quickly. 7. Vibrations happen when something moves a. solid and liquid b. back and forth c. moving motion d. slow 8. When the sound wave is big the sound is a. Very soft b. slow c. fast d. loud 9. Why do we not hear sound in outer space? a. there is no one out there to hear it. b. it is so cold c. it is a vacuum or space d. there are too many stars that are exploding 10. What is a sound wave? a. a wave that moves out in all directions from an object b. an ocean wave c. thunder d. fast and slow movements
