Chemistry Glossary Terms Starting with the Letter U

Chemistry Glossary and Dictionary

Ultraviolet light is invisible, but black lights or UV-lamps also emit some visible violet light.
Ultraviolet light is invisible, but black lights or UV-lamps also emit some visible violet light. Kallemax, wikipedia.org

This chemistry glossary offers definitions for terms which are commonly used in chemistry and chemical engineering. The words start with the letter U.

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ultra high frequency - Ultra high frequency (UHF) is part of the electromagnetic spectrum in the radio waves region with frequencies between 300 and 3000 MHz. Also Known As: decimeter band

ultra low frequency - Ultra low frequency (ULF) is the part of the electromagnetic spectrum with frequencies between 300 and 3000 Hz.

ultraviolet radiation

UN ID

UN number

unimolecular reaction - A unimolecular reaction is a chemical reaction involving only one molecule. Unimolecular reactions are either isomerizations (rearrangement of atoms in the molecule) or a decomposition into two or more pieces.

unit

unit cell - A unit cell is the smallest unit of a crystal, which, if repeated, could generate the whole crystal.

universal gas constant

universal indicator

universal solvent

unpaired electon - An unpaired electron is a single electron occupying an orbital by itself.

unsaturated

unsaturated fat

unsaturated solution

ununhexium - Ununhexium was the placeholder name for the element with atomic number 116, which is now known as livermorium. The symbol for ununhexium is Uuh.

ununoctium - Ununoctium is the placeholder name for the element with atomic number 118.

ununpentium - Ununpentium is the placeholder name for the element with atomic number 115.

The symbol for ununpentium is Uup.

ununquadium - Ununquadium is the placeholder name for the element with atomic number 114. The symbol for ununquadium is Uuq.

ununseptium

ununtrium - Ununtrium is the placeholder name for the element with atomic number 113. The symbol for ununtrium is Uut.

uranium - Uranium is the name for the element with atomic number 92 and is represented by the symbol U.

It is a member of the actinide group.

useful work - The work produced during a change in state in excess of that required to achieve the change. Example: In the reaction H2O (l) → H2O (g), since the volume of the gas is larger than the volume of the liquid, work of expansion will be required to push back the air in order to make room for the water vapor. In this case, the useful work is the work done during the change which is in excess of the work of expansion.

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