Give reasons:
(i) Gold is found in nature as an element in the free state.
(ii) Iron sheets are galvanised before use.
(iii) Aluminium does not corrode easily. (iv) Steel is used to make cooking vessels.
Answers
Answer:
(i) Platinum and gold have high negative values of oxidation potentials. they do no possesses tendency to form positive ions at all . therefore, they do not occur in combined state unlike other metals and hence, they occur free in nature
(ii) The iron sheets are galvanized before use to prevent it from rusting. the iron sheets are dipped into the solution containing zinc qnd this zinc makes a thin layer on iron. it prevents the iron rusting and corrosion in two ways . it being more reactive than iron reacts first and under goes oxidation
(iii) Aluminium does not rust (corrode) because its surface us protected by a natural layer od of aluminium oxide . this prevents the metal below from coming into contact with air (containing oxygen) . unlike rust which can flake off the surface of iron and steel objects , the layer of aluminium oxide does not flake off
(iv) Most of the cooking vessels are made of metals. as cooking is a process that involves using heat, the vessel of cooking should be a tolerant of rapid changes in temperature. to be heat tolerant that material should have a very high melting point.