General Science GK Questions with Answers – Page 80

Marie Curie discovered radium; the first two pairs have their discoveries swapped. Marie Curie and Pierre Curie discovered the radioactive elements polonium and radium in 1898, and Marie Curie went on to win Nobel Prizes in both physics (1903) and chemistry (1911).

Both changes let more molecules escape from the surface each second. Evaporation is a surface process: only molecules at the surface with enough energy break away into the air.

Nichrome has a high resistivity and does not oxidise easily when red hot, so it is the standard heating element.

Charge equals current multiplied by time, and here that is 15 A × 600 s = 9000 C. Electric current is the rate of flow of charge, I = Q/t, so Q = I × t. The SI unit of charge, the coulomb, is the charge carried by one ampere…

Ligaments are bands of dense connective tissue that join one bone to another at a joint. Ligaments are rich in tough, slightly elastic fibres, so they hold the bones of a joint together while still allowing movement.

One parsec equals about 2,06,265 astronomical units, which rounds to 2 × 10⁵ A.U.

At the top of its flight all the kinetic energy of the ball has turned into gravitational potential energy. The mass is 350 g, that is 0·35 kg.

Platelets, or thrombocytes, gather at a cut and start the process that forms a clot and stops bleeding. Platelets are tiny cell fragments without a nucleus, broken off from large cells called megakaryocytes in the bone marrow.

Glass is made by melting silica sand with fluxes and stabilisers, and this option lists the standard batch. Silica, from pure sand, forms the glassy network.

Chemical messengers called neurotransmitters are released from the nerve endings, the tips of the axon, into the synapse. A nerve impulse travels from the dendrites through the cell body and along the axon as an electrical signal.

Baking soda, sodium hydrogen carbonate, is a mild base, so a small amount shifts fresh milk, whose pH is about 6.6, slightly above 7.

Ethyne, C2H2, has its two carbon atoms joined by a triple bond, each carbon also holding one hydrogen. Carbon has a valency of four.

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

Water molecules are strongly polar, so they can pull apart the positive and negative ions of a salt and surround them.

The anther is the top part of the stamen, the male organ of a flower, and pollen grains form inside it.

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

Breaking calcium carbonate into quicklime and carbon dioxide needs a steady supply of heat, so the reaction absorbs energy. An endothermic reaction takes in heat from its surroundings, while an exothermic reaction gives heat out.

Platinum is a noble metal and does not combine with oxygen even when heated in air. Metals low in the reactivity series, such as gold and platinum, hold on to their electrons very firmly, so oxygen cannot pull them away under ordinary conditions.

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.

Copper exposed to moist air slowly gains a green layer of basic copper carbonate, a form of cupric carbonate. Copper does not rust like iron, but it corrodes.