Get documents about "For the Teacher
Document Sample
For the Teacher
Reciprocal Teaching
Defining the Strategy:
The concept behind Reciprocal Teaching (RT) is that we learn best what we
have to teach to others. Reciprocal teaching allows students to become the
instructors of the content that they are studying. Working in groups of four, the
students read a text passage together, following a protocol for predicting,
questioning, clarifying, and summarizing― skills that the teacher has modeled
over a series of lessons until students are comfortable assuming these assigned
roles. These student-directed discussion groups can then monitor their own
comprehension and reinforce their understanding. The structure of the dialogue
and the interactions of the group members require that all students participate.
Background:
This is how RT works: A student, working in a small group, reads aloud a brief
passage of text and immediately generates a question. This strategic use of
questioning requires the student to make sense of the text, processing information
automatically. After other members of the group have answered several questions,
the student attempts to clarify any difficult words, phrases, or confusing sentences
from the reading selection. Clarifying encourages the development of self-
monitoring, an essential component of independent reading. The student now
generates a summary, a task that entails identifying the main ideas in a reading
selection and constructing a clear, concise description of what has been read.
Finally, the student predicts what is likely to occur next and provides evidence from
the text to support the prediction. The role of group leader rotates to the next
student, and the process continues until all the assigned text has been read and
discussed.
We know that effective learners and strategic readers process information and
construct meaning from material they read or view. They use “fix-up” strategies as
they process and comprehend text. The strategies include:
Activating background knowledge
Predicting
Searching to identify unknown words
Rereading, adjusting the rate of reading
Self-monitoring understanding
Inferring
Interacting with unfamiliar/difficult forms, formats
Forming mental images
Reciprocal Teaching is designed to help students practice and learn these effective
strategies for reading comprehension. Students are taught to question, clarify,
summarize, and predict in a cooperative group context.
1
For the Teacher
Reciprocal Teaching
Reciprocal teaching has proved to be useful with a widely diverse population of
students, even though it was originally designed for low-achieving middle school
students. The procedure was designed to improve the reading ability of those
students who were adequate decoders, but had poor comprehension. However,
modifications have been used to teach students who were poor decoders, second
language learners, or non-readers. Poor decoders used the procedure as a read-
along activity; second language learners used it to practice developing skills, while
non-readers learned it as a listening comprehension activity. Teachers have
observed that even average and above-average students profit from the strategy.
The experience of helping other students in their groups decode and understand
what is being read extends understanding and stimulates deeper thinking in these
higher achieving students. (We really do learn best what we teach to others!)
Career/technical teachers frequently teach procedures through modeling and
demonstration. Their students get to see an accomplished person performing the
task, and this gives them insight into how to handle the process. Reciprocal teaching
is an activity that capitalizes on this same relationship for learning. Before you can
expect reciprocal teaching to be successful in your classroom, students need to
have been taught, and had time to practice, the four skills that are utilized in the
model. Expert scaffolding is essential as students move from spectator to performer
after repeated modeling by the teacher. RT is not a quick, easy procedure for
students to learn. It takes a great deal of time and effort to achieve the smooth
independent dialogue characteristic of the reciprocal phase. Even when all students
in a class have received the same instruction, some groups may enter the reciprocal
phase before others. Students need a model of a cooperative and productive group
member. The teacher should select “expert” group members to model their
participation skills in front of the class.
Most RT problems can be avoided by careful placement of students in groups where
they are likely to work successfully. Very weak students and students with special
needs should be placed in groups with higher achievers who are likely to be
supportive rather than impatient. Students with behavior problems must be
separated from other students who are easily drawn off task.
In addition to careful group design, the teacher must prepare students to work
effectively in collaborative groups. Students who behave appropriately while the
teacher is providing direct instruction do not always demonstrate acceptable
behavior during cooperative group activities. Explicit behavioral expectations should
be communicated to the students during the early stages of RT implementation.
Appropriate behavior during group work must be modeled, practiced, and reinforced
in a similar manner to the instruction in RT strategies. Ideally, students internalize
the behaviors necessary for productive group work before beginning independent RT
activities.
