General Science Previous Year Questions (PYQ) with Answers – Page 95

Chemical equilibrium is a dynamic state: both reactions go on, but at the same speed, so no net change is seen.

Silver bromide is the standard example of an ionic crystal that carries both kinds of point defect at the same time.

Ampere-turns per metre, written AT/m, is the unit of magnetic field strength, because H is the magnetomotive force set up per unit length of the magnetic path.

An emulsion is a colloid in which one liquid is spread as fine droplets through another liquid that does not mix with it.

Three grams of hydrogen, 48 grams of oxygen and 42 grams of nitrogen each come to 1.5 moles, while two grams of carbon is only about 0.17 mole, so carbon holds a different number of particles.

In an astronomical telescope set for normal adjustment, the magnifying power equals the focal length of the objective divided by the focal length of the eyepiece.

Heating a liquid makes its molecules move faster and sit a little further apart, so the attraction between them weakens, and both properties depend on that attraction.

Boric acid dissolves in water to give a true solution, in which the dispersed particles are individual molecules small enough to pass through a filter paper and even a parchment membrane, and the mixture shows no Tyndall effect.

A planimeter measures the area of any flat shape, however irregular its outline. The user simply traces the boundary of the shape on the map with the instrument's pointer, and a wheel and dial record the area swept, which is then multiplied by the square of the map scale.

Bacteria are prokaryotes, so their DNA lies free in the cytoplasm instead of being packed inside a nucleus. The single circular chromosome sits in a region of the cytoplasm called the nucleoid, which has no nuclear membrane around it.

Baking soda is sodium hydrogen carbonate, NaHCO3, a mild base made by the Solvay process from brine, ammonia and carbon dioxide.

Melting means breaking the particles free of the forces holding them in a fixed lattice, so a higher melting point means stronger forces of attraction.

The two strips are joined and carry the load together, so they suffer the same strain. Since stress equals the modulus multiplied by the strain, the stress in steel is three times the stress in aluminium.

Distilled water has had its dissolved salts removed, so it holds almost no free ions to carry charge and does not conduct electricity.

A dilute solution of iodine gives a deep blue-black colour with starch, which is a polysaccharide and therefore a carbohydrate.

Adrenaline, also called epinephrine, is made by the medulla of the adrenal gland and is the body's emergency hormone; it makes the heart beat faster and stronger and narrows the small blood vessels, so blood pressure rises within seconds.

A body that slides down a smooth slope turns all of its potential energy mgh into translational kinetic energy and reaches the bottom with a speed equal to the square root of 2gh.

The law of conservation of linear momentum follows straight from Newton's second law: the rate of change of the momentum of a system equals the net external force acting on it, so when that force is zero the total momentum stays the same in size and in direction.

Dynamic viscosity measures how strongly a fluid resists flowing, and in the centimetre gram second system it is measured in poise, a unit named after the French physician Jean Louis Marie Poiseuille, who studied the flow of blood in narrow tubes.

Once the athlete's feet leave the ground they move as a projectile, and the horizontal distance covered, called the range, is given by R equal to u squared into sin 2 theta divided by g. The range is largest when sin 2 theta has its greatest value of one, which…