In physical chemistry, supersaturation occurs with a solution when the concentration of a solute exceeds the concentration specified by the value of solubility at equilibrium. Most commonly the term is applied to a solution of a solid in a liquid, but it can also be applied to liquids and gases dissolved in a liquid. A supersaturated solution is in a metastable state; it may return to equilibrium by separation of the excess of solute from the solution, by dilution of the solution by adding solvent, or by increasing the solubility of the solute in the solvent.
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👉 Supersaturation in the context of Crystallization
Crystallization is a process that leads to solids with highly organized atoms or molecules, i.e. a crystal. The ordered nature of a crystalline solid can be contrasted with amorphous solids in which atoms or molecules lack regular organization. Crystallization can occur by various routes including precipitation from solution, freezing of a liquid, or deposition from a gas. Attributes of the resulting crystal can depend largely on factors such as temperature, air pressure, cooling rate, or solute concentration.
Crystallization occurs in two main phases. The first is nucleation, the appearance of a crystalline phase from either a supercooled liquid or a supersaturated solvent. The second step is known as crystal growth, which is the increase in the size of particles and leads to a crystal state. An important feature of this step is that loose particles form layers at the crystal's surface and lodge themselves into open inconsistencies such as pores, cracks, etc.
In this Dossier
Supersaturation in the context of Cloud physics
Cloud physics is the study of the physical processes that lead to the formation, growth and precipitation of atmospheric clouds. These aerosols are found in the troposphere, stratosphere, and mesosphere, which collectively make up the greatest part of the homosphere. Clouds consist of microscopic droplets of liquid water (warm clouds), tiny crystals of ice (cold clouds), or both (mixed phase clouds), along with microscopic particles of dust, smoke, or other matter, known as condensation nuclei. Cloud droplets initially form by the condensation of water vapor onto condensation nuclei when the supersaturation of air exceeds a critical value according to Köhler theory. Cloud condensation nuclei are necessary for cloud droplets formation because of the Kelvin effect, which describes the change in saturation vapor pressure due to a curved surface. At small radii, the amount of supersaturation needed for condensation to occur is so large, that it does not happen naturally. Raoult's law describes how the vapor pressure is dependent on the amount of solute in a solution. At high concentrations, when the cloud droplets are small, the supersaturation required is smaller than without the presence of a nucleus.
In warm clouds, larger cloud droplets fall at a higher terminal velocity; because at a given velocity, the drag force per unit of droplet weight on smaller droplets is larger than on large droplets. The large droplets can then collide with small droplets and combine to form even larger drops. When the drops become large enough that their downward velocity (relative to the surrounding air) is greater than the upward velocity (relative to the ground) of the surrounding air, the drops can fall as precipitation. The collision and coalescence is not as important in mixed phase clouds where the Bergeron process dominates. Other important processes that form precipitation are riming, when a supercooled liquid drop collides with a solid snowflake, and aggregation, when two solid snowflakes collide and combine. The precise mechanics of how a cloud forms and grows is not completely understood, but scientists have developed theories explaining the structure of clouds by studying the microphysics of individual droplets. Advances in weather radar and satellite technology have also allowed the precise study of clouds on a large scale.
Supersaturation in the context of Hydrothermal mineral deposit
Hydrothermal mineral deposits are accumulations of valuable minerals which formed from hot waters circulating in Earth's crust through fractures. They eventually produce metallic-rich fluids concentrated in a selected volume of rock, which become supersaturated and then precipitate ore minerals. In some occurrences, minerals can be extracted for a profit by mining. Discovery of mineral deposits consumes considerable time and resources and only about one in every one thousand prospects explored by companies are eventually developed into a mine. A mineral deposit is any geologically significant concentration of an economically useful rock or mineral present in a specified area. The presence of a known but unexploited mineral deposit implies a lack of evidence for profitable extraction.
Hydrothermal mineral deposits are divided into six main subcategories: porphyry, skarn, volcanogenic massive sulfide (VMS), sedimentary exhalative (SEDEX), and epithermal and Mississippi Valley-type (MVT) deposits. Each hydrothermal mineral deposit has different distinct structures, ages, sizes, grades, geological formation, characteristics and, most importantly, value. Their names derive from their formation, geographical location or distinctive features.
Supersaturation in the context of Cloud chamber
A cloud chamber, also known as a Wilson chamber, is a particle detector used for visualizing the passage of ionizing radiation.
A cloud chamber consists of a sealed environment containing a supersaturated vapor of water or alcohol. An energetic charged particle (for example, an alpha or beta particle) interacts with the gaseous mixture by knocking electrons off gas molecules via electrostatic forces during collisions, resulting in a trail of ionized gas particles. The resulting ions act as condensation centers around which a mist-like trail of small droplets form if the gas mixture is at the point of condensation. These droplets are visible as a "cloud" track that persists for several seconds while the droplets fall through the vapor. These tracks have characteristic shapes. For example, an alpha particle track is thick and straight, while a beta particle track is wispy and shows more evidence of deflections by collisions.