The particles are the farthest apart in the gaseous state of matter. In this state, particles have the most energy and move freely, occupying all the available space in their container. The distance between particles is much greater compared to solids and liquids, allowing gases to be compressed more easily.
In contrast, particles in a solid are tightly packed together in a fixed arrangement, while particles in a liquid are close together but can move past one another. The gaseous state, therefore, has the least density and the most space between particles.