CBSE Class 10 Science 2020 · Paper 31/4/3 · Question 26

(a) An alloy is a homogeneous mixture of two or more metals, or of a metal and a non-metal, in definite proportions. An amalgam is an alloy in which one of the metals is mercury. The alloy used for welding electric wires together is solder, whose constituents are lead ($\text{Pb}$) and tin ($\text{Sn}$); it has a low melting point. (b) (i) Brass: copper ($\text{Cu}$) and zinc ($\text{Zn}$). It has a much lower electrical conductivity than copper. (ii) Stainless steel: iron ($\text{Fe}$), chromium ($\text{Cr}$) and nickel ($\text{Ni}$). It does not rust (corrode) easily, whereas iron rusts. (iii) Bronze: copper ($\text{Cu}$) and tin ($\text{Sn}$). It has a much lower electrical conductivity than copper. Another correct difference in each case is greater hardness: brass and bronze are harder than copper, and stainless steel is harder than pure iron.