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SCIENCE Chapter 4: Materials: Metals and Non-Metals
(1) MATERIALS: METALS AND NON-METALS 04 Materials: Metals and Non-Metals Elements can be divided into metals and non-metals on the basis of their physical and chemical properties. Metals • The elements which are hard, shiny can be beaten into sheets, drawn into wires and are good conductor of heat and electricity are generally metals. For example: iron, copper, gold etc. • In nature most metals occur in the combined state as minerals and they are reactive. • Only a few unreactive metals like gold, silver, platinum are found as free metals in the earth’s crust. • Minerals from which metals can be profitably extracted are called ores. For example: calcium occurs in limestone (calcium carbonate) or iron in the ore haematite. Non-metals • The elements which are brittle, dull cannot be beaten into sheets or drawn into wires and are poor conductors of heat and electricity are generally non-metals. • For example: oxygen and nitrogen occur in free state in air and in combined state in earth’s crust. Sulphur occurs both in free and the combined state in earth’s crust.
(2) MATERIALS: METALS AND NON-METALS 04 • The noble gases, helium, neon, argon, krypton, xenon occurs only in Free State. Physical Properties of Metals and Non-metals Physical Property Metals Non-metals Malleability • Metals are malleable. • The property which allows metals to be hammered into thin sheets is called malleability. Example: Aluminium metal can be hammered into a thin aluminium foil. • Non-metals are not malleable. Example: Carbon (i.e. coal) breaks into smaller pieces when hammered. • The property due to which non-metals break on hammering them is called brittleness. Ductility • Metals are ductile, i.e. they can be drawn into thin wires. • The property which allows the metals to be drawn into wires is called ductility. • Non-metals are not ductile, i.e. they cannot be drawn into wires. • Sulphur and phosphorus break into pieces on stretching and do not form wires. Conductivity • Metals are good conductors of heat and electricity. • Copper, silver, gold, aluminium and iron are good conductors of heat and electricity. • Non-metals are poor conductors of heat and electricity, i.e. they do not allow heat and electricity to pass through them. Sonority • Metals are sonorous, i.e. they produce a ringing sound when struck (sonorous means capable of producing a ringing sound). • Solid non-metals do not make a ringing sound when we strike them. Thus, we can say that non-metals are not sonorous.
(3) MATERIALS: METALS AND NON-METALS 04 Lustre • Metals have a shiny appearance. So, we can say that metals are lustrous or shiny. • Non-metals are dull and not lustrous.