CHEMISTRY GLOSSARY

Gauss’ law for electrostatics    →   Gaussov zakon za elektrostatiku

Gauss’ law describes the relation between charge and electric field in static situations, so it is equivalent to Coulomb’s law, which can be derived from Gauss’ law. Gauss’ law states that the net flux of electric field, Φ, through an imaginary closed surface, S, - a Gaussian surface - is equal to the net charge, q, inside that closed surface:

where electric flux Φ through Gaussian surface is given by:

ε₀ is the permittivity constant and dS is a surface element.

Gibbs phase rule    →   Gibbsov zakon faza

Gibbs phase rule is the relationship used to determine the number of state variables, usually chosen from among temperature, pressure, and species composition in each phase, which must be specified to fix the thermodynamic state of a system in equilibrium:

where C is the number of components in a mixture, P is the number of phases, and F is the degrees of freedom, i.e., the number of intensive variables that can be changed independently without affecting the number of phases.

global warming    →   globalno zatopljenje

Global warming or greenhouse effect is an effect occurring in the atmosphere because of the presence of certain gases (greenhouse gases) that absorb infrared radiation. Light and ultraviolet radiation from the sun is able to penetrate the atmosphere and warm the Earth’s surface. This energy is re-radiated as infrared radiation which because of its longer wavelength, is absorbed by such substances as carbon dioxide. The overall effect is that the average temperature of the Earth and its atmosphere is increasing (so-called global Warming). The effect is similar to that occurring in a greenhouse, where light and long-wavelength ultraviolet radiation can pass through the glass into greenhouse but the infrared radiation is absorbed by the glass and part of it is re-radiated into the greenhouse.

The greenhouse effect is seen as a major environmental hazard. Average increases in temperature could change weather patterns and agricultural output. It might also lead to melting of the polar ice caps and a corresponding rise in sea level. Carbon dioxide, from fossil-fuel power stations and car exhausts, is the main greenhouse gas. Other contributory pollutants are nitrogen oxides, ozone, methane, and chloroflourocarbons.

half-wave potential    →   poluvalni potencijal

Half-wave potential (E_1/2) is a potential at which polarographic wave current is equal to one half of diffusion current (i_d). In a given supporting electrolyte, the half-wave potential is unique for each element and its different valence states and chemical forms. Observation of a current peak at a specific half-wave potential therefore identifies the chemical species producing the current.

hassium    →   hassij

Hassium was discovered by Peter Armbruster, Gottfried Münzenber and their co-workers at the Heavy Ion Research Laboratory (Gesellschaft für Schwerionenforschung, GSI) in Darmstadt, Germany in 1984. The origin of the name is the Latin word Hassias meaning Hess, the German state. It is synthetic radioactive metal. Hassium was produced bythe bombardment of lead-208 with iron-58.

Hooke’s law    →   Hookeov zakon

Hooke’s law stating that the deformation of a body is proportional to the magnitude of the deforming force, provided that the body’s elastic limit (see elasticity) is not exceeded. If the elastic limit is not reached, the body will return to its original size once the force is removed. The law was discovered by English physicist Robert Hooke in 1676.

If a body on elastic spring is displaced from its equilibrium position (i.e. if the spring is stretched or compressed), a restitution force tries to return the body back in its equilibrium position. The magnitude of that force is proportional to the displacement of the body

Where F is the restitutional (elastic) force, x is the displacement of the body and k is the spring constant, which depends on dimensions, shape and material of the spring.

ideal gas law    →   jednadžba stanja idealnog plina

The generalized ideal gas law is derived from a combination of the laws of Boyle and Charles. Ideal gas law is the equation of state

which defines an ideal gas, where p is pressure, V molar volume, T temperature, and R the molar gas constant (8.314 JK^-1mol^-1).

supersaturated solution    →   prezasićena otopina

Solution is supersaturated when it contains greater quantity of dissolved substance in itself than it corresponds to solubility of that substance at that temperature. It is said to be in an unstable state, and by shaking the vessel containing that such a solution separation of salt surplus can occur.

vapour    →   para

Vapour is the gaseous state of some matter which can be converted into liquid when exposed to pressure.

zero law of thermodynamics    →   nulti zakon termodinamike

Zero law of thermodynamics states: If some body A is in thermal equilibrium with body B and with body C, then bodies B and C are also in thermal equilibrium.