2
For the Teacher
Reciprocal Teaching
Smoothly functioning RT groups depend on cooperation and hard work by all group
members. Teachers must carefully monitor groups that appear to be having difficulty.
In addition to observing students while they work, teachers can provide peer
evaluation forms to help determine the source of the problem. Students having
difficulty functioning in RT groups must be dealt with as quickly as possible so that
the group’s progress is not inhibited.
The four RT strategies are presented in a sequence that we have determined to be
effective. However, there is no consensus that this particular order must be followed.
Teachers should feel free to sequence the instruction and implementation of the
strategies in any order that works well for them. Although the sequence of instruction
can vary, a consistent approach is most likely to be effective during the early stages
of RT instruction. As strategies are learned and internalized, the dialogue becomes
more natural and strategies are implemented in a more flexible manner.
Think carefully about the text provided for modeling during the learning phase.
The ability level of the students should be taken into account, as well, before
choosing a challenging text.
Materials:
Informative text (multiple passages)
RT worksheets or sticky notes
3
For the Teacher
Reciprocal Teaching/Questioning
Introduce:
Questions are the master key to understanding. They clarify confusion and take us
deeper into reading. Nobel-prize winning physicist, Richard Feynman, refers to
questioning as “puzzle drive.” Teachers must nurture this same “puzzle drive” in their
students and teach them to ask substantive questions. Asking questions engages us
and keeps us reading. When our students ask questions and look for answers, we
know that they are monitoring comprehension and interacting with the text to
construct meaning, which is exactly what we hope for in readers.
Consider the statement, “School is the only place where experts ask all the
questions.” Within the context of reciprocal teaching, questioning becomes the
responsibility of the student, not the expert. One way to model this skill is to remind
students of the who, what, when, where, why, and how words that often begin
questions. In order for this skill to be effective, however, students must be explicitly
taught how to formulate questions that go beyond the literal comprehension level.
(More why and how and less who, what, when, and where!)
Thin Questions:
Answers are contained in the text (“right there”)
Call for a brief response
There is a right answer
Require recall of factual information
Thick Questions:
Answers not always explicit in the text (“think and search” and “author and
me”)
Call for more elaborated responses
May/may not be one right answer
May be conceptual in nature (require higher order thinking)
4
For the Teacher
Reciprocal Teaching/Questioning
Model the strategy:
Direct students’ attention to a small section of text passage. Think out loud as you
formulate a variety of thick and thin questions over the information.
Sample social studies questions:
How large is the continent? (thin)
Why do you think Antarctica is mostly covered in ice? (thick)
Compare Antarctica’s seasonal calendar to that of our own. (thick)
What is the annual snowfall in Antarctica? (thin)
How does the climate of inland Antarctica differ from the coastal climate?
(thin)
Why do you think this climate difference exists? (thick)
What is the temperature range in Antarctica? (thick-info must be “sifted”)
Guided Practice:
Provide guided practice using the next few sub-headings of the same text passage.
Ask students to work with ONE partner to develop questions for each subheading in
the article. Remind them to consider guidelines discussed earlier. We want to
include as many THICK questions as possible. Have pairs share some of their
questions with the entire group, and ask other students to label according to “thick or
thin.”
Independent Practice:
Provide independent practice with another text passage. Assign students a new
partner to take turns reading and questioning. Remind them to try to formulate as
many “thick” questions as possible.
5
For the Teacher
Reciprocal Teaching/Clarify
Introduce:
Students react to difficult or unfamiliar material in various ways. Competent readers
seek clarification when needed, but weaker ones often do not. Teaching and
modeling the skill of clarifying can provide important support for these readers by
helping them clear up confusing parts of text. We know that confusion can lead to
misinterpretation; therefore, it’s important to clarify.
Clarifying is the process of identifying aspects of the text that are not totally clear. A
proficient reader might use a number of fix-up strategies to clarify or patch-up
comprehension:
re-reading
going on in hope that confusions will be eventually resolved
zeroing in on difficult vocabulary
consulting with another reader
There are a number of methods that students need to learn and apply to unfamiliar
words in a text. (Without explicit instruction in clarification, students tend to skim over
difficult words or phrases, often missing clues that are central to the meaning of a
reading passage.) The purpose of the clarification strategy is to teach students to
focus on meaning, helping them become more independent readers.
