Confusion with phase

First of all states of matter must not to be confused with Phase. A phase is a region of space or a thermodynamic system, throughout which all physical properties of a material are essentially uniform or vary continuously. Examples of physical properties include density, index of refraction, magnetization and chemical composition. A simple description is that a phase is a region of material that is chemically uniform, physically distinct, and (often) mechanically separable. In a system consisting of ice and water in a glass jar, the ice cubes are one phase, the water is a second phase, and the humid air is a third phase over the ice and water. The glass of the jar is another separate phase.

The term phase is sometimes used as a synonym for state of matter, but there can be several immiscible phases of the same state of matter. Also, the term phase is sometimes used to refer to a set of equilibrium states demarcated in terms of state variables such as pressure and temperature by a phase boundary on a phase diagram. Because phase boundaries relate to changes in the organization of matter, such as a change from liquid to solid or a more subtle change from one crystal structure to another, this latter usage is similar to the use of « phase » as a synonym for state of matter. However, the state of matter and phase diagram usages are not commensurate with the formal definition given above and the intended meaning must be determined in part from the context in which the term is used.

 States of matter

The three fundamental states

Gas

A gas is a compressible fluid. A gas will not only conform to the shape of its container but it will also expand to fill the container, it diffuses throughout all the offered space. The particles are subjected to thermal agitation and moves following completely chaotic movements.

Liquid

A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a constant volume. A liquid is much denser and less compressible than a gas. It differs from the order of magnitude gas forces of attraction between the molecules. Molecular interactions are sufficient to prevent the liquid from diffusing like a gas. There are “capillaries” forces in the vicinity of its free surface. Intermolecular (or inter-atomic or inter-ionic) forces are important, but the molecules have enough energy to roll relatively to each other and the structure is mobile. This means that the shape of a liquid is not definite but is determined by its container. The volume is usually greater than that of the corresponding solid, the best known exception being water, H2O.

Solid

We will only consider the crystalline solid witch is more easy to understand. In a solid, constituent particles (ions, atoms, or molecules) are closely packed together. The forces between particles are so strong that the particles cannot move freely but can only vibrate. As a result, a solid has a stable, definite shape, and a definite volume. Solids can only change their shape by force, as when broken or cut. the particles (atoms, molecules, or ions) are packed in a regularly ordered, repeating pattern. There are various different crystal structures, and the same substance can have more than one structure (or solid phase). For example, iron has a body-centered cubic structure at temperatures below 912 °C, and a face-centered cubic structure between 912 and 1394 °C. Ice has fifteen known crystal structures, or fifteen solid phases, which exist at various  temperatures and pressures.

Non-classical states

There are also more exotic states, but we We will not go deeper into their existence. We will only speak about some examples.

Amorphous solids

Glasses and other non-crystalline solids are called amorphous. An amorphousis a corps that lacks the long-range order that is characteristic of a crystal. Nowadays, « glassy solid » or « amorphous solid » is considered to be the overarching concept, and glass the more special case: Glass is an amorphous solid that exhibits a glass transition. Glass transition, is the gradual and reversible transition in amorphous materials from a hard and relatively brittle « glassy » state into a viscous or rubbery state as the temperature is increased. An amorphous that exhibits a glass transition
is called a glass. The reverse transition, achieved by supercooling a viscous liquid into the glass state, is called vitrification.Polymers are often amorphous. Other types of amorphous solids include gels, thin films, and nanostructured materials such as glass doors and windows.

Supercritical state

A supercritical fluid is a gas whose temperature and pressure are respectively above the critical temperature and critical pressure. In this state, the distinction between liquid and gas disappears. A supercritical fluid has the physical properties of a gas, but its high density confers solvent properties in some cases, which leads to useful applications. it extracts like a liquid but insinuates itself like a gas. For example, supercritical carbon dioxide is used to extract caffeine in the manufacture
of decaffeinated coffee.

plasma state

Like a gas, plasma does not have definite shape or volume. Unlike gases, plasmas are electrically conductive, produce magnetic fields and electric currents, and respond strongly to electromagnetic forces. Positively charged nuclei swim in a « sea » of freely-moving disassociated electrons, similar to the way such charges exist in conductive metal, where this electron « sea » allows matter in the plasma state to conduct electricity.

 Phase transition

The term phase transition is used to describe transitions between solid, liquid, and gaseous states of matter, as well as plasma in some cases. Examples of phase transitions include the transitions between the solid, liquid, and gaseous phases of a single component, due to the effects of temperature and/or pressure: