CHEMISTRY GLOSSARY

conduction    →   kondukcija

This process occurs most significantly in solids. The atoms or molecules in a solid state do not leave their mean positions, but continue to vibrate about their mean positions. They transfer heat energy from one atom to another. This happens because of the coupling between them due to mutually attractive forces.

cosmic rays    →   kozmičke zrake

Cosmic rays are high energy (10¹⁵ eV- 10¹⁷ eV) nuclear particles, electrons, and photons, originating mostly outside the solar system, which continually bombard the Earth’s atmosphere.

ball mill    →   kuglični mlin

Ball mill is a grinder for reducing hard materials to powder. The grinding is carried out by the pounding and rolling of a charge of steel or ceramic balls carried within the cylinder. The cylinder rotates at a relatively slow speed, allowing the balls to cascade through the mill base, thus grinding or dispersing the materials.

Type of ball mills, centrifugal and planetary mills, are devices used to rapidly grind materials to colloidal fineness (approximately 1 μm and below) by developing high grinding energy via centrifugal and/or planetary action.

battery    →   baterija

Battery a device that converts chemical energy to electrical energy. The process underlying the operation of a battery involves a chemical reaction in which electrons are transferred from one chemical species to another. This process is carried out in two half-reactions, one that involves the loss of electrons and one that involves their gain. The battery is an electrochemical cell divided in two half-cells, and reaction proceeds when these are connected together by an electrically conducting pathway. The passage of electrons from one half-cell to the other corresponds to an electric current. Each half-cell contains an electrode in contact with the reacting species. The electrode which passes electrons into the circuit when battery discharges is called anode and is negative terminal. The electrode which receives electrons is called cathode, and is the battery’s positive terminal. The electrical circuit is completed by an electrolyte, an electrically conducting substance placed between the two electrodes which carriers a flow of charge between them. In wet cells, the electrolyte is a liquid containing dissolved ions, whose motion generates an electrical current; in dry cells the electrolyte is basely solid, for example, a solid with mobile ions or porous solid saturated with an ionic solution.

degenerate orbitals    →   degenerirane orbitale

Degenerate orbitals are orbitals with the same energy. This degeneracy can sometimes be "lifted" by external electric or magnetic fields.

electron spin    →   elektronski spin

Electron spin (s) is the quantum number, equal to 1/2, that specifies the intrinsic angular momentum of the electron.

electron volt    →   elektronvolt

Electron volt (eV) is a non-SI unit of energy used in atomic and nuclear physics, equal to approximately 1.602 177×10^-19 J. The electron volt is defined as the kinetic energy acquired by an electron upon acceleration through a potential difference of 1 V.

Boltzmann constant    →   Boltzmannova konstanta

The Boltzmann constant (k or k_B) is the physical constant describing the relationship between the thermodynamic temperature and the average kinetic energy of particles in a gas. It equals the molar gas constant R divided by the Avogadro constant N_A and has the value 1.380 648 52(79)×10^-23 J/K. It is named after the Austrian physicist Ludwig Eduard Boltzmann (1844-1906).

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.

endothermic reaction    →   endotermna reakcija

Endothermic reactions are the ones in which heat is absorbed and are facilitated by an increase in temperature (ΔH° > 0).

If the reaction is endothermal in one direction, in the opposite direction the reaction is exothermal.