The following are clarification strategies students can use to clarify unfamiliar
vocabulary:
Consider the text. Students are encouraged to look at a broader context
rather than just the individual sentence in attempting to figure out the
meaning of an unfamiliar word.
Substitute a synonym. Students are encouraged to substitute a word that they
think has a similar meaning to the unknown word and to check to see if it
makes sense in the passage.
Study the structure. Use structural analysis clues like root words, prefixes,
suffixes, etc.
Ask an expert. As other members of the group for help.
Place a sticky note. Insert a small sticky note on a page to mark any unknown
word that you need to check in a reference book. (This is best done after
reading in order to avoid distracting students from attending to the meaning of
the text.)
6
For the Teacher
Reciprocal Teaching/Clarify
Model the strategy:
Choose a text passage to model the skill of clarifying for students. Demonstrate the
first few paragraphs or sub-headings of the passage as they listen.
Sample Think Aloud:
Antarctica/Climate
(As the clarifier, my role is to screen the passage for possible confusions the group
may experience. Sometimes I am looking for sentences that may be difficult to
understand, or I may be looking for vocabulary words that are unfamiliar. Other times
I may be looking for context clues to help figure out unknown or confusing
information. It‟s my responsibility to note/recognize these situations and bring them
up for group discussion.)
Note the word kilometer (“I know the root word is meter. A meter is a measure
of distance in the metric system. Kilo is a prefix that means a thousand. It
must mean a thousand meters. How does this compare with a mile? Does
anyone in the group know?”)
Look at the last sentence of the second paragraph. (“Is this confusing to
anyone else? I had to reread the sentence to understand it. It just illustrates
the point that there‟s very little of the continent NOT covered with ice. The
numbers are confusing.”)
Guided Practice:
Provide guided practice for clarifying with the next few paragraphs or sub-headings
of the same text passage. Assign students a partner in order to screen the sections
for possible confusions that may interfere with comprehension. Remind them to look
for unfamiliar vocabulary words or confusing parts of the text. Review the methods to
use for clarifying unfamiliar vocabulary (presented earlier).
Independent Practice:
Provide independent practice with another text passage. Students should be
assigned a new partner. They will take turns reading and practicing the role of
clarifier.
7
For the Teacher
Reciprocal Teaching/Summarize
Introduce:
Summarizing is an important skill that helps students find clues in their reading that
focus their attention, provide a purpose for reading, and build comprehension. It’s an
important strategy for students at all grade levels and is especially recommended for
struggling readers in grades 6-12. Students first survey a passage looking for sub-
headings and key topics. Students then use these topics to formulate a summary of
their reading. Students must identify key concepts/main ideas, differentiate important
from less important information, and then condense the information. Since this is a
sophisticated reading process, it’s especially important to model this skill explicitly.
When you ask students to summarize they typically:
Copy word for word
Write down everything
Choose nonessential information
Write next to nothing
Explain that when you want to summarize nonfiction, you look for key details as you
read. You ask yourself what the subject is, what is said about it, and what 3-4 things
stand out? In other words, we are trying to identify the “gist of the text.” Summarizing
doesn’t mean restating everything. When we are finished deleting, selecting, and
combining, only 10 to 25% of the original materials should be used. If more than
25% of the original material is included in the summary, we’ve not encapsulated
enough.
In order to be more explicit, explain that they should think about these things when
summarizing text:
General subject (Look at subheadings/key topics/sub-titles.)
Supporting details (What info narrows or restricts the general statement or
topic/sub-title/sub-heading?)
What is essential vs. what is interesting? (“Weed the garden!”)
Illustrations/examples (What examples illustrate the topic or restrictions?)
Model the summarizing strategy:
1. Ask students to survey a selected text passage and identify major topics
addressed within the reading. Specifically, ask them to look for sub-headings.
2. Divide a piece of chart paper into columns or sections, one for each of the
key concepts, subheads. List the concepts/subheadings on your chart
paper. (Use an overhead transparency if you prefer.)
