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The increase in the entropy of a substance as it goes from a perfectly ordered crystalline form at 0 °K (where its entropy is zero) to the temperature in question.

Entropy is a measure of the “dilution” of thermal energy.

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Binary Acid

A binary compound in which H is bonded to one or more of the more electronegative nonmetals.

Foam

Colloidal suspension of a gas in a liquid.

Electromotive Series

The relative order of tendencies for elements and their simple ions to act as oxidizing or reducing agents, also called the activity series.

Coulometry

The quantitative application of Faraday's Law to the analysis of materials. The current and time are the usual variables measured.

Fractional Distillation

The process in which a fractioning column is used in distillation apparatus to separate components of a liquid mixture that have different boiling points.

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Control Rods

Rods of materials such as cadmium or boron steel that act as neutron obsorbers (not merely moderaters) used in nuclear reactors to control neutron fluxes and therfore rates of fission.

Reversible Reaction

Reactions that do not go to completion and occur in both the forward and reverse direction.

xenon hexafluoride

A colorless, crystalline compound, XeF6, that melts at 50°C to a yellow liquid, and boils at 75°C.

Isotopes

Two or more forms of atoms of the same element with different masses, atoms containing the same number of protons but different numbers of neutrons.