General Science Mixed Quiz: Set 2

The SI system, adopted in 1960 by the General Conference on Weights and Measures, rests on seven base units: the metre, the kilogram, the second, the ampere, the kelvin, the mole and the candela.

One newton is the force that gives a mass of one kilogram an acceleration of one metre per second squared, which follows directly from the equation force equals mass times acceleration.

The cooking temperature is set by the pressure inside the cooker, and that pressure is fixed by the weight sitting on the vent and the area of the hole under it.

At great heights the air is thin, so the atmospheric pressure acting on the body is much lower than at sea level.

For a lens, magnification m is the image height divided by the object height, which also equals v divided by u. A plus sign means the image is erect and virtual, and a value of 2 means it is twice as tall as the object.

Water is densest at about 4 degrees Celsius, and 4 plus 273 gives roughly 277 kelvin. Most liquids keep shrinking as they cool, but water behaves oddly: below 4 degrees Celsius it starts to expand again because its molecules begin forming the open, hexagonal pattern of ice.

In 1831 the British scientist Michael Faraday showed that a changing magnetic field produces an electric current in a nearby coil.

Starlight has to cross many layers of air before it reaches the eye, and these layers keep changing in temperature and density, so their refractive index keeps changing too.

Lead has 82 protons in its nucleus, so its atomic number is 82. Its symbol is Pb, from the Latin plumbum, the root of the word "plumber", because Roman water pipes were made of lead.

A healthy human ear can hear sound waves with frequencies from about 20 hertz to 20,000 hertz (20 kHz); this band is called the audible range.

Ammonia is NH3, so one nitrogen atom of mass 14 is joined to three hydrogen atoms of mass 1 each, giving 14: 3 by mass.

This is Kirchhoff's first law, the current law or junction rule, which he stated in 1845. It says the total current entering a junction equals the total current leaving it, because charge cannot pile up or vanish at a point.

Milk of magnesia is a milky white suspension of magnesium hydroxide, Mg(OH)2, in water. It is a mild base, so it neutralises the extra hydrochloric acid in the stomach that causes acidity and heartburn; the reaction gives magnesium chloride and water.

Zinc has atomic number 30, meaning every zinc atom has 30 protons in its nucleus. It is the last element of the first transition series in period 4 of the modern periodic table, with the electronic configuration [Ar] 3d10 4s2, and it is placed in group 12.

Roasting means heating a sulphide ore strongly in plenty of air, so that the sulphide turns into an oxide and the sulphur escapes as sulphur dioxide gas.

The name itself gives the formula: 'hexa' means six, so sulphur hexafluoride has one sulphur atom joined to six fluorine atoms, SF6.

Milk of magnesia is a white suspension of magnesium hydroxide, Mg(OH)2, in water, and its milky look gives it the name.

Both pairs are wrong. Amyloplasts store starch, a carbohydrate, and aleuroplasts store proteins; oils and fats are stored by elaioplasts.

Each human kidney has about one million nephrons, and every nephron begins with a cup-shaped Bowman's capsule that encloses a knot of capillaries called the glomerulus.

The pancreas is both an exocrine gland, pouring digestive enzymes into the intestine, and an endocrine gland. Its endocrine part is made of small clusters of cells called the islets of Langerhans.