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Chapter 7, Metals, •, •, •, •, •, •, •, •, •, •, •, •, , Metals have some general characteristics., They are thermal conductors and electrical conductors., Metals can be beaten into thin sheets by hammering (malleability)., Metals can be drawn into thin fine wires (ductility). Hardness is yet another property of metals., The surface newly formed when metals are cut, has a shining appearance (metallic lustre)., Metals have the ability to produce sound when tapped with a hard material (sonority)., Metals have high melting point and density., Making use of these characteristics of metals they are used in various purposes., Metals are used to make electric wire because of its electrical conductivity., They are used to make utensils as the metals are thermal conductors., Metals have high density. So they are used to make farming tools., The sonority of metal is utilised to make bells in the places of worship., , There are some similarities in chemical properties of metals., •, •, •, •, •, •, •, •, , Almost all the metals get tarnished when they are exposed to air for some days. This is because, they are react with various components of atmospheric air., Metals react with water. Metals like sodium, potassium etc reacts with cold water to liberate, hydrogen., Zinc, aluminium, iron, magnesium etc. react with dilute hydrochloric acid to form hydrogen, along with salt of metal. There are some metals which does not react with acids.Ex : Copper., As the metals react with atmospheric air and water vapour causes corrosion., The iron reacts with air and water vapour. So it undergoes corrosion., Verdigris is formed on copper by reacting with the components of air., Iron and a number of other metals react with different components of air and form new, products. This process is known as corrosion of metals., Painting on the metal, electroplating with non corrosive metals are some methods to prevent, the corrosion.