General Science Questions and Answers

Answer: B

Correct answer: Nitrogen

Nitrogen makes up about 78% of dry air by volume, with oxygen at roughly 21% and argon just under 1%. Carbon dioxide, despite its importance to climate, accounts for only about 0.04%.

Answer: C

Correct answer: NaCl

Common salt is sodium chloride, NaCl. NaOH is caustic soda, KCl is potassium chloride and CaCO3 is calcium carbonate, the chief constituent of limestone.

Answer: D

One kilometre is about 0.62 miles.

\[ 1\ \mathrm{km} = \frac{1}{1.609} \approx 0.621\ \mathrm{mile} \]

The mile is 1.609 km, so the two conversions are reciprocals of each other.

Answer: C

A chronometer measures time - a clock accurate enough to keep time at sea.

John Harrison's marine chronometer, perfected in the 1760s, solved the longitude problem: comparing local noon with the time at a reference meridian gives longitude directly.

Answer: A

Nuclear fission is triggered by the impact of a neutron.

Being uncharged, a neutron is not repelled by the nucleus and can reach it at low energy. Each fission releases two or three more neutrons, which is what makes a chain reaction possible.

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.

Answer: A

Under Avogadro's hypothesis, the smallest particle of an element or compound that can exist independently is the molecule.

An atom of most elements cannot exist alone - oxygen occurs as O₂, nitrogen as N₂. Cations and anions are charged particles and are always found paired with an opposite charge.

Answer: D

An atom consists of electrons and a nucleus. The nucleus holds the protons and neutrons and nearly all the mass; the electrons occupy the space around it.

Rutherford's gold-foil experiment showed that the positive charge and the mass are concentrated in a nucleus about 10,000 times smaller than the atom itself.

Answer: C

Epoxy resins are used as adhesives, and also as coatings and casting materials.

They are supplied as two parts - resin and hardener - that cross-link on mixing into a rigid solid, bonding strongly to metal, glass and ceramics.

Answer: B

Nylon is a polyamide - its monomers are joined by the amide linkage -CO-NH-, the same bond that links amino acids in a protein.

Terylene is a polyester, Orlon a polyacrylic, and rayon is regenerated cellulose rather than a synthetic polymer at all.