Physical Science Worksheet - · PDF filePhysical Science Worksheet GRADE ... you estimated the speed of the sound ... investigation that answers the question, “How is sound transmitted

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Physical ScienceWorksheet

GRADE LEVEL: Seventh

Topic: Waves and Vibrations

Grade Level Standard: 7-5 Compare and contrast the characteristics and effects

of various waves.

Grade Level Benchmark: 1. Explain how sound travels through different media.

(IV.4.MS.1)

Learning Activity(s)/Facts/Information

Central Question:How does sound travel through different media?

1. “Sound Thinking”

2. “Investigation of Sound Transmission”

Activity is attached

Resources

SciencePlus, p. 381-382.Holt Rinehart, Winston,Harcourt Brace. (1997)

Process Skills:

New Vocabulary: media, solids, liquids, gases, vacuum

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Figure 2

SOUND THINKING

1. Here are illustrations of what you might see if the air around avibrating tuning fork were visible. Locate the places where theparticles are pushed together (compression) and where they aremuch farther apart (expansion). In Figure 1, how many wavesare shown in the indicated region? How many times has the forkvibrated within that region?

2. Measure the wavelength in Figure 1 with a ruler. For waves ofthe length shown, how many centimeters would a compressionmove to the right when the tuning fork vibrates once? When itvibrates five times?

3. Figure 1 is a scale drawing of what would happen in the air with atuning fork of a certain frequency. In the figure, 1 cm along thewave represents approximately 40 cm. How far would the soundtravel during four complete vibrations of the tuning fork? Duringone vibration?

4. The tuning fork in the illustration vibrates 440 times in 1 second.How far (in centimeters) would a wave travel through the air in 1second? How many meters would this be?

5. In question 4 you calculated the distance through the air in 1second. In so doing, you estimated the speed of the soundwave. Complete the following equation:wavelength x ? = speed of sound waves

6. Suppose a tuning fork vibrates at the rate of 220 times persecond. What would be its wavelength, given the value for thespeed of sound that you obtained in question 5? How would anillustration of the sound wave produced by this tuning fork differfrom Figure 1 above?

7. Figure 2 shows what happens during one complete vibration ofthe fork. Add four more drawings to show what happens duringthe second vibration of the fork. Include the motion of the firstvibration in your new drawings.

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SOUND THINKING

As students answer each question, they should discover the relationship among thewavelength, frequency, and speed of sound. You may wish to remind students that onecomplete wavelength includes both a compression and an expansion.

Answers to Sounding Thinking1. Three waves are shown. Therefore, the fork must have produced three complete

vibrations.

2. The wavelength is about 2 cm. This means that the compression moves to the righta distance of one wavelength, or 2 cm, for each complete vibration of the fork.Therefore, the compression moves to the right 2 cm x 5, or 10 cm for five completevibrations of the fork.

3. In the drawing, 1 cm represents 40 cm. In 4 vibrations of the fork, sound travels adistance of 4 x 2 cm x 40 = 320 cm. In 1 vibration of the fork, sound travels adistance of 2 cm x 40 = 80 cm.

4. For 440 vibrations of the fork, the sound would move 440 x 2 cm x 40 = 35,200 cm =352 m.

5. Wavelength x frequency = speed of sound waves.

6. Wavelength x 220 vibrations/s = 35,200 cm/s ÷ 220 vibrations/s = 160 cm. In Figure1, the distance between compressions would be 160 cm ÷ 40 = 4 cm. Therefore,the figure would show half the number compressions it currently has.

7. The drawings should show the generation of a second wave consisting of acompression and an expansion as well as the outward movement of the first wave.

CROSS-DISCIPLINARY FOCUSMathematicsIn question 5 of Sound Thinking, students derived a formula for the speed of sound(speed = wavelength x frequency). Give students more practice with the formula byasking them to calculate the wavelength of a 200 wave-per-second tuning fork, a500-wave-per-second tuning fork, and an 800 wave-per-second tuning fork.Students should assume that sound has the same speed that they determined inquestion 4 (352 m/s). Ask students which of these tuning forks would have thehighest pitch. (The wavelengths are 1.76 m, 70.4 cm, and 44 cm, respectively. Thefirst fork would have the lowest pitch, and the third fork would have the highestpitch.)

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INVESTIGATIONS OF SOUND TRANSMISSION

In sound transmitted through wood, metal, cardboard, plastic, and other materials?Find out by doing the following activities.

1. Hold one end of a wooden rod (at least 2 cm in diameter) close to your ear. Whiledoing so, scratch the other end with a tack. Can you hear the sound through thewood? Could you hear the same sound in air?

2. Hold a vibrating tuning fork against the end of the rod away from your ear. Thenrepeat the experiment, substituting, plastic, metal paper objects for wood.

Be Careful: Use objects whose diameters are larger than that of your ear canal.Carefully place each object so that it is very close to the outside of your ear canal butnot touching.

Which material transmits sound most loudly? In other words which material is mostefficient in conducting sound energy? Is there a material that will not transmitsound?

3. Which transmits sounds more efficiently—air or water? Try the following activity: Hittwo spoons together in air and then in water, listening carefully to the sound eachtime.

4. Try the following combination at home in the bathtub.

Caution: Do not submerge your head under water, and keep all electrical devices awayfrom the water.

a. Sound source in water—ears in air, ears in waterb. Sound source in air—ears in air, ears in water

5. You’ve probably seen a movie in which someone put his or her ear to the ground tohear the sound of horse hoofs before the sound could be heard through the air.Design an experiment to test this idea, using the floor. You will need a very quietroom.

6. Do some humming. While you hum, plug your ears. What difference(s) do younotice in the sound? Why does this occur?

Make sure students understand that an efficient transmitter of sound is one thattransmits sound loudly. The quality of the sound need not be considered in thisExploration.

Answers to Investigations of Sound Transmission1. The scratching noise is louder when wood is the only medium the sound travels

through.

2. Metal is the most efficient at conducting sound energy. All of the materials transmitsome sounds.

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3. The sound of the spoons is more easily heard in water than in air.

4. Students should first find that water transmits sound more efficiently than air doesand that they hear sounds best when their ears are in the same medium as thesound source. Students may infer that some of the sound is reflected when itreaches a different medium.

5. Students solutions will vary. Students should discover that sound travels moreefficiently through the floor than through the air.

6. The sound is louder because it is traveling through the bones and muscles of thehead rather than through the air. Plugging the ears make the sound louder byblocking out other sounds.

FOLLOW-UPReteachingPresent students with the following scenario: You have been asked to write an entryfor a children’s encyclopedia to explain how sound travels from a source to alistener. Use illustrations and examples to clarify your explanations, and rememberto use words the students can understand.

AssessmentHave students compare the sound from a vibrating tuning fork that is brought neartheir ear with one that touches the bone of their skull just behind the ear. Havestudents explain the difference in sound. (Sound travels through bone moreefficiently than it does through air.)

ExtensionHave students try this experiment to find out if sound can be channeled and if it cantravel around bends. They will need a garden house with a funnel attached to eachend. Using this apparatus, ask them to find out how the loudness of a soundtraveling through the hose compares with the loudness of a sound traveling throughthe open air. Have them use this same apparatus to find out if sound travels aroundbends inside the hose.

ClosureAsk students to find out how far sound can be channeled through differentmaterials. They will need a watch that ticks audibly and various materials to test,such as a long board or a metal curtain rod. They should then place the watch atone end of the board or rod. Ask them to safely place their ear at different positionsalong the object (and above and below it) to hear how well and how far the soundtravels.

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AssessmentGrade 7

WAVES AND VIBRATIONS

Classroom Assessment Example SCI.IV.4.MS.1

After students have described the differences in the particles composing solids, liquids, and gasesand have examined several musical instruments, they will work in small groups and conduct aninvestigation that answers the question, “How is sound transmitted by a telephone?”

Each group will make a cup phone consisting of two plastic cups and a piece of string heldbetween the cups. Students will take turns and whisper to one another from a fixed distance. Onestudent will speak into one cup while another student listens for the first student’s voice in theother cup. Students will test different distances.

Each student will complete a lab report that includes answers to the following questions:

1. How is sound transmitted from one cup to the other?2. Why is sound not transmitted when the string is held by one of the students?3. What is the difference in transmission through different mediums such as air vs. string?

Students should include the following terms in their writings: particles or molecules of matter,vibration, and collisions between particles.

(Give students rubric before activity.)

Scoring of Classroom Assessment Example SCI.IV.4.MS.1

Criteria Apprentice Basic Meets Exceeds

Correctness ofexplanation

Explains how acup phone worksusing the term“vibration” butdoes not connectparticles andcollisions to thatvibration.

Explains how acup phone worksusing the term“vibration” andconnects particlesand collisions tothat vibration.

Explains how acup phone worksusing the threecriteria (termsfrom theassessment).

Explains how acup phone worksusing the threecriteria (termsfrom theassessment) andexplainsconditions thatwould prevent thecup phone fromworking and thereasons why.

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of various waves.

Grade Level Benchmark: 2. Explain how echoes occur and how they are used.

(IV.4.MS.2)


Central Question:How do echoes occur and how are they used?

1. “More About Echoes”

2. “Echolocation at its Best”


Resources

SciencePlus, p. 387-390 HoltRinehart, Winston, HarcourtBrace. (1997)

Process Skills: Hypothesizing, Inferring, Analyzing, Communicating

New Vocabulary: echo, sonar, reflections

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MORE ABOUT ECHOES

GETTING STARTEDHave students read the introduction, How Do the Blind "See"? Then ask them to constructtheir own theories about how blind people could sense and avoid obstacles. Give studentsthe opportunity to debate their theories with one another.

MAIN IDEAS1. Blind individuals can detect objects in their surroundings by listening to echoes of

sounds reflected by these objects, a process known as echolocation.

2. Some animals such as bats and dolphins detect the presence of objects by usingecholocation.

TEACHING STRATEGIESANSWER TO CAPTION (A)The quality of the sound that echoes from a tapped object will be different for differentobjects. A blind person identifies objects by tapping them and listening to the sound qualityof the echoes.

MEETING INDIVIDUAL NEEDSGIFTED LEARNERSAsk students if they have ever noticed how the sound of a car changes as it approachesand then passes by. Explain to students that this change in pitch and frequency is known asthe Doppler effect. Have students research what causes this effect, and illustrate theirfindings on a poster board. If possible, have students record the sound of a train or car as itpasses by. They should then make a second recording from within the moving vehicle. Askstudents to play their recordings for the class in order to compare the sounds.

TIME REQUIRED1 class period

PROCESS SKILLShypothesizing, inferring, analyzing, communicating

NEW TERMEcholocation: Using echoes to detect the presence and location of objects.

MATERIALS (per student group)A Research Project: one index card per student

TEACHING RESOURCESMath Practice Worksheet, p. 33SourceBook, pp. S112 and S121

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A RESEARCH PROJECTTell students that people often jump to conclusions without having solid evidence to supporttheir beliefs. Ask students if they can think of examples when they have done this. Explainthat scientists must train themselves to be as objective as possible and to try not to jump toconclusions prematurely. The research project that they will read about will give thempractice in carefully considering evidence before drawing conclusions.

This research project is adapted from the book, Echoes of Bats and Men (DoubledayScience Study Series). The research project was set up to determine how blind peopleavoid obstacles.

The article allows students to act as researchers and to speculate on how they would carryout each step of the research described in the article. Questions are provided to help themin this role. Students should provide answers to the questions before reading about what theresearchers actually did. One way to accomplish this is to use an index card to cover thediscussions in the blue print as suggested in the text. You may wish to divide the class intoresearch teams of two or three students. After they discuss each question, have students'read from the text to discover what the researchers actually did.

After students have finished reading what the researchers actually did, use the followingquestions to aid in your discussion of the article: What was the most surprising part of thestory? If the students had been in the position of the researcher, when might they haveconcluded their experimentation? What were the steps researchers followed in conductingtheir research?

Allow students to try echolocation for themselves. Have them work in pairs. One student ineach pair should be blindfolded while the other student acts as a spotter. Tell them to checkfor a change in the sound of their heels on the floor as they walk down a corridor and pass aclassroom with an open door. Then have them compare the sounds of a meter stick hittingthe floor far away from a wall and when close to a wall. For safety reasons, you may wish toset this up as a demonstration or allow only a few students to do this activity at one time.

ANSWERS TO A Research Projecte. If the subjects bumped into the obstacle while wearing the armor but avoided the

obstacle while not wearing it, students should suggest that the experiment supported theskin-pressure hypothesis. If the subjects avoided the obstacle in both cases, studentsshould suggest that the experiment did not support the hypothesis. (Make sure studentsunderstand that errors can occur in every experiment and that one test cannot beconsidered conclusive.)

g. If the subjects bumped into the obstacle while their ears were plugged, students shouldsuggest that the experiment supported the sound hypothesis. If the subjects avoidedthe obstacle, student should suggest that the experiment did not support the hypothesis.(Make sure students understand that errors can occur in every experiment and that onetest cannot be considered conclusive.a0

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COOPERATIVE LEARNING A Research ProjectGROUP SIZE

2 to 3 students

GROUP GOALTo develop hypotheses and interpret data from actual scientific research studies.

POSITIVE INTERDEPENDENCEThe group will work together to read, discuss, and answer the questions featured in “AResearch Project.” Assign roles as follows: reader #1 (to read each of the questions [ a-m]), reader # 2 (to read the text describing the researcher’s actions in [ a-m]), recorder(to record the group’s responses).

INDIVIDUAL ACCOUNTABILITYHave each student role-play the part of a researcher by writing a letter to a friend inorder to describe his or her research on echolocation.

CROSS-DISCIPLINARY FOCUSMUSIC

Have students do biographical research on blind musicians (for example, Stevie Wonderor Ray Charles) to find how their lack of sight has affected their sensitivity to sound.

PORTFOLIOYou may wish for students to keep the results of “A Research Project” in their Portfolio asevidence of their ability to apply the scientific method in a realistic research setting.

REPORTING YOUR FINDINGSEncourage students to make their letter as interesting, thorough, and accurate as possible.You may wish to have some students read their letter to the rest of the class.

PORTFOLIOStudents may wish to include their letter from Reporting Your Findings in their Portfolio.

ECHOLOCATION AT ITS BEST!Have students read this section silently. Interested students can pick one of the animalslisted and do additional research to find out more about how it uses echolocation to survive.

ANSWER TO “Echolocation at Its Best” In-Text Question(A) If a bat chirps 200 times per second, the time between chirps is 1 s ÷ 200 = 0.005 s.

The time requires for the chirp to research the object is 0.005 s ÷ 2 = 0.0025 s, and thespeed of sound is 345 m/s.

Distance = speed x time= 345 m/s x 0.0025 s= 0.86 m, or 86 cm

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FOLLOW-UPRETEACHINGAsk students to write a letter to a second-grader in order to explain how bats useecholocation to navigate and to catch insects. Encourage students to include pictures withtheir explanations.

ASSESSMENTAsk students how they would design an experiment to determine whether a certain fish usesecholocation to navigate. Have students submit summaries of their hypotheticalexperiment.

EXTENSIONHave interested students find out more about how geophysicists use echolocation to studythe structure of the crust and upper mantle of the Earth.

CLOSUREHave the class read a newspaper or magazine article that discusses a recent scientificbreakthrough. Students should evaluate the research described in the article by writingtheir own interpretation of the hypotheses that were tested, the observations that weremade, and the conclusions that were reached. You may wish to give each student anopportunity to read aloud from the article.

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(A) How might blindindividuals use the tappingsound of their can to identifyobjects around them?

MORE ABOUT ECHOES

HOW DO THE BLIND "SEE"?

