General Science GK Questions with Answers – Page 63

Urea is the body's way of getting rid of the nitrogen that comes from breaking down proteins, and only proteins among these contain nitrogen.

This is the false statement: glass cools into an amorphous solid without any regular crystal structure. When molten glass cools, its viscosity rises so quickly that the atoms have no time to arrange themselves in an ordered crystal lattice.

Plastics are long chains of carbon atoms joined by strong covalent bonds, which water, air and most microbes cannot easily break.

For an object launched horizontally, the time of fall depends only on the height, because its starting vertical speed is zero.

The body makes nitric oxide (NO) itself, and it relaxes the walls of blood vessels so that they widen and carry more blood.

Toothpaste is mildly basic so that it can neutralise the acid that causes tooth decay. Bacteria in the mouth break down sugar and food particles left on the teeth and produce acids.

For an ideal gas in a fixed volume at a fixed temperature, pressure is proportional to the number of molecules, so half the molecules give half the pressure.

Both have 10 electrons, the same number as a neon atom, so they are isoelectronic. Isoelectronic species have the same number of electrons.

About an axis through the centre, a solid disc has I = ½MR² while a solid sphere has I = ⅖MR², and ½ is larger than ⅖.

At this one temperature the Celsius and Fahrenheit scales show the same number. The two scales are linked by F = (9/5)C + 32.

This follows the reactivity series of metals, in which zinc lies above iron, iron above lead and lead above copper.

This is double fertilisation, a feature found only in flowering plants. The pollen tube carries the two male gametes into the embryo sac.

Litmus is a purple dye extracted from certain lichens, such as species of Roccella, and it turns red in acid and blue in base.

The heat needed to turn unit mass of a liquid into vapour at constant temperature is its specific latent heat of vaporisation.

Average force equals the change in momentum of the coin divided by the time of contact.

Temporary hardness comes from dissolved calcium and magnesium hydrogencarbonates (bicarbonates), and it can be removed simply by boiling. On boiling, calcium hydrogencarbonate breaks down into insoluble calcium carbonate, water and carbon dioxide, and the carbonate settles out; this is the scale seen inside kettles.

The stinging hairs on nettle leaves break on touch and inject methanoic acid, also called formic acid, into the skin, which causes the burning pain.

Outside a long straight wire the field is B = μ₀I/(2πr), so at a fixed distance r it is directly proportional to the current I. Hans Christian Oersted found in 1820 that a current deflects a compass needle, showing that a current produces a magnetic field.

Magnesium does not react with cold water; it reacts with hot water and burns in steam to form magnesium oxide and hydrogen.

With constant acceleration the distance covered is s = ut + ½at², and the first term contains the initial velocity u. This is the second equation of motion.