General Science GK Questions with Answers – Page 35

Petroleum ether is a solvent and petroleum jelly is spread on metal surfaces as a protective coating, while the uses given for petroleum wax and white spirit have been swapped around.

Standard atmospheric pressure at sea level is defined as the pressure of a 760 mm column of mercury at 0 °C. In 1643 Evangelista Torricelli showed that air pressure holds up a column of mercury about 760 mm (76 cm) tall in a glass tube, inventing the mercury barometer.

Sound travels as compressions and rarefactions, while light is a transverse electromagnetic wave. In a longitudinal wave the particles of the medium vibrate back and forth along the direction in which the wave moves.

Fullerenes are made of carbon atoms alone, with no surface to trap other substances, so they are counted as the purest form of carbon.

Surface gravity is g = GM/R², so doubling the mass doubles g while doubling the radius divides it by four, leaving g₁ × 2/4 = g₁/2.

Methane makes up the largest share of biogas, usually about 55 to 75 per cent, and it is the gas that burns.

The lemon looks bigger because light from it bends as it passes from water through the curved glass into air.

. Orbits of fixed energy were proposed by Niels Bohr in 1913; Rutherford's experiment said nothing about the energy of electrons.

. Oral contraceptive pills prevent pregnancy mainly by stopping the ovary from releasing an egg.

Stainless steel is an alloy of iron with chromium and usually nickel and a little carbon; tin is not one of its components.

The car loses a momentum of 1000 kg × 20 m/s in 0.2 s, so the force is 20,000 ÷ 0.2 = 100,000 N, that is 100 kN.

Mature sclerenchyma cells have thick walls hardened with lignin and lose their living contents, so they are dead cells that give the plant strength.

Only statement II is correct: a small amount of gypsum is added to cement to slow down its setting. Portland cement is made by heating limestone and clay to form clinker, which is then ground with about 2 to 3 per cent gypsum (calcium sulphate dihydrate).

In graphite each carbon atom is sp² hybridised, not sp³, so statement A is the one that is not true.

Zinc gives up electrons most readily, copper less so and silver least, so the order of electron-releasing tendency is Zn > Cu > Ag.

For a spherical mirror of small aperture, the radius of curvature is twice the focal length, so f = R/2.

In the list of natural sources of acids that school science teaches, tomato is matched with oxalic acid.

A single compound, silver chloride, breaks down into two simpler substances, silver and chlorine, which is exactly what a decomposition reaction is.

Ethanol does not change the colour of either red or blue litmus, because it is neutral. Ethanol, C₂H₅OH, is an alcohol.

By Newton's third law, the gravitational force that the first planet exerts on the second is equal and opposite to the force the second exerts on the first.