Thermal expansion of solids, liquids and gases — Explain

Why do gases expand more than liquids, and liquids more than solids, for the same rise in temperature?

In a solid, particles are held in fixed positions by strong forces and, on heating, only vibrate with greater amplitude, giving a small expansion. In a liquid, forces between particles are weaker, so increased particle motion pushes particles further apart on average, giving greater expansion than a solid. In a gas, forces between particles are negligible, so heating causes particles to move much faster and spread apart significantly, giving by far the largest expansion.