Gases are mostly empty space, and this is evident because gases can be easily compressed. It is easy to reduce the volume of a gas as compared to reducing the volume of a solid. ... Gases expand spontaneously to fill any container (rapid motion).

Can gas spread out and fill any space?

The atoms and molecules in gases are much more spread out than in solids or liquids. They vibrate and move freely at high speeds. A gas will fill any container, but if the container is not sealed, the gas will escape. Gas can be compressed much more easily than a liquid or solid.

Why do gases fill up the available space?

Since gases have higher kinetic energy than liquids and solids, the molecules move with a very high speed and fill up all the space they are left in. The atoms and molecules in a gas are moving much faster and further away from each other.