General Science Questions and Answers

Answer: C

The tobacco leaf contains nicotine, an alkaloid making up about 0.6 to 3 per cent of the dry weight.

The plant produces it in the roots and stores it in the leaves as a defence against insects; in humans it is the substance that makes smoking addictive.

Answer: C

Diamond is an allotrope of carbon. Every atom is bonded to four others in a rigid tetrahedral network, which is what makes it the hardest natural substance.

Graphite, charcoal and the fullerenes are the other allotropes; they differ only in how the same atoms are arranged.

Answer: D

Fullerene is regarded as the purest form of carbon. C₆₀, buckminsterfullerene, is a closed cage of sixty carbon atoms arranged like a football, discovered in 1985.

Unlike graphite or diamond it is a discrete molecule with a definite formula, so it can be obtained in a genuinely pure state.

Answer: B

Graphite is not a mixture - it is an element, pure carbon in one of its allotropic forms.

Glass and steel are mixtures, and the aluminium of everyday use is an alloy rather than the pure metal.

Answer: C

Very short intervals are measured by atomic clocks, which count the oscillations of a caesium atom between two energy levels.

The second is defined as 9,192,631,770 such oscillations. The best atomic clocks would gain or lose less than a second in the age of the universe, and they are what the GPS system depends on.

Answer: C

The decibel measures the loudness or intensity of sound.

It is logarithmic: 10 dB is a tenfold increase in intensity, so the scale can cover the enormous range the ear handles. Frequency, which determines pitch, is measured in hertz instead - cycles per second.

Answer: C

Hydrochloric acid is secreted by the stomach to aid digestion. It brings the stomach contents to about pH 1.5 to 3.5.

That acidity activates pepsinogen into pepsin, which digests protein, and it also kills most swallowed bacteria.

Answer: C

Mudumalai National Park is in Tamil Nadu, in the Nilgiris district where the state meets Karnataka and Kerala.

It became India's first wildlife sanctuary in 1940 and was declared a tiger reserve in 2007. It adjoins Bandipur in Karnataka and Wayanad in Kerala.

Answer: B

The normal fasting blood sugar level is about 80 to 120 mg per 100 ml of blood.

It is held in this range by insulin, which lowers it, and glucagon, which raises it. A persistently higher level indicates diabetes mellitus.

Answer: C

Isotopes are separated by fractional distillation, and by other methods that exploit the small difference their masses make - diffusion, centrifugation, electromagnetic separation.

Chemical methods cannot separate them, since isotopes of an element are chemically identical; only the mass differs, and the difference is largest for the lightest elements.