It's not quite "just empty space" in between gas molecules. While there's a lot of space between them compared to liquids and solids, that space isn't a complete void. Here's a breakdown:

* Empty space is the dominant factor: Gas molecules are far apart, constantly moving and colliding. This makes the space between them much larger than the space occupied by the molecules themselves.

* Intermolecular forces still exist: Even though weak, there are attractive forces between gas molecules. These forces are much weaker than in liquids and solids, but they still contribute to the overall behavior of the gas.

* Electromagnetic fields: The molecules themselves have electromagnetic fields, and these fields interact with each other, influencing the space between them.

In summary:

While the space between gas molecules is mostly empty, it's not a complete vacuum. There are weak intermolecular forces and electromagnetic fields that still exist, influencing the behavior of the gas.