Youngstown City Schools
SCIENCE: GRADE 7
UNIT #2: ENERGY TRANSFER AND WAVES - - (4 Weeks)
SYNOPSIS: Students will study the behavior of energy and the different methods by which it may be transferred or
transformed - - but never lost. Students will investigate the law of conservation of energy. Students will design, build, and
demonstrate a musical instrument, or they will create a plan to improve the sound quality within an existing space; or they
will create a new and more efficient way to conduct sound for a particular purpose.
Enablers: Objects with energy have the ability to cause change. Energy can transfer from one location or object to another
and can be transformed from one form to another.
PS.7.2 Energy can be transformed or transferred but is never lost.
PS.7.2.a When energy is transferred from one system to another, the quantity of energy before transfer equals the quantity of energy
PS.7.2.b When energy is transformed from one form to another, the total amount of energy remains the same.
PS.7.3 Energy can be transferred through a variety of ways.
PS.7.3.a Mechanical energy can be transferred when objects push or pull on each other over a distance.
PS.7.3.b Electromagnetic waves transfer energy when they interact with matter.
RST 2 Determine the central ideas or information of a primary or secondary source; provide an accurate summary of the source distinct
from prior knowledge or opinions.
RST 9 Analyze the relationship between a primary and secondary source on the same topic.
WHST 7 Conduct short research projects to answer a question (including a self-generated question), drawing on several sources and
generating additional related, focused questions that allow for multiple avenues of exploration.
MOTIVATION TEACHER NOTES
1. Class brainstorms different types of energy. Ask the students Handout on page 7 of
whether energy can "disappear" (no – it can only change form). Teacher asks students for unit plan
examples of energy transformations and makes list on chart paper. (attachment: Waves
& Energy Notes)
2. Teacher mentions that students will be studying about waves in
this unit and asks them to brainstorm their ideas about what the following have in
common: microwave oven, X-ray, red food warmer lamp at McDonalds, motion sensor,
and remote control. Teacher records ideas on chart paper which is posted in room.
Students are asked to name other devices that would fit in this list (e.g., TV, radio, Wi-Fi, Handout on pages 8-9
ultraviolet – tanning bed) and what are the attributes that these devices might have in of unit plan
common (since they are functioning with electromagnetic waves). Teacher uses a
diagram (attached) to show what electromagnetic waves are and that they are found
3. Teacher reminds students how their Notes are to be taken and
how they will be “evaluated;” explain that students will be asked not only to record key
8/1/2012 YCS Grade 7 Science: Unit 2 - - Energy Transfer and Waves 2012-13 1
MOTIVATION TEACHER NOTES
information but write reactions and reflections like a scientist would write, as per
designate tasks, audiences, and purposes.
4. Students set person and academic goals and record for reference
at the end of the unit
5. Teacher previews for students what the Authentic Assessment will
be and what they will be expected to do
kinetic energy mechanical energy amplitude energy transformation
energy transfer frequency wave crest
compression mechanical force pitch longitudinal wave
media (medium) rarefaction transverse trough
TEACHING-LEARNING TEACHER NOTES
1. Teacher asks the students for a definition of kinetic energy (energy of motion).
Teacher holds up a golf ball and asks whether the ball has any kinetic energy (no –
it is not moving). Teacher asks them to come up with ways of giving the ball kinetic
energy (throw it, drop it, and hit it with another object). Teacher asks what all of the
actions have in common; students discuss possible answers in terms of the action being
described (energy being transferred); teacher records comments on chart paper.
2. Teacher explains that energy can be transferred (moved) from one object to another and
transformed (changed) from one form to another; students give examples for both. Handout on pages 10-11
Students read an article, “A Model for the Principle of Energy Conservation” (attached) of unit plan
and discuss how the model applies to class work. Teacher introduces the conservation of
energy (attached Energy Conservation notes); students record notes. Students analyze the
relationship between the primary and secondary source on the topic of energy conservation.
