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2016 Junction City High School Summer Reading Assignments Grade 8
Please Note: These assignments were distributed to each student in a blue folder the last week of school.
ALL 8TH GRADERS
Read all four science-themed articles and complete the corresponding questions. Be ready to turn in
completed assignments to your science teacher on the first day of school in August.
Nonfiction Science Articles [distributed to each student in a Blue Folder]
o “Biosphere 2: An Experiment in Isolation”
o “Limiting Factors”
o “Particles in Motion”
o “The Crater that Ended the Reign of the Dinosaurs”
PRE-AP 8TH GRADE
In addition to the reading assignment for all 8th graders, read the Short Story “Flowers for Algernon”
by Daniel Keyes and complete the attached assignments. Be ready to turn in completed assignments
to your English teacher on the first day of school in August.
Short Story Map
Short Story Character Sheet
Short Story Response #1
Short Story Response #2
Finalized 5/04/16 CG
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BIOSPHERE 2:
An Experiment in Isolation
Can human beings live in an airtight building for 2 years with
no life support except for the organisms they bring inside with
them? Can they set up an ecosystem that provides for their every
need and the needs of the other populations around them?
These were the big questions that Biosphere
2 was built to answer. In 1984 construction
began on the world’s largest isolated
environment. The location was the Sonoran
Desert, a short distance north of Tucson in
Arizona. This part of the country
experiences a high percentage of days
without cloud cover. Sunshine is essential
for an experimental ecosystem because it is
the only energy source to sustain the
humans and hundreds of other species in
the closed system.
One critically important factor was sealing
the 3.1-acre live-in terrarium from the
outside environment. That means no gases
or organisms entering or leaving the system.
First a 500-ton stainless-steel liner was laid
down to isolate Biosphere 2 from the earth.
Then a massive glass, steel, and concrete
greenhouse was constructed on the steel
base to isolate Biosphere 2 from the
atmosphere. The $150 million chamber was
ready for business in 1991.
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Four men and four women were identied
as the rst team. But before they closed the
door, they had to populate Biosphere 2 with
other organisms in order to turn the newly
nished building into an ecosystem. The
ecologists working on the project spent a
long time selecting organisms. They knew
that they needed plants, animals, and
microorganisms. They needed to have food
for eight people and life support for the
organisms that would provide the food.
They needed organisms to refresh the air
and dispose of waste materials. The
planning was complex and detailed—lives
depended on getting it right.
The First Mission
In September 1991 the door was closed and
sealed with the eight Biospherians and 1800
other populations on the inside. The
challenge faced by the humans was the
same one astronauts will probably face
during our rst visits to other planets. The
trip to the Moon takes a few days. A trip to
Mars might take a year. The most efcient
way to make such a journey would be in a
miniecosystem, where everything needed
for life recycles.
Biosphere 2 had surprises for the scientists
inside. Before long they noted that the
oxygen concentration began to drop. The
oxygen started at 21%, the concentration of
oxygen in Earth’s atmosphere, but got down
to 14%. This was a dangerous level for the
people. Where was the oxygen going?
Analysis revealed that the soil in Biosphere
2 was too rich in organic matter. The
populations of microbes were growing out
of control, using too much of the oxygen.
The scientists reasoned that if the oxygen
concentration was going down, the carbon
dioxide (CO2) concentration should be
going up. But the concentration of CO2 was
not going up as fast as the scientists
calculated. It was later discovered that the
CO2 was being taken up by the massive
amount of concrete that was still curing.
On the biotic side, a problem came up with
ants. An uninvited species, known as crazy
ants, got into Biosphere 2 somehow and
caused disruptions in the community. Not
only did the ants put pressure on other
organisms in the ecosystem, they clogged
vents and chewed on wiring, creating quite
a nuisance.
How could tiny organisms like ants cause
a major problem in the Biosphere 2? Crazy
ants form “super colonies.” Super colonies
have many queens and many nests. All of
the ants work together to search for food,
share food, and distribute resources. Most
other species of ants form colonies with a
single queen in a single nest and are highly
territorial toward other colonies of the same
species of ant. Crazy ant colonies, on the
other hand, cooperate with one another.
This gave them an advantage over other
species of ants in Biosphere 2. While crazy
ants are not aggressive to others of their
species, they are very aggressive in
searching out and attacking prey. They can
effectively communicate the exact location
of the prey to other ants in the super colony.
