cycles.
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Nitrogen (N2) comprises the bulk of the atmosphere (approximately 78%).
Nitrogen cycles slowly through the earth's system. To most of the biosphere,
nitrogen in the atmosphere is like the ocean to a thirsty person—amazingly
abundant but not quite in the right chemical form.
A molecule of nitrogen gas is made up of 2 atoms very tightly bound together.
It takes tremendous amounts of energy, such as produced by lightning or fires, to
break the bond.
Amazingly, an assortment of bacterial species that specialize in taking nitrogen
from the air can also convert nitrogen into different usable forms. These bacteria
also release nitrogen from organic material back into the atmosphere. Nitrogen is
the one element found almost entirely in the atmosphere—there's very little on
land or in the sea. Nitrogen is essential to life, a key element in proteins and DNA.
Oxygen is found in the atmosphere at about 21%. Because it is a reactive
element, it can quickly combine with other elements and disappear from the
atmosphere. It is the cycling of oxygen through photosynthesis (the process by
which plants utilize a combination of sunlight, carbon dioxide and a self-produced molecule,
called, Chlorophyll, to produce a kind of sucrose, or sugar, that is simply, food. Plants are
the only organisms on Earth that can produce their own food) and respiration (breathing)
that accounts for its presence and stability. A world without cycles, without life,
would retain little if any oxygen in its atmosphere.
Oxygen does more than simply move between organisms and the atmosphere.
Some of the atmospheric oxygen ( ) finds itself lofted high into the upper
reaches of the atmosphere called the stratosphere. There, in a series of reactions
powered by solar radiation, it is converted into a new compound, ozone ( ). Ozone
serves to absorb biologically damaging ultraviolet (UV) radiation from the sun. (that
means it keeps us from getting lethal sunburns) Without an ozone layer, the earth's
surface would be bathed in high intensity UV radiation; with an ozone layer, the
amount of UV radiation received at the surface is small.
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Eventually, each ozone molecule will come apart, reform , and may either be
carried elsewhere in the atmosphere or may take part again in the ozone-forming
reactions. Over hundreds of millions of years, these ozone-forming and destroying
reactions have generally been in equilibrium, forming a balanced cycle within
the greater cycle of atmospheric oxygen.
Because oxygen is highly reactive, it does ignite fairly easily. A simple spark will
start a fire that will continue as long as oxygen is available to burn.
Okay, first, let’s understand oxygen. The chemical name is 02. That means,
there are two oxygen atoms bonded together to form a molecule. A molecule is
two or more atoms bonded together. So, in reality, oxygen is not a single atom,
but, rather, two atoms joined together to make a molecule that we call, oxygen, it’s
real name is, dioxide. Di=two, and oxide=oxygen atom.
The Atmosphere in Dynamic Equilibrium
Oxygen and nitrogen are not the only elements that cycle through the
biosphere. Most elements critical to life constantly cycle. This is why earth's
atmosphere can be described as being in a state of dynamic equilibrium. Things are
constantly moving and changing—substances enter and leave the atmosphere,
forming different compounds at different times and in different places.
On earth, the dynamic equilibrium changes with season. For example, in the
spring and summer, growing plants take carbon from the soil and atmosphere. In
the fall and winter, plants release carbon to the soil and the atmosphere. Because
most of the plant life on earth is found in the Northern Hemisphere, there are
global seasonal changes of carbon dioxide in the atmosphere. An atmosphere in
static equilibrium indicates a dead world. All the reactions have taken place and
the elements have found their most stable chemical form. The atmosphere of a
living planet, like ours, is quite different. Unstable, interesting, and improbable
reactions happen all the time,
thanks to cycles!
History
Earth, according to one scientific
theory, is believed to have formed
about 5 billion years ago.
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In the first 500 million years a dense atmosphere emerged from the vapor and
gases were expelled during degassing of the planet's interior. These gases may
have consisted of hydrogen (H2), water vapor, methane (CH4), and carbon oxides.
Prior to 3.5 billion years ago the atmosphere probably consisted of carbon dioxide
(CO2), carbon monoxide (CO), water (H2O), nitrogen (N2), and hydrogen.
