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Describes processes that release heat energy.

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Saponification

Hydrolysis of esters in the presence of strong soluable bases.

Conduction Band

A partially filled band or a band of vacant energy levels just higher in energy than a filled band, a band within which, or into which, electrons must be promoted to allow electrical conduction to occur in a solid.

Hybridization

Mixing a set of atomic orbitals to form a new set of atomic orbitals with the same total electron capacity and with properties and energies intermediate between those of the original unhybridized orbitals.

Hydrogen

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.

ytterbium

A rare metallic element found in gadolinite and forming compounds resembling those of yttrium. Symbol: Yb, at. wt.: 173.04, at. no.: 70, sp. gr.: 6.96. Cf."rare-earth element."

 

Frasch Process

Method by which elemental sulfur is mined or extracted. Sulfur is melted with superheated water (at 170°C under high pressure) and forced to the surface of the earth as a slurry.

 

Flash Point

The temperature at which a liquid will yield enough flamable vapour to ignite. There are various recognized industrial testing methods, therefore the method used must be stated.

Avogadro's Law

At the same temperature and pressure, equal volumes of all gases contain the same number of molecules.

Distilland

The material in a distillation apparatus that is to be distilled.

Dumas Method

A method used to determine the molecular weights of volatile liquids.