CHEMISTRY GLOSSARY

electrolytic cell    →   elektrolitska ćelija

Electrolytic cell is an electrochemical cell that converts electrical energy into chemical energy. The chemical reactions do not occur spontaneously at the electrodes when they are connected through an external circuit. The reaction must be forced by applying an external electric current. It is used to store electrical energy in chemical form (rechargeable battery). It is also used to decompose or produce (synthesise) new chemicals by the application of electrical power. This process is called electrolysis, e.g., water can be decomposed into hydrogen gas and oxygen gas. The free energy change of the overall cell reaction is positive.

equivalent    →   ekvivalent

Equivalent (eq) is a unit for describing the amount of a chemical species. In contrast to the mole, the amount of a substance contained in one equivalent can vary from reaction to reaction.

equivalent weight    →   ekvivalentna masa

Equivalent weight of a substance participating in a neutralization reaction is that mass of substance (molecule, ion, or paired ion) that either reacts with or supplies 1 mol of hydrogen ions in that reaction.

Equivalent weight of a substance participating in an oxidation/reduction reaction is that weight which directly or indirectly produces or consumes 1 mol of electrons.

eutectic    →   eutektik

Eutectic is a solid solution consisting of two or more substances and having the lowest freezing point of any possible mixture of these components.

Eutectic point is the lowest temperature at which the eutectic mixture can exist in a liquid phase. A liquid having the eutectic composition will freeze at a single temperature without a change of composition.

extensive property    →   ekstenzivno svojstvo

Extensive property is a property that changes when the amount of matter in a sample changes. Examples are mass, volume, length, and charge.

electron    →   elektron

The electron is an elementary particle with a negative electric charge of (1.602 189 2±0.000 004 6)×10^-19 C and a mass of 1/1837 that of a proton, equivalent to (9.109 534±0.000 047)×10^-31 kg.

In 1897 the British physicist Joseph John (J.J.) Thomson (1856-1940) discovered the electron in a series of experiments designed to study the nature of electric discharge in a high-vacuum cathode-ray tube. Thomson interpreted the deflection of the rays by electrically charged plates and magnets as evidence of bodies much smaller than atoms that he calculated as having a very large value for the charge to mass ratio. Later he estimated the value of the charge itself.

Electrons are arranged in from one to seven shells around the nucleus; the maximum number of electrons in each shell is strictly limited by the laws of physics (2n²). The outer shells are not always filled: sodium has two electrons in the first shell (2×1² = 2), eight in the second (2×2² = 8), and only one in the third (2×3² = 18). A single electron in the outer shell may be attracted into an incomplete shell of another element, leaving the original atom with a net positive charge. Valence electrons are those that can be captured by or shared with another atom.

Electrons can be removed from the atoms by heat, light, electric energy, or bombardment with high-energy particles. Decaying radioactive nuclei spontaneously emit free electrons, called β particles.

energy    →   energija

Energy (E, U) is the characteristic of a system that enables it to do work. Like work itself, it is measured in joules (J).

The internal energy of a body is the sum of the potential energy and the kinetic energy of its component atoms and molecules.

Potential energy is the energy stored in a body or system as a consequence of its position, shape, or state (this includes gravitation energy, electrical energy, nuclear energy, and chemical energy).

Kinetic energy is the energy of motion and is usually defined as the work that will be done by a body possessing the energy when it is brought to rest. For a body of mass m having a speed v, the kinetic energy is mv²/2. Kinetic energy is most clearly exhibited in gases, in which molecules have much greater freedom of motion than in liquids and solids.

In an isolated system energy can be transferred from one form to another but the total energy of the system remains constant.

fermentation    →   fermentacija

Fermentation is a class of biochemical reactions that break down complex organic molecules (such as carbohydrates) into simpler materials (such as ethanol, carbon dioxide, and water). Fermentation reactions are catalyzed by enzymes.

Fermi level    →   Fermijev nivo

Fermi level is the highest energy of occupied states in a solid at zero temperature. The Fermi level in conductors lies in the conduction band, in insulators it lies in the valence band, and in semiconductors it falls in the gap between the conduction band and the valence band. It was named after the Italian physicst Enrico Fermi (1901 - 1954).

Fick’s law    →   Fickov zakon

Fick’s law is the statement that the flux J of a diffusing substance is proportional to the concentration gradient, i.e.,

where D is called the diffusion coefficient.