Gibbs free energy (G) is an important function in chemical thermodynamics, defined by
where H is the enthalpy, S the entropy, and T the thermodynamic temperature. Gibbs free energy is the energy liberated or absorbed in a reversible process at constant pressure and constant temperature. Sometimes called Gibbs energy and, in older literature, simply free energy.
Changes in Gibbs free energy, ΔG, are useful in indicating the conditions under which a chemical reaction will occur. If ΔG is negative the reaction will proceed spontaneously to equilibrium. In equilibrium position ΔG = 0.
Kinetic energy (Ek) 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.
In the special theory of relativity Einstein demonstrated that neither mass nor energy were conserved separately, but that they could be traded one for the other and only the total "mass-energy" was conserved. The relationship between the mass and the energy is contained in what is probably the most famous equation in science,
Where m is the mass of the object and c is the velocity of light. Cockcroft and Walton (1932) are routinely credited with the first experimental verification of mass-energy equivalence.
Potential energy (Ep) 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.
Absolute zero is theoretically, the lowest attainable temperature. It is the energy at which the kinetic energy of atom and molecules is minimal and is equivalent to -273.15 °C.
For any ionising radiation, absorbed dose (D) is the mean energy imparted to an element of irradiated matter divided by the mass of that element.
Accelerator is a device (machine) used for acceleration of charged particles (protons, deuterons, α-particles). Particles are accelerated under the influence of an electric field and with the help of a magnetic field are kept inside a certain space. When the particles reach enough acceleration (that is sufficient energy), they are directed on a target we wish to bomb. Best known types cyclotron, synchrotron, betatron.
Accelerator is a substance that increases the rate of chemical reaction, i.e. a catalyst.
Activated complex is an intermediate structure formed in the conversion of reactants to products. The activated complex is the structure at the maximum energy point along the reaction path; the activation energy is the difference between the energies of the activated complex and the reactants.
Active site is a pocket or crevice on an enzyme molecule that fits reactant molecules like a hand in a glove. The active site lowers the activation energy for reaction
Generalic, Eni. "Undispersed energy." Croatian-English Chemistry Dictionary & Glossary. 29 June 2022. KTF-Split. {Date of access}. <https://glossary.periodni.com>.
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