Homogeneity (Greek: homo - of ( ὁμοῖος / ὅμοιος ) homoios same; -tions designed arise from ( γίγνομαι ) gígnomai; homogenos: of equal incurred, so the same nature ) refers to the equality of a physical characteristic over the entire extent of a system or the similarity between elements of a system. The term has a wide application and can contain different meanings in detail.
Opposites to homogeneity
What is not homogeneous, is called non-homogeneous or heterogeneous.
Is to distinguish between these two terms usually, the word usage is somewhat staggering.
- Heterogeneous, however, is a body of macroscopically various components, such as a concrete slab with a steel reinforcement.
The figure shows the differences of homogeneity, heterogeneity and inhomogeneity are depicted from left to right.
In physics, matter is considered atomic, generally not homogeneous, since the building blocks of matter have no uniform space filling. As early as the atom itself, the mass and charge distribution is not homogeneous, as they unevenly distributed across the nucleus and the nuclear envelope. When the atoms or molecules, however, are approximately uniformly (not necessarily with the regularity of the crystal lattice, but with no macroscopic changes from place to place ) are distributed, from a practical standpoint, the material is homogeneous. Even fields are either homogeneous or inhomogeneous.
A physical field, eg, a magnetic field is called homogeneous if the field strength at each location is the same, otherwise inhomogeneous.
Depending on the size scale
An example of material that is heterogeneous on a microscopic level, viewed macroscopically, however, appears to be homogeneous, is milk. Microscopically, in the milk to distinguish areas that contain fat, and those containing water. And although they can not mix, both areas are so small that they appear distributed viewed macroscopically homogeneous. Nevertheless, it may happen in such mixtures that their shares over time and separate in the case of milk, this no longer appears macroscopically homogeneous since their aqueous spaces are clearly defined by their high fat areas (cream ) differ. In order to prevent these segregation or separation, you can for example ensure, by way of homogenizing for even after a long time yet even distribution of fat and water.
In chemistry, homogeneous substances are either pure substances or homogeneous mixtures, which are also called solutions.
Importance of homogeneous materials
Obtaining sufficiently homogeneous starting materials and / or intermediates for the industry, for example in the production of various semiconductor components of modern electronics and computer industry, one of the key problems of scientific and technological development. It requires (especially in the recovery of high-purity substances and / or reducing their error tolerances ) are often high effort.
Follow the chemical homogeneity
Homogeneous matter has the same overall density and composition. When in a large tank with a homogeneous material, such as a gas, at a point a subset V1 included this contains the same amount of material as a subset of the same volume V1 elsewhere. Dividing the total molar amount into two equal volumes, so they each containing equal amount of substance (in this case, half of the original ). It follows:
The amount of substance is reversed for homogeneous substances at constant pressure and constant temperature proportional to the volume, or:
The volume of homogeneous substances is proportional at constant pressure p and constant temperature T to substance.
For T = const and p = const so the following applies:
These laws apply to all homogeneous materials, as long as the temperature and pressure remain unchanged, including the ideal gas, for which the ideal gas equation. The ratio is molar volume, the quotient of the concentration. The relations above are also the basis of volumetry.
For homogeneous materials, the relations are