CHEMISTRY GLOSSARY

Peclet number    →   Pecletova značajka

Péclet number (Pe) is a dimensionless quantity used in fluid mechanics, defined by

where v is velocity, l is length, and a is thermal diffussivity.

phase diagram    →   fazni dijagram

Phase diagram is a graphic representation of the equilibrium relationships between phases (such as vapour-liquid, liquid-solid) of a chemical compound, mixture of compounds, or solution.

The figure shows a typical phase diagram of an element or a simple compound. The stability of solid, liquid and gas phases depends on the temperature and the pressure. The three phases are in equilibrium at the triple point. The gas and liquid phases are separated by a phase transition only below the temperature of the critical point.

plastic    →   plastika

Plastic is a material that can be shaped by the application of heat or pressure. Most are based on synthetic polymers although some are the product of natural substances (such as cellulose derivatives, but excluding the rubbers.). They are usually light and permanent solids, being also heat and electric isolators. If the materials soften again when reheated, they are said to be thermoplastic. If, after fashioning, they resist further applications of heat, they are said to be thermoset.

potential energy    →   potencijalna energija

Potential energy (E_p) 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). Gravitational potential energy is the energy associated with the state of separation between bodies that attracts each other via gravitational force. Elastic potential energy is the energy associated with the state of compression or extension of an elastic object. Thermal energy is associated with the random motions of atoms and molecules in a body.

Prandtl number    →   Prandtlova značajka

Prandtl number (Pr) is a dimensionless quantity used in fluid mechanics, defined by

where η is viscosity, ρ is density, and a is thermal diffusivity.

Rayleigh number    →   Rayleighova značajka

Rayleigh number (Ra) is a dimensionless quantity used in fluid mechanics, defined by

where l is length, g is acceleration of gravity, α is cubic expansion coefficient, T is temperature, ρ is density, η is viscosity, and a is thermal diffusivity.

reflux condenser    →   povratno hladilo

Reflux condenser is used for repeated transformation of vapour in liquid in order to prevent the loss due to evaporation.

salt water    →   slana voda

Salt water is the water of the sea and the ocean. This water contains a relatively high percentage of dissolved salt (about 35 g of salt per 1 000 g of sea water.). About 90 % of that salt would be sodium chloride, or ordinary table salt.

The salinity of ocean water varies. It is affected by such factors as melting of ice, inflow of river water, evaporation, rain, etc.

silver    →   srebro

Silver has been known since ancient times. The origin of the name comes from the Latin word argentum meaning silver. It is silvery-ductile and malleable metal. Stable in water and oxygen. Reacts with sulfur compounds to form black sulfides. Silver is found in ores called argentite (AgS), light ruby silver (Ag₃AsS₃), dark ruby silver (Ag₃SbS₃) and brittle silver. Used in alloys for jewellery and in other compounds for photography. It is also a good conductor, but expensive.

sodium    →   natrij

Sodium was discovered by Sir Humphry Davy (England) in 1807. The origin of the name comes from the Latin word natrium meaning sodium carbonate. It is soft silvery-white metal. Fresh surfaces oxidize rapidly. Reacts vigorously, even violently with water. Reacts with water to give off flammable gas. Burns in air with a brilliant white flame. Sodium is obtained by electrolysis of melted sodium chloride (salt), borax and cryolite. Metallic sodium is vital in the manufacture of organic compounds. Sodium chloride (NaCl) is table salt. Liquid sodium is used to cool nuclear reactors.