Here's why:

* Composition: Air is primarily composed of nitrogen (78%), oxygen (21%), and other gases like argon, carbon dioxide, and trace amounts of others.

* Temperature and States of Matter: The state of matter (solid, liquid, or gas) depends on the temperature. At room temperature, the molecules in air have enough kinetic energy to move freely and independently, making it a gas.

While air can be liquefied under extremely low temperatures and high pressure, it's naturally a gas at room temperature.