The hydrosphere (water world) was formed 4 billion years ago from the
condensation of water vapor, resulting in oceans of water in which sedimentation
(from our rock unit) occurred.
The most important feature of the ancient environment was the absence of
free oxygen. Evidence of this is hidden in early rock formations that contain many
elements, such as iron and uranium. Elements in this state are not found in the
rocks of mid-Precambrian (a fancy word meaning early age of Earth) and younger
ages, less than 3 billion years old.
One billion years ago, early aquatic organisms (water critters) called blue-green
algae began using energy from the Sun to split molecules of H2O and CO2 and
recombine them into organic compounds and molecular oxygen (O2). This solar
energy conversion process is known as photosynthesis. Photosynthesis simply means
plants use sunlight, carbon dioxide, and a molecule in their systems, called,
Chlorophyll, to make food. Plants are the only organisms on Earth that can make
their own food. During this process, the waste produced from this procedure is
expelled back into the air – that waste product is called, oxygen (02).
Some of the photosynthetically created oxygen combined with organic carbon
to recreate CO2 (carbon dioxide) molecules. The remaining oxygen accumulated in
the atmosphere. As oxygen in the atmosphere increased, CO2 decreased.
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Atmospheric Properties
The thin envelope of air that surrounds our planet is a mixture of gases, each
with its own physical properties. The mixture is far from evenly divided. Two
elements, nitrogen and oxygen, make up 99% of the volume of air. The other 1% is
composed of "trace" gases, the most prevalent of which is the inert gaseous
element argon. The rest of the trace gases, although present in only minute
amounts, are very important to life on earth. Two in particular, carbon dioxide and
ozone, can have a large impact on atmospheric processes.
Another gas, water vapor, also exists
in small amounts. It varies in
concentration from being almost nonexistent over desert regions to about 4%
over the oceans. Water vapor is important
to weather production since it exists in
gaseous, liquid, and solid phases and
absorbs radiant energy from the earth.
Structure of the Atmosphere
The atmosphere is divided vertically
into four layers based on temperature:
the troposphere, stratosphere, mesosphere, and thermosphere. Throughout the
Cycles unit, we'll focus primarily on the layer in which we live - the troposphere.
Troposphere
word troposphere comes from tropein,
The
meaning
to turn or change. All of the earth's
weather occurs in the troposphere.
The
troposphere has the following
characteristics.

It extends from the earth's
to an average of 12 km (7 miles).
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

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The pressure ranges from 1000 to 200 millibars (29.92 in. to 5.92 in.).
The temperature generally decreases with increasing height up to the
tropopause (top of the troposphere); this is near 200 millibars or 36,000 ft.
 The temperature averages 15°C (59°F) near the surface and -57°C (71°F) at the tropopause.
 The layer ends at the point where temperature no longer varies with
height. This area, known as the tropopause, marks the transition to
the stratosphere.
Winds increase with height up to the jet stream.
The moisture concentration decreases with height up to the tropopause.
 The air is much drier above the tropopause, in the stratosphere.
The troposphere is 70%
and 21% . The lower density of
molecules higher up would not give us enough
to survive.
 The sun's heat that warms the earth's surface is transported
upwards largely by convection and is mixed by updrafts and
downdrafts.
Atmospheric Processes
In the Cycles overview, we learned
that water is an essential part of
the earth's system. The oceans
cover nearly three-quarters of the
earth's surface and play an
important role in exchanging and
transporting heat and moisture in the atmosphere.
a.) Most of the water vapor in the atmosphere comes from the oceans.
b.) Most of the precipitation falling over land finds its way back to oceans.
c.) About two-thirds returns
to the atmosphere via the
water cycle.
You may have figured out by now
that the oceans and atmosphere
interact extensively. Oceans not
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only act as an abundant moisture source for the atmosphere but also as a heat
source and sink (storage).
The exchange of heat and moisture has profound effects on atmospheric
processes near and over the oceans. Ocean currents play a significant role in
transferring this heat poleward. Major currents, such as the northward flowing
Gulf Stream, transport tremendous amounts of heat poleward and contribute to
the development of many types of weather phenomena. They also warm the climate
of nearby locations. Conversely, cold southward flowing currents, such as the
California current, cool the climate of nearby locations.