Ask a blind person how he or she is able to sense and avoid obstacles in his or herpath. You may get answers like these:

“I feel the presence of the object. ""There are pressures on my skin that tell me an object

is there. "" I sense danger.”“I have facial vision. "

There is a story about a six-year-old blind boy who learnedhow to ride his tricycle on the sidewalks near his home. Henever had an injury or an accident. He could veer aroundpeople, and he knew when to turn corners without goinginto the street. How did he "see"?

For years, there was a blind cyclist who rode his bike indowntown Toronto, Canada. With less than 10 percentvision, he could not see traffic lights, jaywalkers, or roadrepair crews. How did he "see"?

A RESEARCH PROJECT

A Cornell University professor and two of his students, one of whom was blind,wondered how blind people are able to avoid obstacles even though they can't seethem. The research team designed a project to find out.

Think like a researcher: What steps might you follow? The questions below will assistyou. Each question is followed by an explanation of what the researchers actually did.Cover these explanations with a card, revealing them only after you have suggested apossible answer.

The researchers were particularly interested in testing the following hypotheses: Skin-Pressure Hypothesis: Obstacles send out signals that produce pressure on the

skin, enabling the blind person to be aware of the obstacles. Sound Hypothesis: Sounds hit obstacles and bounces back, alerting the blind

person to their presence.

a. What kind of people would you use for the experiment—blind, blindfolded, or both?

The Cornell team decided to use both blind and blindfolded subjects. They gave specialtraining to the blindfolded people. After a little practice, they too could avoid obstaclesplaced in their path.

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b. What kind of experimental situation would you set up totest the avoidance of obstacles?

The experimenters walked down a long hallway toward afiberboard screen. The experimenters changed the positionof the screen from trial to trial. Before long, each subjectcould walk down the hallway, detect the presence of thescreen, and stop. On average, subjects detected the screenwhen they were about 2 m away from it

c. Which hypothesis would you test first?

The researchers tested the hypothesis that blind peoplemention most often, the skin-pressure hypothesis.

d. What would you do to the subjects to prevent their skin from being affected by thescreen?

The subjects had to wear an "armor" of thick felt over their heads and shoulders andheavy leather gloves on their hands. While clothed this way, they couldn't even feel theair from an electric fan, but they could still hear sound.

e. If they bumped into the obstacle when wearing the armor but didn't bump into theobstacle when they were without it, what would you conclude? If they avoided theobstacle when wearing the armor, what would you conclude?

The subjects wearing the armor avoided the obstacle. However, they tended toapproach it more closely, on average, than they did before. They stopped 1.6 m away,as compared with 2 m without the armor. The researchers concluded that the skin-pressure hypothesis was not correct. Blind people do not "feel" the pressure ofobstacles with their hands and face.

f. What would you do to test the sound hypothesis?

Ear coverings of wax, cotton, earmuffs, and paddingwere worn by the subject They could not even hear theirown footsteps. Their faces and hands were leftuncovered.

g. If they bumped into the screen while their ears wereplugged, what would you conclude? If they stoppedshort of the obstacle, which would you conclude?

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Spectacular results! Both blind and blindfolded people bumped into the obstacle. Theblind people said that all sensation of "feeling" had gone. The sound hypothesis bestexplained the researchers observations.

h. Some scientists objected this conclusion. Perhaps the ear coverings changed thepressure on the ear and ear canal-pressure that would have resulted from theobstacle's presence. What could you do now to determine the avoidance of theobstacle was due to sound rather than the some sort of pressure on the ears?

The subjects were placed in a soundproof room somedistance away from a hallway where an experimenterwalked with a microphone. The sounds of theexperimenter's footsteps were picked up by themicrophone and carried by a telephone line to thesubjects. The subjects were asked to locate the screen bylistening to the sounds picked up by the microphone.

i. What results would you expect if the sound hypothesiswere true?

The subjects were able to detect the screen from thesounds picked up by the microphone. The closestapproach was 1.9 m. That’s more proof for the soundhypothesis! The ability of blind people to avoid obstacles isapparently due to sound—not to pressure on the ear.

j. Some scientists saw weaknesses in this approach as well.Can you think of any?

The experimenter's pace and breathing might have given the subjects hints about theobstacle's presence.

k. What other experiment might you design to check this possible weakness?

The experimenters decided to use a motor-drivencart to carry the microphone toward the screen, anda loudspeaker to make sounds. The movements ofthe cart were controlled remotely by the subjects inthe soundproof room.

l. What conclusions would you draw if thesubjects detected the screen?

Although the average closest approach was a littlecloser than in previous experiments, the subjectsalways detected the screen. Therefore, signalsfrom the breathing or pace of the walker could not explain why the subjects were able to

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detect the screen. The experimenters made three general conclusions.

1. Blind people locate obstacles by sound and by the reflection of this sound—that is,by echoes from the obstacles.

2. With practice, sighted people can also learn to detect obstacles by this means.

3. We are often not aware of how our senses and brain are working. Blind peoplesense that they "feel" the presence of objects around them. But scientificexperiments show that they are, instead, hearing changes in sound as theyapproach obstacles.

m. What further experiments might you now do?

The researchers are still interested in sending different kinds of sounds through theloudspeaker. Through experimentation, they may discover what sounds are best suitedfor the echolocation of objects.

REPORTING YOUR FINDINGS

Often, the final step of a research project is a written reportin a scientific journal. In addition, scientists, like manypeople, enjoy sharing their interests with friends by writingletters. (Galileo, for instance, wrote many fascinatingletters about his work to his friends.) Write a letter to afriend, telling him or her of your exciting discoveries in yourrole as a researcher into how blind people "see."

ECHOLOCATION AT ITS BEST!

Whales and dolphins make clicks and other noises thatreflect off objects as echoes. Using echolocation, river-

dwelling dolphins can thread their way among logs and fallen trees in muddy rivers. Inthe open sea, dolphins accurately echolocate the fish they eat.

Bats, too, use echolocation to find food. They hunt flying insects in the dark by sendingout pulses of high-frequency sound waves (about 45,000-100,000 vibrations persecond—too high to be audible to humans) . The waves bounce off of the insects, andthe bats find their prey by listening for the echoes. In one experiment, a North Americanbrown bat was able to echolocate and catch 175 mosquitoes in 15 minutes. If a batwere unable to echolocate, it might have to fly all night with its mouth open beforecatching one mosquito.

A bat usually chirps about 20 times per second. This number increases to 200 shorterchirps per second as it approaches its prey. How far away from its prey could a bat beand still hear a separate echo? (A)

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Many ships have a navigation system that uses echoes to find the depth of the water,the presence of schools of fish, and even the structure of the rock on the ocean bottom.This system is called sonar, which stands for sound navigation and ranging. Sonarworks much the same way that echolocation works for a bat. The sonar device sendsshort pulses of sound waves through the water. When the sound waves hit the oceanfloor, some of the waves are reflected back as an echo. The echo is then detected by areceiver. The gathered information can then be displayed on video monitors.

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AssessmentGrade 7



Students will sketch and label their location in a setting where an echo was produced. Thefollowing should be noted for each location: distance from the reflecting surface, the type ofreflecting surface, and any objects that might interfere with the sound reflection. Students willthen present and explain this information to the teacher.




Accuracy ofexplanation

Identifies some ofthe conditionsneeded to producean echo andexplanation isincomplete.

Identifies andexplainsconditions neededto produce anecho or simplyidentifiesconditions.

Identifies andexplains allconditions neededto produce anecho (appropriatedistance,reflecting soundwaves, andappropriatereflectingsurface).

Identifies andexplains allconditions neededto produce anecho (appropriatedistance,reflecting soundwaves, andappropriatereflecting surface)and determinesthat the distancemust be greaterthan seventeenmeters.

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of various waves.

Grade Level Benchmark: 3. Explain how light is required to see objects.

(IV.4.MS.3)


Central Question:How is light required to see objects?

1. “Light’s Path”

2. “The Riddle of Color”


Resources

SciencePlus, page 443, 450,456, Holt Rinehart, Winston,Harcourt Brace. (1997)

Process Skills: Observing, Analyzing, Inferring, Contrasting, Measuring

New Vocabulary: light sources, object, eye as a detector, illumination, path of

light, reflection, absorption

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LIGHT’S PATH

GETTING STARTEDDiscuss the term light ray with your students. Explain that a light ray is a symbol thatrepresents the path taken by a group of light waves. The arrow on a light ray shows thedirection in which the light waves move. Draw several luminous objects on the blackboard,such as a candle, the sun, or a lamp, and draw the rays emanating from them to show howlight rays represent the path of light.

MAIN IDEAS1. Light travels very quickly.2. Light travels in straight lines.3. Shadows are evidence that light travels in straight lines.

TEACHING STRATEGIES Answers to In-Text Questions(A) Students probably noticed that the edges of the beam were fairly well defined and that

the beam's direction was in a straight line. When the smoke disappears, however, thepath of the light beam is no longer visible, even though the light is still present.Students may wish to include their analysis of Exploration 1 as evidence to supporttheir answer.

(B) Answers will vary, but students should realize that they would see a relatively sharpshadow of the comb on the screen. As the comb moves out of the path of the lightbeam, the shadow becomes fuzzier.

(C) Since the time lag between the motion of the comb and the motion of its shadow isundetectable, students should conclude that light moves quickly. The fact that the teethof the comb are visible in the shadow suggests that light travels in straight lines.

(D) The shadow on the top screen is larger but slightly fuzzier than the shadow on thebottom screen.

(E) The difference sizes of the shadows result from the different sizes of light bulbs, andthe shadows would not occur at all if light did not travel in straight lines. (Note: For bestresults, students should extend the lines in their diagrams from the light bulb all the wayto the screen.)

The boarders of both shadows are fuzzy in part because the light sources does notcome from one point. At the edge of the shadow, some light will be blocked and somewill not be. At the center, virtually all light is blocked.


PROCESS SKILLSobserving, analyzing, inferring, contrasting, measuring

NEW TERMNone

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MATERIALS(per student group)Light’s Path: flashlight; sheet of white cardboard; plastic comb

TEACHING RESOURCESExploration Worksheet, p. 30SourceBook, pp. S132

FOLLOW-UPRETEACHINGDraw ray-tracing diagrams of the candle, pinhole, and screen on the blackboard, anddiscuss the diagrams with students. Have students make similar drawings to trace thepaths of rays using an arrow as the object.

ASSESSMENTAsk students to develop three quiz questions (with answers) based on Exploration 2. Collectthe questions and generate a quiz for the class.

EXTENSIONHave students research the first camera, the camera obscura. Students can includediagrams that show how the camera worked and make a model of it.

CLOSUREHave students use their phone-image makers to examine other small, brightly lit objectsaround the classroom. For example, have students observe how the writing on a light bulbis magnified as they move the image maker closer to the bulb.

EXPLORATION 2Students will need to try several pinholes of different sizes to produce an adequate image.Warn students that the image produced will be quite dim and indistinct.

ANSWERS TO Exploration 22. The image of the candle flame is the same size as the actual flame but is inverted. The

angle formed by the lines of light from the top and bottom of the flame is the same onboth sides of the pinhole (forming congruent, vertical angels). Because the lined cardis the same distance from the pinhole as the pinhole is from the flame, the image is thesame size as the actual flame. The image is inverted because light travels in straightlines. Thus, light from the top of the flame can pass through the pine hole only at adownward angle, and light from the bottom of the flame can pass through only at anupward angle.

3. The image gets smaller as the screen is moved closer to the pinhole (a) and gets largeras the screen is moved farther from the pinhole (b). The image gets larger as thepinhole is moved closer to the flame (c) and gets smaller as the pinhole is movedfarther from the flame (d).

4. Answers will vary but should include details similar to those discussed in steps 2 and 3.

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LIGHT’S PATH

Through your light-box experiments you were able to determine some characteristicsabout light. For example, you observed that light traveling through space is invisible, butyou can see its path through air if smoke is present or through water if a bit of milk isadded.

Now take a look at the diagram on page 444. Think about the path of the light beamyou studied in Exploration 1. What did you observe about the edges of the beam? Whatwas the beam's direction? When you observe a light beam passing through smoky air,what happens when the smoke completely disappears? Is light still there? List someevidence in your Science Log to support your answer. (A)

Examine the diagram below. What would you expect to observe on the white cardboardscreen? (B) Try setting up this experiment. Observe the screen. Then move the combin and out of the path of the light beam, watching the screen as you do so.

Based on the comb's shadow on the screen and the observations you made during thelight-box experiments, what can you say about the way light travels? Does it moveslowly or quickly? What evidence suggests that light moves in straight lines?

LIGHT LINESStudy the shadows of a ball illuminated by different-sized light sources. Examinescreens closely. How are the shadows different? (D)

Sketch the light-bulb diagrams inyour Science Log. Using a ruler,draw two straight lines from the topof the large light bulb—one to thetop of the ball casting the shadow,the other to the bottom of the ball.Now draw two lines from the bottomof the large light bulb—one line tothe top of the ball, the other to thebottom. Draw similar lines on the

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diagram with the small light bulb. Do the lines suggest an explanation for the two typesof shadows cast on the screens? Write your explanation in your Science Log. Lookagain at the diagrams in your Science Log. Would shadows occur if light did not travelin straight lines? (E)

In the next Exploration you will further investigate "light lines" by examining light as itpasses through a pinhole. As you perform the experiment, look for evidence that lighttravels in straight lines.

EXPLORATION 2 - PINHOLE IMAGES

YOU WILL NEED• a card with a pinhole • a candle• a lined white index card • matches• a metric ruler • several cards with pinholes of different• 2 clothes pins sizes

• a small jar lid

WHAT TO DO1. Perform the experiment in a darkened room. Arrange the apparatus as shown in

the diagram.

2. Start with the pinhole about 3 cm from the candle flame and the screen 3 cmfrom the pinhole. You should get a good image of the flickering flame. Describethe image. Can you explain its appearance? (Hint: Make a drawing of the setupas shown below. Then draw thin "lines of light" from the top and bottom of theflame through the pinhole and to the screen.)

3. Observe the size of the image as the screen is moved (a) closer to the pinholeand (b) farther from the pinhole. Now examine the image as the pinhole ismoved (c) closer to the flame and (d) farther from the flame. Make drawings of(a) through (d) using "light lines" to show how each image is formed.

4. Write a letter about light lines to a younger sibling or friend. Ten him or her howto obtain pinhole images and explain how these images suggest that light travelsin straight lines.

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THE RIDDLE OF COLOR

GETTING STARTEDHave students use a magnifying glass to examine the colored illustrations in this book. Askstudents if they can identify what basic colors were used to make the dots that, whencombined, produce all of the colors of the illustrations. Guide students to observe closely.You may wish to provide the hint that they are three basic colors plus black and white thatare used in “four-color printing” and that the colors are not the same as the primary lightcolors studies earlier. Tell students they will find out why as they proceed through thelesson.

MAIN IDEAS1. We see objects by the color of light they reflect.2. Mixing light of different colors tends toward white; mixing paint of different colors tends

toward black.3. The primary colors of the paint that artists use are red, blue, and yellow.

TEACHING STRATEGIES Answers to In-Text QuestionsA. Students should recall that a white surface reflects white light, a black surface reflects

no light, and the red cardboard reflects red light. Students should thus label thereflected light in the diagram as red light and the absorbed light as all light but red.

B. Student answers will vary but should reflect the questions answered in the firstparagraph on this page.

C. In red light, for example, only the red portion of a sweater would be unchanged. Othercolors would tend to appear black. White would appear red.

LEARNERS HAVING DIFFICULTYFor extra reinforcement, you may wish to have students repeat Exploration 4 using greencellophane.

