individual or aggregate state of matter characterized by its specific properties under specific conditions (pressure and temperature).That is, it may be a solid, liquid or gaseous.Change the aggregation states of matter leads to a change in its physical properties (density, entropy, free energy).Being in a solid state, it can maintain a fixed volume and shape.Turning to the fluid at the same volume, it changes shape, adapting to the vessel or container.Being gaseous, it is not a substance retains not only the shape but also the amount, as expands and fills the whole space.
example, the state of aggregation of water can be solid, liquid or gaseous.In this chemical formula (H2O) and the molecule (two hydrogen atoms and one oxygen atom) do not change.At temperatures between 0 ° C and lower than it is in solid state is called ice.From 0 ° C to 99.944 ° C is colorless (for smaller volumes) of a clear liquid, odorless and tasteless.At a temperature of 99,944 ° C passes into the gaseous phase and is called steam.This example shows that the state of matter changes with environmental conditions.In this case, almost no changing ambient pressure, but a change in temperature, the ice melts at 0 ° C and converted to water, and that boils at 99,944 ° C and evaporates, turns into steam.
water, one might say, is different in its properties, being in different states of aggregation.The density of ice is equal to 0.917 g / cc, liquid water under standard conditions 0.9982 g / cc, water vapor (also under standard conditions) - less than 0.001 g / cc.Dynamic viscosity of water at the temperature of melting ice (freezing point of water) is equal to: μ = 1,793 · 103 Pa · s, and 20 ° C dynamic viscosity of water is: μ = 1,003 · 10ˉ³ Pas.Thus, the state of matter and its properties change at the phase transition.This transition is characterized by a melting point (solid matter becomes liquid) equal to the crystallization temperature (liquid solidifies) and boiling (liquid enters gas) equal to the condensation temperature (the gas becomes liquid).
It should be emphasized that the state of matter depends on its composition.For example, under identical external conditions, various substances differ in their properties.Under normal conditions, water H2O - it is a liquid.Hydrogen H2 and oxygen O2 - are gases.Iron Fe - solid (its melting point 1538,9 ° C, the boiling point of 2860,9 ° C).But the same state of aggregation for different substances may have some similarities.
example, for gas, typically, low intermolecular forces.Therefore, their molecules are separated from each other by large distances.As a result, the gases are able to greatly shrink.The gas molecules are constantly moving, and traffic is chaotic.That is what explains the ability of gases uniformly fill the entire volume, it provided: gases take the shape and volume of the container in which they are located.
fluid between gases and solids occupy an intermediate position.As the temperature increases, they become more similar to gases, but with decreasing temperature, they are more like solids.Liquid molecules more tightly arranged through prominent forces of attraction between them.X-ray studies have shown them that they have some rudiments resembling crystal structure.
solids are always certain forms and volumes.To change them, you need to spend effort, as molecules, atoms and ions are strongly linked.The particles of solid matter can not move freely as preserve the relative position of the equilibrium and near the centers perform ordered fluctuations.We know two states of solids - crystalline and amorphous.The crystals are characterized by certain recent form for them.For example, sodium chloride, NaCl crystals resemble the shape of a cube, potassium nitrate KNO3 - prism and so on.The structure of amorphous - it randomly sagregatirovannye molecule.Unlike crystalline substance melting at a certain temperature, characterized by amorphous broad melting temperature range.Sometimes they are treated as a liquid with a very high viscosity.As conditions change, in which the hardening agent occurs, it can happen, as in the crystalline and amorphous state.
physical state of matter is sometimes described as a plasma or liquid crystals.But this is not the correct definition.The issue requires a separate and more detailed study, so in this article is not affected by the state of matter.