CHEMISTRY GLOSSARY

sp hybrid orbital    →   sp hibridna orbitala

An sp hybrid orbital is an orbital formed by the linear combination of one s and one p orbital of comparable energy (such 2s and 2p orbitals) on a same atom. The two sp hybrid orbitals are aligned in a straight line in opposite direction (bond angles are 180°). The remaining two p orbitals are at right angles to one another and to the line formed by the two sp orbitals.

sp2 hybrid orbital    →   sp2 hibridna orbitala

An sp² hybrid orbital is an orbital formed by the linear combination of one s and two p orbitals of comparable energy (such 2s and 2p orbitals) on a same atom. The three sp² hybrid orbitals lie in a plane with angle of 120°. The remaining p orbital remains unchanged and is perpendicular to the plane of the three sp² orbitals.

sp3 hybrid orbital    →   sp3 hibridna orbitala

An sp³ hybrid orbital is an orbital formed by the linear combination of one s and three p orbitals of comparable energy (such 2s and 2p orbitals) on a same atom. The four sp³ hybrid orbitals point toward the corners of a regular tetrahedron with the bond angle of 109.5°.

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.

thermodynamic laws    →   termodinamički zakoni

Thermodynamic laws are the foundation of the science of thermodynamics:

First law: The internal energy of an isolated system is constant; if energy is supplied to the system in the form of heat dq and work dw, then the change in energy dU = dq + dw.

Second law: No process is possible in which the only result is the transfer of heat from a reservoir and its complete conversion to work.

Third law: The entropy of a perfect crystal approaches zero as the thermodynamic temperature approaches zero.

thermosetting plastic    →   termostabilna plastika

Thermosetting plastics (thermosets) refer to a range of polymer materials that cure, through the addition of energy, to a stronger form. The energy may be in the form of heat (rubber), through a chemical reaction (two part epoxy), or irradiation. Thermoset materials are usually liquid or malleable prior to curing, and designed to be molded into their final form, or used as adhesive.

Thermoset polymer resins transformed into plastics or rubbers by cross-linking into a rigid, 3-D structure. A thermoset material cannot be melted and re-molded after it is cured.

work    →   rad

Work is the energy required to move an object against an opposing force. Work is usually expressed as a force times a displacement.

When a constant force F acts on a point-like object while the object moves through a displacement s, the force does work W on the object. If force and displacement are at a constant angle Θ to each other, the work is expressed by the scalar product of these two vectors:

When the force F on a point-like object is not constant that is, it depends on the position of the object, the work done by force while object moves from initial position with coordinates (x_i, y_i, z_i) to final position with coordinates (x_f, y_f, z_f)is given by expression:

Where F_x, F_y and F_z are scalar components of the force.

SI unit for work is joule (J); 1 J = 1 Nm = 1 kg m² s^-2. The electron-volt (eV) is commonly used in atomic and nuclear physics.

Zeeman effect    →   Zeemanov efekt

Zeeman effect is the splitting of the lines in a spectrum when the source of the spectrum is exposed to a magnetic field. The effect was discovered in 1896 by the Dutch physicist Pieter Zeeman (1865-1943) as a broadening of the yellow D-lines of sodium in a flame held between strong magnetic poles.

The Zeeman effect has helped physicists determine the energy levels in atoms. In astronomy, the Zeeman effect is used in measuring the magnetic field of the Sun and of other stars.

Lennard-Jones potential    →   Lennard-Jonesov potencijal

The Lennard-Jones potential (or 12-6 potential) is a mathematically simple model that describes the interaction between two non-bonded and uncharged atoms (known as the van der Waals interaction). It was first proposed in 1924 by British physicist Sir John Edward Lennard-Jones (1894-1954). The Lennard-Jones Potential is given by the following equation

where V is the intermolecular potential between the two atoms or molecules, ε is the well depth and a measure of how strongly the two particles attract each other, σ is the distance at which the intermolecular potential between the two particles is zero, r is the distance of separation between centres of both particles.