Vapor

Steam is chosen in science and technology as a term for a chemically pure gaseous substance, when viewed in relation to its liquid or solid state. Steam, by evaporation of the liquid or sublimation of the solid arise and be converted by condensation back into this.

Steam referred in slang usually an admixture of air, which is visible as it is present to some extent in the form of very small droplets, ie in liquid form.

Vapor -liquid equilibrium

With time and if no fault occurs, a dynamic equilibrium is established, on the same number of particles of liquid or solid phase to pass into the gaseous phase, and conversely to switch back from the gas. The steam is then saturated, and is also referred to as a vapor, Brodem or vapors. How many particles move from one phase to the other is dependent, inter alia, strongly on the pressure and temperature of the system considered. In art, the equilibrium between liquid and gaseous phase plays an important role in thermal separation processes.

Superheated steam

The gas phase is not associated with the liquid or solid phase in contact with the steam, and is further fed to heat, it is superheated and is present as superheated steam before. The stronger this heating, the further away one of the area in which you can still speaks of steam, and approaches a behavior, which is then referred to as gas -like. Itself

Condensation

Is cooled slowly from the superheated steam, the so-called dew point is eventually reached at which the steam is saturated again, and condensed into a liquid again upon further cooling. In the case of direct transition from the gaseous to the solid state, ie at a Resublimation, called this point Frost point.

Critical temperature

Above the critical temperature is a gas by increasing the pressure no longer condensable. Therefore, a supercritical material will be referred to not as a vapor, but only as a gas. Also common is the term used for a supercritical fluid substance.

Meanings of steam in the language

While steam as a substrate formed of a liquid gas - apart from substance intrinsic stains - is invisible, one usually speaks in everyday life with steam from a visible mixture of air and fine liquid droplets, as it forms, for example, the condensation of water vapor and example from many chimneys can be seen entweichend. For the same form of finely divided, small water droplets in air, the terms are used contrail fog ( near the ground ) or cloud ( at the output of a turbine aircraft ) or large-scale weather phenomena ( in the sky ) in everyday language in addition. The correct scientific term for a mixture of finely divided liquid droplets in a gas is fog. At extremely small liquid drops ( and / or solid particles ) is called this mixture as an aerosol. In the special case of water is referred to the art of wet steam.