Here's why:

* Kinetic Molecular Theory: The behavior of gases is explained by the kinetic molecular theory. This theory states that gas particles are in constant, random motion and have negligible interactions with each other.

* No Strong Attractions: Unlike liquids and solids, gas particles have very weak intermolecular forces between them. This means they don't stick together and can move freely.

* Large Distance: Gas particles are far apart compared to their size, giving them ample space to move without bumping into each other too often.

Other Examples:

While gas particles are the most notable example, other particles can also move independently under specific conditions:

* Plasma: In a plasma state, electrons are stripped from atoms, creating a collection of charged particles that can move freely.

* Dilute Solutions: In very dilute solutions, solute particles can be far enough apart to move independently.

It's important to remember that even in these cases, particles still interact with each other to some extent. They just have significantly less interaction compared to the other states of matter.