General Science Mixed Quiz: Set 170

Specific heat is a property of the material, not of the size or shape of the particular body. It is the amount of heat needed to raise the temperature of unit mass (1 kg or 1 g) of a substance by one degree.

Escherichia coli is a bacterium whose harmful strains reach the body through drinking water or food contaminated with sewage, and the infection they produce shows itself as diarrhoea and abdominal pain, which places it among the classic water-borne illnesses along with cholera, typhoid and hepatitis A. Option A is wrong…

An angle of incidence of zero means the ray falls along the normal, that is, perpendicular to the surface. By Snell's law, n₁ sin i = n₂ sin r; if i is zero, sin i is zero, so sin r is also zero and the angle of refraction is zero.

Mendel chose it because it breeds true, is easy to cross by hand, completes a generation in a single season and offers seven pairs of sharply contrasting characters such as tall against dwarf stem and round against wrinkled seed.

The magnetic force on a moving charge is F = q(v × B), and only an upward field turns a westward-moving positive charge towards the north.

In 1928 Fleming noticed that a mould of the genus Penicillium which had contaminated a culture plate in his London laboratory had killed the staphylococcus bacteria around it, and he named the active substance penicillin.

Rutherford's gold foil experiment showed that an atom has a tiny, dense, positively charged centre, which he called the nucleus.

A floating body displaces its own weight of fluid, so the fraction of its volume that lies below the surface equals the ratio of its density to the density of the fluid, here 920 divided by 1000, which is 0.92.

A reducing agent is the substance that is itself oxidised while it reduces something else. In hydrazine, N₂H₄, nitrogen has an oxidation number of −2; in nitrogen gas, N₂, it is 0.

In the core of the Sun, at temperatures of millions of degrees, hydrogen nuclei fuse in stages to form helium, and the small amount of mass lost in the process appears as energy according to Einstein's mass-energy relation.

Lime water is a clear solution of calcium hydroxide, Ca(OH)₂. When carbon dioxide is passed through it, insoluble calcium carbonate, CaCO₃, forms as a fine white precipitate, which makes the lime water turn milky.

A full-wave rectifier conducts during both halves of the input cycle, since one pair of diodes handles the positive half and the other pair the negative half.

At room temperature and normal pressure only two elements are liquids: mercury, a metal, and bromine, a non-metal. Mercury melts at about −39 °C and is used in thermometers and barometers because it stays liquid over a wide range and does not wet glass.

Calcination is the heating of an ore in the absence or a limited supply of air and below its melting point, so that water of hydration and carbon dioxide are driven off; it is therefore the step used for carbonate ores such as calamine and for hydrated ores such as…

Potassium hydroxide gives potassium soaps, which are softer and milder than sodium soaps. Saponification is the reaction in which an oil or fat is heated with an alkali to give soap, the sodium or potassium salt of a long-chain fatty acid, and glycerol.

Its calorific value is about 150 kilojoules per gram, the highest of any known fuel, roughly three times that of petrol, and its only combustion product is water vapour, which makes it a clean fuel as well.

Plaster of Paris is made from gypsum, not from common salt. When gypsum, calcium sulphate dihydrate (CaSO4·2H2O), is heated to about 373 K, it loses part of its water and becomes calcium sulphate hemihydrate (CaSO4·½H2O), which is Plaster of Paris; it sets hard again when mixed with water and is…

Adipose tissue is a loose connective tissue whose cells, called adipocytes, are built to store fat. Each cell holds a large droplet of fat that pushes the nucleus and cytoplasm to one side.

As one climbs, air pressure falls, so each breath delivers oxygen at a lower partial pressure and less of it passes from the lungs into the blood.

Drug resistance grows in microbes when antibiotics are misused, and both wrong doses and farm use of antibiotics are forms of misuse.