3. Ask students to read the passage silently, using the first two subtopics on
the chart to focus their reading. After they have read the text, model the
information (in sentence form) from the first few sections of the text passage
on the chart paper or transparency. Think out loud as you preview the title
and subheadings to find out the general subject. Now ask what information
narrows or restricts the general statement. Distinguish what is essential vs.
8
For the Teacher
Reciprocal Teaching/Summarize
what is interesting. Are there examples that illustrate the topic? (See
sample dialogue below)
THINK ALOUD:
Antarctica, the Continent
“Looking at the first section, we know that it deals with the continent of
Antarctica. Now consider what important information narrows the topic. What
is important to know about Antarctica? It was recently discovered and
mapped as a continent. What about the statement that it was once thought to
be made up of islands? This is an interesting detail that elaborates on the big
idea, but it isn‟t essential information. The gist of the second paragraph is
that Antarctica is the 5th largest continent and that it‟s mostly covered in ice.
We eliminate the comparison to other continents because, while interesting,
it‟s not essential information. We also eliminate the numerical reference to
size because that only serves to strengthen the point that the continent is
mostly covered with ice.”
Climate
“Looking at the second section, we know that it deals with the
climate of Antarctica. There are so many numbers in this paragraph that it‟s
confusing. I need to focus only on the big ideas and consider what useful
information narrows the topic. What is the climate of Antarctica? I see that the
temperature is 94 degrees below zero in the winter, and the high in the
summer is 32 degrees Fahrenheit. To summarize this information I could say,
„The temperature varies from winter to summer, but it is always freezing.‟ Now
I understand that the inland is dry and the coast gets 24 inches of snow
annually. So I could say, „Precipitation varies from the dry inland to the
moister coastal area.‟ The climate of Antarctica is extremely harsh.”
Guided Practice:
1. Assign students to work with a partner to summarize the next few sections of
the same text. Give each pair a piece of chart paper on which to write the
subtopics and summaries. Remind them to follow the same steps you
modeled.
2. After they have finished, have volunteers post their charts and share
summaries (and thought processes) with the entire group. As one group
reads their summary, ask the others to highlight the parts of their own
summaries they have in common with the reader. After all have shared,
students should recognize that the highlighted parts are most likely the key
points. Ask them to look closely at the points that were not highlighted to
determine if they should be.
9
For the Teacher
Reciprocal Teaching/Summarize
Independent Practice:
Provide independent practice for summarizing using another text passage. Have
students work with a new partner to take turns reading and practicing the role of
summarizer for each assigned subheading of the article. They will follow the same
procedure as in the guided practice activity.
10
For the Teacher
Reciprocal Teaching/Predict
Introduce:
Predicting is an ongoing process of hypothesizing for understanding. It helps
students interact with text, just as they interact with a movie. (Do you sometimes
change predictions about will happen next as a movie progresses?) Through
predictions students recall what they already know about a topic and hypothesize
about what might happen next. They then read to confirm, disprove, or revise their
hypotheses.
We know that proficient readers are constantly thinking ahead, predicting/
anticipating where a passage may be going. This skill sets a purpose for reading the
next section and encourages you to read actively, seeking answers to your
predictions. The nature of informational text makes predicting a somewhat easier
task because the reader can preview titles, headings, subheadings, etc. for
clues in order to make predictions about what is coming in the next segment of text.
Model the Strategy:
Direct students’ attention to the first few paragraphs or subheadings of a selected
text passage. Think out loud as you anticipate/preview the first few subheadings.
Looking at the first subheading and explain that, since this is the first section of the
article, you predict it will give us general information about … (Read to confirm or
disprove your prediction and discuss. Ask if the “hypothesis” needs to be revised
any.) The next subheading will surely tell us something about … (Read to see if your
prediction is accurate.)
Guided Practice:
Ask students to look at the next few subheadings of the same article or text passage.
Ask them to anticipate what the next section of text might be about. (Read to confirm
or disprove. Any revision necessary?) What about the next sub-heading? Ask for a
volunteer to anticipate the subject/direction of the section. (Read to confirm or
disprove. Did the reader have to revise the prediction in any way?)