(PS 7.2, PS 7.2 a, b ; RST 9)
3. Students use computer simulations to explore the interaction between kinetic and potential
energy; students write in a paragraph how kinetic and potential energy are related in a real-
world example. ( PS 7.2, PS 7.2 a, b)
4. Teacher makes copies of article (attached - Mechanical Energy )which explains Handout on pages 12-15
of unit plan
mechanical energy; students read the article to determine the central ideas of the source,
complete directed reading guide and summarize the article in their own words from new
knowledge gained. Teacher lectures about mechanical energy and students take notes
(PS.7.3.a, RST 2)
5. Students, working in pairs, use wind-up toys – wound 2-3 times and released. Students
measure the distance the toy travels and repeats the procedure the next time winding the
toy 3-4 times. Students record data, and compare the distances traveled and write 2
sentences which explain the relationship between the number of times the toy was wound to
the distance it traveled. (PS.7.3, PS.7.3.a)
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TEACHING-LEARNING TEACHER NOTES
6. Teacher asks students to consider how waves can show mechanical energy and energy
transfer; class discusses topic and teacher records responses on chart paper. Student
volunteers demonstrate a wave using first a piece of rope and second, using a slinky (note –
slinky may be placed on the table, on the floor, and/or suspended from the ceiling).
Students volunteer to do the demo while teacher makes sure they are doing it correctly by
asking questions of the rest of the class. (Questions: What is needed to start the wave? Is
there a pattern created by the object making a wave? What pattern does each make? Are
the patterns alike? How are they different? ) With teacher’s supervision, students doing the
demo may have to change their initial attempt in order for the results to reveal the intended
outcome. Students record diagrams of what they see in their notebooks and answer
discussion questions after the demonstration. (PS.7.3, PS.7.3.a)
7. Teacher demonstrates the action of waves (#1) using a clear Pyrex baking dish with an inch Handout on page 16 of
of water in it that is set on the overhead. An object (such as a pencil, finger) is used to unit plan
create one wave. Students observe trials of the demo and record the time how long it takes
for the wave to completely stop. Students record answers on Data Sheet (attached).
8. Teacher demonstrates the action of waves (#2) using a clear Pyrex baking dish with an inch
of water in it that is set on the overhead. An object (such as a pencil, finger) is used to
create a steady series of waves. Students observe and verbally describe the action of the
waves in terms of: the direction the wave traveled, what happens when the waves hit the
opposite side, what happens when the outgoing waves meet the returning waves. Students
record answers on Data Sheet and should observe the following: the direction waves
traveled was in a semicircle radiating outward from the disturbance. When the waves hit the
side they bounce back toward the source. When outgoing waves meet incoming waves
they may either cancel each other or reinforce each other depending on how the waves
meet (i.e., crest to crest or trough to trough). (PS.7.3.a )
9. Teacher demonstrates the action of waves (#3) using the same procedure with vegetable oil
instead of water; students record results. Students complete a graphic organizer (e.g.,
Venn diagram, T-chart) to illustrate similarities and differences between the two media and
the time it takes the waves to stop. Students write a summary to explain the results of the
comparison in terms of the energy transfer. Teacher asks students to discuss when and
where the energy transfers where in relation to the medium and why the wave stops.
Teacher relates the connection between a mechanical force and the movement of waves
in terms of medium and time it takes for them to move. (PS.7.3.a)
10. Teacher introduces “anatomy” of a wave for each of the two types of waves one at a time,
transverse and longitudinal, by using an unlabeled diagram of the waves(using overhead,
Smartboard, Promethean, etc.) and a vocabulary word list ( crest, trough, frequency,
wavelength, amplitude, rarefaction) Students volunteer to label diagram using the correct
term from the wordlist . (PS.7.3.b)
11. Teacher draws/ uses overhead diagram to explain how energy of the wave is related to its
frequency and wavelength;; students record similar diagram in their notes with the
explanation. Teacher uses diagrams to illustrate amplitude (loudness) and pitch; students
record similar diagrams in their notes with the explanation. (PS.7.3.b)
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TEACHING-LEARNING TEACHER NOTES
12. Teacher refers to earlier motivation question and introduces electromagnetic waves and
uses an internet interactive site to show students how wave properties alter the resulting
wave pattern; students use simulation to explore relationship between frequency,
wavelength, and energy to adjust the intensity of radiation and set the wave in motion.
