Here's why:

* Air Composition: Air is a mixture of gases, primarily nitrogen (78%), oxygen (21%), and argon (1%), along with trace amounts of other gases like carbon dioxide.

* Gas Properties: Gases have the following properties:

* Indefinite shape and volume: They take the shape and volume of their container.

* High compressibility: They can be easily compressed into a smaller volume.

* Low density: They have a much lower density than liquids or solids.

* Free movement of particles: Gas particles move freely and randomly.

* Jar as a Container: The jar confines the air, preventing it from expanding and escaping, but it doesn't change the fact that the air itself is a gas.

Therefore, the air sealed in a jar retains its gaseous properties and is classified as a gas.