Phase change is a concept from thermodynamic physics that describes the transfer of a material from one physical state to another. When a material undergoes a phase change, such as from liquid to gas, the material's atoms are rearranged into new configurations, generally leading to an increase in entropy. It is important to note that phase changes require energy to occur—either creative energy, such as heating, or dissipative energy, such as cooling. This energy is stored in the material and is released or absorbed during the course process. Phase changes are critical to understanding the behavior of materials in various phases, and can have applications such as cryogenic engineering and HVAC systems.

See also: phase transition, emergence, agent-based modeling, evolutionary computing, evolutionary psychology