General Science GK Questions with Answers – Page 73

Orangutans shape sticks into tools and use them to pull insects, honey and termites out of holes in trees and logs.

Groundnut, horse-gram and soybean are all legumes of the family Fabaceae (Leguminosae), the pea family. Members of the pea family bear their seeds in pods and carry root nodules in which Rhizobium bacteria fix atmospheric nitrogen.

This statement is wrong: the gravitational force between two bodies depends on their masses and on the distance between them.

Three parts of oxygen-16 and one part of oxygen-18 give an average of (3 × 16 + 1 × 18) ÷ 4 = 66 ÷ 4 = 16.5 u. Isotopes are atoms of the same element with the same atomic number but different mass numbers, because they have different numbers…

In boiling, bubbles of vapour form throughout the liquid; in evaporation, only molecules at the surface escape.

Gypsum (calcium sulphate dihydrate) is not a raw material for glass; it is added to cement to slow down its setting.

Bacteria turn the lactose in milk into lactic acid, a new substance, so souring is a chemical change that cannot be reversed.

One kilowatt-hour is the energy used by a 1 kW appliance running for one hour: 1000 W × 3600 s = 3.6 × 10⁶ J. The joule is too small for household bills, so electricity companies charge in kilowatt-hours, commonly called units.

This is the thermite reaction, which is highly exothermic: it gives out so much heat that the iron formed comes out molten.

X-rays have wavelengths from about 0.01 nm to 10 nm, so 1 nm lies well inside the X-ray band. In the electromagnetic spectrum, wavelength decreases from radio waves through microwaves, infrared, visible light and ultraviolet to X-rays and gamma rays.

The element with atomic number 8 is oxygen, which gains two electrons to complete its octet and forms sodium oxide, Na₂O. Oxygen's electrons are arranged as 2, 6, so it needs two more to reach the stable arrangement 2, 8 of neon.

Chemical energy is the energy stored in the bonds that link atoms together in molecules. When a chemical reaction breaks old bonds and forms new ones, this stored energy is released or absorbed.

This statement is wrong: soda glass is the soft glass, while pyrex is a hard borosilicate glass. Ordinary soda-lime glass is made from silica (sand), sodium carbonate and limestone; it softens at a fairly low temperature and is used for windows, bottles and tumblers.

Crude petroleum is a mixture of hydrocarbons with different boiling points, and fractional distillation separates them. In a refinery, crude oil is heated to about 400 °C and its vapour enters a tall fractionating column that is hot at the bottom and cooler towards the top.

Diagnostic laboratories spin blood samples in a centrifuge to separate the plasma or serum from the blood cells. In centrifugation a sample is rotated at high speed, so the denser particles are pushed to the bottom of the tube and the lighter liquid stays on top.

One pascal is defined as a force of one newton acting on an area of one square metre. Pressure is force per unit area, and its SI unit, named after the French scientist Blaise Pascal, is the pascal (Pa): 1 Pa = 1 N/m².

A floating body is stable only when its metacentre lies above its centre of gravity. When a floating body tilts slightly, its centre of buoyancy, the centre of the displaced liquid, shifts to one side.

A simple periscope has two plane mirrors facing each other in parallel, each tilted at 45° to the tube. Light from the object enters the top opening and strikes the upper mirror, which is set at 45° and turns the light through 90° down the tube.

This is false, because variations differ in how well they suit the environment, and that difference is the basis of natural selection.

Unsaturated hydrocarbons have a high carbon content and burn with a yellow, sooty flame, while saturated ones usually burn with a clean blue flame.