CHEMISTRY GLOSSARY

low-weight fractions    →   lake frakcije

Low-weight (petroleum) fractions have low boiling points and short carbohydrates chains.

mass number    →   maseni broj

Mass number (A) is a characteristic property of a specific isotope of an element, equal to the sum of the number of protons and neutrons in the nucleus.

dipole moment    →   dipolni moment

Electric dipole moment (μ) is a product of the positive charge and the distance between the charges. Dipole moments are often stated in debyes; The SI unit is the coulomb metre. In a diatomic molecule, such as HCl, the dipole moment is a measure of the polar nature of the bond; i.e. the extent to which the average electron charges are displaced towards one atom (in the case of HCl, the electrons are attracted towards the more electronegative chlorine atom). In a polyatomic molecule, the dipole moment is the vector sum of the dipole moments of the individual bonds. In a symmetrical molecule, such as tetrafluoromethane (CF₄) there is no overall dipole moment, although the individual C-F bonds are polar.

electric cell    →   električni članak

Electric cell (battery) is a device that is capable of changing some form of energy, such as chemical, nuclear or radiant energy, into electricity. A solar cell, for example, consists of a semiconductor junction that converts sunlight directly into electricity. A dry cell battery converts chemical energy into electricity.

electric field    →   električno polje

If a small amount of charge experience a force, there is an electric field in the vicinity. Electric field E is defined in terms of electrostatic force F that would be exerted on positive test charge q_p placed in the field:

SI unit for electric field is N C^-1, or V m^-1.

The electric field due to a point charge q at distance r from it given by:

where ε₀ is permittivity constant, and is ε_o=8.85×10^-12 C² N^-1 m^-2.

meson    →   mezon

Meson is a positively or negatively charged subatomic particle of very short life age with a mass about 200 times greater than the one of electron. It is produced artificially in particle accelerators.

micelle    →   micele

Micelle is an electrically charged colloidal particle, usually organic in nature, composed of aggregates of large molecules, e.g., in soaps and surfactants. For aqueous solutions, the hydrophilic end of the molecule is on the surface of the micelle, while the hydrophobic end (often a hydrocarbon chain) points toward the centre.

molar enthalpy of evaporation    →   molarna entalpija isparavanja

Molar enthalpy of evaporation (Δ_l ^gH) is a change of enthalpy during evaporation divided by molarity of a liquid, and is equal to the heat energy spent when the evaporation is conducted under constant pressure, Δ_l ^gH=Q.

molar enthalpy of melting    →   molarna entalpija taljenja

Molar enthalpy of melting (Δ_s ^lH) is a change of enthalpy during melting divided by the molarity of a solid matter, and is equal to the energy used when melting is conducted under constant pressure.

electrical double layer    →   električni dvosloj

Electrical double layer is the structure of charge accumulation and charge separation that always occurs at the interface when an electrode is immersed into an electrolyte solution. The excess charge on the electrode surface is compensated by an accumulation of excess ions of the opposite charge in the solution. The amount of charge is a function of the electrode potential. This structure behaves essentially as a capacitor. There are several theoretical models that describe the structure of the double layer. The three most commonly used ones are the Helmholtz model, the Gouy-Chapman model, and the Gouy-Chapman-Stern model.