CHEMISTRY GLOSSARY

coenzyme    →   koenzim

Coenzyme is an organic nonprotein molecule, such as a vitamin, that associates with an enzyme in catalysing biochemical reactions. Coenzymes usually participate in the substrate-enzyme interaction by donating or acepting certain chemical groups.

collision theory    →   teorija sudara

Collision theory is theory that explains how chemical reactions take place and why rates of reaction alter. For a reaction to occur the reactant particles must collide. Only a certain fraction of the total collisions cause chemical change; these are called successful collisions. The successful collisions have sufficient energy (activation energy) at the moment of impact to break the existing bonds and form new bonds, resulting in the products of the reaction. Increasing the concentration of the reactants and raising the temperature bring about more collisions and therefore more successful collisions, increasing the rate of reaction.

colloid    →   koloid

Colloids are systems in which there are two or more phases, with one (the dispersed phase) distributed in the other (the continuous phase). Moreover, at least one of the phases has small dimensions, in the range between 1 nm and 1 μm (10^-9 m – 10^-6 m). Dimension, rather than the nature of the material, is characteristic. In this size range, the surface area of the particle is large with respect to its volume so that unusual phenomena occur, e.g., the particles do not settle out of the suspension by gravity and are small enough to pass through filter membranes. Macromolecules (proteins and other high polymers) are at the lower limit of this range; the upper limit is usually taken to be the point at which the particles can be resolved in an optical microscope.

Colloidal particles may be gaseous, liquid, or solid, and occur in various types of suspensions:

Sols - dispersions of small solid particles in a liquid.

Emulsions - colloidal systems in which the dispersed and continuous phases are both liquids.

Gels - colloids in which both dispersed and continuous phases have a three-dimensional network throughout the material.

Aerosols - colloidal dispersions of liquid or solid particles in a gas.

Foams - dispersions of gases in liquids or solids.

isotropy    →   izotropija

Isotropy is the property of molecules and materials of having identical physical properties in all directions.

ligand field theory    →   teorija ligandnog polja

Ligand field theory is a description of the structure of crystals containing a transition metal ion surrounded by nonmetallic ions (ligands). It is based on the construction of molecular orbitals involving the d-orbitals of the central metal ion and combinations of atomic orbitals of the ligands.

liquid crystal    →   tekući kristal

Liquid crystals or crystalline liquids are a physical state between crystals and melts. The liquid crystalline phase - the so-called mesophase - is formed at the melting point. The most important (usable) mesophases are nematic, cholesteric and smectic phase, having different molecular orientations.

London’s force    →   Londonova sila

London’s force is an intermolecular attractive force that arises from a cooperative oscillation of electron clouds on a collection of molecules at close range.

colloid ion    →   koloidni ion

Colloid ions emerge when colloid particles adsorb certain type of ion from solution and thus become charged with the same charge. The charge can also originate form a chemical reaction of colloid particle’s surface. Colloid ions formed by absorption of silver chloride particle can be show as follows:

Adsorbed layer is monomolecular (one molecule thick) and which type of ion will be formed depends upon which ions are present in a greater number in the solution in. Because of this colloid particles are charged with the same charge, mutual repelling occurs, and the colloid solution becomes stable. Colloid charge can be determined by electrophoresis.

condensation    →   kondenzacija

1. Condensation is a process of changing from a gaseous to a liquid or solid state, usually done by cooling.

2. Condensation, in colloid systems, is a process where smaller particle join in one colloid size particle

3. Condensation, in chemical terms, is a sort of chemical reaction in which small molecules like water, carbon dioxide, or ammonia single out.

conformation    →   konformacija

Conformation is one of the very large numbers of possible spatial arrangements of atoms that can be interconverted by rotation about a single bond in a molecule. The conformation of a molecule is not fixed, though one or another shape may be more likely to occur. There are two extreme cases:

Staggered conformation (antiperiplanar) is a conformation about a carbon-carbon single bond in which the atoms on one carbon are as far apart as possible from the atoms on an adjacent carbon.

Eclipsed conformation (syn-periplanar) is a conformation about a carbon-carbon single bond in which the atoms on one carbon are as close as possible to the atoms on an adjacent carbon.