Independent Practice:
Provide independent practice with a new text passage. Assign students partners to
take turns reading and predicting what will come next in the text. Remind them to
provide “evidence” for their guesses. (Follow the same procedure as in the guided
practice activity.)
11
For the Teacher
Reciprocal Teaching/Putting It All Together
After students have become experienced with the thinking skills behind reciprocal
teaching, they are ready to apply this strategy in cooperative groups. Students will
not be ready for this level of independent RT until they have had a great deal of
instruction, modeling, and practice.
Model the Strategy:
Teachers will model the RT process using a selected text passage. (Recruit 3
capable class members/volunteers to assist you.) Group members will number from
1-4. Student #1 will begin by reading the first two paragraphs aloud (or having group
members read silently), then modeling the roles of questioner, clarifier, summarizer,
and predictor for this portion of the article. Then Student #2 will read and assume the
four RT roles for the next part of the passage. Continue until all group members
have performed the four skills and the entire passage has been read and processed.
Guided/Independent Practice:
Provide GUIDED/INDEPENDENT PRACTICE for the reciprocal teaching process by
having participants form groups of four. Remember to partner special needs
students with higher achieving students in the classroom who will be patient and
willing to provide them necessary support. Give each participant a copy of the
reciprocal teaching worksheet and/or provide them sticky notes to help track and
record thinking. Students will number themselves 1-4, with Student #I becoming the
first to assume the role of group leader. Each of the other students in the group is
responsible for participating in the dialogue. The leader will read the assigned
sections of the text passage aloud (or all group members may read it silently) and
then model the four RT strategies for this section. The next student (#2) then
assumes the role of group leader and performs the same tasks for the next assigned
section. Student #3 will assume the discussion leader’s role for the next assigned
portion of text. Finally, Student #4 will model the four roles for the remainder of the
passage.
12
Reciprocal Teaching/ Skills Model
Antarctica
Antarctica, the Continent
The southern-most of all continents, Antarctica, was discovered relatively recently. Until
1840 most geographers believed it was a group of islands. Only in the 20th century have
scientists discovered and mapped the continent, and much of this work has taken place
since World War II.
In size, Antarctica is the fifth largest continent after Asia, Africa, North and South
America. It is larger than Australia or Europe. Its 14 million square kilometers are
estimated at about 13.7 million square kilometers covered with ice and 280,000 square
kilometers free of ice.
Climate
The climate varies from dry, extremely cold inland areas to the moister and milder
coastline where the annual snowfall is about 24 inches a year. Winters in this low
southern hemisphere last from May through September where the temperature might be
as low as 94˚ F below zero. Summer (November through February) temperatures rise to
between -31˚F and 5˚F, but on the coast may reach as high as 32˚F. Wind-chill factors
drop these temperatures considerably, as the winds may gust from 45 mph to 120 mph.
Life Forms of Antarctica
Moss is the most common Antarctic plant, as few other specimens of plants could live in
this intemperate climate. In the northern areas, though, a hardy grass and an herb have
been discovered. Algae and lichens also survive in some spots. On land there are few
living creatures besides a few insects. However, the oceans surrounding Antarctica have
abundant wildlife. Whales and seals migrate in these waters, and laws have been
passed to protect them from being killed. Most famous among bird life on the continent
are its penguins. Over 40 flying birds visit or nest there.
Scientific Studies
From July 1957 until December 1958, scientists researched Antarctica during the
International Geophysical Year. Over 50 scientific stations were built by 12 countries in
different parts of the continent to study magnetism of the South Pole as well as solar
activity, gravity, weather, and the geography of the region. Later, in 1959, these
countries signed the Antarctic Treaty to allow only tourism, exploration, and research on
the continent. The scientists must share the results of their experiments; nuclear
weapons, nuclear waste, and military forces are not allowed. A more recent document,
the Madrid Protocol, signed in 1991, has been in effect since 1998. It sets aside the
continent of Antarctica as a natural reserve.
The largest community in Antarctica is McMurdo Station where approximately 1,000
researchers work in the summertime. Among the most significant research is the study
of the ozone layer.
