CHEMISTRY GLOSSARY

heat transfer    →   prijenos topline

From observations and experiments it has been found that heat energy can be transferred from one position to another through three different modes: conduction, convection and radiation.

chain reaction    →   lančana reakcija

Chain reaction is a reaction done in three steps: initiation in which usually radicals are made which react with other molecules in stage of propagation and, when all reactants are spent, it ends by termination when all available radicals are completely spent.

Nuclear chain reaction refers to a process in which neutrons released in fission produce an additional fission in at least one further nucleus. Nuclear power plants operate by precisely controlling the rate at which nuclear reactions occur. On the other hand, nuclear weapons are specifically engineered to produce a reaction that is so fast and intense it cannot be controlled after it has started.

change of state    →   promjena stanja

Change of state is a physical change which appears when a substance crosses from one state into another. This usually happens because of the change of energy of particles provoked by heating or cooling.

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).

irreversible process    →   ireverzibilni proces

If a system is taken from one state to another but cannot be brought back to the same initial state, then the process is called irreversible. Some examples are free expansion of a gas; dissipation of energy due to friction, or the mixing of two gases or liquids etc.

joule    →   džul

Joule (J) is the SI derived unit of energy, work, and heat. The joule is the work done when the point of application of a force of one newton is displaced a distance of one metre in the direction of the force (J = N m). The unit was named after the British scientist James Prescott Joule (1818-1889).

Knudsen number    →   Knudsenova značajka

Knudsen number (Kn) is a dimensionless quantity used in fluid mechanics, defined by

where λ is mean free path and l is length.

chlorophyll    →   klorofil

Chlorophyll is a green pigment present in green plants and cyanobacteria. Chlorophyll is essential in the transformation of light energy to chemical energy in photosynthesis. Chlorophyll absorbs light mostly in the blue and red ends of the visible spectrum, and very little in the green wavelengths. That green light is reflected, giving us the leaf colour we see.

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.

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.