Which non-metal is a good conductor of electricity?

The correct answer is C, zinc. Calamine is zinc carbonate, and since it is a carbonate ore it is converted to the oxide by calcination, that is by heating in the absence of air, before being reduced to the metal. The other important ore of zinc is zinc blende, which is the sulphide and is roasted rather than calcined. Option A is wrong because the chief ore of tin is cassiterite, the oxide. Option B is wrong because magnesium is obtained from magnesite, dolomite and from sea water as its chloride. Option D is wrong because copper comes mainly from copper pyrites, also called chalcopyrite, and from cuprite. A pair of definitions is worth keeping ready for this topic: calcination is heating a carbonate ore without air, while roasting is heating a sulphide ore in air, and both give the oxide.

The correct answer is B, silver. Silver is an element, a pure metal with its own place in the periodic table, so it cannot be an alloy; an alloy is a homogeneous mixture of two or more metals, or of a metal with a non-metal such as carbon. Option A, solder, is an alloy of lead and tin, valued for its low melting point when joining electrical wires. Option C, bronze, is an alloy of copper and tin, the metal that gave its name to an age of human history. Option D, brass, is an alloy of copper and zinc, used for utensils, fittings and musical instruments. The trap here is German silver, which contains copper, zinc and nickel and no silver at all, so it is an alloy despite its name, while silver itself is not.

The correct answer is A, gold. Ductility is the property of being drawn into a wire, and gold is the most ductile metal known; it is also the most malleable, so a very small quantity can be beaten into an extremely thin sheet or drawn into a very long wire. Option C, silver, is the next most ductile and is the best conductor of both heat and electricity, which is why it is easy to confuse the two superlatives; remember that silver leads in conduction while gold leads in ductility and malleability. Option B, copper, is ductile enough to be drawn into the wires used in household wiring, but far less so than gold. Option D, iron, is ductile when hot but comparatively hard and is valued for strength rather than for being drawn out.

The correct answer is D, copper and zinc. Brass takes the workability of copper and the hardness of zinc, resists corrosion and is easy to cast, which is why it is used for utensils, locks, taps, fittings and wind instruments. Option A, copper and tin, is bronze, and the brass and bronze pair is the single most frequently confused item in this chapter, so fix zinc with brass and tin with bronze. Option B, copper and nickel, is cupronickel, used in coins and in condenser tubes. Option C, copper and iron, is not a standard alloy of this kind, though iron and copper occur together in the ore copper pyrites. Related alloys are worth learning with these: German silver is copper, zinc and nickel; gun metal is copper, tin and zinc; and bell metal is copper with a larger proportion of tin.

The correct answer is B, mercury. Mercury is the only metal that is liquid at ordinary room temperature, which is why it was long used in thermometers and barometers; it is also the metal that forms amalgams, alloys in which mercury is one component. Option A, sodium, is a solid, although a very soft one that can be cut with a knife and must be stored under kerosene because it reacts violently with air and water. Option C, lead, is a soft, dense solid with a low melting point, but it is far from liquid at room temperature. Option D, tungsten, has the highest melting point of the metals, which is exactly why it is used for the filament of an incandescent lamp. Among non-metals, bromine is the one that is liquid at room temperature, and gallium and caesium are metals that melt in the warmth of the hand.