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A substance of a known high degree of purity that undergoes one invariable reaction with the other reactant of interest.

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Second Law of Thermodynamics

The universe tends toward a state of greater diorder in spontaneous processes.

Zone Refining

A method of purifying a bar of metal by passing it through an induction heater, this causes impurties to move along a melted portion. This method applies the fact when a metal crystallizes on cooling, impurities are automatically expelled as they do not form part of the crystal.

Equilibrium or Chemical Equilibrium

A state of dynamic balance in which the rates of forward and reverse reactions are equal, the state of a system when neither forward or reverse reaction is thermodynamically favored.


A small, calibrated electroscope worn by laboratory personnel and designated to detect and measure incident ionizing radiation or chemical exposure.


A favourable interaction of two electrons with opposite m , values in the same orbital.

Molecular Geometry

The arrangement of atoms (not lone pairs of electrons) around a central atom of a molecule or polyatomic ion.


The amount of heat required to raise the temperature of one gram of water from 14.5°C to 15.5°C. 1 calorie = 4.184 joules.


Discovered : by Henry Cavendish in 1766.
Isolated in London, UK.
Origin : The name is derived from the Greek ‘hydro genes’, meaning water forming.
Description :A colourless, odourless gas that burns and can form an explosive mixture with air. It is currently manufactured from methane gas, but is also produced by the electrolysis of water and aqueous salts. The gas is used to make such key materials as ammonia, cyclohexane and methanol, which are intermediates in the production of fertilisers, plastics and pharmaceuticals. Some see hydrogen gas as the clean fuel of the future - generated from water and returning to water when it is oxidised. Hydrogen-powered fuel cells are increasingly being seen as pollution-free sources of energy.

yttrium metal

Any of a subgroup of rare-earth elements, of which the cerium and terbium metals comprise the other two subgroups.

Fast Neutron

A neutron ejected at high kinetic energy in a nuclear reaction.