Then they can launch an attack that will
overwhelm even a large insect such as a
cockroach.
Crazy ants, like other ants and many other
animals, communicate with each other by
using pheromones. Pheromones are scent
chemicals that send signals to other animals
of the same kind. For example, ants leave
pheromones on the ground to mark a trail
for other ants in the colony to follow. While
most other ants are thought to have only
one trail pheromone, crazy ants have at least
three different ones. Some of these
pheromones evaporate faster than others, so
they stay on the trail for only 2–3 minutes,
while other pheromones may last for 24
hours. Crazy ants, with more than one
pheromone, can provide more information
to other ants so the colonies can adjust
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quickly to changing conditions. The
superior communications and the super
colony cooperation seem to be the
characteristics that gave the crazy ants the
advantage over the other insect species in
Biosphere 2 and allowed the crazy ants to
displace most of the other arthropods.
The Biospherians made it through the 2-year
mission, but just barely, and not without a
little assistance. The oxygen problem could
be solved only by pumping in extra from
outside. A second mission in 1994 lasted 6
months. Following the second mission, a
decision was made. Biosphere 2 would no
longer be a live-in facility, but would be
transformed into a unique ecological
research center. In 1996 Columbia
University took over management of
Biosphere 2 and continues to oversee the
important international research going on
there.
The Current Research
It is fairly easy to do an experiment with the
plants and animals in your terrarium or
aquarium. You could add some CO2 to one
terrarium but not the other, to see if it made
plants grow faster or slower. You could
increase the temperature of an aquarium
and monitor the health of the sh. But
would your experimental results tell you
what would happen in the rain forest or the
ocean?
How do you study an entire ecosystem? A
real ecosystem is much larger and more
complex than the ones you can build in
class. To try to answer some of these
questions, you could add CO2 gas to a eld
or forest to see how plant growth might
change, but the wind would soon blow the
CO2 away. You could study the weather
over a coral reef for a period of 40 or 50
years to see if there are any patterns, but it
would be impossible to control variables.
You might notice a difference in plant
growth and health when you compare a
wet, cold, rainy year to a hot, dry, sunny
year. Is the difference because of the rain,
the moisture in the air, the temperature, or
the amount of sunlight? It is impossible to
say with so many variables changing at
once.
What you really need is a box like your
terrarium or aquarium that is big enough to
hold a whole ecosystem. Then you could do
experiments and control all the variables
except the one you are studying. Where can
you nd such a box? Biosphere 2.
Biosphere 2 covers almost as much area as
four football elds. Inside are seven
different environments: rain forest, desert,
tropical ocean, marsh, savanna, thorn scrub,
and agroforest.
One area of intensive study is the tropical
rain forest ecosystem. Tropical rain forests
can soak up CO2, a greenhouse gas that
contributes to global warming. Tropical rain
forests are sometimes called the lungs of the
planet because they take in so much CO2
and produce so much oxygen during
photosynthesis. Dense vegetation and long
days of direct sunlight year-round enable
rain forest plants to carry out
photosynthesis at a higher rate than
anywhere else on Earth. Some scientists
think rain forests have great potential for
controlling the rising CO2 level.
Another possibility is that more CO2 in the
atmosphere will result in rising global
temperatures all over Earth. Warmer
temperatures could result in less rain,
because less water vapor will cool enough to
condense into raindrops. Water and CO2
are both needed for photosynthesis to take
place. If there is less rain, photosynthesis
slows down, which means less CO2 will be
removed from the atmosphere. Increased
CO2 heats the atmosphere even more,
reducing rainfall even further. Over time
this can cause the average global
temperature to rise, which can have a
signicant effect on many ecosystems.
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Biosphere 2 hope to answer these and many
other questions about how the rain forest
ecosystem responds to change.
Coral reefs have been called the rain forests
of the sea because there is so much diversity
of life in coral reef ecosystems. Coral
denes the ecosystem. Algae, sh, crabs,
and many other kinds of sea organisms live
on, in, and around the coral structures.
Microscopic phytoplankton (single-celled
algae and photosynthetic bacteria) are
essential to the health of ocean ecosystems.
Phytoplankton, which conduct
photosynthesis, are food for coral and other
small animals, which in turn are food for
larger sea animals. Phytoplankton are the
base of marine food chains just like green
plants are the base of terrestrial food chains.
John Adams, senior research specialist, ascends a canopy access system inside
the Biosphere 2 Tropical Rain Forest to check leaves sealed in a branch bag.
