The strength of the interatomic and intermolecular bonds in a material as well as the temperature and pressure determine the state of matter that it assumes. Material states at different temperatures and pressures are represented by phase diagrams.
The most common states of a material include solids, liquids and gases. Materials assume a solid state when the intermolecular and interatomic bonding energies exceed the kinetic energy of the material molecules or atoms due to thermal vibration.
Materials assume a liquid state when the intermolecular and interatomic bonding energy are comparable with the thermal kinetic energy. Stronger interaction between liquid molecules results in higher viscosity.
Materials assume a gaseous state when the intermolecular and interatomic bonding energy are much lower than the thermal kinetic energy. In many cases, the interaction between gas atoms or molecules can be completely neglected. The larger the thermal kinetic energy becomes, the more insignificant the interactions between gas atoms or molecules are.
Thermal energy is described by the temperature of the material. This energy is often proportional to some value containing the product of the Boltzmann constant and the temperature in degrees Kelvin, called the absolute temperature. Higher pressure can cause atoms and molecules to come closer together, leading materials to assume solid or liquid states at temperatures below their melting or boiling points, respectively.