Matter is made up of very tiny particles called atoms. These atoms are held together by inter-particle forces of attraction.
The order of interparticle forces in different physical states of matter is as below:
Solid > Liquid > Gas
One state of matter can be converted into another by supplying enough kinetic energy to escape the interparticle forces of attraction through heat or removing the kinetic energy by cooling.
Solid⇌Liquid⇌Gas
The inter-partice forces of attraction and kinetic energy are the two factors that determine the physical state of matter.