13
Reciprocal Teaching/ Guided & Independent Practice for Skills
Global Warming
I. What is Global Warming?
When the Earth’s surface average temperature increases, global warming
occurs. In the 19th and 20th centuries, the average temperature of Earth rose
about 1° Fahrenheit. During the past 20 years, this trend is accelerating
according to recent evidence. Scientists are apprehensive that this warming
will have serious consequences on the future of Earth and its peoples.
II. Causes of Warming
It is uncertain exactly how the earth is responding to the warmer
temperatures. Gases like carbon dioxide, nitrous oxide, and methane amend
the chemical composition of Earth’s atmosphere by trapping heat on the
earth’s surface. Gas from the burning of fossil fuels like coal, oil, and natural
gas are a major cause. In addition, as people cut down trees and clear land
for homes and farms, the air becomes polluted. This practice eliminates the
important plant life that takes carbon dioxide out of the atmosphere, cleaning
the air.
III. Greenhouse Effect
Climate and weather come from the sun. Energy from the sun heats the
Earth’s surface and the Earth radiates energy back into space. Natural
atmospheric gases trap the energy and keep the Earth from becoming too
cold. Scientists call this the “greenhouse effect” because heat is held close to
Earth like the glass panels in greenhouses hold heat. This process is
important for sustaining life on Earth at a comfortable average temperature of
around 60°F. However, if the greenhouse gases intensify, the Earth heats up.
The United States is the greatest producer of carbon dioxide gases in the
world. Throughout the globe, the average person contributes only about 6
tons of carbon dioxide in one year, but in the United States, that number is 22
tons. Automobiles, home heating, and manufacturing contribute to this
number.
IV. Effects of Warming
Scientists fear the greenhouse effect will mutate weather patterns, harming
delicate plants and animals in the oceans and seas, destroying animal
habitats, causing floods and storms, and leading to the melting of the polar
ice.
14
Reciprocal Teaching/Guided & Independent Practice for Skills
Global Warming, continued
If the water temperature rises in the oceans, coral reefs begin to die. The
coral bleaches because it throws off the algae that feed it and give it color.
When the ecosystem is in trouble like this, it can cause a domino effect that
may harm all plants and animals in the sea.
Scientists from many countries are currently testing the changes of climate in
the polar zones and its effects on the animal and plant life. The northern
regions have warmed noticeably since 1950. For instance, Alaska’s average
temperature has risen 4° F. over the past 50 years. Arctic temperatures now
are the warmest they have been in the past 400 years, and the ice is 40%
thinner in some places. Ice in the Antarctic is also thinning. These trends
have serious consequences for plants, animals, and humans.
When the Earth’s temperature rises, bodies of water dry up and plant life dies.
Desert areas increase and crop yields decrease. Animals migrate to other
areas for their food; some species become threatened with extinction
because they cannot adapt.
V. Solutions
At every level, from scientists to everyday people, efforts are under way to
study and make changes that will curb the growth of global warming.
Countries around the world are committed to working on this difficult problem.
Carbon dioxide can be decreased in the atmosphere by national, state, and
local efforts to find alternative fuels for automobiles and other engines using
fossil fuels. Alternatives include the wind, sunlight, geothermal energy
(underground steam), and nuclear energy.
Automobile manufacturers and engineers are finding ways to improve the
efficiency of the fuels needed to run cars and trucks. Already available are the
“hybrid” cars that combine electricity with a small gasoline engine. Fuel cell
powered cars may also be available in the near future.
Keeping the ecosystem alive helps reduce carbon in the atmosphere. Plant
life ingests carbon dioxide, so emphasis on strong forests, plants, and
cropland is important to the future. This involves scientific oversight of the
lands and reduction in the numbers of acres that are cleared for human use.
15
Reciprocal Teaching/Model
(Putting It All Together)
States of Matter
Think back to breakfast this morning. You may have had solid toast, liquid milk or
juice, and of course, you breathed air, which is a gas. If you have seen a
lightning bolt during a summer storm, you have seen matter in its plasma state.
On Earth matter occurs in four physical states. These four states are solid, liquid,
gas, and plasma. What causes the differences among these four states of
matter?
