Write any two purposes of making an alloy with one example each.
a) To improve the hardness of metal: - E.g. Pure gold & silver are soft, hence they are hardened by the addition of a small amount of copper in them. b) To lower the melting point: - Pure metals are having high melting point can be lowered by of alloying elements. E.g. Wood‟s metal is an alloy of Bi, Pb, Sn, Cd. It has the M.P. 710C which is much lower than those of its constituents. c) To increase the tensile strength: - E.g. The addition of 1% carbon increase the tensile strength of pure iron by about 10 times. d)To increase corrosion resistance:- E.g. Pure iron is corroded fastly but its alloy stainless steel resist corrosion. e) To get good castings:- E.g. Bronze (an alloy of Cu & Zn) possess good casting property. f) To modify color: - E.g. Brass is an alloy of copper (red) and Zinc (Silvery white) and is yellow in color. g) To reduce malleability and ductility :- E.g. a small amount of copper is added to gold and silver to reduce their malleability and ductility. h) To change (alter) chemical reactivity: E.g Sodium is highly reactive metal but when it is alloyed with mercury to form an alloy called sodium – amalgam (Na-Hg), it becomes less reactive.