Three main aggregate states of substance are known: gas, liquid and solid body. Very viscous liquids by sight can resemble solid bodies, but differ from them on the nature of melting. The modern science marks out also the fourth aggregate state of substance – the plasma having many unusual properties.
In physics aggregate state of substance it is accepted to call its ability to keep the form and volume. Additional sign – ways of transition of substance of their one aggregate state in another. Proceeding from it, mark out three aggregate states: solid body, liquid and gas. Visible their properties are as follows:
- The solid body – keeps both a form, and volume. Can pass as into liquid by melting, and directly into gas by sublimation.
- Liquid – keeps volume, but not a form, that is has fluidity. The spilled liquid seeks to spread beyond all bounds on a surface on which it is poured out. Into a solid body liquid can pass by crystallization, and into gas – by evaporation. - Gas – does not keep either a form, or volume. Gas out of some receptacle seeks to extend beyond all bounds extensively. Only gravity can prevent it in it thanks to what the terrestrial atmosphere does not dissipate in space. Gas passes into liquid by condensation, and directly can pass into a solid body by sedimentation.
Phase transitions
Transition of substance from one aggregate state in another is called phase transition as a scientific synonym of aggregate state – a substance phase. For example, water can exist in a firm phase (ice), liquid (usual water) and gaseous (water vapor). On the example of water the sublimation is also well shown. The linen which is hung out in the yard on drying in frosty windless day immediately freezes through, but after a while it is dry: ice sublimates, directly passing into water vapor. As a rule, phase transition from a solid body to liquid and gas demands heating, but environment temperature at the same time does not increase: thermal energy leaves on a rupture of internal communications in substance. It is the so-called hidden warmth of phase transition. Upon the return phase transitions (condensation, crystallization) this warmth is distinguished. For this reason burns are so dangerous by steam. Getting on skin, it is condensed. The hidden warmth of evaporation/condensation of water is very big: water in this regard – abnormal substance; for this reason life on Earth is possible. At a burn the ferry the hidden warmth of condensation of water "proshparivat" the burned place very deeply, and consequences of a steam burn are far heavier, than from a flame on the same area of a body.
Pseudo-phases
The fluidity of a liquid phase of substance is defined by its viscosity, and viscosity – the nature of internal communications to which the following section is devoted. The viscosity of liquid can be very high, and such liquid can flow imperceptibly for an eye. A classical example – glass. It is not a solid body, and very viscous liquid. Pay attention that sheets of glass never store in warehouses leaned obliquely against a wall. In several days they will cave in under own weight and will be unsuitable to the use. Other examples of pseudo-solid bodies – shoe var and construction bitumen. If to forget an angular piece of bitumen on a roof, during the summer it will spread in flat cake and will stick to a basis. Pseudo-solid bodies can be distinguished from the presents on the nature of melting: the presents at it or keep the form until at once spread (solder when soldering), or become swollen, starting up puddles and streamlets (ice). And very viscous liquids are gradually softened as the same var or bitumen. Extremely viscous liquids which fluidity is not noticeable for many years and decades is plasticity. Their high ability to keep a form is provided with the huge molecular weight of polymers, in many thousands and millions of atoms of hydrogen.
Structure of phases of substance
In a gas phase of a molecule or atoms of substance will defend from each other very far, it is many times more, than distance between them. They interact among themselves occasionally and irregularly, only at collisions. Interaction elastic: faced as firm balls, and immediately scattered. In liquid molecules/atoms constantly "feel" each other due to very weak communications of the chemical nature. These communications are torn all the time and immediately are again restored, liquid molecules continuously move relatively each other therefore liquid and flows. But to turn it into gas, it is necessary to break all links at once, and on it a lot of energy is necessary therefore liquid and keeps volume. Water in this regard differs from other substances in the fact that its molecules in liquid are connected by so-called hydrogen communications, quite strong. Therefore water can also be liquid at a temperature, normal for life. Many substances with a molecular weight of tens and hundreds times more, than at water, in normal conditions – gases, as at least usual household gas. In a solid body all its molecules strongly stand on the places thanks to strong chemical bonds between them, forming a crystal lattice. Crystals of the correct form demand special conditions for the growth and therefore in the nature meet seldom. The majority of solid bodies represent the conglomerates of small and smallest kristallik which are strongly linked by forces of the mechanical and electric nature – crystallites. If the reader happened to see, for example, the cracked half shaft of the car or a pig-iron grid-iron, then grains of crystallites on demolition are visible with the naked eye there. And on splinters of the broken porcelain or faience ware they can be observed under a magnifying glass.
Plasma
Physics marks out also the fourth aggregate state of substance – plasma. In plasma the electrons are torn off from atomic kernels, and it represents mix electrically of charged particles. Plasma can be very dense. For example, one cubic centimeter of plasma from the depths of stars – white dwarfs, weighs tens and hundreds of tons. Plasma is emitted in separate aggregate state because it actively interacts with electromagnetic fields because its particles are loaded. In free space plasma seeks to extend, cooling down and passing into gas. But under the influence of electromagnetic fields it can keep a form and volume out of a vessel as a solid body. This property of plasma is used in fusion power reactors – prototypes of power stations of the future.