Unit Plan 30 (Grade 8 Science): Sound Waves & Vibrations
Sound as a mechanical wave: students explore vibrations, models, and how sound transfers energy through media—without moving matter.
Focus: Investigate sound as a mechanical wave that begins with vibrations, travels through different media (solids, liquids, gases), and transfers energy but not matter; develop and use particle models to explain how sound moves through materials.
Grade Level: 8
Subject Area: Science (Physical Science • Waves & Energy)
Total Unit Duration: 5 sessions (one week), 50–60 minutes per session
I. Introduction
In this unit, students zoom in on sound waves as a special type of mechanical wave. They explore how vibrations of a source create longitudinal waves that move through air, liquids, and solids, transferring energy while the particles in the medium mostly vibrate in place. Through hands-on activities (tuning forks, speakers, rubber bands, cup/string phones, etc.), students observe that sound can travel differently in various media and that it cannot travel through a vacuum. They develop and use particle models and energy-flow diagrams to show compressions and rarefactions, connecting everything back to the core idea that waves transfer energy but not matter.
Essential Questions
- How is sound created, and why do we say sound is a mechanical wave?
- How do particles in air, water, or solids move when a sound wave passes through them?
- How can models (particle diagrams, arrows, energy-flow representations) help us see that sound waves transfer energy but not matter?
- Why does sound travel differently in different media, and what evidence do we have that it needs a medium?
II. Objectives and Standards
Learning Objectives — Students will be able to:
- Explain that sound is produced by vibrating objects and travels as a mechanical longitudinal wave through gases, liquids, and solids.
- Develop and use particle models showing how particles in a medium vibrate back and forth (compressions and rarefactions) as a sound wave passes.
- Demonstrate, with examples and models, that sound waves transfer energy (e.g., causing objects to move, vibrate, or change) while particles mostly vibrate in place and are not transported from source to listener.
- Compare how sound travels through different media (e.g., through air vs. through a solid) and use models/observations to explain differences in speed and intensity qualitatively.
- Construct a written or visual explanation or CER that uses models to support the claim that sound waves transfer energy but not matter.
Standards Alignment — 8th Grade (NGSS-based custom)
- MS-PS4-2 — Develop and use a model to describe that waves transfer energy but not matter.
- In this unit, students focus on sound waves as mechanical waves, building particle diagrams and energy-flow models to explain their observations.
Success Criteria — Student Language
- I can describe sound as a mechanical wave that begins with vibrations and needs a medium.
- I can draw or use a particle model of a sound wave with compressions and rarefactions and correctly show particle motion and wave direction.
- I can give at least two examples where sound waves cause changes (like making objects vibrate or move), showing energy transfer without matter traveling from source to receiver.
- I can explain how sound behaves differently in air, water, and solids, using observations and models.
- I can write or present a clear argument that sound waves transfer energy but not matter, using my models and experiments as evidence.