chemical bonding

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Matter, in science, general term applied to anything that occupies space and has the attributes of gravity and inertia. In classical physics, matter and energy were considered two separate concepts that lay at the root of all physical phenomena. Modern physicists, however, have shown that it is possible to transform matter into energy and energy into matter and have thus broken down the classical distinction between the two concepts (see Mass; Relativity). When dealing with a large number of phenomena, however, such as motion, the behaviour of liquids and gases, and heat, scientists find it simpler and more convenient to continue treating matter and energy as separate entities. Microsoft® Encarta® Encyclopedia. © 1993-2001 Microsoft Corporation. All rights reserved.

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Certain elementary particles combine to form atoms; in turn, atoms combine to form molecules. The properties of individual molecules and their distribution and arrangement give to matter in all its forms various qualities such as mass, hardness, viscosity, fluidity, colour, taste, electrical resistivity, and heat conductivity, among others. See Antimatter; Chemistry; Electricity; Heat; Matter, States of. Microsoft® Encarta® Encyclopedia. © 1993-2001 Microsoft Corporation. All rights reserved.

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In philosophy, matter has been generally regarded as the raw material of the physical world, although certain philosophers of the school of idealism, such as the Irish philosopher George Berkeley, denied that matter exists independently of the mind. See Greek Philosophy; Kant, Immanuel. Most modern philosophers accept the scientific definition of matter. Microsoft® Encarta® Encyclopedia. © 1993-2001 Microsoft Corporation. All rights reserved.

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Most substances are solid at low temperatures, liquid at medium temperatures, and gaseous at high temperatures, but the states are not always distinct. The temperature at which any given substance changes from solid to liquid is its melting point, and the temperature at which it changes from liquid to gas is its boiling point; (see Freezing Point). The range of melting and boiling points varies widely. Helium remains a gas down to -269° C (-452° F), and tungsten remains a solid up to about 3370° C (about 6100° F). Microsoft® Encarta® Encyclopedia. © 1993-2001 Microsoft Corporation. All rights reserved.