When this happens, one needs to introduce one or more extra variables to describe the state of the system. This is an example of a phase diagram. In a vapor, there are molecules with high and low kinetic energy that often collide with surfaces and each other. This results in the fusion of the substance.
Phase Changes Each substance has three phases it can change into; solid, liquid, or gas 1. When pressure increases or temperature decreases, it's easier for atoms and molecules to settle into a more rigid structure.
Examples of second-order phase transitions are the ferromagnetic transition, superconducting transition for a Type-I superconductor the phase transition is second-order at zero external field and for a Type-II superconductor the phase transition is second-order for both normal-state—mixed-state and mixed-state—superconducting-state transitions and the superfluid transition.
When water vapor condenses an equilibrium fractionationthe heavier water isotopes 18O and 2H become enriched in the liquid phase while the lighter isotopes 16O and 1H tend toward the vapor phase. While in the liquid state, the particles in a substance possess enough kinetic energy to move around in close proximity to each other.