Energy Heat Transfer
Practically all of the energy
that reaches the earth comes
from the sun. Intercepted first
by the atmosphere, a small part
is directly absorbed, particularly
by certain gases such as ozone
and water vapor. Some energy is
also reflected back to space by
clouds and the earth's surface.
Energy is transferred between the earth's surface and the atmosphere via
conduction, convection, and radiation.
Conduction is the process by which heat energy is transmitted through contact
with neighboring molecules.
Some solids, such as metals, are good conductors of heat while others, such as
wood, are poor conductors. Air and water are relatively poor conductors.
Since air is a poor conductor, most energy transfer by conduction occurs right
at the earth's surface. At night, the ground cools and the cold ground conducts
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heat away from the adjacent air. During the day, solar radiation heats the ground,
which heats the air next to it by conduction.
Convection transmits heat by transporting groups of molecules from place to place
within a substance. Convection occurs in fluids such as water and air, which move
freely.
In the atmosphere, convection includes large- and small-scale rising and sinking
of air masses and smaller air parcels. These vertical motions effectively distribute
heat and moisture throughout the atmospheric column and contribute to cloud and
storm development (where rising motion occurs) and dissipation (where sinking
motion occurs). A great demonstration is my steam machine. Once the water is
heated and I pull the trigger, watch what happens to the steam. Why?
To understand the convection cells that distribute heat over the whole earth,
let's consider a simplified, smooth earth with no land/sea interactions and a slow
rotation. Under these conditions, the equator is warmed by the sun more than the
poles. The warm, light air at the equator rises and spreads northward and
southward, and the cool dense air at the poles sinks and spreads toward the
equator. As a result, two convection cells are formed.
Meanwhile, the slow rotation of the earth toward the east causes the air to be
deflected toward the right in the
northern hemisphere and toward the
left in the southern hemisphere. This
deflection of the wind by the earth's
rotation is known as the Coriolis
effect.
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Radiation is the transfer of heat energy without the involvement of a physical
substance in the transmission. Radiation can transmit heat through a vacuum.
Atmospheric Processes – Radiation
Heat Transfer
Practically all of the energy that reaches the earth comes from the sun.
Intercepted first by the atmosphere, a small part is directly absorbed, particularly
by certain gases such as ozone and water vapor. Some energy is reflected back to
space by clouds and the earth's surface. Most of the radiation, however, is
absorbed by the surface.
Energy is transferred between the earth's surface and the
atmosphere in a variety of ways, including
radiation, conduction, and convection. The
graphic below uses a campstove to summarize
the various mechanisms of heat transfer. If
you were standing next to the campstove, you
would be warmed by the radiation emitted by
the gas flame. A portion of the radiant energy
generated by the gas flame is absorbed by the
frying pan and the pot of water. By the process
of conduction, this energy is transferred
through the pot and pan. If you reached for the metal handle of the frying pan
without using a potholder, you would burn your fingers!
As the temperature of the water at the bottom of the pot increases, this layer
of water moves upward and is replaced by cool water descending from above. Thus
convection currents that redistribute the newly acquired energy throughout the
pot are established.
As in this simple example using a campstove, the heating of the earth's
atmosphere involves radiation, conduction, and convection, all occurring
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simultaneously. A basic tenet of meteorology is that the sun warms the ground and
the ground warms the air. In this activity, we will focus on radiation, the process
by which the sun warms the ground. Energy from the sun is the driving force
behind weather and climate, and ultimately, life on earth.
Radiation
What do trees, snow, cars, horses, rocks, centipedes, oceans, the atmosphere,
and you have in common? Each one is a source of radiation to some degree. Most of
this radiation is invisible to humans but that does not make it any less real.
Radiation is the transfer of heat energy by electromagnetic wave motion. The
transfer of energy from the sun across nearly empty space is accomplished
primarily by radiation. Radiation occurs without the involvement of a physical
substance as the medium. The sun emits many forms of electromagnetic radiation
in varying quantities.
About 43% of the total radiant energy emitted from the sun is in the visible
parts of the spectrum (A rainbow of colors). The bulk of the remainder lies in the
near-infrared (49%) and ultraviolet section (7%). Less than 1% of solar radiation is
emitted as x-rays, gamma waves, and radio waves.