Students use tabs at the site to make changes with the variables Teacher asks questions at
the end of the computer session: As frequency increases what happens to amplitude and
frequency. What is the importance of the color change in the waves? Students write
sentences to explain the relationships (using two prompts – 1. As _?__increases,
__?__decreases. 2. As __?__ decreases, __?__ increases. (PS.7.3.b)
13. Students read pages 7-8 in Sound & Light textbook and write in their own words why waves
are called transverse or longitudinal (compression as noted in Content Elaboration of
Model Curriculum) in terms of the direction of movement of the medium. (PS.7.3a,b RST9)
14. Teacher introduces sound waves and asks how sound travels differently than water waves, Handout on pages 17-18
Slinky waves, electromagnetic waves; student responses are recorded on chart paper. of unit plan
Teacher demonstrates how sound travels as a longitudinal wave using a Slinky. Students
read article, “Sound as a Longitudinal Wave” and complete a directed reading guide
(attached). Class discusses questions.
15. Teacher demonstrates how sound waves transmission can be interrupted using tuning Handout on pages 19-20
forks placed in/on different surfaces. Students are asked to rate the best and the worst of unit plan
materials for sound transmission and explain what caused the sound to travel differently.
Students work in small groups and explain real-world examples sound differences (e.g.,
police car siren, whales communicate underwater, an approaching train some distance
away can be heard through railroad tracks, jet breaks the sound barrier, high pitched
sounds of a dog whistle, talking is the least effective way to communicate). Teacher has
students read a new article about a new hearing aid which uses your teeth to conduct the
sound (attached) Students determine the central ideas of the source; provide an accurate
summary of what they learned from the source that they did not know before reading the
article. (PS.7.3a; RST 2)
16. Teacher demonstrates how sound can be interrupted or lessened by acoustical materials
such as Styrofoam – a metal hanger is hung loosely on your thumb and is struck with a
spoon; then using the same set-up a piece of Styrofoam block is placed between the hanger
and your thumb. Students talk about the difference in sound and how Styrofoam made a
difference (soundproofing). Students brainstorm materials that are used for specific
acoustical applications because of their properties. Teacher reminds students of their
authentic assessment related to waves. (PS.7.3)
17. Students are asked the reason that sound waves are different from electromagnetic waves
(answer: they need a medium) and how that makes sound waves different. Students create
a graphic organizer (e.g., Venn diagram, T-chart) to show similarities and differences
between them; students describe the attributes of two different patterns that have been
demonstrated. ( PS.7.3a, PS.7.3b)
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TEACHING-LEARNING TEACHER NOTES
18. Teacher and students demonstrate sound-making devices using materials of choice (e.g.,
straws, rubber bands, metal pieces, etc.) that the class collects in a box from beginning of
the year and it can give students ideas for building a musical instrument. Students write a
self-generated question and plan for designing, testing, and modifying their own created
musical instrument. Throughout the research projects, students cite several sources to
generate additional related, focused questions that allow for multiple avenues of exploration
on the same topic. (PS.7.3.a WHST 7)
19. Teacher introduces activity for students to design and conduct their own investigation to Handout on page 21 of
determine what will happen to the kinetic energy of a golf ball when it hits three different unit plan
surfaces (see attachment Kinetic Energy –Golf Ball Activity). In this lesson, students will
be introduced to the concepts of reflection and absorption as they relate to light energy. A
bouncing ball will be used to illustrate what happens when a light ray (energy) hits a
reflecting (e.g. tin foil) or absorbing (e.g. asphalt) surface. Students record data and
summarize their findings. Class discusses results and identifies differences between
reflection and absorption of energy and how light is affected by these types of transmission.
