CHEMISTRY GLOSSARY

metalloid    →   polumetal

Metalloid (semimetal) is any of a class of chemical elements intermediate in properties between metals and nonmetals. The classification is not clear cut, but typical metalloids are boron (B), silicon (Si), germanium (Ge), arsenic (As), and tellurium (Te). They are electrical semiconductors and their oxides are amphoteric.

coulomb    →   kulon

Coulomb (C) is the SI unit of electric charge. It is equal to the charge transferred by a current of one ampere in one second (C = A s). The unit was named after the French physicist C. A. Coulomb (1736-1806).

nonelectrolyte    →   neelektrolit

Nonelectrolytes are substances which in solutions do not dissociate into ions and they do not conduct electric current.

ohm    →   om

Ohm (Ω) is the SI derived unit of electric resistance. The ohm is the electric resistance between two points of a conductor when a constant difference of potential of one volt, applied between these two points, produces in this conductor a current of one ampere, this conductor not being the source of electromotive force (Ω = V/A). The unit was named after the German physicist Georg Simon Ohm (1789-1854).

Peltier effect    →   Peltierov efekt

Peltier effect is the absorption or generation of heat (depending on the current direction) which occurs when an electric current is passed through a junction between two materials.

siemens    →   simens

Siemens (S) is the SI derived unit of of electrical conductance of a conductor in which a current of one ampere is produced by an electrical potential difference of one volt (S = A·V^-1 = Ω^-1). The unit was named after the German scientist Ernst Werner von Siemens (1816-1892).

strong electrolyte    →   jaki elektrolit

Strong electrolytes are those electrolytes which in water solutions completely dissociate into their ions. They conduct electric current very well.

temperature rating    →   temperaturno područje

Temperature rating is the maximum and minimum temperature at which the material may be used in continuous operation without loss of its basic properties. For example, temperature ratings are often quoted for electrical insulators, specifying the maximum temperature at which they provide adequate protection against electrical breakdown.

electrochemical cell    →   elektrokemijski članak

Electrochemical cell is a device that converts chemical energy into electrical energy or vice versa when a chemical reaction is occurring in the cell. It consist of two electronically conducting phases (e.g., solid or liquid metals, semiconductors, etc) connected by an ionically conducting phase (e.g. aqueous or non-aqueous solution, molten salt, ionically conducting solid). As an electric current passes, it must change from electronic current to ionic current and back to electronic current. These changes of conduction mode are always accompanied by oxidation/reduction reactions.

An essential feature of the electrochemical cell is that the simultaneously occurring oxidation-reduction reactions are spatially separated. E.g., in a spontaneous chemical reaction during the oxidation of hydrogen by oxygen to water, electrons are passed directly from the hydrogen to the oxygen.

In contrast, in the spontaneous electrochemical reaction in a galvanic cell the hydrogen is oxidised at the anode by transferring electrons to the anode and the oxygen is reduced at the cathode by accepting electrons from the cathode. The ions produced in the electrode reactions, in this case positive hydrogen ions and the negative hydroxyl (OH^-) ions, will recombine in the solution to form the final product of the reaction: water. During this process the electrons are conducted from the anode to the cathode through an outside electric circuit where the electric current can drive a motor, light a light bulb, etc. The reaction can also be reversed: water can be decomposed into hydrogen and oxygen by the application of electrical power in an electrolytic cell.

volt    →   volt

Volt (V) is the SI derived unit of electric potential. One volt is the difference of potential between two points of an electric conductor when a current of 1 ampere flowing between those points dissipates a power of 1 watt. It was named after the Italian physicist Alessandro Volta (1745-1827).