A perfect radiating body emits energy in all possible wavelengths, but the wave
energies are not emitted equally in all wavelengths; a spectrum will show a distinct
maximum in energy at a particular wavelength depending upon the temperature of
the radiating body. As the temperature increases, the maximum radiation occurs at
shorter and shorter wavelengths.
The hotter the radiating body, the shorter the wavelength of maximum
radiation. For example, a very hot metal rod will emit visible radiation and produce
a white glow.
On cooling, it will emit more of its energy in longer wavelengths and will glow a
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reddish color. Eventually no light will be given off, but if you place your hand near
the rod, the infrared radiation will be detectable as heat.
Darker-colored objects absorb more visible radiation, whereas lighter-colored
objects reflect more visible radiation. That's why we usually choose light-colored
clothing on really hot days.
Every surface on earth absorbs and reflects energy at varying degrees, based
on its color and texture.
Atmospheric Processes — Conduction
Background
Conduction is one of the ways that energy is
transferred from the earth's atmosphere to the
air. Conduction is the process by which heat
energy is transmitted through collisions
between neighboring molecules.
Think of a frying pan set over an open camp stove.
The fire's heat causes molecules in the pan to vibrate faster, making it hotter.
These vibrating molecules collide with their neighboring molecules, making them
also vibrate faster. This process continues until the entire pan has heated up due
to the vibrating and colliding molecules. If you've ever touched the metal handle of
a hot pan without a potholder, you have first-hand experience with heat
conduction!
Some solids, such as metals, are good heat conductors, while others, such as
wood, are poor conductors. Air and water are relatively poor conductors and thus
are called insulators. Not surprisingly, many pots and pans have insulated handles.
What does conduction have to do with the
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atmosphere? Air is a poor conductor of heat energy but a good insulator. Imagine
that you're a mountaineer, climbing Mt. Everest. Near the summit, you'll probably
be wearing a thick down jacket and pants to guard against the extreme cold.
It's not the down itself that keeps you warm. Rather, it's the enormous number
of tiny air spaces trapped between the down filaments that retard the conduction
of heat from your body out to the frigid environment. If air were not such a good
insulator, no amount of down would allow survival under such conditions.
Because air is such a poor energy conductor, large vertical temperature
gradients can exist near the ground, particularly on clear and windless days. On
such days, the land surface may experience a great deal of heating, as direct solar
radiation is absorbed and converted to infrared radiation (heat energy). However,
a series of thermometers mounted at different heights above the ground would
reveal that air temperature falls off rapidly with height due to the poor
conductivity of air.
Atmospheric Processes — Convection
Background
Heat moves in fluids through several processes, including convection. Convection
is the transfer of heat by the actual movement of the heated material.
Any substance that flows is considered a fluid. This includes such things as
water, shampoo, sunscreen, and even honey. Although not necessarily obvious, even
gases, such as air, can be classified as fluids.
Consider what happens to the water in a pot as it is heated over an open camp
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stove.
The water at the bottom of the pot heats up first. This causes it to expand.
Since the warmed water has a lower density than the water around it, it rises up
through the cooler, dense water. At the top of the pot, the water cools, increasing
its density, which causes it to sink back down to the bottom.
This up and down movement eventually heats all of the water. The continual
cycling of the fluid is called a convection current.
Convection currents are found in many places and on many scales, from huge
convection currents in the atmosphere, oceans, and even in the earth's interior to
smaller convection currents found in a cup of hot cocoa or a fish tank.
Meteorologists usually use "convection" to refer to up and down motions of air.
Heat gained by the lowest layer of the atmosphere from radiation or conduction is
most often transferred by convection.
A Return to the Composition of the Atmosphere
Nitrogen makes up 78% of our atmosphere, while Oxygen makes up another
21%. But, what about the remaining 1%?
Well, there’s Argon - 0.9% - Used in light bulbs. Carbon Dioxide - 0.03% Plants use it to make oxygen. Acts as a blanket and prevents the escape of heat
into outer space. Scientists are afraid that the burning of fossil fuels such as coal
and oil are adding more carbon dioxide to the atmosphere. Trace gases - gases
found only in very small amounts. They include neon, helium, krypton, and xenon.
