Here's why:
* Spacing: Gas molecules have a lot of space between them. This is because they are not strongly attracted to each other.
* Movement: Because of the weak attraction, gas molecules move very quickly and randomly in all directions. They collide with each other and the walls of their container.
In contrast:
* Liquids: Liquid molecules are closer together than gas molecules but still have some freedom of movement.
* Solids: Solid molecules are tightly packed and vibrate in place, with very limited movement.
Let me know if you'd like more details about the properties of gases!