Answer:
They move fast enough to overcome the forces of attraction that hold them together, becoming a gas.
Step-by-step explanation:
Particles in matter are always in motion. Motion of the particles gives rise to kinetic energy. Gases have high kinetic energy. Liquids have kinetic energy that is greater than solids but less than gases. When the kinetic energy of liquids increases they undergo phase transition and get converted to gas. The higher kinetic energy helps to overcome the strong intermolecular forces of attraction between the liquid particles.