Finally, also in the air is, Water Vapor - 0.0 to 4.0% Essential for life processes. Also prevents heat loss from
the earth.
Structure
The Atmosphere is divided into layers according to
major changes in temperature. Gravity pushes the layers
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of air down on the earth's surface. This push is called air pressure. 99% of the
total mass of the atmosphere is below 32 kilometers.
Troposphere - 0 to 12 km - Contains 75% of the gases in the atmosphere.
This is where you live and where weather occurs. As height increases,
temperature decreases. The temperature drops about 6.5 degrees Celsius
for every kilometer above the earth's surface.
Tropopause - located at the top of the troposphere. The temperature
remains fairly constant here. This layer separates the troposphere
from the stratosphere. We find the jet stream here. These are very
strong winds that blow eastward.
Stratosphere - 12 to 50 km - in the lower part of the stratosphere. The
temperature remains fairly constant (-60 degrees Celsius). This layer contains the
ozone layer. Ozone acts as a shield for in the earth's surface. It absorbs
ultraviolet radiation from the sun. This causes a temperature increase in the upper
part of the layer.
Mesophere - 50 to 80 km - in the lower part of the stratosphere. The
temperature drops in this layer to about -100 degrees Celsius. This is the coldest
region of the atmosphere. This layer protects the earth from meteoroids. They
burn up in this area.
Thermosphere - 80 km and up - The air is very thin. Thermosphere means
"heat sphere". The temperature is very high in this layer because ultraviolet
radiation is turned into heat. Temperatures often reach 2000 degrees Celsius or
more. This layer contains:
Ionosphere - This is the lower part of the thermosphere.
It extends from about 80 to 550 km. Gas particles absorb
ultraviolet and X-ray radiation from the sun.
The particles of gas become electrically charged (ions).
Radio waves are bounced off the ions and reflect waves back to
earth. This generally helps radio communication. However, solar
flares can increase the number of ions and can interfere with the
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transmission of some radio waves.
Exosphere - the upper part of the thermosphere. Extends from
about 550 km for thousands of kilometers. Air is very thin here.
This is the area where satellites orbit the earth.
Magnetosphere - the area around the earth that extends beyond the
atmosphere. The earth's magnetic field operates here. It begins at
about 1000 km. It is made up of positively charged protons and
negatively charged electrons. This traps the particles that are given
off by the sun. They are concentrated into belts or layers called the
Van Allen radiation belts. The Van Allen belts trap deadly radiation.
When large amounts are given off during a solar flare, the particles collide with
each other causing the aurora borealis or the northern lights.
Name the first gases that made-up the Atmosphere
Name the gases and percentages of those gases present in today’s atmosphere
Name the three ways energy can be transferred.
Give one example of each way.
a.
b.
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c.
Purpose:
You will describe the development of the atmosphere from the past to the
present and predict the state of the future atmosphere.
Procedure:
Study the History of the Atmosphere and Composition of the Atmosphere and
become knowledgeable about the past and present composition of the atmosphere.
Either you or your parents are following the news about our environment. If
you don’t know, ask them, about what is going on with global warming, polar ice
melting, the price of gasoline and oil. . . After examining the state of our present
atmosphere, predict what you think our atmosphere will be like in the year 2025.
Will it be the same?
worse?
better?
What makes you think this? Please explain in at least 5-7 sentences.
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Use Your Own Paper—two class periods
Imagine that you are the sun, a water molecule, or a rock. You have been around
since the earliest atmosphere. Choose one of the following to describe the changes
and the experiences you have encountered. Make a prediction about the future
atmosphere based on your recent experiences.
A. An Illustrated Poem





Must describe the development of the present atmosphere and
predict the future atmosphere
Must use ALL words (History of the Atmosphere)
Must contain at least 24 lines
Words must rhyme
At least one illustration per 8 lines
B. A Comic Strip





Must describe the development of the present atmosphere and
predict the future atmosphere
Must use ALL words (History of the Atmosphere)
Must have at least eight frames
Must have a cartoon picture for each frame
Each frame must have a caption or dialogue box
C. An Illustrated Story


Must describe the development of the present atmosphere and
predict the future atmosphere
Must use ALL words (History of the Atmosphere)
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

Must have at least three parts to the story: past,
present, and future
Must have at least one illustration per part
Grading for poem, comic strip or story – Counts as a test grade.