TIME REQUIRED2 class periods

PROCESS SKILLSobserving comparing, inferring,

NEW TERMPrimary colors of paint: the three colors of paint—red, blue, and yellow—from which allother colors of paint can be created

MATERIALS (per student group)Exploration 4: cardboard tube; scissors; sheet of white paper; red, yellow, blue, and purplecrayons; 2 pieces of dark blue cellophane, about 10 cm x 10 cm each; 2 pieces of redcellophane, about 10 cm x 10 cm each; 2 rubber bands

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TEACHING RESOURCESExploration Worksheet, p. 31SourceBook, pp. S137

EXPLORATION 4Give the students at least 30 minutes to make their observations. Caution the students tomake accurate observations, looking not only for the principal effect, but also for secondaryeffects. A student may view a red mark under a blue filter and report a purple color, whenthe principal effect is actually black with a slight purplish tinge. The students think they seedark purple because there may be some residual blue reflected to the eye as well as somered due to the extraneous white light.

ANSWERS TO Exploration 43. The red mark is black, the blue mark is blue, the yellow mark is blackish, the purple

mark is very dark blue, and the background in blue. With the second piece of bluecellophane, the blue mark, the purple mark, and the background are even darker blue,and all of the other marks are black.

4. Predictions will vary but should be clear and logical. Students should find that with a redfilter the red mark looks a darker red, the blue mark looks black, the yellow mark looksred, the purple marks looks very dark red, and the background looks red.

INTEGRATING THE SCIENCESLIFE AND PHYSICAL SCIENCESPlace a red and blue filter side by side on an overhead projector and project the light onto awhite screen. Ask students to stare at the screen for a minute or two and then to describethe image they see when they close their eyes. (Students should be able to see a ghostimage that has the same shape as the projected image but different colors. The ghostimage, or afterimage, should be green where the original image was red and yellow wherethe original image was blue.) Have students research successive contrast and designexperiments like the one mentioned above to find out more about this phenomenon. Besure to check students’ proposed procedures for safety before allowing them to proceedwith any experiment.

HOMEWORKHave students make cellophane viewers in class by taping a piece of red, blue, or greencellophane to a window cut out of an index card. Have students use the viewer while athome and note any reactions they have to objects being colored differently. They shouldreport their findings to the class on the next day. (For example, students may find that foodappears unappetizing under filtered light.)

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THE RIDDLE OF COLOR

When you shone light on the green cardboard inExploration 3, what color did the cardboard reflect? Thisis how we perceive color in objects—by the colored lightthat they reflect. What colors does a white surfacereflect? a black surface? If you substituted red cardboardfor the green cardboard in the light-box experiment onpage 453 and shone white light on it, what do you thinkwould happen? How would you label the colors in thediagram at right, which shows this experiment? (A)

Look at the illustrations below, and then explain why Lisasees the color she does. (B)

Do objects have the same color when they are viewedunder white light as they do under light of another color?For example, if Lisa viewed her friend’s sweater in thedim red light of a photographer’s developing lab, wouldthe sweater be the same color? Perhaps you havenoticed that sometimes a sweater bought in a storeilluminated by artificial light seems a different color whenyou look at it in the sunlight or that the color of a jacket at night under certain streetlights looks different from when the jacket is viewed in sunlight. Does the light shiningon an object have an effect on the color you see? In the following Exploration you’llhave the chance to find out. (C)

EXPLORATION 4 ChangingColors

YOU WILL NEED• a cardboard tube• a white piece of paper• red, yellow, blue, and

purple crayons• tape• 2 pieces of dark blue

cellophane• 2 pieces of dark red

cellophane

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WHAT TO DO1. Cut out a small window at the bottom of the tube to construct a cardboard viewer

like the one shown here.

2. Cut the paper into four rectangular pieces. Make a heavy mark on each with oneof the colored crayons.

3. Wrap the blue cellophane over the window of the tub and secure it with a rubberband, as shown below. Now view each mark with this blue filter in place. What isthe color of each mark? of the background? Cover the window with a secondpiece of blue cellophane. Is there any difference?

4. Suppose step 3 was repeated using red filters. Predict the colors of the crayonmarks and the background. Check your predictions.

5. Use your viewer to look at the color photos in this unit under different lights. Howgood have you become at predicting the results of color mixing?

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AssessmentGrade 7



Students will work in small groups and conduct the following investigation to answer the question,“Which color paper reflects light the best?”

1. As seen in the diagram, a white screen (made of white cardboard or paper) should be placed onthe table at an angle.In a darkened room:

2. Observe how a black sheet of paper reflects light by shining a flashlight on a piece of blackconstruction paper lying flat on the table.

3. Observe how a white sheet of paper reflects light by shining a flashlight on a piece of whiteconstruction paper lying flat on the table.

4. Students should repeat this procedure with different colored sheets of paper.

Students will record their results in lab reports and answer the following questions:

1. Which color light reflects the most light?2. Which color paper reflects the least light?3. What must happen to light in order for a human to see an object (describe the path)?

NOTE: If you were to replace the screen in the diagram with an observer, this activity would explaincorrectly how the reflection of light off an object results in the observer’s ability to see that object.





Identifies white asbrightest and blackas dimmest butgives only partialexplanation.

Identifies white asbrightest and blackas dimmest but onlyexplains one ofthem.

Identifies white asbrightest because itreflects more lightand black asdimmest because itreflects a little lightand absorbs most.

Identifies white asbrightest and blackas dimmest with acorrect explanationand describes theimage on the screenas diffused andexplains why.

Accuracy ofdescription - pathof light

Identifies few partsof the path of lightneeded to see anobject and uses fewkey terms correctly.

Identifies someparts of the path oflight needed to seean object and usessome key termscorrectly.

Identifies all partsof the path of lightneeded to see anobject and usesmany key termscorrectly.

Identifies all partsof the path of lightneeded to see anobject and uses allkey terms correctly.

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of various waves.

Grade Level Benchmark: 4. Describe ways in which light interacts with matter.

(IV.5.MS.4)


Central Question:How does light interact with matter?

1. “Light in Action”

2. See www.explorescience.com


Resources

SciencePlus, page 443 Holt,Rinehart, and Winston,Harcourt Brace (1997)

Process Skills: Observing, Analyzing, Hypothesizing, Predicting, Communicating

New Vocabulary: reflection, refraction, absorption, transmission, scattering,

medium, lens, transmission of light

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LIGHT IN ACTION

GETTING STARTEDDisplay a hand mirror and use it to reflect some light around the classroom. Ask students todescribe what is happening. (Light is reflected from the mirror.) Then display somecardboard and a piece of glass. Ask students to describe what happens when light strikesthese materials. (Light that strikes the glass passes through it; light that strikes thecardboard does not.)

MAIN IDEAS1. When light strikes an object it may be reflected, transmitted, scattered, or absorbed.2. A dark-colored surface absorbs more light than a light-colored surface, while a light-

colored surface reflects more light than a dark-colored surface.3. A transparent object transmits most of the light that strikes it, while a translucent object

scatters most of the light that strikes it.4. Objects can be seen clearly through a transparent material but cannot be seen clearly

through a translucent material.

TEACHING STRATEGIESHave students silently read the bulleted statements on this page. Then have themsubstitute their own words and phrases for the words scattered, absorbed, and transmitted.Make sure that students understand that scattering is the reflection of light in all directions.


THEME CONNECTIONStructures

PROCESS SKILLSobserving, analyzing, hypothesizing, predicting, communicating

NEW TERMSAbsorption—the intake of light without reflection or transmission

Scattering—the reflection of light in random directions

Translucent—term used for a material that allows most light to pass through whilescattering the rest so that objects are not clearly visible through the material

Transmission—the passing of light through an object

Transparent —a term used for a material that allows light to pass through without beingscattered

MATERIALS (per student group)Building a Light Box: large shoe box or other cardboard box, about 35 cm x 15 cm x 10cm; metric ruler; scissors; piece of aluminum foil, about 8 cm x 8 cm; roll of masking tape

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Exploration 1, Part 1: light box from Building a Light Box; small flashlight; piece of roughblack paper, about 8 cm x 8 cm; sheet of white paper, about 8 cm x 8 cm; a few sheets ofother colored paper, about 8 cm x 8 cm; wooden splint; a few matches; small ball ofmodeling clay; safety goggles

Part 2: light box from Building a Light Box; small flashlight; piece of window glass, about 8cm x 8 cm; small ball of modeling clay; wooden splint; a few matches; protractor; safetygoggles; (additional teacher materials: 50 cm of masking tape;)

Part 3: light box from Building a Light Box; small flashlight; flat piece of paraffin wax, about8 cm x 8 cm; small ball of modeling clay; wooden splint, a few matches; protractor; safetygoggles (additional teacher materials: knife;)

Part 4: light box from Building a Light Box; small flashlight; small beaker of water; a fewdrops of milk; eyedropper; stirring rod

Part 5: large beaker of or jar of water; small flashlight; a few drops of milk; eyedropper;stirring rod

TEACHING RESOURCESExploration Worksheet, p. 25

BUILDING A LIGHT BOXConstruction of the light boxes can be done by groups of students either as a classroomactivity or as an at-home project. Check the completed boxes to make sure that they meetthe required specifications. The holes in the boxes should be small enough so that theboxes will be effective in a well-lit room.

You may wish to consider several different light sources for the boxes. Normally, aflashlight will do, but a filmstrip, slide, or overhead projector can provide a moreconcentrated beam of light. Bright sunlight is an even better option. Mirrors may be used tofocus the sunlight where it is needed.

EXPLORATION 1The piece of paraffin wax for Part 3 should be about the same thickness as the windowglass used in Part 2. You may need to shave the piece of wax to match the thickness of theglass, a process which requires a sharp knife and may take up to 20 minutes per piece.After each experiment is completed, encourage students to write a brief statement in theirScience Log describing what they have observed and concluded.

COOPERATIVE LEARNING Exploration 1GROUP SIZE3 to 4 students

GROUP GOALTo apply knowledge of light to further investigate various properties of light.

POSITIVE INTERDEPENDENCE:Divide the class into five groups. Assign each group one of the five parts of Exploration 1.Each group should develop a creative way to review the findings of their part of theExploration. Also, they should develop a short quiz to test the class for understanding of

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their part. Give each group time to collect and evaluate the quizzes as well as time toreteach their part to the class if necessary.

INDIVIDUAL ACCOUNTABILITYEach student should be able to answer the questions found in Interpreting YourExperiments.

ANSWERS TO In-Text QuestionsA. Possible responses are as follows

• reflects in many directions• reflected; retained by the paper• allowed to pass through; retained• able to pass through; forced to bounce off

ANSWERS TO Part 11. Most of the light in the box comes from the light that is scattered when the beam hits the

end of the box.2. The inside of the box becomes darker because most of the light that strikes the black

surface is absorbed by it.3. The inside of the box becomes brighter. Black paper absorbs more light than white

paper. White paper reflects more light than black paper or brown cardboard. Asstudents try different colors of paper; they should observe that the darker colors absorbmore light and that the lighter colors reflect more light.

5. a. does not light upb. lights upc. less thand. more thane. less thanf. less light than; more light thang. green; all colors expect greenh. all colors

ANSWERS TO Part 2

1. a. Most of the light bounces off the glass.b. Some of the light is transmitted.c. The reflected beam is brighter because more light is reflected than transmitted.

2. With the glass at 80°, some of the light bounces off the glass, but most is transmitted.The transmitted beam is brighter because most of the light is transmitted. With theglass at 10°, most of the light bounces off the glass, but some is transmitted. Thereflected beam is brighter because most of the light is reflected.

3. Students’ statements will vary but should reflect the following ideas:• Glass transmits light.• When light strikes glass, some of the light is reflected from the surface of the glass.• When a beam of light strikes a piece of glass that is nearly parallel to the path of the

beam, most of the light is reflected rather than transmitted. When a beam of lightstrikes a piece of glass that is nearly perpendicular to the path of the beam, most ofthe light is transmitted rather than reflected.

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ANSWERS TO Part 32. The paraffin appears cloudy in the beam of light while the glass appears clear. The light

passes through the glass at a fixed point, while the light seems to be scattered, ordiffused, throughout the paraffin. The box should appear brighter when the glass is inplace.

3. Students’ summaries will vary but should reflect the following ideas:• When you shine light at glass, the light passes through.• When you shine light at paraffin, most of the light scatters in all directions within the

paraffin. Only a little of the light passes through.• You can see objects clearly through glass but not through paraffin.

ANSWERS TO Part 41. Students should not be able to see the beam of light through the water.2. When the milk is added to the water, the beam of light becomes visible because the milk

particles are reflecting the light. Students should observe that some of the light istransmitted through the slightly cloudy water. The whitish color is evidence that light isscattered by cloudy water.

3. Students’ conclusions will vary but should reflect the following ideas:• Some of the light that strikes slightly cloudy water is transmitted.• Some of the light that strikes the cloudy water is scattered.

ANSWERS TO Part 51. The light will appear to be white. The water has no color when viewed at right angles to

the beam.2. The light becomes visible as a whitish color. The water should still appear to be

colorless or faintly cloudy.4. Students’ descriptions will vary but should reflect the following ideas:

• The milk particles cause the light in the water to scatter.• Seen from the front (or opposite the flashlight), the light beam becomes orange-red

in color as it passes through the water and strikes the milk particles.• Seen from the side, the light beam becomes blue-white in color as the light is

scattered by the milk particles in the water.

HOMEWORKPart 5 of Exploration makes an excellent homework activity.

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LIGHT IN ACTION

Perhaps you’ve heard the words, scattering, transmission, and absorption before.These terms are commonly used by scientists when describing light. What do you thinkthese words mean? Read the following statements, which use forms of these words.Rewrite the sentences and replace the words in boldface type with your own words toconvey what you think these special light words mean. (A)

When a light beam shines on a mirror, it bounces off in a specific directions. However,when a light beam hits a white piece of paper or the white wall of a room, the lightscatters.

• When a white light shines on a blue piece of paper, the blue color in the whitelight is scattered by the paper, while all the other colors are absorbed.

• When white light shines on a red filter, only the red color is transmitted throughthe filter. All the other colors are absorbed by the filter.

• When a beam of white light shines through smoky air, part of the light istransmitted through the smoke. The rest of the light is scattered by the smokeparticles.

A LIGHT BOXBy performing experiments with a light box, you can get a better understanding ofscattering, transmission, and absorption. A light box shuts out most of the unwantedlight in a room, making it easier for you to see the light used in the experiment. Followthe instructions to build your own light box.

BUILDING A LIGHT BOXHere is how to make a lightbox from simple, readilyavailable materials. You willuse this light box for manyexperiments in this unit.

Start with an empty cardboardbox about 35 to 45 cm long, 15to 20 cm wide, and 10 to 15cm high. A large shoe box willwork.

On one end, near the bottomcut out a square window about6 cm on each side. Then cut a square of aluminum foil about 8 cm on each side.About 3 cm from the bottom of the foil square, centered between the left and rightedges, cut a round hole about 1.5 to 2.0 cm in diameter. Tape the square of foil overthe window at the end of the box, as shown in the illustration. Be sure that you can seethrough the hole into the box’s interior.

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Cut two flaps in one side of the box—one near the center, the other one lower and tothe right, at the end of the box away from the foil window. The flap to the right is forputting things into or removing things from the box. It should be about 8 cm on eachside. You may find it easier to move objects into and out of the box by simply removingthe lid before you do any experiment.

EXPLORATION 1 Enlightening Experiences

YOU WILL NEED• a light box • matches• a flashlight • a piece of window glass• rough, black paper • a protractor• modeling clay • a piece of paraffin wax• white paper • a small beaker of water• colored paper • milk• a wooden splint • stirring rod

PART 1A BLACK-SURFACE EXPERIMENT

Set up the light box that you made. Position the flashlight so that its light shinesthrough the foil window. Look through the viewing window.

