Science / Chemistry Glossary

Ammonia: Pure NH3 is a colorless gas with a sharp, characteristic odor. It is easily liquified by pressure, and is very soluble in water. Ammonia acts as a weak base. Aqueous solutions of ammonia are . . . View Full Definition

Ammonium Ion: (NH4+) ammonium NH4+ is a cation formed by neutralization of ammonia, which acts as a weak base.

Amorphous: A solid that does not have a repeating, regular three-dimensional arrangement of atoms, molecules, or ions.

Amperage: The amount of charge moved per second by an electric current, measured in amperes.

Ampere: (A) amp. The SI unit of electric current, equal to flow of 1 coulomb of charge per second. An ampere is the amount of current necessary to produce a force of 0.2 micronewtons per meter betwe . . . View Full Definition

Amperometry: Determining the concentration of a material in a sample by measuring electric current.

Amphi: A prefix used to name certain members of a series of geometric isomers or stereoisomers.

Amphiprotic Solvent: Solvents that exhibit both acidic and basic properties; amphiprotic solvents undergo autoprotolysis. Examples are water, ammonia, and ethanol.

Amphoteric: A substance that can act as either an acid or a base in a reaction. For example, aluminum hydroxide can neutralize mineral acids ( Al(OH)3 + 3 HCl = AlCl3 + 3 H2O ) or strong bases ( Al(OH)3 . . . View Full Definition

Amplitude: The displacement of a wave from zero. The maximum amplitude for a wave is the height of a peak or the depth of a trough, relative to the zero displacement line.

Amylopectin: A form of starch made of glucose molecules linked in a branching pattern.

Amylose: A form of starch made of long, unbranched chains of alpha-D-glucose molecules.

Analysis: Chemical analysis. Determination of the composition of a sample.

Analyte: An analyte is the sample constituent whose concentration is sought in a chemical analysis.

Angstrom: A non-SI unit of length used to express wavelengths of light, bond lengths, and molecular sizes. 1 Å = 10-10 m = 10-8 cm.

Angular Momentum Quantum Number: (ell) azimuthal quantum number; orbital angular momentum quantum number. A quantum number that labels the subshells of an atom. Sometimes called the orbital angular momentum quantum number, . . . View Full Definition

Anhydrous: A compound with all water removed, especially water of hydration. For example, strongly heating copper(II) sulfate pentahydrate (CuSO4·5H2O) produces anhydrous copper(II) sulfate (CuSO4).

Anion: An anion is a negatively charged ion. Nonmetals typically form anions.

Anode: The electrode at which oxidation occurs in a cell. Anions migrate to the anode.

Anodize: To coat a metal with a protective film by electrolysis.

Anthocyanin: A family of pigments that give flowers, fruits, and leaves of some plants their red or blue coloring. Anthocyanins consist of sugar molecules bound to a benzopyrylium salt (called anthocyani . . . View Full Definition

Antibonding Orbital: A molecular orbital that can be described as the result of destructive interference of atomic orbitals on bonded atoms. Antibonding orbitals have energies higher than the energies its consti . . . View Full Definition

Antichlor: A chemical compound that reacts with chlorine-based bleaches to stop the bleaching. Thiosulfate compounds are antichlors.

Antioxidant: Antioxidants are compounds that slow oxidation processes that degrade foods, fuels, rubber, plastic, and other materials. Antioxidants like butylated hydroxyanisole (BHA) are added to food t . . . View Full Definition

Antiozonant: Substances that reverse or prevent severe oxidation by ozone. Antiozonants are added to rubber to prevent them from becoming brittle as atmospheric ozone reacts with them over time. Aromatic . . . View Full Definition

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