Glossary - Chemistry (Intro) - Il mondo come lo vediamo noi
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1 1 Glossary - Chemistry (Intro) Chemistry: The science that studies the properties of substances and how substances react with one another. Chemistry in contrast to physics is involved with the change of the outer electron-layers only, whereas physics involves the state of the nucleus as well. C. Energy: Energy stored within the structural units of chemical substances [J], see thermochemistry. C. Equation: An equation that uses chemical symbols to show what happens during a chemical reaction. C. Equilibrium: A state in which the rates of the forward and reverse reactions are equal. C. Formula: An expression showing the chemical composition of a compound in terms of the symbols for the atoms of the elements involved; see stoichiometry. C. Kinetics: The area of chemistry concerned with the speeds, or rates, at which chemical reactions occur; see stoichiometry. C. Property: Any property of a substance that cannot be studies without converting the substance into some other substances. Electro C.: The branch of chemistry that deals with the use of chemical reactions to produce electricity, the relative strengths of oxidizing and reducing agents, and the use of electricity to produce chemical change. Inorganic C.: The branch of chemistry that deals with compounds other than organic compounds. Organic C.: The branch of chemistry that deals with carbon and usually hydrogen compounds, excluding carbohydrates. Nuclear C.: The study of the structure of nuclei, of the changes this structure undergoes, and of the consequences of those changes for chemistry. Thermo C.: The study of heat changes in chemical reactions. Closed System: A system that allows the exchange of energy (usually in the form of heat) but not mass with its surrounding environment. Cohesion: The intermolecular attraction between like molecules (see physics - matter). Compound: 1) A specific combination of elements that can be separated into elements by using chemical techniques. 2) A substance consisting of atoms of two or more elements in a defined ratio. Distillation: The separation of a mixture by making use of the different volatilities of its compounds. Fractional D.: Separation of the components of a liquid mixture by repeated distillation, by making use of their differing volatilities. Element: A substance that cannot be separated into simpler substances by chemical means; e.g.: C, N, Fe, Na, etc. Notation of E.: Elements of the periodic table are assigned with a mass- and atomic number to quantify its number of protons (Z) and number of protons and neutrons (A); see chemistry atom. Representative E.: Elements in groups 1A through 7A, all of which have incompletely filled s or p subshell of highest principal quantum number. Experiment: A test carried out under carefully controlled conditions. Group: The elements in a vertical column of the periodic table - see period. Isomere: (Gk. isos, equal; meros, part) One of a group of compounds identical in atomic composition but differing in structural arrangement; e.g., glucose and fructose Matter: Anything that occupies space and possesses mass. Properties of M.: 1) A physical property can be measured and observed without changing the composition or identity of a substance. 2) in order to observe it, a chemical change has to be carried out; e.g.: hydrogen burns with oxygen to form water - see chemistry-solid -liquid, -gas. • Extensive P.o.M.: A physical property of a substance that depends of the size of the sample; e.g.: mass, internal energy, enthalpy, entropy, etc. • Intensive P.o.M.: A physical property of a substance that is dependent of the size of the sample; e.g.: density, molar volume, temperature, etc. Mineral: A naturally occurring substance with a range of chemical composition. Mixture: A type of matter that consists of more than one substance and may be separated into components by making use of the different physical properties. Heterogeneous M.: A mixture in which the individual components, although mixed together, lie in distinct regions, even on a microscopic scale; e.g.: a mixture of sand and sugar, ect. Homogenous M.: A mixture in which the individual components are uniformly mixed, even on an atomic scale; e.g.: air, solutions, etc. Ore: The natural mineral source of a metal; e.g.: Fe 2 O 3 , hematite; etc.