WHAT TO DO1. There is now some light in the box. Where does most of the light come from? Is

it from the beam as it passes through the air or from light scattered when thebeam hits the end of the box?

2. Put a piece of rough, black paper in the path of the beam near the end of thebox. Prop it up with modeling clay, as shown below. What happens to thebrightness of light in the box when the black surface is added? What happens tomost of the light when it strikes theblack surface?

3. Replace the black paper with a sheetof white paper. What does this do tothe amount of light in the box?Which color of paper—black orwhite—absorbs more light? Whichcolor reflects more light? Try othercolors of paper as well.

4. Adding some smoke from asmoldering wooden splint. (Caution:Beware of fire.)

The particles of smoke scatter some of the light in all directions, allowing you tosee the path it takes. Be careful not to sue too much smoke. You must be ableto see through the smoky air.

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5. You should now be able to complete the following statements. Write them in yourScience Log, and fill in the answers.a. As a beam of light passes through the air, it (lights up, does not light up) the

box.

b. When the beam of light hits the end of the box, it (lights up, does not light up)the box.

c. When the beam of light hits the black screen, the box is lit up (less than,more than, to the same extent as) in step (b).

d. White light falling on a black surface is absorbed (less than, more than, to thesame extent as) when it falls on a white surface.

e. White light falling on a black surface is scattered (less than, more than, to thesame extent as) it is scattered by a white surface.

f. A colored surface scatters (more light than, less light than, the same amountof light as) a white surface and (more light than, less light than, the sameamount of light as) a black surface.

g. A green surface scatters (what color?) light from its surface. Therefore, itmust absorb (what colors?) of light.

h. A black surface absorbs (what colors?) of light.

PART 2DOING WINDOWS

Replacing the black paper that is in the path of light beam with a square of windowglass. Place the glass near the center of the box, just behind the viewing window.Add smoke so that you can see the light beam. Place the glass at various anglesand observe the results.

WHAT TO DO1. Place the glass at a 45° angle to the

light beam, and then answer thefollowing questions:a. Does the beam of light scatter as it

hits the glass, or does it bounce off(reflect) in a certain direction?

b. Can you see light pass through theglass? In other words, can you seeany transmitted light?

c. Which seems brighter—the reflectedbeam or the transmitted beam? Why?

2. Repeat step 1 again, first placing the glass at a steep angle such as 80°(measured with respect to the horizontal) and then at a shallow angle, such as10°. For each angle, answer the questions in step 1.

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3. Now write several statements like those you completed after Part 1 of thisExploration. They should describe what you have learned by doing thisexperiment.

PART 3WAX FACTS

WHAT TO DO1. Replace the glass with a piece of paraffin wax. Hold the wax at various angles in

the light beam. Be sure to use smoke to help you see the beam.2. How does the appearance of the paraffin compare with that of the glass when

each is in the beam? Is the box brighter when the paraffin is in place or whenthe glass is present?

3. Record your findings in a series of simple statements.

PART 4LIGHT AND WATER

WHAT TO DO1. Put a small beaker nearly filled with water

in the light box. Turn on the flashlight andshine a light beam through the water. Canyou see the beam in the water?

2. Add a drop or two of milk to the water andstir? Is the beam now visible in the water?What are the milk particles doing to thelight? Is there evidence that light istransmitted through the slightly cloudywater? Is there evidence that light is scattered by the cloudy water?

3. Write a conclusion for this experiment using the words transmitted and scattered.

PART 5ANOTHER ANGLE

WHAT TO DO1. Take a large beaker or jar of

tap water, and hold a smallflashlight against one side of it.See the illustrations below.Look at the light from theopposite side of the containeras well as the right angles tothe light beam. You can obtainthe best results in a darkenedroom. What color is the light?

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What color, if any, is the water when viewed at right angles to the beam?4. Add a few drops of milk to the water and stir. What color does the light seem to

be now? What color, if any, is in the water?5. Repeat step 2, adding more milk until faint color effects are observed.6. Describe your results in this experiment.

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AssessmentGrade 7



Students will be given a diagram of a pencil placed in a four hundred ml beaker of water at anangle other than ninety degrees. This diagram will also include the incoming rays of light. Eachstudents will draw the rays of light that are reflected, refracted, and transmitted from the beakerand pencil and write a paragraph that describes the behavior of the light rays.




Correctness ofdiagram

Draws one ray oflight correctly.

Draws two ofthree rays of lightcorrectly.

Draws three raysof light correctly.

Draws three raysof light correctly.

Completeness ofexplanation

Describes onelight behaviorcorrectly.

Describes one ortwo lightbehaviorscorrectly.

Describes allbehaviorscorrectly andclearly.

Describes allbehaviorscorrectly andclearly; explainswhy the pencilimage is bent.

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of various waves.

Grade Level Benchmark: 5. Describe the motion of vibrating objects. (IV.4.MS.5)


Central Question:How may the motion of vibrating objects be describedby frequency, period, and amplitude?

1. “Vibrations: How Fast and How Far”

2. “Spring Fling”


Resources

SciencePlus, page 370-372,378, Holt, Rinehart andWinston, Harcourt Brace(1997)

Process Skills: Observing, Hypothesizing, Analyzing, Inferring, Measuring

New Vocabulary: period, frequency, amplitude

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VIBRATIONS: HOW FAST AND HOW FAR?

GETTING STARTEDShow students a swinging pendulum. Have them estimate how many times thependulum moves back and forth in one second. Explain that if the pendulumproduced sound, the pitch would be too low for humans to hear. Ask: How manytimes per second would the pendulum have to vibrate to produce a sound that wecould hear? (At least 20 times per second.) Point out that in this lesson they willexperiment with a pendulum to understand how vibrations produce sound.

MAIN IDEAS1. A vibration consists of one complete back-and-forth motion.2. The frequency of vibration is the number of times an object vibrates in one

second.3. The frequency of vibration of a pendulum does not change when the amplitude

of the vibration is changed.4. Decreasing the length of a pendulum increases the frequency of vibration.

TEACHING STRATEGIES Exploration 3Because experimental errors may occur, tell students to take several measurementsand average the results. Also, suggest that students tap the table when eachvibration is complete. They should realize that the time between taps remainsconstant for a given length of the pendulum. The time it takes for a pendulum tocomplete one vibration is called the period and does not vary with small changes inamplitude.

TIME REQUIRED1 to 2 class periods

PROCESS SKILLSobserving, hypothesizing, analyzing, inferring, measuring

NEW TERMSAmplitude—the size of a pendulum swing; the greatest distance that a vibratingobject moves from its rest position

Frequency—the number of vibrations in one second

Vibration—one complete back-and-forth movement of an object

MATERIALS (per student group)Exploration 3: heavy button, washer, or large paper clip; metric ruler; watch orclock with a second hand; 25 cm of fine thread; scissors

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TEACHING RESOURCESExploration Worksheet, p. 11SourceBook, p. S109

COOPERATIVE LEARNING Exploration 3

GROUP SIZE2 to 3 students

GROUP GOALTo determine the relationship between the length of a pendulum and the amplitudeand frequency of its vibration

POSITIVE INTERDEPENDENCEAssign the following roles: architect (to read the directions to the group and build thependulum), timer (to hold the pendulum and time the swings), and recorder (to countand record the number of swings.) The groups should conduct the Exploration usinga pendulum system that they construct themselves. Each group should prepare adata chart and graph. To improve accuracy, each group should conduct three trialsfor each activity and average the results. The group should then work together toanswer the in-text questions from Check It Out.

INDIVIDUAL ACCOUNTABILITYEach student should individually answer the questions from Check It Out on thispage.

ANSWERS TO Investigating an Object Vibrating Very Slowly2. One vibration should take about 1 second. The time does not change

appreciably from one swing to the next. To find the time for one vibration,measure the time required for several vibrations and then divide it by the numberof vibrations. For a 25 cm pendulum, there is about 1 vibration/second.

3. No, the time should not appear to change.4. One vibration takes about 0.5 seconds (a frequency of 2 vibrations/second.)

ANSWERS TO Mason’s ProblemStudent answers will vary. You may wish to discuss the meaning of the three termsbefore students write their explanations. Then have volunteers present theiranswers to the class, and discuss which responses are most accurate and whichteaching methods might be most effective.

ANSWERS TO Check It Out1. Agree; the period does not depend on the amplitude of the swing.

2. Disagree; the period does not depend on the amplitude of the swing.

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3. Disagree; the frequency of vibration does not depend on the amplitude of theswing.

4. Agree; the period depends on the length of the pendulum.

5. Agree; if the time for one vibration (the period) is decreased, the frequency isincreased.

6. Agree; this follows from the results of Exploration 3.

7. Disagree; the frequency of vibration depends on the length of the pendulum.

8. Agree, based on the results of Exploration 3, lengthening the string by 4 timesshould double the period.

ANSWERS TO A Sound ExperimentCase 1The frequency in slow motion is 20 ÷ 10, or 2, vibrations/second. Therefore, thefrequency in real motion is 200 x 2, or 400, vibrations/second.

Case 2a. The frequency in slow motion is 31 ÷ 15, or about 2, vibrations/second.

Therefore, the frequency in real motion is about 200 x 2, or 400,vibrations/second.

b. The amplitude in Case 1 is two times the amplitude in Case 2.c. The amplitude does not appreciably affect the frequency of vibration.

Case 3a. The frequency in slow motion is 30 ÷ 10, or 3, vibrations/second. Therefore, the

frequency in real motion is 200 x 3, or 600, vibrations/second.b. The ruler is shorter in Case 3 than in Case 1.c. Yes; as the length is shortened, the frequency increases.

CONCLUSIONSa. Case 1 has the largest amplitude and therefore the loudest sound.b. Case 3 has the greatest frequency and therefore the highest pitch.

FOLLOW-UPRETEACHINGAttach a small weight to a piece of string about 1 m long and swing it from side toside. Remind students that this is a simple pendulum. Identify the frequency bycounting the number of back-and-forth motions in a given time period and dividingby the time. Identify the period by timing the duration of a number of back-and-forthand dividing the number of swings. Point out that the frequency multiplied by theperiod is always 1—they are reciprocals of one another. Repeat the demonstration,but vary the amplitude to show that the period and frequency do not change fromtrial to trial.

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ASSESSMENTUsing thread and a washer, challenge students to make a timer that will accuratelymeasure 4 s. (Students will need to find the proper length of thread so that theperiod of the pendulum is 1 s or a multiple of 1 s. For instance, 25 cm of thread willgive a period of 1 s, 1 m of thread will give a period of 2 s, and so on.)

EXTENSIONHave students research the role of the pendulum in a grandfather clock. Or suggestthat students visit a music store to find out how frets and bridges in guitars and otherstringed instruments affect the sounds produced by those instruments.

CLOSUREBring an encyclopedia to class and read the entry on Alexander Graham Bell. Afterreading the material and discussing how Bell invented the telephone, ask studentsto write mock transcripts of an interview with him. Tell students that their interviewsshould include the terms pitch, frequency, and amplitude.

HOMEWORKThe root word phon comes from the Greek language and means “sound.” Challengestudents to list as many words containing this root as they can. Then discuss thedefinitions of the words they find. (Likely words include phonetics, cacophony,homophone, and telephone.)

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VIBRATIONS: HOW FAST AND HOW FAR?

When a bird sings, the membranes of its syrinx may vibrate as many as 20,000 timesper second. When you pluck middle G on a guitar, it vibrates about 400 times in 1second. The larynx of the humpback whale vibrates about 20 times per second whenmaking its lowest sound.

Objects that produce sound generally vibrate too quickly for the vibrations to be seen.How might you observe the individual vibrations? One way is to take pictures of themwith a high-speed motion picture camera and then project the pictures at a slow speed.You would then see the vibrations in slow motion.

In the following Exploration, you will analyze a slow, “sound-less”vibrating situation. This will help you understand the much fastervibrations that produce sound.

EXPLORATION 3 Investigating an Object Vibrating Very Slowly

YOU WILL NEED• a heavy button, washer, or larger paper clip• a metric ruler• a watch or clock with a second hand• fine thread• scissors

WHAT TO DO1. Make a pendulum by hanging a button from a

thread that is 25 cm long. Pull the button 10 cmto one side and let it go.

2. A vibration is defined as one complete back-and-forth movement of an object, from one sideto the other and back again. Approximately how

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long does one vibration take? Does the timeseem to change from one swing to the next?Devise a way to find the time one vibration takes.About how many vibrations are there in a second?

3. Repeat step 2, but pull the button 20 cm to oneside. The size of the swing—the horizontaldistance from the side position to the centralposition, as shown below —is called theamplitude. Does the time for one vibrationappear to change when the button swings twice as far?

4. Shorten the thread to 6 cm. Pull the button 3 cm toone side and let go. How much does one vibrationtake? How many vibrations are there in 1 second?The number of vibrations in 1 second is called thefrequency of vibration.

MASON’S PROBLEMSuppose you had to explain the meaning of vibration, amplitude, and frequency toMason, a fourth grader. How would you do this, using a metal ruler as your teachingtool? In your Science Log, write down what you would say.

CHECK IT OUTReview what you discovered in doing this previous Exploration. From thestatements below, identify those that you agree with, those that you disagree with,and those that you are unsure about.

1. Changing the amplitude of the swing did not change the time needed for oneswing very much. If I could do the experiment accurately enough, it probablywouldn’t change the time at all.

2. If I double the distance the button swings, I can make a big change in the time ittakes for one vibration to occur.

3. If I were to start the swing only 5 cm out from the center, there would be fewervibrations in 1 second.

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4. If I shorten the thread, the time needed for one vibration to occur will be reduced.

5. If I shorten the thread, the frequency will be greater (the button will completemore swings in 1 second).

6. If I use about one-quarter of the length of thread, the time it takes for onevibration to occur will be about half that required when using the whole length ofthread.

7. Changing the length of the thread does not change the number of vibrations thatoccur in 1 second.

8. If I were to make the thread 100 cm long, the time of one vibration might be 2seconds.

A SOUND EXPERIMENTJennifer wanted to count the vibrations of some metal rulers. She took pictures ofthem with a high-speed movie camera and then projected the film at a much slowerspeed—abut 1/200 of the original speed. Suppose one back-and-forth motion (onevibration) took 1 second when her film was shown at this slower speed. Satisfyyourself that the ruler’s actual frequency of vibrations would be 200 vibrations persecond.

Jennifer counted the number of vibrations in a given time from her screenprojections, as observed in slow motion.

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For Case 1What is the frequency in slow motion? Try calculating the actual frequency.

For Case 2a. What is the frequency in slow motion? in real motion?b. How do the amplitudes in Cases 1 and 2 compare?c. Does the amplitude affect the frequency of vibration?

For Case 3a. What is the frequency in slow motion? in real motion?b. How do the lengths of the two rulers in Cases 1 and 3 compare?c. Do their lengths affect the frequency of vibration?

Conclusionsa. In which Case is the loudest sound produced?b. In which Case is the highest-pitched sound produced?

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KeyC = Compression of

the spring. Thecoils or turns ofthe spring arecloser togetherthan normal.

E = Expansion of thespring. The coilsor turns arespread fartherapart.

SPRING FLING

The steps below match the diagram below.

a. Mario and Kate hold the stretched spring on the floor.

b. Mario gives a quick push on the coiled spring, toward Kate. He then pulls it backquickly to its original position. Do you see the energy being transferred? (A)

c. When the coiled spring is still again, Mario quickly pulls the spring towardshimself. He then returns it quickly to its original position. Do you observe theenergy being transferred? (B)

d. Mario pushes his end of the spring quickly and then pulls it back quickly to itsstarting position. Mario has produced one complete vibration of the end of thespring. Kate says, “I think this is like what happens when a sound is made. Onecompression and one expansion together create a sound wave.”

e. Mario produces two complete vibrations of the end of the spring, one right afterthe other.