Criteria
Possible Points
Followed directions
20
Content:
Correct and Clear
40
Neat, Attractive
20
Earned Points
and Colorful
Creative
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Finding the Percentage of Oxygen in the Atmosphere
Experiment:
Since you cannot see the air you want to measure, we will substitute water.
Engagement:
We will use a sealed container to measure the volume of oxygen in a given air
sample.
Materials:








Shallow glass bowl
Birthday candle mounted on a penny
graduated cylinder
matches or lighter
pencil to mark the test tube
test tube and tongs (test tube holder)
water
safety goggles
To Conduct the Experiment
1. Fill the test tube with water. It should reach the rim of the test tube. Pour
the water into the graduated cylinder to measure the volume of water that fills
a test tube.
Total Test Tube Volume: ____ mL or cc? Have Mr. Z initial.
The volume of the test tube when you measured to the top of the test tube rim
is the total volume of the test tube. That means, the filled test tube
represents all the gases of the atmosphere.
2. Now, pour the water from the graduated cylinder into the shallow bowl. Place
the candle with the penny, in the center of the bowl -- be careful not to get the
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candlewick wet.
3. Take the test tube and attach the tongs (test tube holder). The tongs are
scissor-like, so you squeeze them to open the tongs to hold the test tube.
4. Practice inverting the test tube so the opening will go over the candle in the
bowl, quickly lower the test tube over the candle and stop when the test tube
touches the water to form a seal. You must do this maneuver very, very
quickly to trap air inside the test tube.
5. Remember, do not touch the bottom of the bowl with the test tube.
6. When you are able to lower the test tube over the candle and touch the water
without touching the bowl, you are ready to conduct the experiment.
7. Light the candle, wait for the flame to get established, then, lower the test
tube over the candle and onto the water.
8. As the candle uses the oxygen in the test tube, the candle will go out and water
will be drawn into the tube to replace the oxygen. (mark the water level in the test
tube with your pencil, just enough so you can see the waterline. Do not use a marker.)
9. Now, fill the test tube with water to the mark you made on the test tube.
Notice that you are not replacing all the water with which you started.
10. Pour the water from the test tube into a graduated cylinder and measure the
volume. Remember, we are using water as a substitute for air. So, the volume
of air in the test tube represents the volume of air, minus oxygen. The oxygen
burned away inside the test tube and water was sucked into the tube to replace
the missing oxygen.
What is the volume of the test tube without oxygen? _____ mL or cc?
Have Mr. Z initial
The volume of the test tube after you conducted the experiment represents
all the gases of the atmosphere, except oxygen -- you see, the oxygen was
The Atmosphere – What Is It?
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burned away and was replaced with water.
11. What is the difference?
a. Record your total test tube measurement, here: ____
b. Record your average after experiment measurement:_____
c. Subtract (b) from (a) and record that number, here: _____
This is the average volume of oxygen in the test tube.
12. Let’s call this a practice run. Each member of your group should
practice and complete the data for steps 1 through 11. I will be looking
for each student’s answers for step 11.
13. When you are ready to conduct this experiment, for real, use the data table on
the next page to record your data.
OH! BY THE WAY!!!! Each member of your group should conduct this
experiment three times. The more trials you run, the more accurate your data
becomes. So, if each of you does three trials and finds the median of those
three trials you will be that much closer to finding a true measurement.
14. Once you found the individual median, find the group’s median. Again, it brings
you closer to a true measurement.
15. Since the starting volume does not change, the data table only shows after
experiment measurements. Label the unit of measure.
16. What is your starting test tube volume? ________ mL or cc?
17. Use a calculator to find average.
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18. You will be graded one point for each trial successfully recorded.
Each Student Conducted the Volume Experiment Three Times
Student First and Last Name
First
Second
Third
Trial
Trial
Trial
Average
1.
2.
3.
4.
5.
