General Science Mixed Quiz: Set 184

A light year is the distance light travels in empty space in one year, so despite its name it measures length, not time.

Polythene is an addition polymer: ethene molecules join through their double bonds without losing any small molecule. Polymers form in two main ways.

The force needed equals the rate at which the belt must give horizontal momentum to the falling sand: F = v × (dm/dt) = 2 × 0.1 = 0.2 N. Newton's second law, in its general form, says force equals the rate of change of momentum.

All three are fungi that feed saprophytically: they release enzymes onto dead organic matter, digest it outside their bodies and then absorb the dissolved food.

Power is the work done divided by the time taken, and here the work is the potential energy gained by the mass.

Vitamin D, which the skin makes in sunlight and which is also present in milk, eggs and fish liver oil, is needed for the absorption of calcium and phosphorus from food.

By Newton's law of gravitation, the acceleration due to gravity at the surface is g = GM/R², where G is the universal gravitational constant, M is the mass of the Earth and R is its radius.

Golden Rice carries genes that let the grain make beta carotene, the orange pigment that the human body converts into vitamin A, and the colour of the grain gives the variety its name; the aim is to reduce night blindness and childhood blindness in populations whose diet is mainly rice.

A plane mirror always forms an image that stands upright, cannot be caught on a screen, and has its left and right sides swapped.

2,4-dichlorophenoxyacetic acid is a synthetic auxin, and when it is sprayed in a heavy dose it throws broad-leaved dicot weeds into uncontrolled growth that kills them, while narrow-leaved cereals such as wheat and rice are far less affected, so it clears weeds from a standing crop.

All three kinds of wave reflect, carry energy and exert pressure, but only electromagnetic waves can travel through a vacuum.

Being a red dwarf it cannot be seen with the naked eye, although it is the closest star to us after the Sun.

When a magnet moves inside a coil, the magnetic flux linked with the coil changes, and this change produces an electromotive force and a current.

Agar is obtained chiefly from Gelidium and Gracilaria, members of the Rhodophyceae, and it is used to prepare the solid media on which microbes and plant tissues are grown, as well as in jellies and ice cream.

Rutherford's gold foil experiment of 1911 showed that an atom's positive charge and almost all its mass sit in a tiny central nucleus.

A metal more reactive than hydrogen displaces it from a dilute acid, so zinc with dilute sulphuric acid gives zinc sulphate and hydrogen gas, and this is the standard laboratory preparation of the gas; the test is that it burns with a pop.

When an acid such as hydrochloric acid dissolves in water, it splits into ions: hydrogen ions (H⁺, which join water molecules as hydronium ions, H₃O⁺) and negative ions such as chloride (Cl⁻).

Tungsten is used for the filament because it has the highest melting point of all metals, about 3,422°C, and can glow white-hot without melting.

Adding hydrogen across the double or triple bond of an alkene or alkyne turns it into a saturated alkane; this reaction is called hydrogenation and it needs a catalyst.

Cooking soda, also called baking soda, is sodium hydrogen carbonate, also known as sodium bicarbonate. It is a mild base made from one sodium, one hydrogen, one carbon and three oxygen atoms.