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SPRING FLING

ANSWERS TO In-Text QuestionsA. The energy that travels from Mario to Kate is represented by the compression of

the coils of wire.

B. The energy being transferred from Mario to Kate is represented by the expansionof the coils of wire.

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AssessmentGrade 7



The teacher will give students pictures of sound waves produced by an oscilloscope or diagrams ofsound waves that represent different sounds. Each student will write responses to the followingquestions on frequency, period, and amplitude:

1. Which wave was produced by the object with the longest period? How do you know?2. Which wave had the greatest amplitude? How do you know?3. Which wave was produced by the object with the highest frequency? How do you know?4. Which wave produced the highest pitched sound? Why?

a b c

d e f




Correctness ofidentification

Identifies onepicture correctly.

Identifies twopictures correctly.

Identifies threepictures correctly.

Identifies fourpictures correctly.


Writes onecorrect conclusionbased on incorrector no information.

Writes twocorrectconclusions basedon some correctinformation.

Writes three tofour correctconclusions basedon some correctinformation.

Writes five to sixcorrectconclusions basedon all correctinformation.

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of various waves.

Grade Level Benchmark: 6. Explain how mechanical waves transfer energy.

(IV.4.MS.6)


Central Question:How do mechanical waves transfer energy?

1. “Making Sounds”

2. “Secret Bells” (Seehttp://www.exploratorium.edu/science_explorer/secret_bells.html)

Activity Attached

Resources

SciencePlus, page 362, Holt,Rinehart and Winston,Harcourt Brace (1997)

Process Skills: Observing, Comparing

New Vocabulary: sound energy, absorption, transmission, reflection, media

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MAKING SOUNDS

GETTING STARTEDAsk for a few volunteers and give each volunteer a different classroom object. Tellthem to produce a sound with the object. Then ask: How does the object producethe sound? How can you stop the sound? Can you make the sound higher orlower and softer or louder? (Accept all responses) Point out to students that in thislesson they will learn new ways to modify sounds.

MAIN IDEAS1. Sounds are produced by vibrating objects.2. Sound is a form of energy.3. The larger the vibration of an object, the louder the sound; the faster the

vibrations, the higher the pitch of the sound.4. Animals produce sounds in many different ways and hear different sounds than

humans.

TEACHING STRATEGIES Exploration 1This Exploration works well in stations. Students should record specificobservations from each experiment in their Science Log.

Each student should clean the tuning fork with rubbing alcohol after using it. Makesure there are no operating hot plates, open flames, or other sources of ignitionnearby when using alcohol. Also, to avoid chipping a tooth, students should be verycareful when touching the base of the tuning fork to the base of their teeth. ForActivity 1, make sure that you approve all miscellaneous materials for safety beforestudents test them with the tuning fork.


PROCESS SKILLSobserving, comparing

THEME CONNECTIONSEnergy, Structures

NEW TERMSLarynx—the sound-producing organ in many vertebrates; the “voice box”

Syrinx—the sound-producing organ in birds; the “song box”

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MATERIALS (per student group)Exploration 1, Tuning Fork Sounds: a few tuning forks of different sizes; rubberstopper; glass container of any size filled with water, sheet of paper; plastic cup ordrinking glass; rubbing alcohol; a few cotton balls; miscellaneous objects to test thetuning forks; Ruler Sounds: wooden ruler; metal ruler; Rubber Band Sounds:small cardboard box; rubber band; Straw Sounds: plastic drinking straws; scissors;Simulated Voice Sounds: balloon; 12 cm cardboard tube; rubber band; scissors

Exploration 2, Part 1: meter stick

TEACHING RESOURCESExploration Worksheet, pp. 4 and 9 Transparency 58SourceBook, p. S106 and S121

ANSWERS TO A Symphony of SoundThe following are sample responses:1. All of the objects can be made to produce sound by adding energy to them. It

takes the energy of an applied force doing work on an object to produce sound.2. The object is vibrating as it produces the sound.3. The sound lasts for as long as the object vibrates. This may vary from less than

a second to many seconds.4. The sound can be stopped by “damping” the object (absorbing its energy) so that

it stops vibrating.5. The characteristics of the sound can be changed by changing the characteristics

of the vibrating object, the object’s surroundings, or the size of the applied force.For example, shortening the length or increasing the tension of the vibratingobject raises the pitch of the sound. Applying more force to the object or placingit against certain materials increases the sound’s loudness.

ANSWERS TO Activity 12. The tuning fork vibrates, producing sound.3. Students should feel the movement of the tuning fork. When the tuning fork

touches the container of water, ripples form on the surface of the water. Whenthe tuning fork touches the paper, the paper vibrates.

ANSWERS TO Activity 21. There is a relationship between pitch and how much of the ruler extends over the

edge of the table—the shorter the length of ruler hanging over the table, thehigher the pitch; the longer the length, the lower the pitch.

2. The pitch of the metal ruler will still get higher as the length hanging over thetable gets shorter. However, the sound made by the metal ruler will differ inloudness and quality from that made by the wooden ruler.

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ANSWERS TO Activity 31. The rubber band vibrates and produces a sound. The box makes the sound

louder.2. Yes; the pitch is higher because the tension in the rubber band has increased.3. Yes; the sound has a higher pitch because the pencil shortens the length and

increases the tension of the rubber band.

ANSWERS TO Activity 43. Shortening the straw produces a higher pitch.

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MAKING SOUNDS

EXPLORATION 1 A Symphony of SoundIt’s not difficult to make sounds but it is sometimes difficult to see what is happeningwhen sounds are made. Do several of the Activities that follow. For each Activity,record answers to the following questions:

1. How do I make the object produce the sound?2. What is the object doing as it produces the sound?3. How long does the sound last?4. How can I stop the sound?5. Can I change any characteristics (dimensions) of the sound, such as loudness

and pitch? If so, how?

YOU WILL NEED• tuning fork of different sizes• a rubber stopper• a glass container of water• 2 rulers — one wooded, one metal• a drinking glass• a cardboard box• 2 rubber bands• a pencil• a plastic drinking straw• scissors• a balloon• a cardboard tube (12 cm long)• rubbing alcohol• cotton balls• paper• miscellaneous objects

ACTIVITY 1 Tuning-Fork Sounds1. Strike a tuning fork on the edge of a rubber stopper.

2. Hold the tuning fork close to your ear. What do you observe?

3. Lightly touch the prongs to various parts of your body.

Caution: Do not touch the prongs to your eyes or eyeglasses. Clean the tunningfork with rubbing alcohol and a cotton ball before another student uses it.

After striking the fork again, touch the prongs to the surface of a glass containerof water and then to a loosely held piece of paper. What do you observe?

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4. Next, while the tuning fork is sounding, touch the base to your teeth, to the table,to a cup held over your ear, and to other objects.

5. Try some of these same experiments with a tuning fork of a different size.

ACTIVITY 2 Ruler Sounds1. Hold one end of a wooden ruler firmly on the edge of a table. Push down on the

other end, and then let it go. Try this several times, with various lengths of theruler extending over the end of the table. What do you observe?

2. Substitute a metal ruler for the wooden one, and repeat the activity. What doyou observe now?

ACTIVITY 3 Rubber-Band Sounds1. Pluck a rubber band that has been stretched across a cardboard box. Listen

carefully and observe what happens.

2. Tighten the part of the rubber band that is on the top of the box. Pluck it again.Is there any differences in sound.

3. Put a pencil across the top of the box (the short way), under the rubber band,and pluck again. Do you hear or see any differences? Why or why not?

ACTIVITY 4 Straw Sounds1. Make a “straw saxophone,” as shown below.

2. Adjust the position of the “sax” in your mouth until a steady sound is produced.Try producing different sounds by blowing indifferent ways.

Be careful: Use only your own straw, anddispose of it after completing the Exploration.

3. While blowing a steady sound, use scissors tocut the straw shorter and shorter. Whathappens?

ACTIVITY 5 Simulated Voice Sounds1. Place your fingers on your neck near your vocal

cords. Say “Ah” loudly. What do you feel? Trysome loud sounds and some low sounds.

2. Blow up a balloon. Make the balloon squeal as you slowly release air from it.Try for variations of sound. What must you do to get a higher sound? a lowersound? This is similar to what happens in your throat when you speak.

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3. Make a working model of human vocal cords. Stretch a piece of balloon over theend of a cardboard tube, but not too tightly. Cut a narrow slit in the piece ofballoon, and blow into the tube from the opposite end. Now tighten the balloon(this makes the slit wider), and blow again. What do you observe?

Caution: Blow only into your own tube. Dispose of tube after use.

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What do I need?• scissors• string• wire hanger• table (or a wall, or a

door)• metal spoon

You can also try:• fork• potato peeler• metal spatula• cake rack

What do I do?1. With your scissors, cut a piece of string about 3 feel long. (Grown-

ups should cut a piece about 4 feet long.)

2. Hold the two ends of the string in one hand. The rest of the stringwill make a loop.

3. Lay the loop over the hook part ofthe hanger. Push the two endsthrough the loop, and pull them allthe way through the other side.(This is easier to undo than aknot.)

4. Wrap the loose ends of the string two or threetimes around

the first fingers on each hand.

5. Swing the hanger so it gently bumps against the leg of a table,or against a door. What did it sound like? Probably not much.

6. Now put your hands over the openings of your ear. (Don’t putyour fingers in your ears!) Hold you hands tight to the sides ofyour head. Lean over and gently bump the hanger again.

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7. Wow! Now what does it sound like? Church bells? Chimes?

8. Want to hear what a spoon sounds like? Unwrap yourfinger, then pull on the loop end of the string. The wholestring will come off the hanger, and you can reloop it aroundthe spoon.

Try this with other things from your kitchen.

What's going on when I hear a sound?

You hear sounds when vibrations get inside your ears and stimulate your nerves tosend electrical signals to your brain.

Suppose, for instance, that you are pounding on a drum. The drumhead starts vibrating.As the drumhead vibrates, it bumps into air molecules and starts them bouncing to andfro. Those bouncing air molecules bump into other air molecules and start themmoving. This chain reaction of moving air molecules carries sound through the air in aseries of pulsating pressure waves that we call sound.

Sound waves carry vibrations from the drum into your ears. Inside your ear, moving airmolecules push on your eardrum and start it vibrating. Your eardrum, in turn, pushes onthe bones of your middle ear, the tiniest bones in your body. These bones act like a setof levers, pushing against the thin membrane that covers the opening to your inner ear.

The movement of this membrane makes pressure waves in the fluid inside the cochlea,where cells with tiny sensing hairs transform the waves into electrical signals. Theseelectrical signals travel along the auditory nerve to your brain. When these electricalsignals reach your brain, you hear a sound-the beat of a drum.

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Why can you hear the music of the Head Harp only when the string is around yourhead? How do the Secret Bells work?

When you pluck on the string that's wrapped around your friend's head, the string startsvibrating. To reach your ears, the vibrations in the string must push on the air moleculesto make sound waves that travel through the air. But the string isn't very large and itdoesn't push on very many air molecules. So sound vibrations don't travel easily fromthe string into the air.

When the string is around your own head, the sound can take a more direct route toyour ears. Rather than traveling through the air, the vibrations can travel through yourhands and through the bone of your skull directly to the fluid inside your cochlea in yourinner ear. Instead of traveling from solid to air and back to solid, the vibrations movefrom one solid (the string) to another (your bones), and then into the fluid of yourcochlea. As a result, the sound you hear is much louder and richer.

The same thing happens with Secret Bells. When you put your hands over your ears,you provide a path that lets more of the vibrations reach your ears. When your handsaren't over your ears, you hear a faint, high-pitched, tinny sound. When you put yourhands over your ears, you hear deep, resonant, bell-like tones. The hanger makes thesame sound in both situations, but in one you provide a path that lets more of thesound reach your ears.

http://www.exploratorium.edu/science_explorer/secret_bells.html

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AssessmentGrade 7



Using their bodies as particles, students will work in groups of six to eight to preparedemonstrations showing how a mechanical wave can be transmitted from one person to another.Each group will present to the class.




Accuracy ofdemonstration

Interprets someinformationcorrectly.

Provides aninterpretationwith someunderstanding ofhow the particlemotion is relatedto thetransmission ofthe wave’senergy. (Particlesmove back andforth while theirposition changesonly slightly.)

Provides a correctinterpretation ofhow the vibrationof the particles ofmatter transmitsthe wave’senergy. (Particlesmove back andforth while theirposition changesonly slightly,causing the waveto move from oneend of the chainto the other.)

Provides athorough andaccurateinterpretation of amechanical wavecontinuing totransfer energy asthe source of thevibration causesthe particles ofmatter to continueto vibrate.(Particles moveback and forthwhile theirposition changesonly slightly. Thewave moves fromone end of thechain of studentsto the other andback again.)

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Earth/Space ScienceWorksheet


Topic: Solar System, Galaxy and Universe

Grade Level Standard: 7-6 Compare and contrast earth and sun to other planets

and star systems.

Grade Level Benchmark: 1. Compare the earth to other planets and moons in

terms of supporting life. (V.4.MS.1)


Central Question:How does our planet and sun compare to other planetsand star systems?

1. “Colonizing the Solar System”

2. “Solar System Shuffle” (seehttp://starchild.gsfc.nasa.gov/docs/StarChild/solar_system_level1/activity/solar_system_shuffle.html)

Resources

SciencePlus, Holt, Rinehart,and Winston, Harcourt Brace(1997)

Process Skills: Observing, Analyzing, Hypothesizing

New Vocabulary: gravity, atmospheres, temperature, nitrogen, carbon

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COLONIZING THE SOLAR SYSTEM

GETTING STARTEDAsk: Why would humans want to establish a colony on another planet? Havestudents discuss and list the advantages and disadvantages of establishing a colonyon Mars. (Accept all reasonable responses. Although a colony on another planetwould provide living space for many people, it would be expensive and timeconsuming to establish.)

MAIN IDEAS1. Permanent space stations and a colony on Mars will probably be a reality in the

next century.2. Mars is more like Earth than any of the other planets.

TEACHING STRATEGIES Project MarsCall on a volunteer to read aloud pages 456-466. Provide students with time tostudy the data table at the top of page 465. Then involve them in a discussion ofwhy Mars is the best candidate for colonization. Help students recognize that,based on information in the table, the Martian environment is most similar to that ofEarth.


PROCESS SKILLSobserving, analyzing, hypothesizing

NEW TERMSnone

MATERIALS (per student group)none

TEACHING RESOURCESnone

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COLONIZING THE SOLAR SYSTEM

PROJECT MARSOf all the planets. Mars offers the greatest hope of sustaining a human colony.Why is this so? Why not a colony on Venus, Jupiter, or Pluto? Examine thefollowing table of information to find some answers.

Mars Venus Jupiter, Saturn,Uranus, and

Neptune

Pluto

• very cold: averagetemperature:23°C

• extremely dry• evidence of flowing

water• thin atmosphere• former atmosphere

may have reactedwith soil and rocks

• surfacetemperature: 500ºC

• very denseatmosphere ofcarbon dioxide

• atmosphericpressure 90 timesthat on Earth

• clouds of sulfuricacid

• gaseous• consists mainly of

hydrogen andhelium

• violent storms

• 1/100 the volumeof Earth

• extremely cold:230°C

• receives littlesunlight

• surface may becovered with layerof frozen methane

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SOLAR SYSTEM SHUFFLE

Below you will find the shuffled solar system deck of cards laid out for you. You will also find adescription of each object in the deck. Your job is to match the card with the correct description.At the end of each description, you will find a box. In the box, enter the card number which youfeel best fits the description. Once you have unshuffled the deck, check to see how close youcame to being a “Solar System Shuffle Super StarChild.”

