General Science Questions and Answers

Answer: A

Light is far faster than sound - 3 × 10⁸ m/s in vacuum against about 340 m/s for sound in air, roughly 900,000 times faster.

This is why lightning is seen before the thunder is heard, and why counting the seconds between them gives the distance of the storm at about 3 seconds per kilometre.

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.

Answer: A

Lipids are insoluble in water because they are hydrophobic - their long hydrocarbon chains are non-polar.

Water molecules are polar and hold to one another by hydrogen bonds, which the non-polar chains cannot join. Like dissolves like, so lipids dissolve in ether and chloroform instead.

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: C

Hydrogen does not support combustion. It is itself combustible, burning in air to form water, but it will not keep another substance burning - a lighted splint is extinguished in hydrogen with a pop.

Oxygen supports combustion without burning itself; hydrogen does the reverse.

Answer: C

Red phosphorus is used in safety matches - but on the striking strip of the box, not the match head.

Separating the phosphorus from the oxidiser in the head is what makes the match safe: it will light only on its own box. Red phosphorus is used because white phosphorus is spontaneously flammable and highly toxic.

Answer: A

The seasons are caused by the tilt of the earth's axis, about 23½° to the plane of its orbit, which stays pointed in the same direction as the earth goes round the sun.

Each hemisphere therefore leans towards the sun for half the year and away for the other half, changing both the angle of the sun's rays and the length of the day. Distance from the sun has nothing to do with it - the earth is in fact closest in January.

Answer: B

The study of bones is osteology, from the Greek osteon.

It covers the structure, development and diseases of bone, and is central to anatomy, archaeology and forensic science. Orology is the study of mountains and serology of blood serum.

Answer: B

Glass is made from a mixture of sand (silica) and silicates - sand fused with sodium carbonate and limestone, which give sodium and calcium silicates.

The soda lowers the melting point of silica from about 1,700°C to a workable temperature, and the lime keeps the product from dissolving in water.

Answer: B

The kilowatt measures power - the rate of doing work, one thousand joules per second.

Energy is measured in joules, or in the kilowatt-hour of the electricity bill, which is power multiplied by time.