General Science Previous Year Questions (PYQ) with Answers – Page 59

Adrenaline, released by the adrenal glands into the blood, speeds up the heart beat when the body faces stress or danger.

The alveoli are tiny air sacs at the end of the smallest airways, and oxygen and carbon dioxide pass through their walls.

The parietal (oxyntic) cells in the lining of the stomach secrete hydrochloric acid into the gastric juice. Hydrochloric acid makes the stomach strongly acidic, with a pH of roughly 1.5 to 3.5.

The lower the pH, the stronger the acid, and pH 0 lies at the most acidic end of the common scale.

Annelids such as the earthworm, leech and Nereis are the first coelomates in the usual sequence: their body cavity is lined on all sides by mesoderm.

An ion-exchange resin or zeolite swaps the calcium and magnesium ions that cause permanent hardness for sodium or hydrogen ions.

Copper is less reactive than lead, so it cannot push lead out of its compound. In a displacement reaction, a more reactive metal takes the place of a less reactive metal in its salt solution.

Accelerators speed up the vulcanisation of rubber; they are not a part of paint.

Magnesium burns in air with a dazzling white flame, which is why it goes into fireworks, sparklers and flares. When magnesium ribbon is heated it reacts with oxygen to form white magnesium oxide (2Mg + O2 → 2MgO), giving out intense heat and brilliant white light, including ultraviolet.

The third law does not make one force the cause and the other the effect; action and reaction arise together, at the same instant.

A speed radar measures how much the frequency of its reflected wave changes, and that change depends on the speed of the vehicle.

Bakelite is made by condensing phenol with formaldehyde, and on moulding its chains join to one another by strong covalent cross-links into a single rigid network.

The cornea is the thin, transparent, slightly bulging membrane that forms the front surface of the eyeball, and light must pass through it before reaching anything else.

Boyle s law applies to a fixed mass of gas at constant temperature and states that pressure is inversely proportional to volume, so the product of the two is a constant: P1 into V1 equals P2 into V2.

Gamma rays are electromagnetic waves of the highest frequency and shortest wavelength, given out by the nucleus of a radioactive atom and in nuclear reactions, and their energy lets them kill cancer cells in radiotherapy.

Elektron is the Greek name for amber, the fossilised tree resin which the ancient Greeks found would attract straw, feathers and bits of dust after being rubbed with fur.

Working independently in the 1830s, Michael Faraday in England and Joseph Henry in the United States showed that a changing magnetic flux through a circuit sets up an electromotive force in it, and that the effect depends on the rate of change of flux rather than on the flux itself.

Escherichia coli is a bacterium whose harmful strains reach the body through drinking water or food contaminated with sewage, and the infection they produce shows itself as diarrhoea and abdominal pain, which places it among the classic water-borne illnesses along with cholera, typhoid and hepatitis A. Option A is wrong…

Ultraviolet light is a transverse wave, not a longitudinal one, so this statement is the wrong one. In an electromagnetic wave the electric and magnetic fields vibrate at right angles to each other and to the direction the wave travels, which is the definition of a transverse wave.

When electricity is passed through a sealed tube holding neon at low pressure, the gas atoms are excited and give out a bright orange-red glow, which is why advertising signs are still called neon signs.