If a metal can be drawn into wires relatively easily it is called
Answer: B
A metal that can be drawn out into wire is ductile. Gold is the most ductile of all - a single gram can be drawn into a wire two kilometres long.
A metal that can be hammered into thin sheets is malleable instead. Most metals are both, because their layers of atoms can slide over one another without the bonding breaking.
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A gas used as a disinfectant in drinking water is
Answer: D
Chlorine is used to disinfect drinking water. Added as a gas or as bleaching powder, it forms hypochlorous acid, which destroys bacteria and viruses.
A small residual concentration is left in the supply so that the water stays protected all the way through the distribution pipes.
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Yeast, used in making bread is a
Answer: A
The yeast used in bread-making, Saccharomyces cerevisiae, is a fungus - a single-celled one.
It ferments the sugars in the dough into carbon dioxide and alcohol; the gas raises the loaf and the alcohol evaporates during baking.
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The concept of carbon credit originated from which one of the following?
Answer: B
The concept of the carbon credit came from the Kyoto Protocol of 1997, which set binding emission targets for industrialised countries and created the mechanisms for trading emission allowances between them.
The Rio Earth Summit of 1992 produced the framework convention on climate change, but the tradable credit itself is a Kyoto instrument.
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Thermometer is related to degree in the same way as clock is related to
Answer: C
A thermometer is graduated in degrees as a clock is graduated in hours - in each case the second word names the unit the instrument measures in.
Wall, tower and cock are merely things associated with clocks, not the unit they read.
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The gas predominantly responsible for global warming is
Answer: A
Carbon dioxide is the gas chiefly responsible for global warming. It is not the most powerful greenhouse gas per molecule, but it is released in by far the greatest quantity and persists in the atmosphere for centuries.
Carbon monoxide and nitrogen peroxide are pollutants rather than significant greenhouse gases; nitrous oxide is a greenhouse gas but is present in far smaller amounts.
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Which of the following items will be attracted to the north pole of a permanent magnet by a magnet force?
Answer: B
The north pole of a magnet attracts a piece of iron that is not itself a permanent magnet. The field induces magnetism in the iron, with the near face becoming a south pole, so the two attract.
Two north poles repel each other, and a charged rod carries an electric charge, not a magnetic pole, so a stationary magnet exerts no force on it.
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Crude petroleum is refined by the use of
Answer: B
Sulphuric acid is used in refining crude petroleum, in the treating stages that remove sulphur compounds, unsaturated hydrocarbons and gums from the distilled fractions.
The separation of the crude into fractions is done by distillation; the acid treatment is what cleans those fractions up afterwards.
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The marine animal called dugong which is vulnerable to extinction is a/an
Answer: D
The dugong is a mammal, of the order Sirenia, related to the manatee and distantly to the elephant.
It grazes on sea grass in shallow tropical waters, breathes air and suckles its young. It is listed as vulnerable, chiefly from the loss of sea grass beds and from drowning in fishing nets.
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The oxide of Nitrogen used in medicine as anaesthetic is
Answer: C
Nitrous oxide (N2O) is the oxide of nitrogen used as an anaesthetic. Known as laughing gas, it has been used in dentistry and surgery since the 1840s.
Nitric oxide and nitrogen dioxide are toxic, and nitrogen pentoxide is an unstable solid that reacts violently with water - none of them could be breathed.
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