Ans: Iron displaces copper from CuSO₄ because it is more reactive. Fe + CuSO₄ → FeSO₄ + Cu. The blue color of the solution fades and turns green.

Ans: Fe₂O₃ + 2Al → Al₂O₃ + 2Fe + heat. Al reduces iron oxide. Used for welding railway tracks and joining metals.

Ans: Sodium is extremely reactive. It reacts vigorously with air (oxygen and moisture). Storing in kerosene prevents it from coming in contact with air and water, ensuring safety.

Ans: Anode: Impure copper. Cathode: Pure copper. Electrolyte: Acidified CuSO₄. On passing current, pure copper from anode dissolves and deposits on cathode.

Ans: Galvanisation is the process of coating iron with a thin layer of zinc. Zinc is more reactive than iron; it oxidises preferentially and forms ZnO layer that prevents further corrosion. Even if the zinc coat is scratched, the iron underneath remains protected because zinc corrodes first.

Ans: An alloy is a homogeneous mixture of two or more metals. (1) Brass: Cu + Zn (used in decorative items). (2) Bronze: Cu + Sn (used in making statues/medals).

Ans: (i) 2Al + 3H₂O(g) → Al₂O₃ + 3H₂. (ii) 3Fe + 4H₂O(g) → Fe₃O₄ + 4H₂.

Ans: Black copper(II) oxide is formed: 2Cu + O₂ → 2CuO. It is a basic oxide.

Ans: Aluminium is the reducing agent in the thermite reaction: Fe₂O₃ + 2Al → 2Fe + Al₂O₃ + heat.

Ans: Ionic compounds have strong electrostatic forces of attraction between the oppositely charged ions in the crystal lattice. A large amount of heat energy is required to overcome these forces, so melting points are high.

Ans: It is easier to obtain a metal from its oxide than from its sulphide or carbonate. Sulphide ores are roasted and carbonate ores are calcined to give oxides, which can then be reduced by carbon or other reducing agents.

Ans: Aqua regia is a freshly prepared mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio 3 : 1. It is a powerful oxidising mixture that can dissolve gold and platinum, which are not attacked by either acid alone.

Ans: Magnesium (2, 8, 2) has two valence electrons and oxygen (2, 6) has six. Magnesium loses 2 electrons to form Mg²⁺ (2, 8) and oxygen gains 2 electrons to form O²⁻ (2, 8). The oppositely charged ions Mg²⁺ and O²⁻ attract each other and form an ionic bond, giving MgO.

Ans: (1) Painting or oiling/greasing the surface to keep out air and moisture. (2) Galvanisation: coating iron with a thin layer of zinc, which protects even if the coating is scratched. (3) Alloying: for example stainless steel from iron with nickel and chromium. Other methods include tin plating and chrome plating.

Ans: (1) Metals are lustrous; non-metals are dull (except iodine and graphite). (2) Metals are malleable and ductile; non-metals are brittle. (3) Metals are good conductors of heat and electricity; non-metals are poor (except graphite). (4) Metals usually have high melting points and densities; non-metals have low. (5) Metal oxides are basic (some amphoteric); non-metal oxides are acidic or neutral. (6) Metals form positive ions by losing electrons; non-metals form negative ions by gaining electrons.