CHEMISTRY GLOSSARY

amphoteric    →   amfoternost

Amphoteric is capable of acting either as an acid or base.

alkynes    →   alkini

Alkynes (acetylenes) are acyclic branched or unbranched hydrocarbons having one or more triple carbon-carbon bond. In the systematic chemical nomenclature alkyne names end in the suffix -yne. The general formula is C_nH_(2n+2)-4x were x is the number of triple bonds. Alkynes that have only one triple bond form a homologous series: ethyne (acetylene), CH≡CH, propyne, CH₃CH≡CH, etc. Like alkenes, alkynes undergo addition reaction.

allotrope    →   alotrop

Allotropes are the elements which exist in two or more different forms in the same physical state. Allotropes generally differ in physical properties and may also differ in chemical activity.

Diamond, graphite and fullerenes are three allotropes of the element carbon. Graphite is a soft, black, slippery substance; by contrast, diamond is one of the hardest substances known. The different properties of the allotropes arise from their chemical structures. Diamonds typically crystallize in the cubic crystal system and consist of tetrahedrally bonded carbon atoms. Graphite crystallizes in the hexagonal system. In the fullerenes, the carbon atoms taking the form of a hollow sphere, ellipsoid, or tube.

In some cases, the allotropes are stable over a temperature range, with a definite transition point at which one changes into the other. For instance, tin has two allotropes: white (metallic) tin stable above 13.2 °C and grey (nonmetallic) tin stable below 13.2 °C.

The term allotropes may also be used to refer to the molecular forms of an element. Ozone is a chemically active triatomic allotrope of the element oxygen.

allotropic modification    →   alotropska modifikacija

Different substances of the same elementary system are called allotropes or allotropic modifications. In the case of oxygen, there are two allotropic modifications: "normal" dioxygen (O₂) and trioxygen (O₃) or ozone.

allotropy    →   alotropija

Allotropy (Gr. allos, other, and tropos, manner) is the phenomenon of an element existing in two or more physical forms in the same physical state. The difference between the forms involves either crystaline structure (white, red and black phosphorus), the number of atoms in the molecule of a gas (diatomic oxygen and triatomic ozone), or the molecular structure of a liquid (liquid helium an helium II).

In some cases, the allotropes are stable over a temperature range, with a definite transition point at which one changes into the other. For instance, tin has two allotropes: white (metallic) tin stable above 13.2 °C and grey (nonmetallic) tin stable below 13.2 °C. This form allotropy is called enantiotropy. Form of allotropy, in which there is no transition temperature at which the two are in equilibrium, is called monotropy.

Allotropy does not apply to the substance existing in different physical states as, for example, when ice melts and changes from solid ice to liquid water.

Allotropy is generally restricted to describing polymorphic behaviour in elements, while polymorphism may refer to any material having multiple crystal structures.

alpaca    →   alpaka

Alpaca (alpaka) or Nickel Silver is the generic name for any of a range of non-precious bright silvery-grey metal alloys, composed of copper, nickel and zinc. Despite its name it contains no real silver. It is also commonly called German Silver.

There are many different formulations of alloys which fall within the general term of Nickel Silver. All contain copper, nickel and zinc, while some formulations may additionally include antimony, tin, lead or cadmium. A representative formulation is 65 % copper, 18 % nickel, 17 % zinc. Nickel Silver is widely used for the commercial production of industrial components, housewares, flatware and cutlery, and as the metal substrate for silver-plated goods.

amount concentration    →   količinska koncentracija

Amount concentration (also called molar concentration and in older literature molarity) is the amount of a given substance in a stated unit of a mixture, solution, or ore. The common unit is mole per cubic decimetre (moldm⁻³) or mole per litre (molL^-1) sometimes denoted by M.

The concentration of an atom, ion, or molecule in a solution may be symbolised by the use of square brackets, as [Ca²⁺].

atomic clock    →   atomski sat

Atomic clock is an apparatus for standardizing time based on periodic phenomena within atoms or molecules (ammonia clock; caesium clock).

biogas    →   bioplin

Biogas is a mixture of methane and carbon dioxide resulting from the anaerobic decomposition of such waste materials as domestic, industrial, and agricultural sewage. Methanogenic bacteria carry out the decomposition; these obligate anaerobes produce methane, the main component of biogas, which can be collected and used as an energy source for domestic processes, such as heating, cooking, and lighting.

atmosphere    →   atmosfera

1. Atmosphere is the column of air which is extending several hundred kilometers above the surface the Earth's surface. The density of this air decreases as you proceed up from the surface. The air in the atmosphere consists of 78 % nitrogen, 21 % oxygen, and 0.9 % argon. The remaining 0.1 % of the atmosphere consists of ozone, water vapor, carbon dioxide, methane, helium, and neon. The atmosphere is divided into different regions. The lowest two layers are the troposphere (the layer closest to the earth) and the stratosphere respectively. These two layers contain more than 99 % of the atmospheric molecules.

2. Standard atmosphere (atm) is an obsolete pressure and stress unit which should be discontinued. It is unit of pressure equal to the air pressure measured at mean sea level.

1 atm = 101 325 Pa

Technical atmosphere (at) is an obsolete MKpS pressure and sttress derived unit.

1 at = 98 066.5 Pa

1 atm = 1.033 227 453 at