Solid's particles are very close to their neighboring particles.That's because the attractive forces between the particles are strong and hold them close together.
Liquid's increased particle motion causes the particles to move slightly father apart. As the particles move farther apart, the attractive forces between the particles decrease.The weaker attractive forces allow particles to slip past one another. The weather forces also enable liquids to flow and take shape.
Gases have the particles move faster, such as when matter goes from the solid state to the liquid state, the particle move farther apart. When the particles in matter move even faster, such as when matter goes from the liquid state to gas state, the particles move even father apart. When the distance between particles change, the attractive forces between the particles also change.