A. This ice planet has a moon which is almost as big as it.Matching card number: ______

B. The dirt here is full of iron which makes this space body look red.Matching card number: ______

C. Cold methane gas makes this planet look like a big blue-green ball in the sky.Matching card number: ______

D. This planet moves so fast, it was named after the swift messenger of the ancient Greek gods.Matching card number: ______

E. This beautiful planet is surrounded by over 1000 rings.Matching card number: ______

F. The yellow dwarf star found in our solar system.Matching card number: ______

G. This dirty snowball can be seen from Earth every 76 Earth years.Matching card number: ______

H. The Great Red Spot would make this a terrible place for a vacation.Matching card number: ______

I. The only space body in our solar system, other than Earth, where humans have visited.Matching card number: ______

J. The greenhouse effect is so strong here that this is the hottest planet.Matching card number: ______

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http://starchild.gsfc.nasa.gov/docs/StarChild/shadow/solar_syst.../solar_system_shuffle.htm

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ASSESSMENTGrade 7

SOLAR SYSTEM, GALAXY, AND UNIVERSE

Classroom Assessment Example SCI.V.4.MS.1

Small groups will build a form or a model of an alien from another planet found in our solarsystem. They will use their research information to determine which characteristics the alienmust have to adapt to their planet’s atmosphere, surface features, gravitational pull, andtemperature conditions.

Each group will present its design to the class and support their design with research information.


Scoring of Classroom Assessment Example SCI.V.4.MS.1


Model of alienadaptations

Uses model toexplainrelationships of asingle planetcondition to thecharacteristics ofthe alien.

Uses model toexplainrelationships oftwo or threeplanet conditionsto thecharacteristics ofthe alien.

Uses model toexplainrelationships ofall four planetconditions to thecharacteristics ofthe alien.

Uses model toexplainrelationships ofall four planetconditions to thecharacteristics ofthe alien. Theillustration iscolored withbackgroundeffects.

Quality of model Builds a poormodel.

Builds an averagemodel.

Builds an aboveaverage model.

Builds anexcellent model.

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Topic: Solar System, Galaxy, and Universe

Grade Level Standard: 7-6 Compare and contrast earth and sun to other

planets and star systems.

Grade Level Benchmark: 2. Describe, compare, and explain the motions of solar

system objects. (V.4.MS.2)


Central Question:How do objects in the solar system move?

1. “Round and Round”

2. “Having A Ball With Moon Phases”

3. “Passing the Globe”


Resources

Process Skills: Observing, Comparing, Interpreting data, Generalizing

New Vocabulary: orbit, rotation, axis, gravity, planets, moons, rings, comets,

asteroids, seasons, tilt of the earth on its axis, direct and indirect rays

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ROUND AND ROUND

TOPIC AREAThe elliptical orbits of planets

INTRODUCTORY STATEMENTStudents will construct the shape of planets’ orbits in our solar system by drawingellipses. They will study the effect of several variables on the resulting shape.

MATH SKILLS SCIENCE PROCESSESMeasurement ObservingConstructing ellipses ComparingExamining limits Interpreting data

Generalizing

MATERIALSPushpinsCardboard sheets (8.5" x 11")StringStudent worksheetsPencilsMetric rulers

KEY QUESTIONSWhat is the shape of a planet’s orbit?

BACKGROUND INFORMATIONThe closer the planet is to the Sun, the more circular the orbit. The farther theplanet is from the Sun, the more elliptical the shape of the orbit.

An ellipse has two foci, represented by pushpins in this investigation. If the foci areseparated by a distance equal to one-half the length of the closed loop, then theellipse will be at one limit: a straight line. Note that the loop would then be drawntight. If the pushpins would have no thickness the loop would just be a double line.The other limit is reached when the two foci are at one position. In that case, theresult would be a circle.

In the first investigation, the length of string forming the loop will be 20 centimeterslong and remain as the constant. The variable will be the distance between the fociranging from where both are the same position at A (only one pin should beinserted); to where they are separated by 10 cm at F, and F2, in which case astraight line results.

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In the second investigation the length of string will be the variable and the distancebetween the foci the constant. The shorter the string, the flatter the ellipse and thelonger the string the more nearly circular will be the ellipse.

MANAGEMENTIt is best to do this activity in centers with 3-4 students in each group. They canalternate drawing the ellipses.

PROCEDURE1. Supply each group with the two student worksheets, two pushpins, cardboard

backing, string, and metric ruler.2. Have students tie the string very carefully to produce the size loops specified.3. Demonstrate how to make the construction as shown below. The pencil must be

held tightly against the string to draw the line.4. Have students complete both investigations.

DISCUSSION1. If the length of the loop is held constant, what happens as the distance between

the foci increases? When does it become a line? a circle?2. If the distance between the foci is held constant, what happens as the length of

the loop increases?

EXTENSIONHave the students use different colored construction paper to make the differentellipses described below or others decided upon by the class. Then have themmount the smallest on the next larger, etc. to create a colorful display. Here is anexample of the patterns:

Centers Tacks-Distance String-Length

# 1 9 cm 25 cm

# 2 8 cm 25 cm

# 3 12 cm 30 cm

# 4 15 cm 35 cm

# 5 13 cm 35 cm

# 6 11 cm 40 cm

# 7 14 cm 40 cm

# 8 10 cm 45 cm

# 9 12 cm 50 cm

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Conclusion: ______________________________________________________

165

Conclusion: _______________________________________________________

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HAVING A BALL WITH MOON PHASES

MATERIALSStyrofoam ballpencil25-W light source for entire group

1. Place the 25-W light bulb in the middle of the room. Participants stand around the roomfacing the bulb, and at arms length from all other participants.

2. The light bulb represents the sun. The Styrofoam ball represents the moon. Your headwill represent the earth. Stick the Styrofoam ball on a pencil. Hold the pencil in your handand turn so that the “moon” is between you and the “sun”.

3. Describe the appearance the moon.

_______________________________________________________________________

_______________________________________________________________________

4. Raise the moon slightly so that you can just see the sun under the moon. Describe theappearance of your moon.

_______________________________________________________________________

_______________________________________________________________________

5. Holding th pencil in your left hand, slowly move the moon around your head to the left.Notice the edge of the shadow as it moves across the moon. This edge is called theterminator. Describe what happens to the appearance of the moon as you move it straightout to your left.

_______________________________________________________________________

_______________________________________________________________________

6. How many degrees of separation are there now between the sun and the moon? Whatphase is the moon in at this position?

_______________________________________________________________________

_______________________________________________________________________

7. Continue moving the moon counterclockwise until it is behind your head. As you do, watchthe moon pass through its waxing gibbous phase. You will need to raise the moon slightlyso that the shadow of your head does not fall on the moon. How many degrees separationare there now between the sun and the moon?_______________________________________________________________________

_______________________________________________________________________

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8. How much of the illuminated side do you see now? What do we call this moon?

_______________________________________________________________________

_______________________________________________________________________

9. Continue moving the moon until it is straight out to your right. As you do so, watch it passthrough the waning gibbous phase. How many degrees separation are there between thesun and the moon when it is directly out to your right? What phase is the moon in now?

_______________________________________________________________________

_______________________________________________________________________

10. Now bring the moon back again to the original position. As you do so, watch it passthrough the waning crescent phase. How many degrees separation are there nowbetween the sun and the moon when both are directly in front of you? What phase is themoon in now?______________________________________________________________________

______________________________________________________________________

11. Which phase of the moon, which you have seen, would be found in the morning sky?Which would be in the late afternoon sky?______________________________________________________________________

______________________________________________________________________

12. Now you can model lunar and solar eclipses with your earth-sun-moon model. A lunareclipse occurs when the shadow of the earth falls across the moon. A solar eclipse occurswhen the shadow of the moon falls across the surface of the earth. Where would you needto place the Styrofoam ball moon in relation to the sun in order to create a lunar eclipse?What phase is the moon in when a lunar eclipse occurs? Model this for yourself now.______________________________________________________________________

______________________________________________________________________

13. Where would you need to place the Styrofoam ball moon in relation to the sun in order tocreate a solar eclipse? What phase is the moon in when a solar eclipse occurs? Modelthis for yourself.______________________________________________________________________

______________________________________________________________________

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PASSING THE GLOBE

MATERIALS25-W light bulb and holderearth globe with a relatively shiny surface (either a desk model or a larger inflatedglobe is fine)

a. Set up the chairs in the room in an ellipse (a slightly flattened circle). Toward oneend of the ellipse (but not too far from the center) see the lightbulb in its holder on atable. Turn the light bulb on.

b. With a person sitting in each chair, designate the person at the end of the ellipsecloset to the sun as “winter”. The person at the end of the ellipse, furthest from thesun is “summer”. Spring and fall each lie in between and on either side of summerand winter, as shown.

c. Hold the globe so that it is situated at a 23.5° tilt. If your globe comes on a stand,the stand should already be titled at this angle for you. If you are using aninflatable globe, it may have a hook at the top for hanging that holds it at theappropriate tilt. Remember that the globe must always be tilted at this angle withrespect to the sun.

d. With the globe hanging at the proper angle, situate the globe so that thegeographic north pole points to a spot directly over the head of the person youhave called “winter”. Mark this spot on the wall and remember to always keep theearth’s north pole pointed toward this spot at all times. This spot is called the NorthStar.

e. Hand the globe to the person sitting in the seat labeled “spring” and ask them tohold the globe at 23.5° pointed to the north star. Have them adjust the height of theglobe with respect to the lightbulb until the people on the opposite side of the circlesee the lightbulb shining directly over the earth’s equator. This is what reallyhappens on the first day of spring.

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f. Maintaining this height and angle configuration, slowly pass the globe around thecircle first to summer, then fall and then winter. As you pass the globe, allow it topause at each location for a moment as people on the other side of the circle notethe location of the sun and the earth. The sun should be shining directly over 23.5°N latitude (the Tropic of Cancer) on the first day of summer and should be 23.5° Slatitude (the Tropic of Capricorn) on the first day of winter. It should be directly overthe equinox on the first day of fall.

g. Is the earth closer to the sun during our summer or our winter?

_______________________________________________________________________

Does this have to do with our distance from the sun or the tilt of the earth’s axis orboth?

_______________________________________________________________________

h. Based on the earth’s tilt with respect to the sun, what season is it in the southernhemisphere when it is summer in the northern hemisphere?

_______________________________________________________________________

i. For each position of the earth, is there any part of the earth that gets no light duringthat season? If so, which?

_______________________________________________________________________

_______________________________________________________________________

j. The word “equinox” means ‘equal night’. Why do you suppose the first day ofspring and the first day of fall are called equinox?

__________________________________________________________________

_______________________________________________________________________

k. Is there any part of the United States in which the sun is directly overhead at sometime during the year? If so, where?

__________________________________________________________________

_______________________________________________________________________

l. If you live in the continental United States, which direction must you always look tosee the sun? What if you live in Australia?

__________________________________________________________________

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AssessmentGrade 7



Students will work in pairs, taking on the identity of a particular planet, to write and perform arole-play about how (in terms of revolution duration) and why (in terms of gravitationalattraction) objects move around the Sun. One student should move around the Sun as his or herpartner does the following:

Explains where his or her “planet” (partner) is in relationship to other planets Explains why his or her partner is moving in a particular path Gives examples of other planets or heavenly bodies that affect his or her planet’s location

in space. Gives the number of satellites (moons) and gives possible reasons for thisnumber

Explains why planets or other heavenly bodies affect his or her partners’ location in space

Each pair of students will write explanations to the above considerations (These should bewritten prior to the role-play). Role-plays should include many different approaches so allstudents might fully comprehend the effect that heavenly bodies have on one another.




Completeness ofexplanation

Explains therevolution of aplanet bythoroughlyaddressing onepoint.

Explains therevolution of aplanet bythoroughlyaddressing twopoints.

Explains therevolution of aplanet bythoroughlyaddressing threepoints.

Explains therevolution of aplanet bythoroughlyaddressing all fivepoints.

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Topic: Solar System, Galaxy, and Universe

Grade Level Standard: 7-6 Compare and contrast earth and sun to other planets

and star systems.

Grade Level Benchmark: 3. Describe and explain common observations of the

night skies (V.4.MS.3)


Central Question:How do objects in the solar system move?

1. “Making Sense of the Skies”

2. “Comets—What Are They?”


Resources

SciencePlus, page 433-435,458, Holt, Rinehart, andWinston, Harcourt Brace(1997)

Process Skills:

New Vocabulary: moon phase, eclipse, stars, constellations, planets, milky way,

comets, meteors

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MAKING SENSE OF THE SKIES

EXPLORATION 2Divide the class into pairs of students. Suggest that they answer all of the questionsraised and draw each of the models as described.

1. Aristotle (384-322 B.C.)You may wish to share the following information with students: Aristotle was bornin Stagira, a small town in northern Greece. When he was about 18, Aristotleentered the Academy, Plato’s school in Athens. He studied there for the next 20years. Around 334 B.C., Aristotle founded his own school, the Lyceum.

Aristotle’s view that everything was made up of combinations of the fourelements (air, earth, fire, and water) was accepted for nearly 2000 years. It wasnot until the seventeenth century that scientists began to insist that directobservation and experimentation, rather than abstract philosophy, should be thebasis of scientific thought.

ANSWER TO In-Text QuestionB. To an observer on Earth, it appears that Earth is motionless and that everything

else moves around it. Two observations that might give the impression thatcelestial objects are attached to spheres revolving around Earth are (1) the Sunmoving across the sky, while Earth does not seem to move and (2) seeing thestars near the axis of rotation (near Polaris) move in a circle each night.

2. Aristarchus of Samos (3rd century B.C.)You may wish to share the following information with students. Based on cleverreasoning and observation, Aristarchus was the first to arrive at the radicalconclusion that Earth revolved around the Sun and that the Sun, not Earth, wasthe center of the solar system. During his lifetime, Aristarchus was reviled for hisideas and was threatened with prosecution for alleged impiety against theprevailing views of the time.

ANSWERS TO In-Text QuestionA. Good ideas and reasoning are often disregarded when they do not blend neatly

with prevailing notions of what is true.

3. Ptolemy (2nd century A.D.)You may wish to share the following information with students: Ptolemy, alsoknown as Claudius Ptolemaeus, made most of his astronomical observations inAlexandria, Egypt. He compiled his ideas in a 13-volume work that becameknown as the Almagest, a Greek-Arabic term that means “the greatest.”

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Much of what Ptolemy taught was pure astrology. He cataloged existing beliefsabout how the positions of the planets and stars controlled everything on Earth.In spite of his mysticism, Ptolemy was a tireless observer. He cataloged thecelestial latitude and longitude of over 1000 stars. He also discovered theirregularity of the Moon’s orbit. The Almagest survived the collapse of Greeceand endured the fall of the Roman Empire to become the backbone of theRoman Catholic Church’s view of the universe. The heavens, as defined byPtolemy, were perfection, with Earth at the center. This view prevailed until thesixteenth century.

ANSWERS TO In-Test Questions When Mars was on the far side of a small circle, it would appear faint. Then,

as Mars came around its epicycle, it would appear to be closer and brighterand to be moving in the opposite direction. Retrograde motion in this modeloccurs when the planet’s motion on the small circle is opposite to its motionaround the Sun.

Another explanation for retrograde motion could be the Earth is moving fasterin its orbit than Mars is. Much like a faster car on the inside lane of aracetrack, as Earth passes Mars, Mars seems to go backward.

