General Science Questions and Answers

Answer: C

Magnesium is extracted commercially from sea water, which contains about 1.3 kg of it per tonne.

Lime is added to precipitate magnesium hydroxide, which is converted to the chloride and then electrolysed to the metal. More than half the world's magnesium has been won this way.

Answer: B

Penicillin is isolated from a fungus, the mould Penicillium notatum.

Alexander Fleming noticed in 1928 that a stray colony of it had killed the bacteria around it on a culture plate. Florey and Chain later purified the drug, and the three shared the Nobel Prize in 1945.

Answer: D

An object weighs least at the centre of the earth, where it weighs nothing at all.

There the mass of the earth surrounds it equally in every direction, so the pulls cancel exactly and \( g = 0 \). Weight is greatest at the poles, where the radius is smallest and there is no rotational effect.

Answer: A

Garampani sanctuary is near Diphu in Assam, in the Karbi Anglong district.

It is known for its hot springs and waterfalls, and for the hoolock gibbon and golden langur among its wildlife.

Answer: B

Crabs have teeth in their stomach. The gastric mill is a set of chitinous plates in the foregut that grinds food after it is swallowed.

Crustaceans have no jaws capable of chewing, so the grinding is done internally, and the mill is worked by muscles attached to the stomach wall.

Answer: B

Rhyolite caldera complexes are the most explosive volcanoes of all.

Their magma is silica-rich, so it is extremely viscous and traps gas until the pressure blows the whole chamber apart and its roof collapses into a caldera. Yellowstone and Toba are examples; a single eruption can eject thousands of cubic kilometres.

Answer: B

Van Vihar National Park is in Madhya Pradesh, on the shore of the Upper Lake in Bhopal.

It is unusual in being both a national park and a zoological park: the animals live in near-natural enclosures, and most were rescued or born in captivity.

Answer: C

Plants that grow in saline water or salty soil are halophytes, from the Greek halos, salt.

Mangroves are the best-known example; they exclude salt at the root, excrete it through leaf glands, or shed it in old leaves. Hydrophytes grow in fresh water and sciophytes in shade.

Answer: D

There are three teaspoons in a tablespoon.

A tablespoon is 15 ml and a teaspoon 5 ml in metric measure, so the ratio holds in either system.

Answer: D

Radiocarbon dating estimates the age of fossils and other once-living material - wood, bone, charcoal, cloth.

Carbon-14 has a half-life of 5,730 years, so the method works back to about 50,000 years. It cannot date rock or soil, which never contained living carbon.