Here's why:

* Low density: Gases have very low densities compared to liquids or solids. This means the particles are spread far apart.

* High kinetic energy: Gas particles have high kinetic energy, meaning they are constantly moving and colliding with each other.

* Weak intermolecular forces: The attractive forces between gas particles are very weak. This allows them to move freely and independently.

Think of it like this: Imagine a room full of people. If the room is very crowded, that's like a liquid or solid. If the people are spread out and moving freely, that's like a gas.