•   Solid
•   Liquid
•   Gas
•   Plasma

Each state of matter in this sequence possesses increasing amounts of energy, as reflected by the temperature ranges that they exist in.

The fundamental units of a substance consist of atoms and molecules. The 4 phases of matter represent the degree of compactness in which these units are packed and how much energy they possess. The diagram above shows how matter in one physical state can change into another phase. The relationship between these phases as a function of pressure and temperature is illustrated on a phase diagram.

 

How are the phases of matter affected by temperature and pressure?

The figure above is a phase diagram for a pure substance, as a function of temperature and pressure. Besides the main phases of solid, liquid and gas, two other areas exist - vapor and supercritical fluid. If plasma was shown, it would be on the extreme right beyond the temperatures for gases. 

A vapor is a gas existing below the substance's critical temperature (temperature at the critical point, c.p.). Below the critical temperature, a vapor can be transformed to a liquid or solid if a large enough pressure is applied to it. If the pressure and temperature both exceed those of the critical point, the distinction between gas and liquid vanishes and the substance behaves like a supercritical fluid. The vapor and supercritical fluid behavior are intermediate between those of liquids and gases.

 

How do the Characteristics of Liquid Crystal Compare and Contrast with Other Phases?  

The physical properties of a substance can be divided into macroscopic and nanoscopic behaviors.
 
 

Macroscopic Behavior
Phase	Retains volume	Retains Shape	Compressible	Flow Rate	Diffusion Rate
Crystalline Solids	Yes	Yes	No	Slowest    Fastest	Slowest    Fastest
Liquid Crystals	Yes	No	No
Liquids	Yes	No	No
Gases	No	No	Yes

 

Nanoscopic Behavior
Phase	Orientational Ordering	Translational Ordering	Inter-molecular Forces	Separation Distance
Crystalline Solids	Yes	Yes	Strongest    Weakest	Smallest  Largest
Liquid Crystals	Yes	No
Liquids	No	No
Gases	No	No