ANSWERS TO Thinking Further1. Accept all reasonable responses. Students may recognize that the Earth-

centered theory proposed by Aristotle and Ptolemy is the best explanation fortheir observations, even though it is incorrect.

2. Accept all reasonable responses. Students might try to explain the Earth’srevolution in terms of seasonal changes.

3. It explained the motions of the Sun and stars in the simplest way.4. Heliocentric means that the Sun is at the center of the solar system. Geocentric

means that the Earth is at the center of the solar system.

INDEPENDENT PRACTICEEncourage students to research and discover more about the early astronomersdiscussed in the Exploration. Students should discover as many biographical factsas they can, along with information about the scientific contributions that theseastronomers made. Students should share their information with the class.

FOLLOW-UPRETEACHINGSuggest that students make an astronomical calendar showing events that can beobserved for several months or throughout the year. Suggest that their calendarinclude information on the phases of the Moon, when and where planets will bevisible, when eclipses will occur, and so on.

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ASSESSMENTPresent students with the following scenario: Imagine that an alien has just arrivedfrom a distant planet. The alien knows a lot about the universe but doesn’t knowwhat it looks like from Earth.

Ask students to explain what the alien is likely to see in terms of the motion ofheavenly bodies. Suggest that students role-play this scenario after they havewritten their responses as an essay.

EXTENSIONHave interested students research the contributions of women astronomers. Somepossibilities include Helen S. Hogg and Maria Mitchell. Have students present theirfindings in a report to the class.

CLOSUREHave students graph the time at which the Sun rises and sets each day. Thisinformation can be found in most newspapers.

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MAKING SENSE OF THE SKIES

If you had lived 2000 years ago, when there were no telescopes or spaceships, and theonly means of observing celestial objects was with the naked eye, how would you haveexplained observations like the ones made so far in this unit? With a friend, weaveyour explanations into a theory that explains as many of your observations as possible.Can your theory explain the reasons for night and day? the star trials? why the calendarwheel works? Are there observations that your theory cannot explain? Does this meanthat your theory is not useful?

In Exploration 2, you will be able to compare your theory with those of a number of earlythinkers and observers.

EXPLORATION 2 The Early ObserversLiving in Greece and Egypt over 2000 years ago were many keen observers andthinkers. How did they explain their observations of the heaves? As you read aboutthree of them, think of the observations on which they may have based their ideas.

1. Aristotle (384-322 B.C.)Aristotle (pronounced air us TAHT ul) was the mostinfluential thinker of his time. He suggested thateverything in the universe is composed of four elements:earth, air, fire, and water. He proposed that eachelement has a natural resting place, with earth at thecenter, surrounded by spheres of water, air, and fire.

His model of the universe contained a total of eightspheres revolving around Earth. The first seven spherescarried the Moon, the Sun, and the five known planets.Aristotle proposed that beyond these seven spheres, thestars were tiny lamps fixed to another revolving sphere.

He theorized that the sphere carrying the Sun revolved around Earth each day,causing day and night. The motion was much like following the threads on acorkscrew. With each revolution around Earth, the Sun was carried higher (orlower) in the sky. He proposed that this movement causes the seasons.• How is this theory based on everyday observations? (B)• Try drawing a diagram based on Aristotle’s ideas.

2. Aristarchus of Samos (3rd Century B.C.)Aristarchus (pronounced air us TAR kus) combined mathematics with goodobservation to come up with another theory that is surprisingly close to our currentunderstanding of the solar system. He suggested that the Sun is the center of theuniverse—not the Earth. He proposed that Earth and the other planets revolvearound the Sun, causing the cycle that we call the year. Day and night, Aristarchus

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suggested, are caused by the rotation of Earth on its axis. He was the first tomeasure the distance to the Sun and Moon. He concluded that the Sun is muchfarther away and much larger than previously thought. The stars, he reasoned, areunimaginably far away. Although Aristarchus’s theory explained observations aswell as Aristotle’s theory did, it was not accepted by the people of his day and wasforgotten for nearly 2000 years.• What do you think about Aristarchus’s theory?• Why do you think good ideas and reasoning are sometimes disregarded in favor

of other ideas? (A)• Try drawing a diagram that illustrates Aristarchus’s ideas.

3. Ptolemy (2nd Century A.D.)Ptolemy (pronounced TAHL uh mee) supported the ideas of Aristotle. He reasonedthat if Earth really moved, the tremendous winds caused byEarth’s movement would blow birds off their perches andleaves off the trees. Ptolemy supported Aristotle’s idea thatthe Sun revolves around a stationary Earth; he noted thatevery day, we see the Sun actually moving across the sky.

But Ptolemy recognized that Aristotle’s model had twoserious flaws. First, it could not explain why the wanders,or planets, varied in brightness from year to year. If theyorbited Earth at fixed distances, their brightness should notvary greatly. Second, the paths that the planets traveledwere more erratic than the paths suggested by Aristotle’stheory. A planet such as Mars, for instance, appears tomake a loop in the sky, going backward for a while before continuing its forwardmotion. This curious backward motion is called retrograde motion.

Ptolemy’s solution was to add another motion to a planet. He suggested that aplanet not only revolves in a circular orbit around Earth but also makes smallerrevolutions about points on its main orbit—like a small wheel turning on thecircumference of a larger wheel. To get a good picture of Ptolemy’s ideas, imaginethe rocking seat of a Ferris wheel actually making a complete turn as the Ferriswheel itself turns. The motion of the seat is like the motion of a planet in Ptolemy’smodel.• Study the model below, which shows how Ptolemy thought Mars moved. How

does Ptolemy’s “solution” explain the apparent changes in brightness and theapparent backward (retrograde) motion of a planet such as Mars, as viewed fromEarth?

• Can you think of another explanation for retrograde motion?

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THINKING FURTHER1. Is the theory you proposed similar to any of the early Greek and Egyptian

observer’s theories? Which theory seems to best explain your observations ofthe heavens? Why?

2. Imagine that you live at the time of Aristotle, but your ideas match those ofAristarchus of Samos. What could you say to convince Aristotle that Earthrevolves around the Sun? Remember, they had no telescope or spaceships backthen.

3. For 1500 years, people believed that Earth was the center of the universe. Whydo you think this was such a popular view?

4. Aristarchus of Samos proposed a heliocentric model of the solar system.Aristotle and Ptolemy both proposed geocentric models. Based on theirtheories, what do you think these terms mean?

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COMETS—WHAT ARE THEY?

You may find the following information helpful: Today astronomers believe that cometsexist in two forms. In the more familiar form, they are visible to the naked eye and havelong tails. In the second form, the volatile gases have been burned off and the rockycomet is almost indistinguishable from an asteroid. In this form, comets can be seenonly with the aid of a telescope.

In 1577, the Danish astronomer Tycho Brahe declared that comets travel in paths farbeyond the Moon, and not just within the Earth’s atmosphere. Toward the end of theeighteenth century, Isaac Newton concluded that comets travel in elongated ellipticalorbits. During the same period, Edmund Halley tracked the orbits of 24 comets. In1950, the Dutch astronomer Jan H. Oort suggested that a cloud of comets exists at theouter reaches of the solar system. There, about 100 billion comets—the vast majorityof the known comets—are located, thousands of times farther away than the planetPluto is from Earth. Held weakly by the Sun’s gravitational pull, comets in the Oortcloud follow huge orbits that take thousands of years to complete.

THE COMET OF LIFETIMEShare the following information with students: By calculating the orbit of a comet heobserved in 1682, Halley proved that it was the same one that astronomers hadseen in 1531 and 1607. He correctly predicted its return in 1758. The comet,named after Halley has returned at approximately 76-year intervals ever since. OnMay 21, 1910, Earth is believed to have passed through the tail of Halley’s comet.

HOMEWORKHave students answer the following questions: How old will you be when Halley’scomet makes its next appearance? Why do you think this comet is sometimes called“the comet of a life”? (During an average person’s lifetime, they would have theopportunity to see the comet only once.)

DID YOU KNOWThe first reported sightings of Halley’s comet were made by Chinese astronomersaround 240 B.C.

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COMETS—WHAT ARE THEY?

The tail of a comet is a clue to its makeup. Think for a moment about what substances,when vaporized by the Sun’s heat, can be made to glow. Did you name ice? If so,you’ve discovered one part of a comet’s makeup.

In the outer reaches of the solar system, trillions of frozen ice masses are held in sloworbit around the Sun by gravitational forces. Besides frozen water, these ice massesconsist of dust and frozen gases. The orbits of some of the ice masses send themspeeding toward the Sun, at which time they may be seen by observers on Earth. Asthe comet nears the Sun, the rise in temperature turns the ice to steam and causesdust particles to be swept away from the head of the comet. These substances formthe comet’s tail. The tail becomes visible when the gas glows and the particles reflectand scatter light.

THE COMET OF A LIFETIMEIn 1682 Edmund Halley (pronounced HAL ee) observedthe comet that now bears his name. After calculating itsorbit around the Sun, Halley predicted that the cometwould return in about 76 years. Few believed him, and hedid not live to see his prediction come true, but it did. Thereturn of the comet in 1758 proved that comets aremembers of the solar system and that they revolve aroundthe Sun.

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AssessmentGrade 7



Pairs of students will create a three-dimensional or poster model that shows the Earth-Moon-Sun system.The model should be detailed, colorful, and easy to understand. It should include the phases of the Moonwith consideration given to the misconceptions that the new moon phase is not the 1st Quarter phase andthat a lunar eclipse does not occur with each full moon. Each pair of students will explain their model tothe class. Each student should be prepared to answer teacher-and student-posed questions about thefollowing:

1. Reasons for the various phases we see2. Conditions for an eclipse to occur3. Length of revolution4. Effect on the Earth’s rotation5. The amount of reflected light that one sees from Earth




Construction ofmodel

Fails to construct amodel that attemptsto showrelationships in thesystem.

Constructs a modelthat shows correctand somewhatdetailedrelationships withinthe system.

Constructs a modelthat accuratelyshows relationships,is correct, and iseasy to understand.

Constructs a modelthat is very detailed,interesting, andcould easily be usedas a teaching tool inshowing Earth-Moon-Sun systemrelationships.

Explanation ofmodel

Attempts to explainor illustrate requiredconcepts.

Correctly illustratesat least seventy-fivepercent of theconcepts and detailsrequired.

Correctly illustratesmost phases of theMoon and usesmodel todemonstratechanging phases, aneclipse, and rotationand revolution.

Correctly illustratesand manipulates themodel to show allphases of the Moon;demonstrateschanging phases, aneclipse, and rotationand revolution.

Correctness ofanswers

Correctly answers atleast fifty percent ofthe posed questions.

Correctly answersseventy-five percentof the posedquestions with anattempt to use themodel as areference.

Correctly answersall questions, oftenusing the model as ateaching tool.

Correctly answersall questions,effectively using themodel as a teachingtool.

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Science ProcessesWorksheet


Topic: Science Processes

Grade Level Standard: 7-7 Construct new scientific knowledge.

Grade Level Benchmark: 1. Use the scientific processes to construct scientific

knowledge. (I.1.MS.1-5)


Observing - observation of shells.

Communicating - labeling of Junk food ingredients.

Classifying - Have student sort nuts and bolts (other activitybinary classification of insects).

Measuring - Length of body parts.

Controlling variables - Swing of pendulum.

Developing models - model of teeth.

Activities are attached

Resources

Process Skills:

New Vocabulary:

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LEVEL 4

OBSERVING

MaterialsObserving assessment sheeta shellcolored markers or pencils

ProcedureHave the student observe the shell using the senses of sight, hearing, smell, andtouch. Ask the students to describe the shell’s color, shape, size, texture, sound,and odor. Tell the student to record the observations. Have the student draw andcolor a picture of the shell.

COMMUNICATING

MaterialsCommunicating assessment sheeta container or label from food or other household product

(Note: It might be interesting for students to read the contents of “junk” foods.)

ProcedureTell the students to read and record the ingredients listed on the label. Explain thatingredients are listed in order of abundance. Then have the student tell what thelabel communicates about the product.

CLASSIFYING

MaterialsClassifying assessment sheet20 different screws and boltscolored markers or pencils

ProcedureHave the student sort the screws and bolts into two groups by placing them in thecircles. Ask the student to trace around the screws and bolts and color them. Thenhave the student label each of the groups and describe how the items in eachgroup are alike. Ask the student to sort the screws and bolts into two groups in adifferent way. Have the student trace around the screws and bolts and color them.Ask the student to label each of these groups. Then have the student describe howthe items in each group are different.

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MEASURING

MaterialsMeasuring assessment sheetmetric tape measure

ProcedureHave each student estimate the length of the body parts listed on the assessmentsheet by ordering them from shortest to longest. Tell the student to determine thelength of his or her body parts with the metric tape measure. Have the studentrecord the lengths and order the body parts from shortest to longest. Then havethe student compare the actual lengths of each body part with the estimatedlengths.

CONTROLLING VARIABLES

MaterialsControlling Variables assessment sheet6 pieces of string (10 cm, 20 cm, 30 cm, 40 cm, 50 cm, and 60 cm in length)6 washers (one tied to the end of each string)penciltapetimer

ProcedureExplain to the student that counting the number of times the pendulum swings in 15seconds will help determine if the length of the pendulum makes a difference in thenumber of times it swings. Demonstrate how to tape the pencil to the edge of thetable, hang the pendulum in motion by pulling it up to the level of the table andreleasing it. Start the timer at the same instant the pendulum is released. Tell thestudent to count the number of times each pendulum swings back and forth in 15seconds. Ask the student to record the length of each pendulum and the number ofswings for each pendulum and answer the questions about the investigation.

MAKING MODELS

MaterialsMaking Models assessment sheetblack and orange crayons or markersscissorswhite glue

ProcedureHave the student outline the teeth with the black crayon or marker and color thegums orange. Tell the student to carefully cut the shape on the solid lines, andthen fold it along the dotted lines and glue it together. Have the student answer thequestions on the assessment sheet.

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Name ________________________________________________________________

OBSERVING

1. Use your eyes, ears, hands, and noseto observe the shell.

2. Describe the color of the shell. _______________________________________

________________________________________________________________

3. Describe the shape of the shell. ______________________________________

________________________________________________________________

4. Describe the size of the shell. ________________________________________

________________________________________________________________

5. Describe the texture of the shell. ______________________________________

________________________________________________________________

6. Describe the sound of the shell. ______________________________________

________________________________________________________________

7. Describe the odor of the shell. _______________________________________

________________________________________________________________

8. Draw and color a picture of the shell in the box below.

© Addison-Wesley Publishing Company, Inc. All rights reserved.

185

186

Name ______________________________________________________________

CLASSIFYING

1. Sort the screws and bolts into two groups in the circlesbelow.

2. Trace around the screws and bolts and color them.

Label ____________________ Label ______________________

3. How are the items in each group alike?

________________________________________________________________

________________________________________________________________

________________________________________________________________

________________________________________________________________


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Name ________________________________________________________________

4. Sort the screws and bolts in a different way into two groups in the circlesbelow.

5. Trace around the screws and bolts and color them.

Label ____________________ Label _____________________

6. How are the items in each group different?

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________


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Name ________________________________________________________________

MEASURING

1. Estimate the length of each of your body parts by puttingthem in order from shortest to longest: the length of thethumb, hand, foot, arm, and leg; the distance around theknee, head, neck, wrist, and ankle.

Body PartEstimated Order

1=shortest 10=longest MeasurementActual Order

1=shortest 10=longest

2. Use the metric tape measure to measure your body parts and write theactual measurements in centimeters.

3. Use the actual measurement to order your body parts from shortest tolongest, using 1 for the shortest and 10 for the longest.


