General Science GK Questions with Answers – Page 61

Brine is a concentrated solution of common salt, sodium chloride (NaCl), in water. Brine occurs naturally in seawater, salt lakes and underground deposits.

Zinc reacts with dilute sulphuric acid to form zinc sulphate and hydrogen gas: Zn + H2SO4 gives ZnSO4 + H2.

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

Graphite, fullerene, diamond and graphene are all allotropes of carbon, made only of carbon atoms arranged in different ways. Allotropes are different structural forms of the same element.

Quartz is a crystalline solid, and crystals show different physical properties in different directions, which is called anisotropy. In a crystalline solid the particles are arranged in a regular, repeating pattern, so the arrangement looks different along different directions.

An alloy is made by melting and mixing its components, which keep their own properties and are not joined in a fixed ratio by chemical bonds.

Brine is a concentrated solution of sodium chloride, common salt, in water. Brine is the starting point of the chlor-alkali process: passing electricity through it gives sodium hydroxide, chlorine gas and hydrogen gas, which is why the process is named after chlorine and alkali.

An LED is a semiconductor p–n junction diode that gives out light when current flows through it in the forward direction.

Average velocity is total displacement divided by time, and the car ends where it started, so its displacement is zero.

When red and green light are added together, the eye sees yellow. Red, green and blue are the primary colours of light.

Outside a long straight wire, the field is B = μ₀I/(2πr), so doubling the distance halves the field. This result follows from Ampère's circuital law, or from the Biot–Savart law applied to a long wire.

Sugar dissolves in water as whole, neutral molecules and releases no ions, so its solution does not conduct electricity. A solution conducts only when it contains free ions that can carry charge between the electrodes.

Prokaryotic cells, such as bacteria, have no true nucleus; their DNA lies free in the cytoplasm in a region called the nucleoid.

While collecting nectar, a honey-bee carries pollen from one flower to the stigma of another, which lets the plant form seeds.

Heating weakens the attraction between the molecules of a liquid, so its surface pulls less tightly. Surface tension arises because molecules at the surface are pulled inward by their neighbours, making the surface behave like a stretched skin.

For any real object, a convex mirror forms a virtual, erect and smaller image behind the mirror, between the pole and the focus.

A metal filament's resistance rises as it heats up, so the current falls and the resistor gets a smaller share of the voltage.

The stinging hairs of the nettle plant inject methanoic acid, also called formic acid, into the skin. Each nettle hair is a fine, brittle tube that breaks on touch and pushes its contents into the skin like a tiny needle.

It contains hydrochloric acid and has a pH of about 1.5 to 2, the lowest of the four, so it has the most hydrogen ions.

A nanometre is 10⁻⁹ m and an ångström is 10⁻¹⁰ m, so one nanometre holds ten ångströms.