General Science Questions and Answers

Answer: A

Faded old writing can be read under infrared light. Different inks and the paper beneath them absorb and reflect infrared differently, so the writing shows up in an infrared photograph even where it is invisible to the eye.

The technique is standard in manuscript study and in forensic document examination.

Answer: B

The ozone layer, in the stratosphere between about 15 and 35 km, shields the earth from the sun's harmful ultraviolet radiation.

Ozone absorbs almost all UV-C and most UV-B, which would otherwise cause skin cancer, cataracts and damage to crops and plankton. Absorbing that energy is also what warms the stratosphere.

Answer: D

Canada is the country listed without cryogenic engine technology.

Only a handful of nations have mastered it - the United States, Russia, France, Japan, China and India. India's first indigenous cryogenic stage flew successfully on GSLV-D5 in January 2014.

Answer: D

Peat still shows recognisable traces of the plants it formed from - leaves, twigs and roots are often visible in it.

It is the first stage of coal formation, with only about 25 to 35 per cent carbon. With increasing pressure and time it becomes lignite, then bituminous coal, then anthracite, and all plant structure is lost.

Answer: D

Nylon was the first fully synthetic fibre, developed by Wallace Carothers at DuPont and put on sale in 1938.

It is built from small molecules rather than from a natural polymer. Rayon came earlier but is regenerated cellulose, so it is not fully synthetic.

Answer: C

The bar measures atmospheric pressure. One bar is 10⁵ pascals, very close to the average pressure at sea level, which is 1.013 bar.

Meteorologists usually work in millibars or the identical hectopascals, so standard sea-level pressure is 1013 mb.

Answer: B

Lithium is the lightest metal, with a density of 0.53 g/cm³ - about half that of water, so it floats.

It is also the lightest solid element of any kind. Its low weight and high electrochemical potential are what make lithium-ion batteries so effective.

Answer: D

Insect-pollinated flowers have pollen that is rough and sticky, often with spines or a sticky coating, so that it clings to the visiting insect's body.

Wind-pollinated pollen is the opposite: small, smooth, dry and light, produced in enormous quantity so that a little of it reaches a stigma by chance.

Answer: B

Transistors are made from silicon and germanium.

Both are group 14 semiconductors, whose conductivity can be controlled precisely by doping with traces of boron or phosphorus. Germanium was used in the first transistors; silicon replaced it because it withstands higher temperatures and forms a stable oxide.

Answer: B

Deliquescence is the property of absorbing so much moisture from the air that the substance dissolves in it, forming a solution.

Calcium chloride and sodium hydroxide are deliquescent. The opposite is efflorescence, where a hydrated crystal loses its water to the air and crumbles to powder.