CHEMISTRY GLOSSARY

helium    →   helij

Helium was discovered by Pierre Jules César Janssen (France) and Sir William Ramsay (Scotland) in 1868. The origin of the name comes from the Greek word helios meaning sun. It is light, odourless, colourless inert gas. Second most abundant element in the universe. Helium is found in natural gas deposits from wells in Texas, Oklahoma and Kansas. Used in balloons, deep sea diving and welding. Also used in very low temperature research.

hydrolysis    →   hidroliza

Hydrolysis is a chemical reaction in which water reacts with another substance to form two or more new substances. This involves ionisation of the water molecule, as well as splitting of the compound hydrolysed, e.g.

Examples are conversion of starch to glucose by water in the presence of suitable catalysts and a reaction of the ions of a dissolved salt to form various products, such as acids, complex ions, etc.

ideal solution    →   idealna otopina

Ideal solution is a solution in which solvent-solvent and solvent-solute interactions are identical, so that properties such as volume and enthalpy are exactly additive. Ideal solutions follow Raoult’s law, which states that the vapour pressure p_i of component i is p_i = x_i p_i^*, where x_i is the mole fraction of component i and p_i^* the vapour pressure of the pure substance i.

indicator    →   indikator

Indicator is a substance used to show the presence of a chemical substance or ion by its colour. Acid-base indicators are compounds, such as phenolphtaleine and methyl orange, which change colour reversibly, depending on whether the solution is acidic or basic. Oxidation-reduction indicators are substances that show a reversible colour change between oxidised and reduced forms.

law of chemical equilibrium    →   zakon o kemijskoj ravnoteži

Law of chemical equilibrium (also called the law of mass action) states that the rate at which a substance reacts is proportional to its active mass (i.e. to its molar concentration). Thus, the velocity of a chemical reaction is proportional to the product of the concentration of the reactants.

levorotatory    →   lijevokretan

Levorotatory is refers to an optically active substance that rotates the plane of plane polarised light counterclockwise.

Lewis number    →   Lewisova značajka

Lewis number (Le) is a dimensionless quantity used in fluid mechanics, defined by

where a is thermal diffusivity and D is diffusion coefficient.

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.

kinetic energy    →   kinetička energija

Kinetic energy (E_k) is associated with the state of motion of a body. It is a scalar property and defined to be

Kinetic energy is most clearly exhibited in gases, in which molecules have much greater freedom of motion than in liquids and solids.

law of conservation of mass    →   zakon o očuvanju mase

Law of conservation of mass states that no detectable gain or loss in mass occurs in chemical reactions. The state of a substance may change in a chemical reaction, for example, from a solid to a gas, but its total mass will not change. Note that the energy released (exothermic) or adsorbed (endothermic) in a chemical reaction is a result of energy transfer between atoms and their environment.