General Science Mixed Quiz: Set 147

Pairs I, II and IV describe the electron transfer correctly; pair III calls bromine a reductant when it is the oxidant.

Cryogenics deals with the production of very low temperatures and with the behaviour of materials at those temperatures, where liquefied gases such as liquid nitrogen, oxygen and hydrogen are used; it is applied in rocket engines with cryogenic upper stages, in superconducting magnets and in the preservation of biological material…

Boiling an oil or fat with an alkali splits it into glycerol and the salts of its fatty acids; with potassium hydroxide those salts are potassium salts.

The thyroid is a butterfly-shaped gland in the neck, in front of the windpipe, and is the largest of the ductless or endocrine glands; it secretes thyroxine, for which iodine is essential, and the hormone controls the rate of metabolism, growth and development.

In the order visible light → ultraviolet → X-rays, the wavelength falls and the photon energy rises, so statements 1 and 2 are true and 3 is false.

The middle ear holds three tiny bones, the smallest in the human body, called the malleus, the incus and the stapes, which in everyday English are the hammer, the anvil and the stirrup.

The velocity ratio is the distance moved by the effort divided by the distance moved by the load, that is ten divided by two point five, which is four.

Its reaction is reversible, so passing a current through it in the opposite direction converts the products back into lead and lead dioxide and the cell can be used again; such a cell is called a secondary or storage cell, and the car battery is the common example.

Heavy water is D2O, in which both hydrogen atoms are deuterium, the isotope whose nucleus has one proton and one neutron, so its molecular mass is twenty instead of eighteen.

All three are underground modified stems: the potato is a stem tuber, and onion and garlic are bulbs. A stem can be told from a root by its nodes and buds.

It takes most force to start an object moving, less to keep it sliding and least to keep it rolling.

Charles’s law says that at constant pressure the volume of a fixed mass of gas is directly proportional to its absolute temperature, so V by T stays constant.

In 1905 Einstein explained the photoelectric effect by treating light as made of packets of energy, later called photons, and he received the 1921 Nobel Prize in Physics for this work.

Crown gall is caused by the bacterium Agrobacterium tumefaciens, which enters through a wound near the base, or crown, of the stem and makes the plant grow rough tumour-like swellings there.

Hydrated oxalic acid has a molar mass of 126 and is a dibasic acid, so its equivalent weight is 126 ÷ 2 = 63.

The de Broglie wavelength depends only on momentum, so equal wavelengths mean equal momenta. In 1924 Louis de Broglie proposed that every moving particle has a wave linked to it, with wavelength λ = h/p, where h is Planck's constant and p is the linear momentum.

Evaporation from the leaves pulls a continuous column of water up the xylem, and cohesion and adhesion keep that column from breaking.

Iodine forms a deep blue-black complex with the long coiled chains of amylose in starch, and this colour change is the standard classroom and field test for starch.

Urea, CO(NH₂)₂, has a molar mass of 60 g, of which 28 g is nitrogen and 4 g is hydrogen.

The slightest push makes the ball fall off and it does not come back. A body is in unstable equilibrium when a small displacement lowers its centre of gravity, so the forces acting on it move it further away instead of back.