(PS 7.3a )
20. Teacher asks students why knowing the speed of a wave is important - Teacher asks
students ideas on how to find the speed of a wave (e.g., tsunami occurs in Japan and you
live in Alaska; earthquake occurs on opposite side of globe; watch lightning and count
seconds (5 sec.= ~1 mile)until thunder is heard to determine distance/direction away from
the storm). (PS.7.3.a PS.7.3.a)
TRADITIONAL ASSESSMENT TEACHER NOTES
2. Science Notebooks – includes investigations and demonstrations
3. Unit Test
4. 2- and 4-point response questions
AUTHENTIC ASSESSMENT TEACHER NOTES
1. Students evaluate their goals
2. Students complete an activity to show understanding of how energy transfer and waves
relate in the real world with regard to sound. (PS.7.3.a )
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Motivation Activity #1
1. Energy Types and Transformations
We can think about energy in this way. We can use this idea to track energy transfers during changes. We need to
be careful to look everywhere to ensure that we can account for all the energy. Students may come up with many
possibilities, but make sure that kinetic energy, heat, and light are included in the list.
Some ideas about energy:
Energy is stored in fuels (chemicals).
Energy can be stored by lifting objects (potential energy).
Moving objects carry energy (kinetic energy).
Electric current carries energy.
Light (and other forms of radiation) carries energy.
Heat carries energy.
Sound carries energy.
Chemical (food) ------ mechanical (ride a bike)
Radiant (sun) --------- chemical (plant makes sugar)
Chemical (gas) ------- mechanical (moving car)
Electrical (outlet)------ heat (stove)
Chemical(battery)----- electrical (flashlight)
Heat engine(chemical) ----- heat -----mechanical ----- electrical
Ask students to think of transformations that involve multiple energy transformations
We are exposed to different types of waves every day. Radio waves, microwaves, and UV waves are just a few of
the unseen ones. But of course when we experience visible light, we are perceiving color in the form of a wave's
wavelength and frequency. When we experience audible sound, it's the wave's wavelength and frequency we
perceive. Waves are all around us, in many frequencies and wavelengths. Some are safe, and some are very
dangerous. They help us communicate globally and cook. They can kill cancer or cause it. So what do waves look
like? Let’s find out in Unit #2!
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Motivation Activity #2
+ Visit NASA.gov + Science@NASA + IMAGERS Home
Electromagnetic Waves have different wavelengths
When you listen to the radio, watch TV, or cook
dinner in a microwave oven, you are using
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Radio waves, television waves, and microwaves
are all types of electromagnetic waves. They
differ from each other in wavelength.
Wavelength is the distance between one wave
crest to the next.
Waves in the electromagnetic spectrum vary in size from very long radio waves the size of buildings, to very short gamma-rays smaller than the size
of the nucleus of an atom.
Did you know that electromagnetic waves can not only be described by their wavelength, but also by their energy and frequency? All three of these
things are related to each other mathematically. This means that it is correct to talk about the energy of an X-ray or the wavelength of a microwave
or the frequency of a radio wave. The electromagnetic spectrum includes, from longest wavelength to shortest: radio waves, microwaves, infrared,
optical, ultraviolet, X-rays, and gamma-rays.
To tour the electromagnetic spectrum, follow the links below!
RADIO WAVES | MICROWAVES | INFRARED | VISIBLE LIGHT | ULTRAVIOLET | X-RAYS | GAMMA RAYS
RETURN TO THE ELECTROMAGNETIC SPECTRUM
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Teaching-Learning Activity #2
A Model for the Principle of Energy Transfer
Adapted from Richard Feynman
Imagine Dennis has 28 building blocks, which are all the same. They are absolutely indestructible and
cannot be divided into pieces. His mother puts him and his 28 blocks into a room at the beginning of the
day. At the end of each day, being curious, she counts them and discovers a phenomenal law. No matter
what he does with the blocks, there are always 28 remaining.
