There are many substances that can be found in a variety of types of phases (state of matter) according to the pressure and temperature in which their sample is. Solids are identified by a well-ordered structure of crystals that allows intermolecular interaction to be enhanced. This type of structure is not present when the phase is liquid which means that the liquid has a specific volume however, it does not have a specific shape. Also, a gas does not have no defined shape or any defined volume, however, its particles fill the entirety of a container that is sealed. The principles discussed here illustrate that the same substance may possess different density levels across different phases. It is the amount of mass in a single volume of a sample for the substance within the particular phase.