Inside the rain forest environment in
Biosphere 2 scientists are doing experiments
to determine how drier conditions affect the
amount of CO2 taken up by rain forest
plants. They can control the amount of
“rainfall” with the overhead sprinkler
system. CO2 can be pumped in. The
temperature can be regulated with huge
heating and cooling units. Scientists can
change any of these variables one at a time
to see what effect each has on the amount of
CO2 taken up by the plants.
What will happen if the CO2 level and the
global temperature continue to rise? Will
the rain forests take up more CO2? Will the
rain forests take up less CO2? How will
warmer temperatures or more CO2 affect
the health of the plants? Scientists at
Marine biologists report that there are fewer
and fewer sh and other organisms living
in the coral reef ecosystems around the
world and that the growth rate of coral has
slowed. During the winter of 1997–1998,
one-tenth of the world’s coral reefs died.
The temperature of the water in the affected
areas that winter was 2–3°C above normal,
making it one of the warmest periods on
record. But was it temperature alone that
killed the coral, or was it more complicated
than that?
Several scientists are studying the coral reefs
in the ocean biome at Biosphere 2. The
Biosphere 2 “ocean” holds 2,500,000 liters of
water. The depth ranges from 0 meters (m)
at the beach to 7 m in the deepest part.
Scientists have investigated several factors
they think might affect the health and
survival of the coral.
When they varied the concentration of CO2
dissolved in the water, the health of the
corals declined. They found that excess CO2
dissolved in the water prevented coral from
getting calcium out of the water to build
their skeleton.
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The studies of the coral reefs in Biosphere 2
provide evidence that the changes taking
place in the ocean environment such as
more dissolved CO2 affect the coral reef
ecosystem in negative ways.
As scientists learn more about ecosystems,
two things become very clear. The rst is
that any change in one part of an ecosystem
affects every other part of the ecosystem,
many times in ways that no one could have
anticipated. The second is that the more we
learn, the more we realize how complex
natural ecosystems are and how little we
understand about the way they work or
what effect human activity has on them.
Why should we care? What difference does
it make if rain forests or coral reef organisms
are disappearing? That’s not where we live.
Well, it is where we live. Our planet is
small. The atmosphere surrounds the planet
and the seas wash up on all the continents.
Changes in one ecosystem are
communicated to the rest of the world by
owing air and water. Everything is
connected. Small changes in global
temperature can have a huge effect on
weather patterns. And weather distributes
water, and water is life.
Maybe you can join the small community of
people trying to answer some of these tough
ecosystem questions. College students from
several universities across the country
attend classes at Biosphere 2 for a semester
to study environmental problems. There is
also a summer program for high school
students who are interested in studying
environmental issues. Maybe in a few
years...
More information about these programs is
available on the Biosphere 2 website at
www.bio2.edu.
The Planetary Spheres
One way scientists think about Earth is as a
set of nested, interacting
Scientists gather at Biosphere 2 to conduct rain experiments at the laboratory’s ocean biome.
spheres. The lithosphere
Six inches of fresh water fell into the saltwater ocean over a 2-hour period to measure the effect a
is the rocky, mineral part
freshwater addition would have on the exchange of carbon dioxide into and out of the ocean. The
of the planet that extends
rain and air-water gas exchange experiment was funded, in part, by a grant from the David and
from the solid surface into
Lucile Packard Foundation.
the mantle. This is the
hard part of the planet
that provides a sense of
solidity and stability...
most of the time.
Periodically, we get
reminders in the form of
earthquakes and volcanic
eruptions that the solid
Earth is actually restless
and dynamic.
Wrapped around Earth is
the atmosphere, the thin
layer of gases that
extends, for all practical
purposes, no more than
600 kilometers above the
surface. The atmosphere
is a source of essential
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gaseous chemicals, an energy-transfer
system, a shield protecting us from
extraterrestrial radiation, and an insulator.
It is also an important medium for water
distribution.
sum total of all the living organisms on
Earth is the biosphere. It is this raggletaggle, at times improbable, assemblage of
millions of different kinds of life-forms that
gives Earth its particular avor.
Earth is a water planet. Because of the
temperature on Earth, water exists naturally
in three states: liquid, gas, and solid. All
the water on Earth makes up the
hydrosphere. The hydrosphere includes the
oceans, lakes, rivers, streams, and aquifers.