This continues for some time until one day she only counts 27, but with a little searching she discovers one
under a rug. She realizes she must be careful to look everywhere.
One day later she can only find 26. She looks everywhere in the room, but cannot find them. Then she
realizes the window is open and finds two blocks outside in the garden.
Another day, she discovers 30 blocks. This causes considerable dismay until she realizes that Bruce has
visited that day, and left a few of his own blocks behind. Dennis' mother removes the extra blocks, gives the
remaining ones back to Bruce, and all returns to normal.
Energy transfer & Energy Conservation
This teaching model used by physicist Richard Feynman ( A model for the principle of energy transfer)
involves thinking about energy as a series of units, like a child's bricks.
Energy is transferred within and between systems, some ending up in one location while others end up in
another. In this model of energy, the energy is transferred from one place to another.
Energy is located in particular positions. We speak of:
Energy being transferred from a battery to a bulb by electricity.
Energy being transferred from the bulb to the air (and to our eyes) by light.
Inventing the idea and notion of 'energy conservation' allows us to keep track of things when changes
occur. The idea that there is a number at the start of a change that is the same as the number we calculate
at the end of that change is a very useful idea.
Energy conservation is the key concept that helps us to track changes, account for what is happening and
to make predictions.
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Teaching-Learning Activities #2
Energy Conservation Notes
Energy exists in many forms, including kinetic, potential, chemical, electrical, thermal (heat), and light. A central tenet
of modern science is that energy cannot be "lost", but only change its form. This means that energy lost by an object
must be balanced by a gain of an exactly equal amount of energy by one or more other objects in the universe.
This transfer of energy often, but not always, involves a change in form of at least some of the energy being
transferred. The most common type of energy transformation is that of one form of energy to heat (thermal) energy.
Heat energy can be thought of as a "default setting" for the energy in the universe. When energy of another kind is
transferred between objects, inefficiencies in the system result in a transfer that is not completely efficient and the
"missing" energy is converted to heat energy. Heat energy is almost always the form taken by energy lost due to
The ability for "warm-blooded" animals to regulate their body temperature is a direct consequence of this – when a
mammal (for example) feels cold, its body converts chemical energy (stored in fat and other molecules) to heat via
incomplete energy transfer.
The conversion of other forms of energy to heat also has profound consequences for surface air, water, and soil
temperatures, as well as for building and city planning.
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Teaching-Learning Activity #4
Work is done upon an object whenever a force acts upon it to cause
it to be displaced. Work involves a force acting upon an object to
cause a displacement. In all instances in which work is done, there is
an object that supplies the force in order to do the work. If a World
Civilization book is lifted to the top shelf of a student locker, then the
student supplies the force to do the work on the book. If a plow is
displaced across a field, then some form of farm equipment (usually
a tractor or a horse) supplies the force to do the work on the plow. If
a pitcher winds up and accelerates a baseball towards home plate,
then the pitcher supplies the force to do the work on the baseball. If a
roller coaster car is displaced from ground level to the top of the first
drop of a roller coaster ride, then a chain driven by a motor supplies
the force to do the work on the car. If a barbell is displaced from ground level to a height above a
weightlifter's head, then the weightlifter is supplying a force to do work on the barbell. In all instances, an
object that possesses some form of energy supplies the force to do the work. In the instances described
here, the objects doing the work (a student, a tractor, a pitcher, a motor/chain) possess chemical potential
energy stored in food or fuel that is transformed into work. In the process of doing work, the object that is
doing the work exchanges energy with the object upon which the work is done. When the work is done
upon the object, that object gains energy. The energy acquired by the objects upon which work is done is
known as mechanical energy.
