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Collision between molecules resulting in a reaction, one in which the molecules collide with proper relative orientations and sufficient energy to react.

 

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Valence Electrons

Outermost electrons of atoms, usually those involved in bonding.

Chain Termination Step

The combination of two radicals, which removes the reactive species that propagate the change reaction.

Amine

Derivatives of ammonia in which one or more hydrogen atoms have been replaced by organic groups.

Condensation

Liquefaction of vapor.

Heat of Condensation

The amount of heat that must be removed from one gram of a vapor at it's condensation point to condense the vapour with no change in temperature.

Standard Molar Enthalphy of Formation

The amount of heat absorbed in the formation of one mole of a substance in a specified state from its elements in their standard states.

Melting Point

The temperature at which liquid and solid coexist in equilibrium, also the freezing point.

Flotation

Method by which hydrophobic (water-repelling) particles of an ore are separated from hydrophilic (water-attracting) particles of a metallurgical pretreatment process.

Domain

A cluster of atoms in a ferromagnetic substance, all of which align in the same direction in the presence of an external magnetic field.

Helium

Discovered : by Sir William Ramsay in London, and independently by P.T. Cleve and N.A. Langlet in Uppsala, Sweden in 1895.
Origin : The name is derived from the Greek ‘helios’,sun.
Description :A colourless, odourless gas that is totally unreactive. It is extracted from natural gas wells, some of which contain gas that is 7% helium. It is used in deep sea diving for balloons and, as liquid helium, for low temperature research. The Earth’s atmosphere contains 5 parts per million by volume, totalling 400 million tons, but it is not worth extracting it from this source at present.
Atomic No:2 MAss No:4