It includes the polar icecaps, glaciers,
snowpacks, and permafrost. It also includes
the aerial water vapor and condensates in
the form of clouds, fog, and precipitation.
All four spheres can be bundled into one
global sphere called the ecosphere. The
ecosphere is that portion of a planet that is
inhabited by life. Thus, it includes a portion
of the atmosphere, a portion of the
lithosphere, a portion of the hydrosphere,
and all of the biosphere. We focus on the
biosphere in this course. However, we will
continually consider the interactions
between living organisms and the other
three spheres to reinforce the idea that life is
And nally, creeping, hiding, running,
never disconnected from the physical
burrowing, ying, slithering, and swimming
environment.
through, over, under, onto, and into the
other three spheres is the biosphere. The
T
H
I
N
K
Q
U
E
S
T
I
O
N
S
1. Give at least two examples of how a change in one variable in an ecosystem can start a
chain reaction that affects several other variables.
2. Why is global warming considered by some scientists to be such an important problem?
3. What are some advantages of doing research on ecosystems in Biosphere 2 rather than
in the natural ecosystem? What are some disadvantages?
4. Think about the statement "Every decision has an environmental impact." What
decisions do you make that add carbon dioxide to the environment? What decisions do
you make that would add less carbon dioxide to the environment than you currently
add?
5. Why should we be concerned about species becoming extinct? What endangered
species are found in the area where you live? What has caused them to become
endangered? What is being done to help them survive?
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Limiting Factors
Nothing lives forever. Even the ancient
bristlecone pine trees of the high mountains
of the western United States die after a few
thousand years. Most organisms live much
shorter lives. Many insects live a few
months; sh and small mammals a few
years; many plants, reptiles, birds, and large
mammals a few decades; and a scattering of
others, like trees, a few centuries. Life is a
temporary thing...for the individual.
If a species is to continue to exist on Earth,
the species must produce new individuals
continually. Producing new individuals to
maintain a population is reproduction, and
every species has a way of reproducing.
The rate at which a species can increase its
population is its reproductive potential.
Some species, like elephants, have modest
reproductive potential. A female elephant
reproduces a single offspring every 4 years.
A single female Atlantic cod, on the other
hand, can lay 10 million eggs a year. Clearly
the potential for the cod to increase its
population is much greater than the
potential for the elephant to increase its
population.
So why don’t populations spiral out of
control? Why aren’t there billions of billions
of trillions of Atlantic cod lling all the
oceans from top to bottom after 5 or 10
years? Because there are limiting factors
imposed on every population on Earth.
Limiting factors control the sizes of
populations.
BIOTIC LIMITS: PREDATION
One way that populations are limited is
through predation. Every organism is
desirable to some other organism as a
source of food. As we know, food provides
the energy that is essential for survival.
Therefore, if a species reproduces a lot of
biomass, it will attract predators to take
advantage of the energy source. We see this
kind of population control in Mono Lake
when the brine shrimp feed on the
planktonic algae, reducing their numbers,
and in turn the brine shrimp are eaten by
phalaropes and gulls, reducing the
population of shrimp. Predation can occur
at any stage in the life cycle of an organism,
including eggs and seeds, young, mature,
and old. Populations are limited by
removal of individuals as they are eaten.
Diseases limit populations in the same way.
Even though we don’t usually think of a
large animal or plant being attacked by a
microscopic bacterium, the result can be the
same. A mountain lion capturing a deer, or
a hawk taking a squirrel, removes an
individual organism from the population. A
disease organism can enter a population and
kill many organisms, which also limits the
size of the population.
BIOTIC LIMITS: RESOURCES
Populations are limited by food supply. If
an organism cannot acquire the energy
needed to survive and reproduce, the
population will decline and, with it, the
potential for producing the next generation.
If a snake cannot nd enough mice to
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sustain itself, it will starve to death. Even
if it survives, it may be so weak that it can’t
reproduce. Similarly, if there is a poor crop
of acorns, squirrels may starve. Even if they
survive, they may not be able to feed their
young. In 1982 a reduced population of
brine shrimp in Mono Lake prevented the
California gulls from successfully feeding
their chicks. Most of the gull offspring died
that year. Lack of food is one of the most
important limitations on populations.
