Date: November 10, 1998

Grade Level(s): 4, 5

Subject(s):

• Science/Physics

Description: The students will demonstrate their understanding of sound travel by predicting and explaining why you can hear the sound of a train coming when you put your ear on the track faster than you would by the air.

Goals:

Science understanding:

1. Sound travels in waves.
2. Sound travels through materials in waves.
3. Sound travels at different speeds through different materials.
4. Sound travels faster in solids than air.

Objectives:

The students will demonstrate their understanding of sound travel by predicting and explaining why you can hear the sound of a train coming when you put your ear on the track faster than you would by the air.

Materials:

1. Activity one: Plastic wrap, bowl, rubber band, salt, wooden spoon, and a pan, or tuning fork.
2. Activity Two: Table.
3. Activity Three: Two tin cans, string, and two buttons.

Procedure:

Background Information:

Sounds are caused by vibrations.
Sounds cause the bones in your ear to vibrate allowing people to hear.
Sounds are transmitted from one place to another in waves.

Concept Assessment:

Strike a tuning fork against the heel of your shoe, or hit it with a rubber mallet. Place the tips of the tines (the two vibrating ends of the tuning fork) into a beaker of water and ask: In your concept journals, describe what you observed, what happens when the tuning fork is dipped into the water? What does this event show us about sound?

Concept Exploration:

Three activities will be set up at different stations where students will rotate stations in groups. For each activity have students come up with six questions as a group, and investigate at least three.

1. The "Dancing" Salt.

Stretch a sheet of plastic wrap over the top of the bowl. Secure it with the rubber band. Sprinkle the salt on top of the plastic wrap. Bang a wooden spoon on a pan, or strike a tuning fork and hold it above the salt.

2. Tabletop Messages

Hold you ear against a tabletop while someone taps and scratches lightly against the other end of the table.

3. Tin-Can Telephone

Punch a tiny hole through the end of a tin can. Pull a string through the hole and fasten it to a button on the inside. (The button keeps the string from being pulled out of the can.) Do the same with the other end of the string and a second tin can. The string should be at least as long as the classroom. Have one pupil on each end of the string, holding on to a tin can. Be sure that they pull the string tight. . Have one talk into the can while the other listens.

Concept Introduction:

Ask:

Dancing Salt Activity: Can you formulate a rule to explain why talking causes the salt to dance? Did the object that caused the salt to dance have to be held a certain way? Why ?

Tabletop Messages: How did the sound come through the tabletop? Were the variables controlled at all the times? Were there contrasting sounds coming through the table with those coming through the air?

Tin-Can Telephone: What happened when you changed different lengths and thickness of the string? Were the sounds always easy to hear? Why? Would the telephone have to be held a certain way for best results?

How did the sound travel? How could you hear the sounds better in all the investigations? How were you able to control the variables while drawing inferences? What can we say about sound? How does it travel? What can it travel through?

Assessment:

What would happen if you put your ear down on a railroad track? Why would a railroad worker put his ear against a track? An auto mechanic holds one end of a stick against parts of a car engine while holding his ear against the other end. Why do you think he is doing this?