CHEMISTRY GLOSSARY

catalyst    →   katalizator

Catalyst is a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change. Catalysts that have the same phase as the reactants are homogenous catalysts (e.g. enzymes in biochemical reactions). Those that have a different phase are heterogeneous catalyst (e.g. metals or oxides used in gas reactions).

The catalyst provides an alternative pathway by which the reaction can proceed, in which the activation energy is lower. In thus increases the rate at which the reaction comes to an equilibrium, although it does not alter the position of the equilibrium.

coal tar    →   ugljeni katran

Coal tar is a material obtained from the destructive distillation of coal in the production of coal gas. The crude tar contains a large number of organic compounds (e.g. benzene, naphthalene, methylbenzene, etc.), which can be separated by fractional distillation.

cellulose    →   celuloza

Cellulose, (C₆H₁₀O₅)_n, is a polysaccharide that consists of a long unbranched chain of glucose units linked by (1→4)-β-glycoside bonds. Nature uses cellulose primarily as a structural material to impart strength and rigidity to plants. Leaves, grasses, and cotton are primarily cellulose. The fibrous nature of extracted cellulose has led to its use in textile industry for the production of cotton, artificial silk, etc. Cellulose also serves as raw material for the manufacture of cellulose acetate, known commercially as acetate rayon, and cellulose nitrate, known as guncotton. Gunncotton is the major ingredient in smokeless powder, the explosive propellant used in artillery shells and in ammunition for firearms.

covalent compound    →   kovalentni spoj

Covalent compound is a compound made of molecules - not ions, such as H₂O, CH₄, Cl₂. The atoms in the compound are bound together by shared electrons. Also called a molecular compound.

dissolved substance    →   otopljena tvar

Dissolved substance is a solid, liquid or gas matter dissolved in a solvent. Depending upon the particle size of dissolved substance, solutions differ in properties and can be divided into real solutions (diameter of particles is smaller than 1 nm), colloid solutions (diameter of particles is from 1 nm to 200 nm) and suspensions (diameter of particles is greater than 200 nm).

dry ice    →   suhi led

Dry ice is frozen carbon dioxide (CO₂). It is called dry ice because it sublimates, i.e. it transits to vapour without a prior transition to liquid state. It is a convenient refrigerant because it sublimes at -78 °C.

effervescence    →   pjenušanje

Effervescence is the formation of gas bubbles in a liquid by a chemical reaction. An example of effervescence is the release of carbon dioxide which bubbles as a gas from the liquid when limestone chips, which are composed of calcium carbonate, are added to dilute hydrochloric acid.

effusion    →   efuzija

Effusion is the flow of a gas through a small aperture. The relative rates at which gases effuse, under the same conditions, is approximately inversely proportional to the square of their densities.

elementary reaction    →   elementarna reakcija

Elementary reaction is a reaction that occurs in a single step. Equations for elementary reactions show the actual molecules, atoms, and ions that react on a molecular level.

chlorine    →   klor

Chlorine was discovered by Carl William Scheele (Sweden) in 1774. The origin of the name comes from the Greek word chloros meaning pale green. It is greenish-yellow, disagreeable gas with irritating odour. Gas is toxic and severe irritant by contact or inhalation. Never found in free form in nature. Commercial quantities of chlorine are produced by electrolysis of aqueous sodium chloride (NaCl) from seawater or brine from salt mines. Used in water purification, bleaches, acids and many, many other compounds such as chlorofluorocarbons (CFC).