ABIOTIC LIMITS:
REPRODUCTIVE ENVIRONMENTS
Many organisms require specic conditions
in order to reproduce. If the number of
locations where reproduction can occur or
their quality is limited, reproduction will be
limited. Bank swallows need sandy cliffs in
which to dig nesting burrows. If a sandy
cliff tumbles down during a ood or
earthquake, suitable nesting sites are lost.
Salmon need clean gravel streambeds in
which to lay their eggs, and black bears
need winter dens in which to give birth.
Without an environment that provides for
the physical conditions needed to
reproduce, young will not be born. Lack of
access to required reproductive
environments for a species limits
populations.
ABIOTIC LIMITS: SEASONS
Seasonal changes put pressure on
populations. In the temperate and polar
latitudes, winter is a major factor in
population limitation. During winter, days
are shorter, so primary production by
photosynthetic organisms slows or, in the
case of deciduous trees, stops entirely.
Often winter brings rain, snow, and wind,
each of which adds stress to populations.
Some animals respond to the threat of wind,
ood, and freezing by leaving the area.
Birds, because of their mobility, are famous
for migrating to warm regions. Others, like
the American bison and caribou, go on long
treks to nd greener winter environments.
Some organisms become dormant, basically
shutting down until spring. Frogs, sh,
bears, squirrels, snakes, maple trees, and
hosts of other organisms use dormancy,
reduced activity, and winter sleep to wait
out the winter.
These strategies work if a number of
conditions have been met.
• The wintering place offers sufcient
protection.
• The organism has accumulated
enough fat or has stored enough
food to survive the winter.
Winter is the main limiting factor for many
temperate and polar populations. Many
populations decline to minimal levels, like
the brine shrimp in Mono Lake, and then
expand rapidly in the spring. Seasonal
uctuations in population size such as those
at Mono Lake are normal and healthy.
CARRYING CAPACITY
When you stand back and take the large
view of life on Earth, you realize it is a
struggle to survive there. Every living thing
has fundamental requirements for life, and
if it doesn’t get those things, it dies. One of
the most critical requirements is energy.
Energy enters the ecosystem as sunlight.
Photosynthetic organisms capture the
energy and transform it into carbohydrates,
like sugar, that we call food. The energy is
in the chemical bonds. The amount of food
23
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that can be produced is limited by several
factors, including access to light, space for
living, and availability of resources such as
water, carbon dioxide, and minerals. For
any given ecosystem there is a limit to the
amount of food that the producers can
make.
We know that the other populations in an
ecosystem acquire energy by eating each
other. Primary consumers eat producers,
secondary consumers eat primary
consumers, and so on. The number of
consumers is limited by the amount of
production.
The total number of individuals of a
population that can be sustained
indenitely by an ecosystem is the carrying
capacity for that species. For instance, a
backyard ecosystem might support three
rabbits year after year on the amount of
grass and other vegetation growing there.
The carrying capacity for rabbits is three.
If six rabbits move in, the carrying capacity
of the ecosystem is exceeded. As a
consequence, in order to survive, the rabbits
will eat so much of the vegetation that they
will damage the ability of the producers
to produce in the future. Exceeding the
carrying capacity of an ecosystem always
produces changes that will alter the nature
of the ecosystem.
population would die off. In healthy
ecosystems there are always survivors of
every kind in sufcient numbers to
reproduce and keep the population going.
Usually the primary producers establish the
overall carrying capacity of an ecosystem.
How much food energy is produced by the
photosynthesizers that can be consumed
and distributed throughout the food web of
the ecosystem? When you know the answer
to that question, you are closer to knowing
the carrying capacity of the ecosystem.
Mono Lake is an ecosystem with a
tremendous carrying capacity for its size.
Mono Lake has plenty of light, water,
carbon dioxide, and minerals. The algae
reproduce rapidly. The limiting factor for
Mono Lake algae is one element—nitrogen.
Even so, the biomass of algae produced in
the lake supports trillions of brine shrimp
and brine ies. These in turn nourish
millions of birds and a few coyotes. A lot of
life ows through Mono Lake each year.
Contrast this with a grassland on the Great
Plains. Grasses grow more slowly, thus
taking longer to regenerate their biomass.
The amount of grazing by insects, rodents,
deer, and cattle must not exceed the capacity
of the grasses to regenerate. The carrying
capacity of the grassland is less than the
carrying capacity of Mono Lake.
