One and the same substance in nature has the ability to radically vary its properties depending on temperature and pressure. A good example of this is water, which exists in the form of hard ice, liquid, and steam. These are three states of aggregation of a given substance having the chemical formula H 2 O. Other substances in vivo can change their characteristics in a similar way. But in addition to the above, in nature there is another state of aggregation - plasma. This is a rather rare form of matter in terrestrial conditions , endowed with special qualities.
Molecular structure
What determines the 4 states of matter in which matter resides? From the interaction of atomic elements and the molecules themselves, endowed with the properties of mutual repulsion and attraction. The indicated forces are self-compensating in the solid state, where the atoms are located geometrically correctly, forming a crystalline lattice. In this case, the material object is able to maintain both of the above-mentioned qualitative characteristics: volume and shape.
But if the kinetic energy of the molecules increases, moving randomly, they destroy the established order, turning into liquids. They are fluid and characterized by the absence of geometric parameters. But at the same time, this substance retains its ability not to change the total volume. In the gaseous state, the mutual attraction between the molecules is completely absent, so the gas has no shape and has the possibility of unlimited expansion. But the concentration of the substance decreases significantly. Molecules themselves do not change under normal conditions. This is the main feature of the first 3 of 4 states of matter.
State transformation
The process of transforming a solid into other forms can be carried out by gradually increasing the temperature and varying the pressure indicators. In this case, the transitions will occur abruptly: the distance between the molecules will increase markedly, intermolecular bonds with a change in density, entropy, and the amount of free energy will be destroyed. The transformation of a solid immediately into a gaseous form is also possible, bypassing the intermediate stages. It is called sublimation. A similar process is quite possible in ordinary terrestrial conditions.
But when the temperature and pressure indicators reach a critical level, an ionized gas is formed. The internal energy of matter increases so much that electrons moving at a frantic speed leave their intraatomic orbits. In this case, positive and negative particles are formed, but their density in the resulting structure remains almost the same. Thus, a plasma arises - the state of aggregation of a substance, which is essentially a gas, fully or partially ionized, whose elements are endowed with the ability to interact with each other at large distances.
High Temperature Space Plasma
Plasma, as a rule, is a neutral substance, although it consists of charged particles, because the positive and negative elements in it, being approximately equal in number, cancel each other out. This aggregate state in ordinary terrestrial conditions is less common than others mentioned earlier. But despite this, most cosmic bodies are composed of natural plasma.
An example of this is the sun and other numerous stars of the universe. There the temperatures are fantastic high. Indeed, on the surface of the main body of our planetary system, they reach 5,500 ° C. This is more than fifty times higher than those parameters that are necessary for boiling water. In the center of the fire-breathing sphere, the temperature is 15,000,000 ° C. It is not surprising that gases (mainly hydrogen) are ionized there, reaching the state of aggregation of the plasma.
Low temperature plasma in nature
The interstellar medium filling the galactic space also consists of plasma. But it differs from its high-temperature variety described earlier. Such a substance consists of ionized substance arising from the radiation emitted by stars. This is a low temperature plasma. In the same way, the sun's rays, reaching the limits of the Earth, create the ionosphere and the radiation belt above it, consisting of plasma. The differences are only in the composition of the substance. Although in a similar state may be all the elements presented in the periodic table.
Plasma in the laboratory and its application
According to the laws of physics, plasma is easily obtained in the usual conditions for us. When conducting laboratory experiments, a capacitor, a diode, and a resistance connected in series are sufficient. A similar circuit is connected to a current source for a second. And if you touch the wires to the metal surface, then the particles of it itself, as well as those located near the vapor and air molecules, ionize and end up in the state of aggregation of the plasma. Similar properties of matter are used to create xenon and neon lamps, plasma screens and welding machines.
Plasma and natural phenomena
Under natural conditions, the plasma can be observed in the light of the Northern Lights and during a thunderstorm in the form of ball lightning. The explanation of some natural phenomena, which were previously attributed to mystical properties, is now given by modern physics. The plasma that forms and glows at the ends of tall and sharp objects (masts, towers, huge trees) with a special atmosphere, centuries ago, was accepted by sailors as a messenger of luck. That is why this phenomenon was called the "Lights of St. Elmo."
Seeing the corona discharge in the shape of luminous brushes or beams during a thunderstorm during a storm, travelers took this as a good omen, realizing that they had avoided danger. It is not surprising, because the objects towering above the water, suitable for the "signs of the saint", could talk about the approach of the ship to the shore or predict a meeting with other ships.
Nonequilibrium plasma
The above examples eloquently indicate that it is not necessary to heat the substance to fantastic temperatures in order to achieve a plasma state. For ionization it is enough to use the strength of the electromagnetic field. At the same time, the heavy constituent elements of matter (ions) do not acquire significant energy, because the temperature during the implementation of this process may well not exceed several tens of degrees Celsius. Under such conditions, light electrons, breaking away from the main atom, move much faster than more inert particles.
Such a cold plasma is called nonequilibrium. In addition to plasma TVs and neon lamps, it is also used in the purification of water and food, and is used for medical disinfection. In addition, cold plasma can help accelerate chemical reactions.
Principles of use
A great example of how artificially created plasma is used for the benefit of mankind is the manufacture of plasma monitors. The cells of such a screen are endowed with the ability to emit light. The panel is a kind of "sandwich" of glass sheets, closely spaced to each other. Between them are boxes with a mixture of inert gases. They can be neon, xenon, argon. And on the inner surface of the cells phosphors of blue, green, red color are applied.
Outside the cells, conductive electrodes are connected, between which a voltage is created. As a result of this, an electric field arises and, as a result, gas molecules are ionized. The resulting plasma emits ultraviolet rays absorbed by phosphors. In view of this, the phenomenon of fluorescence arises through the emitted photons. Due to the complex connection of rays in space, a vivid image of a wide variety of shades arises.
Plasma Horrors
The fatal appearance takes this form of matter during a nuclear explosion. Plasma in large volumes is formed during the course of this uncontrolled process with the release of a huge amount of various types of energy. The heat wave resulting from the start-up of the detonator breaks out and heats the surrounding air in the first seconds to gigantic temperatures. At this point, a deadly fireball arises, growing at an impressive speed. The visible area of the bright sphere is increased by ionized air. Clumps, clubs and jets of explosion plasma form a shock wave.
At first, a luminous ball, stepping, instantly absorbs everything in its path. Not only human bones and tissues turn into dust, but also solid rocks, even the most durable artificial structures and objects are destroyed. Armored doors to reliable shelters do not save, tanks and other military equipment are flattened.
By its properties, a plasma resembles a gas in that it does not have certain shapes and volumes, and as a result of this, it is capable of expanding indefinitely. For this reason, many physicists are of the opinion that it should not be considered a separate aggregate state. However, its significant differences from just hot gas are obvious. These include: the ability to conduct electric currents and susceptibility to magnetic fields, the instability and ability of composite particles to have different velocities and temperatures, while interacting collectively with each other.