19. Rerecord your starting volume: ____
What is the overall average volume of your group’s experiment? _____
20. Once you have completed the experiment, please clean-up your area and return
the dried bowl, washed test tube, candle with penny, safety goggles, and
graduated cylinder to the tote tray. The rest of this project is individual work.
21. Below, draw a test tube and show the water level to show the total volume of
water (air) the test tube can hold. Then, draw another illustration of the test
tube and show (approximately), where the water level will be after you have
burned away all the oxygen.
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Let’s Review As To How To Find the Volume of Oxygen
Remember, we have measured in milliliters (mL). This subtraction problem will
tell you determine the volume of oxygen in the test tube, in milliliters (mL).
Refer to your data table on page 25. Find the average volume of oxygen by
finding the medium of all the average volumes you found on that data table.
What is the total volume of the test tube? ____
What is the average volume of oxygen in the test tube? ____
The answer above is the average volume of oxygen measured by your group.
Round it off to the nearest whole number to be an average.
Your rounded volume of oxygen is: ___________________
To Determine the Percentage of Oxygen In the Atmosphere





To determine the percentage of oxygen in the atmosphere, you must use a
fraction comparing total air volume versus average oxygen volume.
Remember, that percent means something is part of a whole. In other
words, a fraction.
So, what is this fraction? Well, let’s look at what makes a fraction. A
fraction compares a part of something over the whole of something.
The bottom number, the denominator, is the whole of something, while the
top number, the numerator, is the part of the whole of something. The
denominator in this case is the total volume of air in the test tube. What
was your total volume of air in the test tube? ________________
In this case, the denominator is the total volume of the test tube, while
the numerator is the average volume of oxygen in the test tube. What
was your average volume of oxygen? __________
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Record your fraction, here: ______ = example: Avg. Volume of Oxygen
Let’s just say I am using a mini 4 mL test tube. That 4 mL is my denominator. Now, let’s say
my measured amount was 1 mL. The part or sample I am dealing with (1 mL) is the numerator.
Look, below, how I set-up my fraction.
0.
0 .2
0.25
0.250
Example: 1 = 4 1 = 4 1. = 4 1. = 4 1.0 = 4 1.00 = 4 1.000
4
GO AT LEAST THREE PLACES OVER FROM THE DECIMAL POINT
(0.ABC).
-- i.e.
Use a calculator.
My fraction as a decimal is: 0.250 mL. As a percentage, it is: 25%
Your fraction as a decimal, is: ______. As a percentage, it is: ______
Hint: To do this on the computer – go to Insert on the toolbar and scroll down to object. Then,
go to Create New -- scroll down to Microsoft Equation 3.0 and click that on. It will give you a
new toolbar. Pick the second panel in on the bottom row. You will see
and then scroll down to
click on that symbol
insert your numbers.
Rubrics: Each question on Pages 22-27 are worth one point each for a total of 20.
Turn Your Data Table from Page 25, into a Bar Graph
Create a bar graph to show the relationship of the table's resulting oxygen
volume. Graph paper is available from Mr. Z. Use the information from your data
table. Remember to title and label and when I mean label, label what you are
showing on “X” axis and “Y” axis.
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Analysis and Drawing Conclusions:
1. Since percentage is a constant number, (a constant is a number that never
changes,) would the same result for the percentage of oxygen in air be obtained if
a larger test tube had been used? How about a larger candle? Why?
2. In the experiment that you conducted, why do you think the water level rose
inside the test tube when the candle burned out?
3. In your reading, you found that nitrogen is the other major component of air
(78.1%). What role did nitrogen play in your experiment? This is a tricky question,
so think about nitrogen as a gas, and what you saw and did each time you conducted
this experiment.
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4. Your experiment should have resulted in 21% oxygen in the atmosphere, give
two possible reasons why you did not achieve that percentage?
5. The percentage of oxygen is 21%. Tell me the volume of oxygen in a 100
gallon bottle of air. Show your work. Hint: you cannot use 21% in any
mathematical equation. Percent must be expressed as a decimal number or a
fraction. If you do not show the work, you will not get credit for this
question.
Rubrics:
Analysis and Drawing Conclusions are worth one point each, for a total of 6
points.
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