General Science Previous Year Questions (PYQ) with Answers – Page 51

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

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

The F2 genotypes come out as 1 TT: 2 Tt: 1 tt, so pure tall plants (TT) and short plants (tt) are equal in number.

A single-celled organism has no organs at all; the one cell takes in food through its surface or by forming temporary structures.

Breaking down carbohydrates to release energy is respiration, which happens in the cytoplasm and mitochondria, not a job of chlorophyll.

Charge equals current multiplied by time, so Q = 1.5 A × 0.010 s = 0.015 C. Electric current is the rate at which charge flows, I = Q/t, so the charge that passes in a given time is Q = I × t. One ampere means one coulomb of…

Hypobromous acid has one hydrogen, one oxygen and one bromine atom, with bromine in the +1 oxidation state. The oxyacids of a halogen are named by how much oxygen they hold.

Friction acts only where two surfaces touch, while a magnet can push or pull an object across a gap. Forces are grouped by whether the bodies must touch.

Jupiter is a planet; it does not make its own light and shines only by reflecting sunlight. A luminous object produces light of its own, as stars do by nuclear fusion in their cores, where hydrogen is turned into helium.

Violet light has the shortest wavelength among the visible colours, so the medium bends it the most. The splitting of white light into its colours is called dispersion.

The product forms a coating that shuts the acid out. Calcium reacts with dilute sulphuric acid to give calcium sulphate and hydrogen gas: Ca + H2SO4 gives CaSO4 + H2.

Common solder is an alloy of lead (Pb) and tin (Sn), often in a ratio close to 40:60. Solder is used to join metal parts, especially wires and components in electrical circuits.

An LED is a p-n junction diode that gives out light when current flows through it in the forward direction.

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).

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.

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.

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.

No pathway of respiration in living cells turns glucose into methanol. Glucose is first split in the cytoplasm into two molecules of pyruvate; this step, glycolysis, is common to all cells.

HIV spreads through body fluids such as blood, semen, vaginal fluid and breast milk, not through droplets from coughing, sneezing or talking.

Smooth muscle is a muscular tissue, one of the four basic animal tissues, not a connective tissue. Animal tissues are of four kinds: epithelial, connective, muscular and nervous.