General Science GK Questions with Answers – Page 51

Curd contains lactic acid, which reacts with copper and brass to form poisonous salts, so it should not be stored in them.

A chloride XCl 2 means X has valency 2, and an ionic chloride with a high melting point points to a Group 2 metal such as magnesium.

A solid that does not vaporise stays behind when the solvent is removed, whether the solvent is boiled off or the solid is made to crystallise out.

Because water is densest at 4°C, the bottom of a lake stays liquid and relatively warm while the surface freezes, so aquatic animals survive there.

Bronze is an alloy of copper and tin, usually about 88 parts copper to 12 parts tin. Adding tin makes copper harder, stronger and easier to cast, and bronze also resists corrosion well.

A hygrometer measures humidity, that is, the amount of water vapour or moisture in the air. The name comes from the Greek "hygros", meaning wet.

The green pigment of leaves is chlorophyll, and a magnesium atom sits at the centre of every chlorophyll molecule.

An accelerometer measures acceleration, including the pull of gravity, and each of the three actions depends on reading it. An accelerometer is a small sensor, today usually a MEMS (micro-electro-mechanical system) chip, that senses changes in speed and the direction of gravity.

Carbon fibre is widely used in cars and aircraft for its strength and low weight, and it can be recovered and recycled.

Mitochondria carry their own small, circular DNA and their own ribosomes. Mitochondria are the powerhouses of the cell, where aerobic respiration makes ATP.

All three are underground modified stems: the potato is a stem tuber, and onion and garlic are bulbs. A stem can be told from a root by its nodes and buds.

A wave moves forward by one wavelength in each cycle, so 150 wavelengths take 150 cycles, and 150 cycles at 300 per second take half a second.

A floating body is in equilibrium, so the upward buoyant force exactly balances its weight. By Archimedes' principle, a body in a liquid is pushed up by a force equal to the weight of the liquid it displaces.

These are the three main divisions of the human brain. The fore brain is the largest part.

Lithium hydrogen carbonate exists only in solution; it cannot be isolated as a solid. All the alkali metals of group 1 form hydrogen carbonates (bicarbonates), but lithium behaves differently from the rest.

Pure water is neutral, and a neutral solution has a pH of 7 at 25 °C. pH is the negative logarithm of the hydrogen ion concentration.

Ultraviolet photons carry more energy than visible light, not less, so this statement is wrong. The energy of a photon is E = hc/λ, so a shorter wavelength means higher energy.

Carrying water and food through the plant is the main job of the stem's vascular tissue, not of the leaf.

The pituitary is a single, pea-sized gland at the base of the brain, while the other three come in pairs.

Intercalary meristem lies between mature tissues, at the base of leaves and of internodes. Meristems are tissues whose cells keep dividing.