189

Name ________________________________________________________________

4. Compare your estimates with your measurements. How close was yourestimated order to the actual order?

____________________________________________________________

____________________________________________________________

____________________________________________________________

5. What surprised you?

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________


190

Name ______________________________________________________________


1. Tape the pencil to the table so that it hangs over the edge. Hang thelongest pendulum from the pencil. Hold the pendulum even with the top ofthe table and release it.

2. Count how many times it swings back and forth in 15 seconds and recordthe number of swings in the chart below. Use the metric tape measure tomeasure the length of the pendulum. Repeat this procedure with the otherfive pendulums.

Length of Pendulumin cm

Number of Swings Backand Forth in 15 Seconds

3. Which variable did you change? __________________________________

4. Which variable responded to the change (what did you count)?

____________________________________________________________

5. Which variables were kept constant? ______________________________

____________________________________________________________

6. How does the length of the pendulum affect the number of times it swings in15 seconds? _________________________________________________

____________________________________________________________


191

Name ___________________________________________________________

MAKING MODELS

1. Outline the teeth in black. Color the gums orange.

2. Cut out the shape on the solid lines. Fold along the dotted lines. Follow thedirections for overlapping and gluing the model.

3. How is this model the same as real teeth?

____________________________________________________________

____________________________________________________________

4. How is this model different from real teeth?

____________________________________________________________

____________________________________________________________


192

193

194

195




Grade Level Standard: 7-8 Reflect on scientific process.

Grade Level Benchmark: 1. Use the scientific processes to reflect scientific

knowledge. (II.6.MS.1-6)


Inferring - make inferences from advertisements.

Interpreting data - table about volcanoes.

Communicating - write a math problem on the board andask students to explain in words what it means.

Hypothesizing - straw experiment.

Predicting - penny toss.

Activities are attached

Resources

Process Skills:

New Vocabulary:

196

LEVEL 4

INFERRING

MaterialsInferring assessment sheetmagazine advertisement

ProcedureAsk the student to list an observation about the advertisement and an inference thatcould be made from the observation. Give an example; e.g., observation: the girl inthe advertisement is petting a cat; inference: the cat is purring. Explain thatobservations can be verified by looking at the advertisement but inferences requireevaluation and judgement based on past experiences and cannot be verified bylooking at the advertisement. Have the student record observations and inferencesand answer the question on the assessment sheet.

INTERPRETING DATA

MaterialsInterpreting Data assessment sheetcalculator

ProcedureExplain to the student that the calculator can be used to answer the questionsabout the active volcanoes of North America. Have the student look at the table ofinformation about active volcanoes in North America and answer the questions onthe assessment sheet.

HYPOTHESIZING

MaterialsHypothesizing assessment sheet6 strawsscissors

ProcedureDemonstrate how to cut one end of the straw to form a point and how to blow intothe pointed end to produce a sound. Explain that hypotheses are educated guessesabout the answer to a question. Tell each student to give a hypothesis (educatedguess) to answer the following question: How does the length of the straw affect thepitch of the sound produced?

197

Have the student test the hypothesis by cutting each straw to a different length andobserving the pitch of the sound produced. Have students place the straws in orderfrom the highest to the lowest pitch and tape the straws to the assessment sheet.Then have the student compare the hypothesis to the results of the activity to tellwhether or not the hypothesis was correct.

PREDICTING

MaterialsPredicting assessment sheetpenny

ProcedureExplain that the penny will be flipped 40 times and the student will record whetherthe coin lands on head or tails. Then the student will use the results of the 40 coinflips to predict what will happen if the coin is flopped 10 more times. Ask eachstudent to test the prediction by flipping the coin 10 more times and recording theresult.

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Name ________________________________________________________________

INFERRING

1. Look at the advertisement. List anobservation and an inference that could bemade about the advertisement in the chartbelow. An example is given for you.

Observation Inference

The girl is petting the cat. The cat is purring.

2. What do you think the advertisers want you to believe will happen if you use theirproduct?

____________________________________________________________

____________________________________________________________


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Name ________________________________________________________________

INTERPRETING DATA

1. Read the table below and answer the questionsabout the information.

Active Volcanoes of North America

Name (year of latest activity) Location Height (in meters)

Colima (1986)Redoubt (1966)Iliamna (1978)Mount St. Helens (1986)Shishaldin (1981)Veniaminof (1884)Pavlof (1984)El Chichon (1983)Makushin (1980)Trident (1963)Great Sitkan (1974)Akutan (1980)Kiska (1969)Sequam (1977)

MexicoAlaskaAlaskaWashingtonAleutian IslandsAlaskaAleutian IslandsMexicoAleutian IslandsAlaskaAleutian IslandsAleutian IslandsAleutian IslandsAlaska

4,2683,1083,0762,9502,8612,5072,5042,2252,0361,8321,7401,3031,3031,054

2. How high is the highest active volcano?

3. How high is the lowest active volcano?

4. What is the difference in height between the highestand lowest volcano?

5. What is the most recent date of volcanic activity?

6. What is the least recent date of volcanic activity?

7. How many years passed between the most recentactivity and the least recent activity?

__________________

__________________

__________________

__________________

__________________

__________________


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Name ________________________________________________________________

HYPOTHESIZING

1. Cut one end of the straws to form a point and blow into thisend of the straw to produce a sound. Observe the pitch ofthe sound produced (high or low).

2. Question: How does the length of the straw affect the pitchof the sound produced?

Your hypothesis (educated guess): ________________________________

____________________________________________________________

____________________________________________________________

3. Trim the five remaining straws to different lengths. Then cut one end ofeach straw, blow into this end, and observe the pitch of the soundproduced.

4. Arrange your six straws in order from the highest to the lowest pitch andtape the straws in the box below.

Highest

Lowest

5. Did your investigation prove your hypothesis is correct? _______________


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Name ________________________________________________________________

PREDICTING

1. Flip the penny 40 times and record in the chart below whether it lands onheads or tails.

Trial No. 1 2 3 4 5 6 7 8 9 10

H or T

Trial No. 11 12 13 14 15 16 17 18 19 20

H or T

Trial No. 21 22 23 24 25 26 27 28 29 30

H or T

Trial No. 31 32 33 34 35 36 37 38 39 40

H or T

2. How many times did the penny land on heads? ______________________

3. How many times did the penny land on tails? _______________________

4. Predict how many times the penny would land on heads and how manytimes on tails if you flipped it 10 more times.

heads __________________ tails ____________________


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Name ________________________________________________________________

5. Flip the penny 10 more times and record the results in the chart below.

Trial No. 1 2 3 4 5 6 7 8 9 10

H or T

6. How many times did the penny land on heads? ______________________

7. How many times did the penny land on tails? _______________________

8. Explain why your prediction might not match the actual number of headsand tails.

____________________________________________________________

____________________________________________________________

____________________________________________________________


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ANSWERS

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Grade Level Standard: 7-9 Use the scientific method for investigation.

Grade Level Benchmark: 1. Use the scientific method to communicate scientific

knowledge gained through investigation.


Scientific MethodQuestionResearch (Collection of Information)HypothesisInvestigation/ExperimentationProceduresResultsConclusions

Resources

Process Skills:

New Vocabulary:

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PRODUCTS OF SCIENCE

The process of science generates certain products which also can be arranged in an hierarchy of

increasing complexity. These products include scientific terms, facts, concepts, principles, laws, theories,

models, and applications.

SCIENTIFIC TERM

A word or words that scientists use to name an entity, object, event, time period, classificationcategory, organism, or part of an organism. Terms are used for communication and would notnormally include names given to concepts, laws, models, or theories.

SCIENTIFIC FACT

An observation, measurement, logical conclusion from other facts, or summary statement,

which is concerned with some natural phenomenon, event, or property of a substance, which,

through an operationally defined process or procedure, can be replicated independently, and

which, through such replication, has achieved consensus in the relevant scientific profession.

Facts include things such as the speed of light or properties of materials like boiling points,

freezing points, or size.

SCIENTIFIC CONCEPT

A regularly occurring natural phenomenon, property, or characteristic of matter which is

observable or detectable in many different contexts, and which is represented by a word(s) and

often by a mathematical symbol(s) is called a scientific concept. When a scientific concept is

fundamental to other concepts and is used extensively in creating such other concepts in

nature, like length (or distance ), mass, electric charge, and time. Most scientific concepts are

derived, that is, defined in terms of basic or other scientific concepts. When a derived scientific

concept is in the form of an equation, it is a mathematical definition, not a natural relationship

(e.g., destiny, speed, velocity acceleration).

SCIENTIFIC PRINCIPLE

A generalization or summary in the form of a statement or mathematical for when expression, a

set of observations of, or measurements for, a variable representing a concept shows a regulardependence on one or more other variables representing other concepts. A principle of scienceis an expression of generalizations that are significant but are not at the level, in terms of broadapplicability or generalizability, to be a scientific law.

EMPIRICAL LAW

An empirical law is a generalization of a relationship that has been established between or more

concepts through observation or measurement, but which relies on no theory or model for its

expression or understanding. Such laws have important application and are of great importance

as cornerstones for theories or models. Examples include Snell's law of refraction, Kepler's

Laws, and evolution (but not the theory of natural selection).

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SCIENTIFIC THEORY

An ordinary-language or mathematical statement created or designed by scientists to accountfor one or more kinds of observations, measurements, principles, or empirical laws, when thisstatement makes one or more additional predictions not implied directly by anyone of suchcomponents. When such prediction or predictions are subsequently observed, detected, or

measured, the theory begins to gain acceptance among scientists. It is possible to createalternative theories, and scientists generally accept those theories which are the simplest ormost comprehensive and general in their accommodation to empirical law and predictivecapability (e.g., atomic theory, kinetic molecular theory, theory of natural selection, theory of

plate tectonics, quantum theory). Theories which can account only for existing laws make no

new predictions, or at least do not have greater simplicity or economy of description when

offered as alternatives to accepted theories, are of little value and therefore, generally do not

displace existing theories.

SCIENTIFIC MODEL

A representation, usually visual but sometimes mathematical or in words, used to aid in the

description or understanding of a scientific phenomenon, theory, law, physical entity, organism,

or part of an organism ( e.g., wave model, particle model, model of electric current,

"Greenhouse" model of the Earth and atmosphere).

UNIVERSAL LAW

A law of science that has been established through repeated unsuccessful attempts to deny itby all possible means and which therefore, is believed to have applicability throughout theuniverse. There are few such laws, and they are basic to all of the sciences (e.g., Law ofUniversal Gravitation, Coulomb's Law, Law of Conservation of Energy, Law of Conservation ofMomentum).

APPLICATION OF SCIENCE

Utilization of the results of observations, measurements, empirical laws, or predictions fromtheories to design or explain the working of some human-made functional device orphenomenon produced by living beings and not otherwise occurring in the natural world. (Somesuch applications depend on several laws or theories, and historically many have been devisedwithout the humans involved having prior knowledge of those theories or laws.) Applicationswould include engineering and technology and the utilization of science in making decisions onissues that have scientific basis, for example, the relative radiation damage possible fromhuman-made sources as compared with natural radiation.

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PROCESS OF SCIENCE

The scientific endeavor involves continually examining phenomena and assessing whether

current explanations adequately encompass those phenomena. The conclusions that scientists

draw never should assume a dogmatic character as science necessarily is tentative. Authorities

do not determine or create scientific knowledge, but rather scientists describe what nature

defines and originates.

Those engaged in the scientific endeavor use and rely on certain processes. The processes

can be arranged in an hierarchy of increasing complexity–observing, classifying, measuring,

interpreting data, inferring, communicating, controlling variables, developing models and

theories, hypothesizing, and predicting–but the process scientists use usually do not and need

not "happen" in this order.

OBSERVING

Examining or monitoring the change of a system closely and intently through direct sense

perception and noticing and recording aspects not usually apparent on casual scrutiny.

CLASSIFYING

Systematic grouping of objects or systems into categories based on shared characteristics

established by observation.

MEASURING

Using instruments to determine quantitative aspects or properties of objects, systems, or

phenomena under observation. This includes the monitoring of temporal changes of size,

shape, position, and other properties or manifestations.

INTERPRETING DATA

Translating or elucidating in intelligible and familiar language the significance or meaning of

data and observations.

INFERRING

Reasoning, deducing, or drawing conclusions from given facts or from evidence such as that

provided by observation, classification, or measurement.

COMMUNICATING

Conveying information, insight, explanation, results of observation or inference or measurement

to others. This might include the use of verbal, pictorial, graphic, or symbolic modes of

presentation, invoked separately or in combination as might prove most effective.


Holding all variables constant except one whose influence is being investigated in order to

establish whether or not there exists an unambiguous cause and effect relationship.

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DEVELOPING MODELS AND THEORIESCreated from evidence drawn from observation, classification, or measurement, a model is amental picture or representative physical system of a phenomenon (e.g., a current in an electriccircuit) or real physical system ( e.g., the solar system). The mental picture or representativesystem then is used to help rationalize the observed phenomenon or real system and to predicteffects and changes other than those that entered into construction of the model. Creating atheory goes beyond the mental picture or representative model and attempts to include othergeneralizations like empirical laws. Theories often are expressed in mathematical terms andutilize models in their description ( e.g., kinetic theory of an ideal gas, which could utilize amodel of particles in a box).

HYPOTHESIZING

Attempts to state simultaneously all reasonable or logical explanations for a reliable set of

observations–stated so that each explanation may be tested and, based upon the results of

those tests, denied. Although math can prove by induction, science cannot. In science, one can

only prove that something is not true. Accumulated evidence also can be used to corroborate

hypotheses, but science remains mainly tentative.

PREDICTING

Foretelling or forecasting outcomes to be expected when changes are imposed on (or are

occurring in) a system. Such forecasts are made not as random guesses or vague prophecies,

but involve, in scientific context, logical inferences and deductions based (1) on natural laws or

principles or models or theories known to govern the behavior of the system under

consideration or (2) on extensions of empirical data applicable to the system. (Such reasoning

is usually described as "hypothetico-deductive.")

Source: The National Science Teachers Association

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TechnologyWorksheet


Topic: Technology

Grade Level Standard: 7-9 Use technology to conduct investigations of science.

Grade Level Benchmark: 1. Use technology to investigate/research scientific

knowledge.


1. Research a well known scientist and their contributions

to the study of the Solar System, Galaxy, and Universe

on the Internet using the list from Gender/Equity.

2. Prepare a report based on research from a CD-ROM

that demonstrates the contributions of a well known

scientist from the list on the Gender/Equity.

Resources

Process Skills:

New Vocabulary:

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Gender/EquityWorksheet


Topic: Gender/Equity

Grade Level Standard: 7-10 Investigate a variety of scientists from different

cultures.

Grade Level Benchmark: 1. Recognize the contributions made in science by

cultures and individuals of diverse backgrounds. (II.1.MS.6)


Organization of Living Things Motions of Objects

Gerty Theresa Cori Maria Geoppert Mayer

Daniel Hale Williams Robert McNair

Robert Jarvik Albert Einstein

Heredity Waves and Vibrations

Barbara McClintock Shirley Ann Jackson

James E. Bowman, Jr. Louis Howard Latimer

Johann Gregor Medel Alexander Graham Bell

Ecosystems Solar System, Galaxy, and

Rachel Louis Carson Universe

Grace Chow Annie Jump Cannon

Aldo Leopold Benjamin Banneker

William Hershel

1. Students will go on-line to “MI CLIMB” to research important

scientific people and their contributions to science.

2. Students will then select any one of the 3 names mentioned

and complete one of the following: oral report, written report

or hands-on project.

Resources

On-line capabilities

Process Skills:

New Vocabulary:

Documents

Physical Science Worksheet - · PDF filePhysical Science Worksheet GRADE ... you estimated the speed of the sound ... investigation that answers the question, “How is sound transmitted