The reason some matter is solid is that its atoms or molecules are in a fixed
position relative to each other. The individual atoms or molecules of a rock may
vibrate, but they don’t switch positions with each other. You can make a mental
model of this. Suppose you have a puzzle with its many pieces in place. The
pieces are packed so tightly that no one piece can switch positions with another
piece. But the pieces can move a little. For example, you can twist the whole
puzzle a few millimeters without breaking it apart. If it’s on a table, you can shake
the table and the puzzle’s individual pieces will vibrate. But the pieces of the
puzzle are held together even though they move. Such atoms or molecules are
strongly attracted to each other and resist being separated.
Atoms or molecules in liquid are also strongly attracted to each other, but they
aren’t as strongly attracted as they are in a solid. Atoms or molecules remain
close to one another in a liquid but are free to change positions with each other.
This allows liquids to flow. When you sit down to breakfast, you may have
several liquids at the table. You may have milk in a glass and syrup on your
pancakes. Both are substances in the liquid state, even though one flows more
freely than the other.
A liquid flows as it takes the shape of the container it’s placed in, but it resists
changes in volume. You can pour orange juice into a short, wide glass and it will
match the shape of the glass. You can then pour the same juice into a tall, skinny
glass and it will flow until it matches the shape of its new container. It does so
because its molecules move over and around each other.
Gases behave the way they do because their atoms or molecules have very little
attractive force on each other. This causes them to move freely and
independently. Air fresheners work because of this property. If an air freshener is
placed in a corner, it isn’t long before molecules from the air freshener have
spread throughout the room. Gases fill the entire container they are placed in.
16
Reciprocal Teaching/ Model
(Putting It All Together)
States of Matter, continued
What’s the most common state of matter? So far we’ve investigated matter in the
solid, liquid, and gaseous states. But most of the matter in the universe is in the
plasma state. Matter in this state is composed of ions and electrons. Many of the
electrons normally in the electron cloud have escaped and are outside of the
ion’s electron cloud. Stars are composed of matter in the plasma state. Plasma
also exists in the magnetic field near Jupiter. On Earth, plasma is found in
lightning bolts.
Matter is changed from a liquid to a solid at its freezing point and from a liquid to
a gas at its boiling point. You are probably familiar with the freezing and boiling
points of water. Water changes from a liquid to a solid at its freezing point of 0˚
C. It boils at 100˚ C. Water is the only substance that occurs naturally on Earth
as a solid, liquid, and gas.
Other substances don’t naturally exist in these three states on Earth. Their
boiling and freezing points are above or below the temperatures we experience.
Temperatures and conditions needed for matter to exist as plasma are even less
common on Earth.
The attraction between atoms or molecules and their rate of movement are two
factors that determine the state of matter. When you melt ice, you increase the
rate of movement of its molecules. They are then able to move apart. Adding
thermal energy to the ice causes this change. Even solid metal can be converted
to liquid when thermal energy is added.
Changes in state can also occur because of increases or decreases in pressure.
You can demonstrate this by applying pressure to an ice cube. It will change to
liquid water even though no thermal energy was added.
Chemical properties of matter don’t change when the matter changes state. But
some of its physical properties change. In which state is water the most dense?
You may be tempted to answer, “When it’s a solid,” but think about this. Although
most materials are denser in their solid state than in their liquid state, ice will float
in liquid water; therefore, ice is less dense than liquid water. This is because
water molecules move farther apart and the water expands as it freezes. Some
physical properties of substances don’t change when they change state. For
example, water is colorless and transparent in each of its states.
17
Reciprocal Teaching/ Guided & Independent Practice
(Putting It All Together)
Mineral Identification
How can you tell the difference between one of your classmates and another?
You can tell the difference between them without even thinking about it because
you observe things about them that make them different. The color of a
classmate’s hair or skin, or the shape of his or her face helps you tell him or her
from the rest of your class. Hair/skin color and facial shape are two properties
unique to individuals.
Appearance
Individual minerals also have unique properties. These properties help us tell the
difference between minerals. Color and appearance are just two of the clues that
are used to identify minerals.
