General Science Mixed Quiz: Set 145

Each reaction is labelled with its correct type, so every pair is matched correctly. In I, iron is more reactive than copper and pushes it out of copper sulphate, a displacement reaction.

Pedology is the study of soils, including their formation from parent rock, their profile and horizons, their classification and their fertility, and it is the science behind soil surveys and land capability maps.

Soaps are sodium or potassium salts of long-chain carboxylic (fatty) acids, not ammonium salts. A soap molecule has a long hydrocarbon tail that mixes with oil and an ionic head that faces water.

The islets of Langerhans are patches of endocrine tissue in the pancreas, and their beta cells secrete insulin, which lowers the level of glucose in the blood by helping cells take it up and by storing the surplus as glycogen; a lack of insulin causes diabetes mellitus.

Plaster of Paris is calcium sulphate hemihydrate, CaSO₄·½H₂O, so one molecule of water is shared by two formula units of calcium sulphate, written (CaSO₄)₂·H₂O. It is made by heating gypsum, CaSO₄·2H₂O, to about 373 K (100 °C), when gypsum loses one and a half molecules of water per formula unit.

The correct answer is A, Kerria lacca, earlier named Laccifer lacca, a tiny scale insect whose female settles on the twigs of a host tree, sucks its sap and secretes the resin we call lac.

Of the four elements of xylem, only xylem parenchyma is made of living cells; tracheids, vessels and xylem fibres are dead at maturity.

This is the incorrect statement, because periodic motion repeats after every interval T, again and again. The time period T of a pendulum is the time for one complete oscillation, that is, the smallest interval after which the bob returns to the same position moving in the same direction.

Arteries have the thickest walls of all blood vessels, not the thinnest, because they carry blood away from the heart under high pressure.

A beam seen from the side is visible only because tiny particles send some of its light sideways. Light travelling in a straight line cannot enter our eyes unless something redirects it towards us.

Iodine exists as diatomic molecules, I₂, in which two iodine atoms share a pair of electrons; so its atomicity is two, not one.

Levers are grouped by where the fulcrum, the load and the effort sit. In a second class lever the load lies between the fulcrum and the effort.

Ramesh is short-sighted with a far point of 2 m, so he needs a concave lens of focal length −2 m, whose power is 1/(−2) = −0.5 dioptre.

In 1932 Chadwick bombarded beryllium with alpha particles and showed that the highly penetrating radiation given off consisted of neutral particles with almost the same mass as a proton.

A nuclear reactor splits heavy nuclei such as uranium-235 in a chain reaction that is kept under control, releasing heat at a steady rate.

Gamma radiation is electromagnetic, carries no charge and no rest mass, and therefore passes through matter far more easily than charged particles; thick lead or concrete is needed to reduce it.

Cetane is the common name of n-hexadecane, C16H34, a straight-chain alkane with sixteen carbon atoms. Cetane ignites very readily when compressed, which is exactly what a diesel engine needs, because diesel fuel is not lit by a spark but catches fire from the heat of compressed air.

Sponges belong to the phylum Porifera, a name that means "pore bearers", because their bodies are full of tiny pores.

Recombinant vector vaccines are made by genetic engineering, and both viruses and bacteria serve as their vectors. In a recombinant vector vaccine, scientists take a harmless or weakened carrier, the vector, and insert into it the gene for an antigen of the disease-causing germ.

Making a genetically modified organism needs all three steps: find the useful DNA, put it into the host, and make sure the host keeps it and passes it on.