Question

why can a gas be easily squashed

Answer 1

Because the interparticle force of attraction are very weak and almost negligible.
the particles are free to move in any direction.

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Answer 2

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 becompressed much more easily than a liquid or solid.