Substances can exist in three states of matter - solid, liquid and gas. All substances are made from particles, and the forces between the particles are different in solids, liquids and gases.

The liquid state of matter is an intermediate phase between solid and gas. Like the particles of a solid, particles in a liquid are subject to intermolecular ... long as these forces of attraction ...

The problem of understanding the forces that hold matter ... phase diagram with two fluid phases (gas and liquid) below the critical point and a solid phase at high densities.