Pure iron is soft and stretches easily when hot
(a) How does this property of iron change when:
(i) small amount of carbon is mixed with it?
(ii) nickel and chromium are mixed with it?
(b) Define an alloy. How is an alloy prepared?
(c) An alloy has low melting point and is therefore used for electrical fuse. Name the alloy and write its constituents.

Explanation

(i) When small amount of carbon is mixed with iron, it becomes an alloy that is called steel. The carbon present in pig iron makes it brittle and therefore, it cannot be used for structural purposes.
(ii) When iron is mixed with chromium and nickel, then stainless steel is obtained. Stainless steel does not rust at all.
Stainless steel is used for making cooking utensils, knives, scissors and surgical instruments etc.
(b) Alloy: An alloy is a homogeneous mixture of two or more metals or a metal and a non-metal. An alloy is generally prepared by heating the mixture of the metal (or metal and non-metals) to the molten state and then cooling the mixture to solidify at room temperature.
(c) A fuse wire is made up of an alloy of tin and copper or tin and lead (composition: 63% tin and 37% lead).