CHEMISTRY GLOSSARY

seawater    →   more

Seawater is a complex mixture of 96.5 % water, 3.5 % salts, and smaller amounts of other substances, including dissolved inorganic and organic materials, particulates, and a few atmospheric gases. The world's oceans cover nearly 71 % (361 840 000 km²) of the Earth's surface (510 100 000 km²), with an average depth of 3 682.2 m.

The density of seawater is higher than that of fresh water because of its higher salinity. Seawater's freezing point is lower than that of pure water and its boiling point is higher. The average salinity of the ocean is 35 ‰, which means that for every kilograms of water, there are 35 g of salt. The relative abundance of the major salts in seawater are constant regardless of the ocean. Only six elements and compounds comprise about 99 % of sea salts: chlorine (Cl^-), sodium (Na⁺), sulfur (SO₄^2-), magnesium (Mg²⁺), calcium (Ca²⁺), and potassium (K⁺).

sedimentary rocks    →   sedimentne stijene

Sedimentary Rocks are formed by the accumulation and subsequent consolidation of sediments into various types of rock. There are three major types of sedimentary rocks:

Biogenic sedimentary rocks are formed from organic processes when organisms use materials dissolved in water to build a shell or other skeletal structure.

Clastic sedimentary rocks are composed directly of the sediments or fragments from other rocks.

Chemical sedimentary rocks are formed through evaporation of a chemical rich solution.

Based on their sizes, sediment particles are classified, based on their size, into six general categories:

• boulder (>256 mm)
• cobble (64 - 256 mm)
• gravel (2 - 64 mm)
• sand (1/16 - 2 mm)
• silt (1/256 - 1/16 mm)
• clay (<1/256 mm)

solubility    →   topljivost

Solubility is the maximum amount of solute that dissolves in a given quantity of solvent at a specific temperature. Generally, for a solid in a liquid, solubility increases with temperature; for a gas, solubility decreases. Common measures of solubility include the mass of solute per unit mass of solution (mass fraction), mole fraction of solute, molality, molarity, and others.

standard hydrogen electrode    →   standardna vodikova elektroda

Standard hydrogen electrode is a system in which hydrogen ion and gaseous hydrogen are present in their standard states. The convention is to designate the cell so that the standard hydrogen electrode is written first.

The electrode is used as a reference (of zero) for the values of other standard electrode potentials.

state of matter    →   agregatno stanje

State of matter is one of the tree physical states in which matter can exist, i.e. solid, liquid or gas. Plasma is sometimes regarded as the fourth state of matter. By means of heating a solid substance will cross to liquid state at its melting point. If we heat up a liquid and beyond, at its boiling point it will cross to gaseous state - vapour.

supercritical fluid    →   superkritični fluid

Supercritical fluid is any substance above its critical temperature and critical pressure (see phase diagram). It shows unique properties that are different from those of either gases or liquids under standard conditions. A supercritical fluid has both the gaseous property of being able to penetrate anything, and the liquid property of being able to dissolve materials into their components. Solublity increases with increasing density (i.e. with increasing pressure). An example of this is naphthalene which is practically insoluble in low pressure carbon dioxide. At 100 bar the solubility is 10 g/L and at 200 bar it is 50 g/L. Rapid expansion of supercritical solutions leads to precipitation of a finely divided solid.

supercritical fluid chromatography    →   superkritična fluidna kromatografija

Supercritical fluid chromatography (SFC) is a hybrid of gas and liquid chromatography. SFC is of importance because it permits the separation and determination of a group of compounds that are not conveniently handled by either gas or liquid chromatography. These compounds are either nonvolatile or thermally labile so that gas chromatography cannot be used and they do not contain functional groups that make possible detection by liquid chromatography. SFC has been applied to a wide variety of materials including natural prodcuts, drugs, foods, pesticides and herbicides, fossil fuels, explosives and propellants.

tear gas    →   suzavac

Tear gases is the common name for substances which, in low concentrations, cause pain in the eyes, flow of tears and difficulty in keeping the eyes open. Tear gases are used mainly in military exercises and in riot control, etc., but have also been used as a method of warfare. Irritating gases have been used in war since ancient times but it was not until after the Second World War that a more systematic search for effective substances was started. Among a long series of substances, three have become of greater importance than the others. These substances are chloroacetophenone (codename CN), orto-chlorobenzylidene-malononitrile (CS) and dibenz(b,f)-1,4-oxazepine (CR).

thermochemical equation    →   termokemijska jednadžba

Thermochemical equation is a compact equation representing a chemical reaction that describes both the stoichiometry and the energetics of the reaction. For example, the thermochemical equation

means When one mole of gaseous methane is burned in two moles of oxygen gas, one mole of carbon dioxide gas and 2 moles of steam are produced, and 2 220 kJ of heat are released.

triple point    →   trojna točka

Triple point is the point in p,T space where the solid, liquid, and gas phases of a substance are in thermodynamic equilibrium.