But these clues alone are not enough to tell most minerals apart. The minerals
pyrite and gold are both gold in color and can appear to be the same. But gold is
worth a lot of money, while pyrite has little value. You need to look at other
properties of minerals to tell them apart.
Hardness
A measure of how easily a mineral can be scratched is its hardness. The mineral
talc is so soft you can scratch it loose with your fingernail. You might be familiar
with talcum powder made from this mineral. A diamond, on the other hand, is the
hardest mineral. Some diamonds are used as cutting tools. A diamond can be
scratched only by another diamond.
In order to compare the hardness of minerals, a list of common minerals and
their hardness was developed by the German scientist, Friedrich Mohs. The ten
common minerals, with 1 being the softest and 10 the hardest, are listed on the
Mohs Scale on the next page. See Table 3-2.
Here’s how the scale works. Let’s say you have a clear or whitish-colored mineral
that you know is either calcite or quartz. You scratch it on your fingernail and
then on a bright, shiny piece of copper. You find that the mineral scratches your
fingernail but doesn’t scratch the copper. Because the hardness of your fingernail
is 2.5 and that of a piece of copper is 3.5, you can determine the unknown
mineral’s hardness to be about 3. Because quartz has a hardness of 7, your
mystery mineral must be calcite.
18
Reciprocal Teaching/Guided & Independent Practice
(Putting It All Together)
Mineral Identification, continued
Table 3-2
Mineral Hardness
Moh’s Hardness Scale
________________________________________________________________
softest Hardness of Common
Objects
Talc 1
Gypsum 2 fingernail (2.5)
Calcite 3 piece of copper (3.5)
Fluorite 4 iron nail (4.5)
Apatite 5 glass (5.5)
Feldspar 6 steel file (6.5)
Quartz 7 streak plate (7)
Topaz 8
Corundum 9
Diamond 10
________________________________________________________________
Luster
Luster describes how light is reflected from a mineral’s surface. Luster is defined
as either metallic or nonmetallic. Minerals with a metallic luster always shine like
metal. Metallic luster can be compared to the shine of a fancy metal belt buckle
or the shiny chrome trim on some cars. When a mineral does not shine like
metal, its luster is nonmetallic. Examples of nonmetallic luster include dull,
pearly, and silky.
19
Reciprocal Teaching/Guided & Independent Practice
(Putting It All Together)
Mineral Identification, continued
Color
The color of a mineral can also be a clue to its identity. A mineral whose color
helps in its identification is sulfur. Sulfur has a distinctive yellow color. However,
just remember that color alone is not enough to identify a mineral.
Streak
Streak is the color of the mineral when it is broken up and powdered. When a
mineral is rubbed across a piece of unglazed porcelain tile, a streak is left
behind. This streak is the powdered mineral. Gold and pyrite can be identified
with the streak test. Gold has a yellow streak and pyrite has a greenish black or
brown-black streak.
The streak test works only for minerals that are softer than the streak plate. Very
soft minerals will leave a streak even on paper. The last time you used a pencil to
write on paper, you used the streak of the mineral graphite. Graphite is used in
pencil lead because it is soft enough to leave a streak on paper.
Cleavage and Fracture
The way a mineral breaks is another clue to its identity. Minerals that break along
smooth, flat surfaces have cleavage. Cleavage, like hardness, is determined by
the arrangement of the mineral’s atoms. Mica is a mineral that has perfect
cleavage. If you were to take a layer cake and separate its layers, you would
show that the cake has cleavage. But not all minerals have cleavage. Minerals
that break with rough or jagged edges have fracture. Quartz is a mineral with
fracture. If you were to grab a chunk out of the side of that cake, it would be like
breaking a mineral with fracture.
Other Properties
Some minerals have unique properties. Magnetite is attracted to magnets.
Lodestone, a form of magnetite, will pick up iron filings like a magnet. Light bends
in two directions when it passes through some calcite specimens, causing you to
see double image. Calcite can also be identified because it fizzes when
hydrochloric acid is put on it.
You can see that you sometimes need more information than just color and
appearance to identify most minerals. You might also need to test its streak, its
hardness, its luster, and its cleavage or fracture. You can be just as good at
identifying minerals as you are at recognizing your friends in class!
20
