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plutonium
(Encyclopedia)plutonium plo͞otōˈnēəm [key], radioactive chemical element; symbol Pu; at. no. 94; mass no. of most stable isotope 244; m.p. 641℃; b.p. 3,232℃; sp. gr. 19.84 at 20℃; valence +3, +4, +5, or ...Ordovician period
(Encyclopedia)Ordovician period ôrdəvĭshˈən [key] [from the Ordovices, ancient tribe of N Wales], second period of the Paleozoic era of geologic time (see Geologic Timescale, tablegeologic timescale, table) fr...soap
(Encyclopedia)soap, a cleansing agent. It cleanses by lowering the surface tension of water, by emulsifying grease, and by absorbing dirt into the foam. Ancient peoples are believed to have employed wood ashes and ...teeth
(Encyclopedia) CE5 A. Upper and lower teeth of an adult B. Cross section of a molar teeth, hard, calcified structures embedded in the bone of the jaws of vertebrates that perform the primary function of masticat...acids and bases
(Encyclopedia)acids and bases, two related classes of chemicals; the members of each class have a number of common properties when dissolved in a solvent, usually water. Another theory that provides a very broad ...carbon
(Encyclopedia) CE5 The three solid forms of pure carbon: In the diamond crystal each carbon atom is surrounded symmetrically by four other carbons (at each of the four corners of a tetrahedron). In the graphite c...interstellar matter
(Encyclopedia)interstellar matter, matter in a galaxy between the stars, known also as the interstellar medium. The interstellar gas, which constitutes about 99% of the interstellar matter, consists mostly of hyd...cheese
(Encyclopedia)cheese, food known from ancient times and consisting of the curd of milk separated from the whey. The numerous cheeses (often named for their place of origin) depend for their distinctive qualities ...endocrine system
(Encyclopedia)endocrine system ĕnˈdəkrĭn [key], body control system composed of a group of glands that maintain a stable internal environment by producing chemical regulatory substances called hormones. The end...sodium chloride
(Encyclopedia)sodium chloride, NaCl, common salt. Salt is important in many ways. It is an essential part of the diet of both humans and animals and is a part of most animal fluids, such as blood, sweat, and te...Browse by Subject
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