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Question
Give reasons for the following:
(a) Steel is used to make cooking vessels.
(b) Gold is found in nature as an element in the free state.
(c) Titanium is used to make the body of a spacecraft.
(d) An alloy of gold is used in dentistry.
(e) Silver is used for making mirrors.
(f) Iron sheets are galvanised before use.
(g) Aluminium does not corrode easily.
(a) Steel is used to make cooking vessels.
(b) Gold is found in nature as an element in the free state.
(c) Titanium is used to make the body of a spacecraft.
(d) An alloy of gold is used in dentistry.
(e) Silver is used for making mirrors.
(f) Iron sheets are galvanised before use.
(g) Aluminium does not corrode easily.
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Solution
(a) Steel is an alloy of iron, but it has resistance to corrosion. Thus, it is used to make cooking vessels.
(b) Gold is a non-reactive metal and does not react with atmospheric gases and water. Therefore, gold is found in nature as an element in the free state.
(c) Titanium is a light metal with high strength. It can sustain very high temperatures. Hence, titanium is used to make the body of a spacecraft.
(d) Gold is a non-poisonous, safe metal. It does not react with acids. It is highly malleable and ductile in nature. Thus, it is suitable for use in dentistry.
(e) Among the known metals, silver has the best reflecting capability. Therefore, it is used for making mirrors.
(f) Iron is a highly reactive metal. It reacts with moist air (water + oxygen) and forms iron oxide, a reddish-brown powdered layer called rust, on its surface. Corrosion of iron is called rusting. To avoid this, iron sheets are galvanised (iron objects are coated with zinc layer) before use.
(g) Aluminium is a highly reactive metal. It reacts easily with oxygen present in the air, forming a layer of aluminium oxide on its surface. This layer of aluminium oxide sticks to the metal and protects it. Thus, aluminium articles become unreactive towards air and water, and do not corrode easily due to the presence of this strong aluminium oxide layer over them.
(b) Gold is a non-reactive metal and does not react with atmospheric gases and water. Therefore, gold is found in nature as an element in the free state.
(c) Titanium is a light metal with high strength. It can sustain very high temperatures. Hence, titanium is used to make the body of a spacecraft.
(d) Gold is a non-poisonous, safe metal. It does not react with acids. It is highly malleable and ductile in nature. Thus, it is suitable for use in dentistry.
(e) Among the known metals, silver has the best reflecting capability. Therefore, it is used for making mirrors.
(f) Iron is a highly reactive metal. It reacts with moist air (water + oxygen) and forms iron oxide, a reddish-brown powdered layer called rust, on its surface. Corrosion of iron is called rusting. To avoid this, iron sheets are galvanised (iron objects are coated with zinc layer) before use.
(g) Aluminium is a highly reactive metal. It reacts easily with oxygen present in the air, forming a layer of aluminium oxide on its surface. This layer of aluminium oxide sticks to the metal and protects it. Thus, aluminium articles become unreactive towards air and water, and do not corrode easily due to the presence of this strong aluminium oxide layer over them.
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