Mechanical energy is the energy that is possessed by an object due to
its motion or due to its position. Mechanical energy can be either kinetic
energy (energy of motion) or potential energy (stored energy of
position). Objects have mechanical energy if they are in motion and/or if
they are at some position relative to a zero potential energy position (for
example, a brick held at a vertical position above the ground or zero
height position). A moving car possesses mechanical energy due to its
motion (kinetic energy). A moving baseball possesses mechanical
energy due to both its high speed (kinetic energy) and its vertical
position above the ground (gravitational potential energy). A World
Civilization book at rest on the top shelf of a locker possesses mechanical energy due to its vertical position
above the ground (gravitational potential energy). A barbell lifted high above a weightlifter's head
possesses mechanical energy due to its vertical position above the ground (gravitational potential energy).
A drawn bow possesses mechanical energy due to its stretched position (elastic potential energy).
Mechanical Energy as the Ability to Do Work
An object that possesses mechanical energy is able to do work. In fact,
mechanical energy is often defined as the ability to do work. Any object
that possesses mechanical energy - whether it is in the form of
potential energy or kinetic energy - is able to do work. That is, its
mechanical energy enables that object to apply a force to another
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object in order to cause it to be displaced.
Numerous examples can be given of how an object with mechanical energy can harness that energy in
order to apply a force to cause another object to be displaced. A classic example involves the massive
wrecking ball of a demolition machine. The wrecking ball is a massive object that is swung backwards to a
high position and allowed to swing forward into building structure or other object in order to demolish it.
Upon hitting the structure, the wrecking ball applies a force to it in order to cause the wall of the structure to
be displaced. The diagram below depicts the process by which the mechanical energy of a wrecking ball
can be used to do work.
A hammer is a tool that utilizes mechanical energy to do work. The
mechanical energy of a hammer gives the hammer its ability to apply a force
to a nail in order to cause it to be displaced. Because the hammer has
mechanical energy (in the form of kinetic energy), it is able to do work on the
nail. Mechanical energy is the ability to do work.
Another example that illustrates how mechanical
energy is the ability of an object to do work can be
seen any evening at your local bowling alley. The
mechanical energy of a bowling ball gives the ball the ability to apply a force to a
bowling pin in order to cause it to be displaced. Because the massive ball has
mechanical energy (in the form of kinetic energy), it is able to do work on the pin.
Mechanical energy is the ability to do work.
A dart gun is still another example of how mechanical energy of
an object can do work on another object. When a dart gun is
loaded and the springs are compressed, it possesses
mechanical energy. The mechanical energy of the compressed
springs gives the springs the ability to apply a force to the dart in
order to cause it to be displaced. Because of the springs have
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mechanical energy (in the form of elastic potential energy), it is able to do work on the dart. Mechanical
energy is the ability to do work.
A common scene in some parts of the countryside is a "wind
farm." High-speed winds are used to do work on the blades of a
turbine at the so-called wind farm. The mechanical energy of the
moving air gives the air particles the ability to apply a force and
cause a displacement of the blades. As the blades spin, their
energy is subsequently converted into electrical energy (a non-
mechanical form of energy) and supplied to homes and industries
in order to run electrical appliances. Because the moving wind
has mechanical energy (in the form of kinetic energy), it is able to
do work on the blades. Once more, mechanical energy is the
ability to do work.
The Total Mechanical Energy
As already mentioned, the mechanical energy of an object can be the result of its motion (i.e., kinetic
energy) and/or the result of its stored energy of position (i.e., potential energy). The total amount of
mechanical energy is merely the sum of the potential energy and the kinetic energy. This sum is simply
referred to as the total mechanical energy (abbreviated TME).
TME = PE + KE
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Teaching-Learning Activity #4
DIRECTED READING GUIDE: MECHANICAL ENERGY ARTICLE
1. Compare and contrast potential energy with kinetic energy.
2. Explain two ways that you can convert potential energy to kinetic energy while using your writing utensil.
3. How is it possible to increase the potential energy of a book resting on a shelf?
4. Describe how mechanical energy may be used to do work in each of the following cases:
Traveling from home to school
Running a race
5. Identify the source of the mechanical energy to complete each of the following:
Riding a bicycle
Juggling three baseballs
Bouncing a basketball
6. In which case is more work done, carrying 5 heavy bags up 3 flights of stairs or making 5 different trips to
carry them up one at a time? Explain your answer.
