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. 
STANDARDS
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 after transfer. 
 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.

LITERACY STANDARDS
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 whether energy can "disappear" (no – it can only change form). Teacher asks students for 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, ultraviolet – tanning bed) and what are the attributes that these devices might have in common (since they are functioning with electromagnetic waves). Teacher uses a diagram (attached) to show what electromagnetic waves are and that they are found everywhere.

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 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	Handout on page 7 of unit plan

Handout on pages 8-9 of unit plan	

UNIT VOCABULARY 	
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.  Students read an article,   “A Model for the Principle of Energy Conservation” (attached) 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)
http://phet.colorado.edu/simulations/sims.php?sim=Energy_Skate_Park
http://phet.colorado.edu/simulations/sims.php?sim=Pendulum_Lab

4. 	Teacher makes copies of article (attached  - Mechanical Energy )which explains 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)

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 of water in it that is set on the overhead.  An object (such as a pencil, finger) is used to 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). (PS.7.3,  PS.7.3.a)

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)

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) (http://micromagnet.fsu.edu/primer/java/wavebasics/ )

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, Slinky waves, electromagnetic waves; student responses are recorded on chart paper.  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 forks placed in/on different surfaces.  Students are asked to rate the best and the worst 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)

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 determine what will happen to the kinetic energy of a golf ball when it hits three different 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)  	

Handout on pages 10-11 of unit plan

Handout on pages 12-15 of unit plan

Handout on page 16 of unit plan

Handout on pages 17-18 of unit plan

Handout on pages 19-20 of unit plan

Handout on page 21 of unit plan

TRADITIONAL ASSESSMENT	TEACHER NOTES	
1. 	Quizzes 
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 )
Joe 

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. 
 Energy Transformations  
•	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
2. Waves  
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!

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 electromagnetic waves.	

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 

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. 

Teaching-Learning Activities #2 
Energy Conservation Notes 
Background Information
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 inefficiency.  
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.  

Teaching-Learning Activity #4
Mechanical Energy
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 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 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

Teaching-Learning Activity #4     
DIRECTED READING GUIDE: MECHANICAL ENERGY ARTICLE
Name _______________________________________
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:
	Playing football

	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.

Teaching-Learning Activity #7
Name________________________________
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 demonstration?

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.

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 transported.

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 
Teaching-Learning Activity #14           
Directed Reading Guide: “Sound as a Longitudinal Wave” article
Name___________________________________
1. All sound waves must have two identifiable components. What are the two components? List them in your own words.

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?

Teaching-Learning Activity #15

New hearing aid conducts sound through tooth
Lesley Ciarula Taylor 
Staff Reporter 

SUPPLIED PHOTO The SoundBite hearing device conducts sound through a back tooth. 
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 concert.
“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 by mid-2010.
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,” Gloria said.
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 musical vibrations.

Teaching-Learning Activity #19 
KINETIC ENERGY:  GOLF BALL ACTIVITY
Purpose:  
To introduce energy transfer and transformation processes. 
Materials:	
•	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	

Procedure:  
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.