In an ecosystem the consumers never eat all
the organisms they prey upon. Squirrels
never eat all the acorns, caterpillars never
eat all the oak leaves, mountain sheep never
eat all the grass, sharks never eat all the
seals, and so on. This is very important
because if they did, the prey species would
be gone. The predators’ offspring would
have nothing to eat, and the predator
24
542-1448_Pop_Eco_pgs_1-70.indd 24
7/7/08 2:52:39 PM
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t io n
o
Par tic le
s in M
Air is matter.
It has mass and occupies
space. Air is a mixture of many gases.
Air is approximately four-fths nitrogen
and one-fth oxygen. All the other gases,
including carbon dioxide and water vapor,
make up only a little more than 1% of the
mass of a sample of air.
same number of particles as every cubic
centimeter of air outside the bottle.
Air is matter in its gas phase. That means
that the nitrogen and oxygen particles in
air are not connected to other particles.
Gas particles y through space as
individuals.
Air particles fly through space as individual particles. Air particles fill an open bottle.
It is important to remember that air
particles are really millions of times
smaller than the representations in the
illustrations. A cubic centimeter of air
actually has about one quintillion air
particles! A quintillion is a one followed
by 18 zeroes (1,000,000,000,000,000,000).
The illustrations are therefore not accurate,
but they are good for thinking about what
is going on at the particle level.
After you drink a bottle of spring water,
you have an excellent container for an air
investigation. The empty bottle, of course,
isn’t empty. It is full of air. Because air
particles are ying all around, they are
going into and out of the open bottle all
the time. The density of air in the bottle is
exactly the same as the density of the air
outside the bottle. That means that every
cubic centimeter of air in the bottle has the
23
542-1505_Chem Inter_TEXT.indd 23
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Particles Have Kinetic
Energy
Not only are air particles incredibly small,
they are always moving. And they move
fast. At room temperature, they are going
about 300 meters per second. That’s equal
to about 670 miles per hour.
Back to the air investigation. Stretch a
balloon over the top of the bottle full of air.
Now the air is trapped inside the bottleand-balloon system. No particles can get
in or out.
Moving objects have energy. It’s called
kinetic energy. Anything that is in motion
has kinetic energy, whether it is an ocean
liner, a bicycle, a y, a snail, you walking
to class, water falling down a waterfall, or
an oxygen particle in the air. They all have
kinetic energy.
Kinetic energy, like all forms of energy,
can do work. Air particles do work when
they crash into things. Air particles push
on each other, on you, on the walls of
containers, and on everything else around
them. Every air particle crashes into
another particle about 10 billion times
every second!
The amount of kinetic energy an object
has depends on two things: the mass of
the object and the speed at which it is
moving. You can’t change the mass of an
air particle, but you can change its speed.
By making a particle go faster, you increase
its kinetic energy. Air particles can be
made to move faster by heating a sample
of air. Heat increases the kinetic energy of
particles.
A balloon can trap the air inside a bottle.
The density of air particles is the same
in the bottle, in the balloon, and in the
air surrounding the bottle-and-balloon
system.
24
542-1505_Chem Inter_TEXT.indd 24
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Now place the bottle-and-balloon system
in a cup of hot water. The hot water
warms the air inside the bottle. Particles
in the warm air start to move faster. After
a few minutes, the bottle-and-balloon
system looks like this.
Why did the balloon inate? The hot
water heated the air in the bottle. As a
result, the air particles began moving
faster. Faster-moving particles have more
kinetic energy. Faster-moving particles
hit each other harder, which pushes
them farther apart. You can see in the
illustration that the particles of warm air
inside the bottle-and-balloon system are
farther apart.
The faster-moving particles also push
on the balloon membrane harder. The
particles push hard enough to stretch the
balloon membrane. The increased kinetic
energy of the particles pushes them farther
apart (air expansion), and the membrane
stretches to hold the increased volume
of air.
Hot water increases the kinetic energy of the air
particles inside the bottle-and-balloon system. The
particles fly faster and hit each other harder. The
particles push farther apart, causing the gas to expand.
25
542-1505_Chem Inter_TEXT.indd 25
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What Happens W hen
Gases, Liquids, and
Solids Heat Up?
Gas. If a sample of matter is gas, its
particles are not bonded (attached) to
other particles. Each particle moves freely
through space. When a sample of air
The particles in gases fly through space in all
directions as individuals.
Liquid. Particles in liquids are in close
contact with one another. Attractions
between the particles keep them from
ying freely through space. The particles
in liquids can, however, move over,
around, and past one another. Individual
particles in liquids are able to move all
through the mass of liquid.
