General Science Mixed Quiz: Set 21

Use the third equation of motion, which links velocity and distance without needing time: v squared equals u squared plus 2as.

Both are tiny algae grown in tanks and sold as protein rich food supplements, and both have been studied as food for astronauts.

Power is the rate of doing work, so power equals work divided by time. Here the work is 120 J and the time is 3 seconds, which gives 120 divided by 3, that is 40 watts.

The BCG vaccine takes its name from Albert Calmette and Camille Guerin, the two French scientists who developed it from a weakened strain of Mycobacterium bovis.

Thrust is the force acting perpendicular to a surface, and the thrust acting on unit area of that surface is called pressure, so pressure = thrust ÷ area.

Distillation separates a liquid from a solution or from another liquid by boiling it and condensing the vapour, so it is used when the components differ in boiling point, as in getting pure water from salt water or separating acetone from water.

On a hot day the air touching the road is heated and becomes rarer than the cooler air above it.

Guava is the classic jam fruit because it is rich in both pectin and acid, the two things a jam needs to set into a firm gel.

A vacuum contains no particles, and a mechanical wave such as sound can travel only by making particles vibrate and hand the disturbance on to their neighbours.

Algae belong to Thallophyta, the simplest division of the plant kingdom. Their body is a thallus, which means it is not divided into root, stem and leaf, and they have no vascular tissue.

By Ohm's law, at a constant temperature the current through a conductor is directly proportional to the potential difference across its ends, since the current equals the potential difference divided by the resistance.

An iron rod is a solid, and the force of attraction between particles is strongest in the solid state. In a solid the particles sit close together in fixed positions and can only vibrate, so a solid keeps its shape, has a definite volume and can hardly be compressed.

The Greek philosopher Democritus, working in the fifth century before the common era, argued that matter could be divided only up to a limit, and he called that smallest indivisible particle atomos, from which the word atom comes.

Boron has three electrons in its outermost shell, so it is a trivalent element and is used as a p-type dopant.

These are the weak attractions that appear when the electron cloud of an atom becomes momentarily lopsided, creating a temporary dipole which then induces a matching dipole in a neighbouring atom.

Calaverite is gold telluride, with the formula AuTe2. It is one of the very few minerals in which gold occurs chemically combined rather than as the free metal, because gold is a noble metal that usually resists reaction.

Malleability is the property by which a metal can be beaten into thin sheets without breaking, which is how aluminium foil and the sheets used in car bodies are made.

Graphite is built of flat sheets of carbon atoms arranged in hexagons, and while the atoms inside a sheet are joined by strong covalent bonds, the sheets themselves are held to one another only by weak van der Waals forces.

Sodium benzoate is the sodium salt of benzoic acid and is the preservative most often added to sauces, salad dressings, jams, pickles and soft drinks.

Permanent tissues are made of cells that have stopped dividing and have taken on a fixed shape, size and function, and in simple permanent tissues such as parenchyma the loosely packed cells leave clear intercellular spaces through which gases can move.