General Science Previous Year Questions (PYQ) with Answers – Page 52

Aerenchyma is a kind of parenchyma whose cells enclose large air-filled spaces. These air cavities keep aquatic plants such as water hyacinth, lotus and Hydrilla afloat and let oxygen move down to roots and stems that sit in waterlogged soil or under water.

Water is densest at 4 °C, where one cubic metre has a mass of almost exactly 1000 kg.

A light year is a unit of distance, not of time or brightness. One light year is the distance light travels through a vacuum in one Julian year.

Graphite has free electrons that can move through it, so it conducts electricity; diamond and fullerene do not conduct well.

The body's weight stays the same, but standing puts it on the small area of the feet, so the pressure is greater.

Animal cells are bounded only by a flexible cell membrane; a rigid cell wall is found in plants, fungi and bacteria.

A short-sighted (myopic) person sees near things clearly but distant things blurred, and a concave lens corrects it.

A real, inverted image of the same size forms only when the object sits at twice the focal length of a convex lens, so 2f = 10 cm and f = 5 cm.

Both kinds of radiation carry energy that food absorbs as heat, and both are used in everyday kitchens. Infrared radiation is the heat radiation given out by hot bodies: a grill, a toaster, an oven element or glowing coals cook the surface of food mainly by infrared rays.

In spontaneous combustion a substance catches fire by itself, without any external flame being brought near it.

Malleability is the property of being beaten into thin sheets and ductility the property of being drawn into wires, and gold possesses both to the highest degree of any metal: a single gram can be beaten into a sheet of about one square metre and drawn into a wire of…

Convection is the transfer of heat by the bodily movement of the particles of a fluid. The part that is heated expands, becomes lighter and rises, and colder, denser fluid sinks to take its place, so a circulating convection current is set up.

A colloid is named according to the states of its two parts, the dispersed phase and the dispersing medium, and an emulsion is defined as a colloid in which a liquid is dispersed in another liquid, so the dispersing medium must itself be a liquid.

Curium is a radioactive man-made element with the symbol Cm and atomic number 96.

An ordinary incandescent bulb is filled with an unreactive gas, nitrogen usually mixed with argon, so that the white-hot tungsten filament does not burn away.

Newcastle disease is called Ranikhet disease in India because the first serious outbreak in the country was reported from Ranikhet in the Kumaon hills, while the name Newcastle comes from Newcastle upon Tyne in England, where it was identified in 1926.

Capra hircus is the scientific name of the domestic goat, in which Capra is the genus and hircus the species, written in the two-word form that Carl Linnaeus gave to biology.

In the SI system the prefix femto, written f, stands for 10 raised to minus 15. The name comes from the Danish and Norwegian word femten, meaning fifteen.

Galileo was the first to argue that, with air resistance removed, every body falls with the same acceleration regardless of its mass.

Litmus is a purple dye taken from lichens, and in the classification used in school science lichens are placed in Thallophyta, the group of simple plants whose body is an undifferentiated thallus with no true root, stem or leaf.