The particles in liquids are held close to each other.
Particles bump and slide around and past
each other.
When liquids get hot, the particles bump and push
each other more. Increased bumping pushes the
particles farther apart. This causes the liquid
to expand.
When gases get hot, the particles fly faster. Faster
particles hit other particles harder, pushing the
particles farther apart. This causes the gas
to expand.
heats up, the particles move faster and hit
each other harder. The result is that the
particles push each other farther apart.
In the illustrations above, a container
of gas has a exible membrane across
the top. When the gas gets warm, the
kinetic energy of the particles increases,
particles hit each other harder, and the gas
expands. As the gas expands, it pushes the
membrane upward.
The motion of particles in a liquid is
kinetic energy. When a liquid gets warm,
the particles move faster. The particles
have more kinetic energy. As a result,
they hit other particles more often and hit
harder. This pushes the particles farther
apart. When particles are pushed farther
apart, the liquid expands.
26
542-1505_Chem Inter_TEXT.indd 26
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Summary
Solid. Particles in solids have bonds
holding them tightly together. The
particles cannot move around at all. The
particles are, however, still in motion.
Particles in solids are always vibrating
(moving back and forth) in place.
General Rule 1. When a sample of solid,
liquid, or gas matter heats up, it expands.
When matter gets hot, its particles gain
kinetic energy. The increased kinetic
energy pushes the particles farther apart.
This causes the matter to expand.
General Rule 2. When a sample of
solid, liquid, or gas matter cools down,
it contracts. When matter cools down,
its particles lose kinetic energy. The
decreased kinetic energy lets the particles
come closer together. This causes the
matter to contract.
The particles in solids are bonded. Particles move
by vibrating, but do not change positions.
Review Questions
1. What is kinetic energy?
2. What are two ways to increase an
object’s kinetic energy?
When solids get hot, the particles vibrate more.
Increased vibration pushes the particles farther
apart, causing the solid to expand.
3. Explain why a balloon inflates when
a bottle-and-balloon system is
placed in hot water.
4. What happens to a sample of matter
when its particles lose kinetic
energy?
The vibrational motion of particles in
solids is kinetic energy. Heat makes the
particles in a solid vibrate faster, giving
them more kinetic energy. Faster-vibrating
particles bump into one another more
often and hit each other harder. This
pushes the particles farther apart. When
particles are pushed farther apart, the
solid expands.
5. How are particles in solids, liquids,
and gases the same? How are they
different?
27
542-1505_Chem Inter_TEXT.indd 27
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Close Reading and Text Dependent Questions in Science The Crater That Ended The Reign Of the Dinosaurs (Planetary Science – Grade 8) The text selection, The Crater That Ended The Reign Of the Dinosaurs, is found in FOSS Student Resource Book, Planetary Science, pgs. 67-‐68. Look in the Student Learning Outcome Document for guidance on when this should be taught. http://bpscurriculumandinstruction.weebly.com/student-‐learning-‐outcomes-‐by-‐grade.html BPS Science Department • 1216 Dorchester Avenue • Dorchester, MA 02125 Phone (617) 635-‐8750 • Fax (617) 635-‐9801 © 2013 BPS Science Department The Crater That Ended The Reign Of the Dinosaurs (Planetary Science – Grade 8) Student Questions 1. Based on the text, paraphrase how sedimentary rocks are formed. 2. The article states that iridium is a rare element. Based on the text, what explanation is offered to explain the unusually high concentration found in the rocks that Dr. Alverez was studying? 3. What possible explanation did Alverez and his research group provide for the reason why they found “high concentrations of iridium in 65-‐million-‐year-‐old rocks” all over the planet? BPS Science Department • 1216 Dorchester Avenue • Dorchester, MA 02125 Phone (617) 635-‐8750 • Fax (617) 635-‐9801 © 2013 BPS Science Department 4. Based on the evidence in the text, what was the scientific model Alverez’s group worked up regarding what happened to the extinction of the dinosaurs? 5. What was one challenge to the model? 6. How did scientists address this challenge? What did they find? 7. What conclusions could the scientists reasonably draw, based on the presence of the Chicxulub Crater, for their model? BPS Science Department • 1216 Dorchester Avenue • Dorchester, MA 02125 Phone (617) 635-‐8750 • Fax (617) 635-‐9801 © 2013 BPS Science Department
