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Home :Glossary

Glossary: U


ultraviolet light. ultraviolet; ultraviolet radiation; ultraviolet region; UV.
Electromagnetic radiation* with wavelength longer than that of x-rays* but shorter than that of visible light*. Ultraviolet light can break some chemical bonds and cause cell damage.

uncertainty principle. Heisenberg's uncertainty principle; Heisenberg principle; indeterminancy; indeterminancy principle.
The exact momentum and exact location of a particle cannot be specified. Werner Heisenberg stated that the product of uncertainties in location and momentum measurements can never be smaller than h/4pi, where h is Planck's constant*.

unimolecular reaction.
A reaction that involves isomerization* or decomposition* of a single molecule.

A standard for comparison in measurements. For example, the meter* is a standard length which may be compared to any object to describe its length.

unit cell.
The simplest arrangement of atoms or molecules that regularly repeats in a crystal structure.

universal indicator.
A universal indicator is an indicator* which undergoes several color changes over a wide range of pH*. The color is used to "indicate" pH directly. Universal indicators are usually mixtures of several indicators.

unpaired spin. (spinup) unpaired electron. Compare with paired spin*.
A single electron occupying an orbital*.

unsaturated compound.
An organic compound with molecules containing one or more double bonds.

unsaturated fat. Compare with saturated fat*.
A lipid* containing one or more carbon-carbon double bonds. Unsaturated fats tend to be oily liquids and are obtained from plants.

unsaturated solution. Compare with saturated solution*.
A solution with a concentration lower than its equilibrium solubility*.


General Chemistry Online! Glossary: U

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Last Revised 02/23/18.URL: http://antoine.frostburg.edu/chem/senese/101/glossary/u.shtml