General Science Questions and Answers

Answer: A

Washing soda is hydrated sodium carbonate, Na₂CO₃·10H₂O.

It softens water by precipitating the calcium and magnesium as carbonates, so soap can lather. Baking soda is a different compound, sodium bicarbonate.

Answer: A

Hormones are produced by the endocrine glands - the ductless glands that secrete directly into the bloodstream.

The pituitary, thyroid, adrenals, pancreas and gonads are all endocrine glands, so naming any one of them alone is incomplete.

Answer: C

Galvanised iron is coated with zinc, usually by dipping the sheet in the molten metal.

The zinc protects in two ways: it seals the surface, and being more reactive than iron it corrodes in preference even where the coating is scratched - sacrificial protection.

Answer: A

Saffron is obtained from the styles and stigmas of Crocus sativus. Each flower yields just three stigmas, picked by hand, so about 150,000 flowers are needed for a kilogram - which makes it the most expensive spice in the world.

Asafoetida comes from a root resin, fennel from the seed and turmeric from the rhizome.

Answer: C

Nitrous oxide and chloroform are the pair used as anaesthetics.

Nitrous oxide, laughing gas, has been used since the 1840s and is still given with oxygen; chloroform was introduced by James Simpson in 1847 but was abandoned as it damages the liver and heart. Nitrogen dioxide is a toxic pollutant and could not be breathed.

Answer: A

Sea water is the best conductor of those listed, because it carries a high concentration of dissolved ions - about 3.5 per cent salt.

It is the ions, not the water, that carry the current: pure distilled water is a very poor conductor, and ordinary tap water conducts only because of the salts dissolved in it.

Answer: A

Laughing gas is nitrous oxide, N₂O.

Humphry Davy noticed its euphoric effect in 1799 and gave it the name; it has been used as a dental and surgical anaesthetic since the 1840s. It is also a potent greenhouse gas.

Answer: B

Anthracite is the highest grade of coal, about 90 per cent carbon.

It is hard, black and lustrous, burns with almost no smoke and gives out the most heat. The rank descends through bituminous coal and lignite to peat, which is barely coal at all.

Answer: D

The chemical name of urea is carbamide, CO(NH₂)₂.

It is the form in which mammals excrete surplus nitrogen, made in the liver from ammonia. Wöhler's synthesis of it from ammonium cyanate in 1828 was the first preparation of an organic compound from inorganic material.

Answer: A

Golden rice is pale yellow because it is rich in beta-carotene.

It was engineered to make beta-carotene in the endosperm, which ordinary rice does not, so that the grain supplies vitamin A. It was intended to address the deficiency that causes childhood blindness in rice-eating populations.