# Understanding Emergence/Examples of phase transitions

During a phase transition of a given medium, certain properties of the medium change as a result of the change of external conditions, such as temperature or pressure. This can be a discontinuous change; for example, a liquid may become gas upon heating to its boiling point, resulting in an abrupt change in volume. The identification of the external conditions at which a transformation occurs defines the phase.
Here are several examples of phase transitions.
* Melting and Freezing:
** The transition from solid to liquid (melting) and from liquid to solid (freezing) is a common phase transition. For example, when ice melts into water or water freezes into ice, a change in temperature can trigger this transition.
* Vaporization and Condensation:
** The transition from liquid to gas (vaporization) and from gas to liquid ([./Https://en.wikipedia.org/wiki/Condensation condensation]) is another important phase change. For instance, water turning into steam when heated and steam condensing into water droplets when cooled are examples of this transition.
* Evaporation and Sublimation:
** Evaporation is the phase transition from the liquid to the gas phase that occurs at temperatures below the boiling point. Sublimation, on the other hand, is the direct transition from solid to gas without passing through the liquid phase. Dry ice (solid carbon dioxide) sublimating into carbon dioxide gas is an example of sublimation.
* Boiling and Condensation:
** Boiling is the rapid vaporization of a liquid when it reaches its boiling point. The opposite process, condensation, occurs when a gas changes into a liquid due to cooling. Water boiling and steam condensing are examples of this transition.
* Ionization and Deionization:
** In plasma physics, ionization is the phase transition where atoms or molecules gain or lose electrons, resulting in the formation of charged particles (ions). Deionization is the reverse process where ions recombine to form neutral atoms or molecules.
* Superconductivity Transition:
** Superconductivity is a phase transition where certain materials, when cooled below a critical temperature, exhibit zero electrical resistance and the expulsion of magnetic fields. This transition allows for remarkable energy transfer and storage capabilities.
* Phase Transitions in Astrophysics:
** In astrophysics, phase transitions can occur under extreme conditions. For example, inside neutron stars, the transition from nuclear matter to quark matter might involve a phase transition that drastically alters the star's properties.
* Liquid Crystals Transitions:
** Liquid crystals exhibit phase transitions between different liquid crystalline phases. These transitions are sensitive to temperature, pressure, and chemical composition, giving rise to displays used in electronic devices.
* Order-Disorder Transitions:
** In materials science, order-disorder transitions occur when atoms in a solid move from a structured arrangement to a more random one, or vice versa. The transition can impact a material's properties, such as its conductivity or magnetic behavior.
* Gelation Transition:
** Gelation is a phase transition where a liquid transforms into a gel, which is a semi-solid material with a network-like structure. This transition is commonly observed in the setting of food preparation, where liquids turn into gels upon cooling.
These examples illustrate the diverse range of phase transitions that occur in nature, driven by changes in temperature, pressure, or other external factors. Each phase transition entails a shift in the arrangement and interactions of particles, leading to distinct properties and behaviors in different phases of matter.