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Teaching-Learning Activity #7
Lab data sheet on waves
1. Observe the creation of a wave demonstrated by the teacher.
How was the wave created?
How long does it take for the wave to travel out and reflect back to the starting point?
How long did it take for the wave to completely stop moving?
2. Observe the creation of several waves demonstrated by the teacher.
In which direction did the waves travel?
What happens when the waves hit the opposite side?
What happens when the outgoing waves meet the returning waves?
3. Complete the same activity as above. This time the wave material will be vegetable oil.
How long does it take for one wave to travel out and reflect back to the starting point?
How long did it take the single wave of the vegetable oil to completely stop moving?
What happens when the waves hit the opposite side?
What happens when the outgoing waves meet the incoming waves?
Record several of the ideas mentioned in the energy transfer discussion that followed the
Students use the graphic organizer provided, and illustrate similarities and differences between the two
media and the time it takes for the waves to stop.
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Teaching – Learning Activity #14
Sound as a Longitudinal Wave
In the first part of Lesson 1, it was mentioned that sound is a mechanical wave that is created by a vibrating object.
The vibrations of the object set particles in the surrounding medium in vibrational motion, thus transporting energy
through the medium. For a sound wave traveling through air, the vibrations of the particles are best described as
longitudinal. Longitudinal waves are waves in which the motion of the individual particles of the medium is in a
direction that is parallel to the direction of energy transport. A longitudinal wave can be created in a slinky if the slinky
is stretched out in a horizontal direction and the first coils of the slinky are vibrated horizontally. In such a case, each
individual coil of the medium is set into vibrational motion in directions parallel to the direction that the energy is
Sound waves in air (and any fluid medium) are longitudinal waves because particles of the medium through which
the sound is transported vibrate parallel to the direction that the sound wave moves. A vibrating string can create
longitudinal waves as depicted in the animation below. As the vibrating string moves in the forward direction, it begins
to push upon surrounding air molecules, moving them to the right towards their nearest neighbor. This causes the air
molecules to the right of the string to be compressed into a small region of space. As the vibrating string moves in the
reverse direction (leftward), it lowers the pressure of the air immediately to its right, thus causing air molecules to
move back leftward. The lower pressure to the right of the string causes air molecules in that region immediately to
the right of the string to expand into a large region of space. The back and forth vibration of the string causes
individual air molecules (or a layer of air molecules) in the region immediately to the right of the string to continually
vibrate back and forth horizontally. The molecules move rightward as the string moves rightward and then leftward as
the string moves leftward. These back and forth vibrations are imparted to adjacent neighbors by particle-to-particle
interaction. Other surrounding particles begin to move rightward and leftward, thus sending a wave to the right. Since
air molecules (the particles of the medium) are moving in a direction that is parallel to the direction that the wave
moves, the sound wave is referred to as a longitudinal wave. The result of such longitudinal vibrations is the creation
of compressions and rarefactions within the air.
Regardless of the source of the sound wave - whether it is a vibrating string or the vibrating tines of a tuning fork -
sound waves traveling through air are longitudinal waves. And the essential characteristic of a longitudinal wave that
distinguishes it from other types of waves is that the particles of the medium move in a direction parallel to the
direction of energy transport.
Go to http://www.physicsclassroom.com/media/waves/tfl.cfm to see simulations
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Teaching-Learning Activity #14
Directed Reading Guide: “Sound as a Longitudinal Wave” article
1. All sound waves must have two identifiable components. What are the two components? List them in your own
2. Use a T chart to compare and contrast compressions and rarefactions.
3. Use dots to represent air particles, and draw a diagram to show compressions and rarefactions of a sound wave.
4. What is your best hypothesis for the reason that sound waves travel faster in a steel bar than in air?
8/1/2012 YCS Grade 7 Science: Unit 2 - - Energy Transfer and Waves 2012-13 17
Teaching-Learning Activity #15
New hearing aid conducts sound through tooth
Lesley Ciarula Taylor
SUPPLIED PHOTO The SoundBite hearing device conducts sound through a back tooth.
