Good Vibrations

Overview

Students will conduct hands-on activities to show that sound is caused by vibrations that move as waves. They will then look at how an earthquake moves away from its epicenter in all directions.

Standards Addressed

Science: Physical Science
Grade 8

6-8 Benchmark
D. Describe that energy takes many forms, some forms represent kinetic energy and some forms represent potential energy; and during energy transformations the total amount of energy remains constant.

Nature of Energy / Y2003.CSC.S03.G06-08.BD.L08.I04

04. Demonstrate that waves transfer energy.

 

Nature of Energy / Y2003.CSC.S03.G06-08.BD.L08.I05

05. Demonstrate that vibrations in materials may produce waves that spread away from the source in all directions (e.g., earthquake waves and sound waves).

Materials

• Slinky toys

• Mixing bowls less than 12 inches in diameter

• Aluminum foil

• Sugar

• Rice

• Compasses

Procedure

Part 1

(This part has been covered in other lessons. If the students need additional practice on the concept of vibrations, it would be good to start here. If they understand the concepts, you can begin with Part 2.)

1. Talk about the following three types of sound:

Noise: Have the children clap their hands, all talk at once or stomp their feet.

Music: Sing a song together or play an instrument.

Speech: Have the class recite the Pledge of Allegiance.

2. Invite two students to the front of the room to hold each end of the Slinky and stretch it until it is nearly flat.

3. Have one of the students squeeze together two or three coils and then quickly let them go. The wave will travel all the way to the end and back several times. This is called a longitudinal wave. Have the students describe the motion. (As the wave moves back and forth, the coils are alternately squeezed together, which is compression, or spread apart, which is rarefaction.) This is called a compression wave.

4. Now do the same experiment, only have the students watch carefully as you compress the coils in the middle of the Slinky. Ask them to tell what they see. (The Slinky moving rapidly back and forth, but in a confined area.)

5. To affirm that sound is vibration, have the students cover a large mixing bowl with a one-foot-square piece of aluminum foil. Instruct them to fold the foil tightly around the edge.

6. Next they should sprinkle about one teaspoon of sugar on the top of the foil.

7. Tell them to clap their hands above the sugar and watch what happens. A tuning fork could also be used. (The sugar jumps on the foil.)

8. Have them try it again, but this time hit a large pan with a wooden spoon directly above the sugar.

9. Try the same experiment using rice instead of sugar.

Part 2

1. Ask your students if they have ever been in an earthquake. Discuss why earthquakes happen.

2. Distribute the Earthquakes student handout. Read the top part together.

3. Introduce the concept of triangulation. This concept is used in a lot of mystery television shows when a criminal is using a cell phone and law enforcement officials triangulate the satellite hits for the cell phone to determine the criminal’s location.

4. Discuss the scale of the map and the directions.

5. Distribute compasses and have the students find the epicenter of the earthquake.

Enrichment: Earthquakes are very complex; this is just an introductory activity. Students can be put with partners or small groups and each group could take one question below and find an answer. They could then present the answers to the class. They could use the following site to find information: http://earthquake.usgs.gov/learning/faq.php. Another option would be to have them use a search engine and use “earthquake” as the search term.

1. What is an earthquake?

2. How is the intensity of an earthquake measured?

3. What is plate tectonics and what part do earthquakes play in it?

4. What causes an earthquake to happen?

5. What is an earthquake fault?

6. How do we know faults exist?

7. What are aftershocks?

8. Do tsunamis have any relation to earthquakes?

9. Can earthquakes be predicted?

10. Can animals sense an earthquake coming?

11. Do earthquakes cause volcanic eruptions?

12. Are there any fault lines in the United States?

Evaluation

Part 1 of this lesson is exploration. Part 2 deals with the concept that earthquake waves go out in all directions. The handout could be marked as correct or incorrect and a percentage of the total could be used.