Deposition is the phase transition in which gas transforms into solid without passing through the liquid phase. Deposition is a thermodynamic process. The reverse of deposition is sublimation and hence sometimes deposition is called desublimation.
One example of deposition is the process by which, in sub-freezing air, water vapor changes directly to ice without first becoming a liquid. This is how frost and hoar frost form on the ground or other surfaces. Another example is when frost forms on a leaf. For deposition to occur, thermal energy must be removed from a gas. When the air becomes cold enough, water vapor in the air surrounding the leaf loses enough thermal energy to change into a solid. Even though the air temperature may be below the dew point, the water vapor may not be able to condense spontaneously if there is no way to remove the latent heat. When the leaf is introduced, the supercooled water vapor immediately begins to condense, but by this point is already past the freezing point. This causes the water vapor to change directly into a solid.
Another example is the soot that is deposited on the walls of chimneys. Soot molecules rise from the fire in a hot and gaseous state. When they come into contact with the walls they cool, and change to the solid state, without formation of the liquid state. The process is made use of industrially in combustion chemical vapor deposition.
There is an industrial coatings process, known as evaporative deposition, whereby a solid material is heated to the gaseous state in a low-pressure chamber, the gas molecules travel across the chamber space and then deposit to the solid state on a target surface, forming a smooth and thin layer on the target surface. Again, the molecules do not go through an intermediate liquid state when going from the gas to the solid. See also physical vapor deposition, which is a class of processes used to deposit thin films of various materials onto various surfaces.
Deposition releases energy and is an exothermic phase change.
See also
 |
To | ||||
|---|---|---|---|---|---|
| Solid | Liquid | Gas | Plasma | ||
| From | Solid | Melting | Sublimation | ||
| Liquid | Freezing | Vaporization | |||
| Gas | Deposition | Condensation | Ionization | ||
| Plasma | Recombination | ||||
References
Gaja, Shiv P., Fundamentals of Atmospheric Modeling, Cambridge University Press, 2nd ed., 2005, p. 525 ISBN 978-0-521-83970-9
Moore, John W., et al., Principles of Chemistry: The Molecular Science, Brooks Cole, 2009, p. 387 ISBN 978-0-495-39079-4
Whitten, Kenneth W., et al., Chemistry, Brooks-Cole, 9th ed., 2009, p. 7 ISBN 978-0-495-39163-0
Focus on Physical Science. Glencoe Science.
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States of matter (list)
State
Solid Liquid Gas / Vapor Plasma
Phase change - en.svg
Low energy
Bose–Einstein condensate Fermionic condensate Degenerate matter Quantum Hall Rydberg matter Rydberg polaron Strange matter Superfluid Supersolid Photonic matter
High energy
QCD matter Lattice QCD Quark–gluon plasma Color-glass condensate Supercritical fluid
Other states
Colloid Glass Crystal Liquid crystal Time crystal Quantum spin liquid Exotic matter Programmable matter Dark matter Antimatter Magnetically ordered
Antiferromagnet Ferrimagnet Ferromagnet String-net liquid Superglass
Transitions
Boiling Boiling point Condensation Critical line Critical point Crystallization Deposition Evaporation Flash evaporation Freezing Chemical ionization Ionization Lambda point Melting Melting point Recombination Regelation Saturated fluid Sublimation Supercooling Triple point Vaporization Vitrification
Quantities
Enthalpy of fusion Enthalpy of sublimation Enthalpy of vaporization Latent heat Latent internal energy Trouton's ratio Volatility
Concepts
Baryonic matter Binodal Compressed fluid Cooling curve Equation of state Leidenfrost effect Macroscopic quantum phenomena Mpemba effect Order and disorder (physics) Spinodal Superconductivity Superheated vapor Superheating Thermo-dielectric effect
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