8/1/2012 YCS Grade 7 Science: Unit 2 - - Energy Transfer and Waves 2012-13 18
A 39-year-old California woman testing a revolutionary new hearing aid that works through
a tooth reports that it made it possible to hear clearly everywhere except at a Metallica
“I had problems holding a conversation while they were playing (I had an ear plug in my
good ear), but my husband said that even for him it was next to impossible,” said Gloria on
a discussion forum for people with deafness.
The woman, who didn’t disclose her last name, described the end of her 60-day clinical trial
of the Sonitus SoundBite on Jan. 23 as “kinda sad.”
Sonitus Medical will apply soon for U.S. government approval for the device, which
conducts sound through a back tooth rather than the conventional method of turning up the
sound on air travelling into the ear. The company hopes to have the device on the market
The hearing aid didn’t interfere with speaking or eating and “continues to give hope to a
huge group of us with single-side deafness who are waiting for something non-invasive,”
SoundBite starts with a custom-built device fitted to a molar and a wireless microphone
within the ear canal. A digital audio device worn as a thin cord behind the ear picks up the
sound from the microphone and transmits it to the tooth device, which produces sound
vibrations that reach the cochleae through the bone. While some hearing aids use bone
conduction to send sounds to the cochleae, they also require a titanium post to be drilled
into the skull.
New Scientist magazine described it as a 21st century version of Beethoven’s method for
circumventing his deafness: a rod attached to his piano then clenched in his teeth to pick up
8/1/2012 YCS Grade 7 Science: Unit 2 - - Energy Transfer and Waves 2012-13 19
Teaching-Learning Activity #19
KINETIC ENERGY: GOLF BALL ACTIVITY
To introduce energy transfer and transformation processes.
golf balls (one for each lab group of students)
firm exercise mat (the type used in school gym classes
soft pillow (down is ideal, but any soft, squishy item will work; it should be softer than the exercise mat)
black- or marker board and chalk/markers
1. Explain to the students that they are going to investigate what will happen to the kinetic energy of a ball when it
hits three different surfaces (floor, mat, pillow). Tell them that they can answer this question using any
procedure they can devise (subject to teacher approval to avoid injuries or overly elaborate procedures),
provided it utilizes only a golf ball, the floor, the gym mat, the pillow, and a ruler and/or yard stick (optional).
2. Divide the students into lab groups (groups of 2-3 are ideal) and give the groups approximately 5-10 minutes to
think of a way to answer the question, along with prediction(s) for the outcome(s). Once their procedure has
been approved and their predictions made, the students can retrieve a golf ball from the teacher and conduct
their experiments with a limited number of trials.
3. When each group has completed their experiment (the students will have to share the gym mat and pillow) and
recorded the results, bring their attention back to the front and ask each group for a short summary of their
experiment and results.
4. The students should have found that the golf ball bounces highest from the hard floor and does not bounce at all
from the pillow. Some possible reasons that some groups may not obtain these results include a) adding
different amounts of kinetic energy to the ball for each target (this is particularly likely if the students chose to
throw the golf ball) or b) adding insufficient kinetic energy to the ball at each trial (such that even when the ball is
dropped to the floor it does not bounce).
5. Ask the students what "happened" to the kinetic energy of the ball when it hit each surface. Introduce the terms
reflection and absorption, and help them understand the meaning of each and the analogies with each surface-
ball interaction. Ensure that they understand that the "absorption" of energy is really just a conversion of one
form of energy (kinetic, in this case) to another (heat and kinetic energy here).
6. Students summarize their findings in their Science notebook.
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