Sound is called longitudinal wave because

Sound in air propagates in form of:

Give reason for the following :
Why sound wave is called a longitudinal wave ?

Describe an experiment to show that in a wave motion, only energy is transferred. but particles of medium do not leave their positions.

Which of the following is mechanical wave?

Assertion :Compression and rarefaction involve changes in density and pressure.
Reason :When particles are compressed, the density of medium increases, and when they are rarefied, the density of medium decreases.

Define - Compression and rarefaction. 

The true statement is

Explain the meaning of terms compression and rarefaction in relation to a longitudinal wave.

Complete the following sentences:
A longitudinal wave is composed of compression and ______.