General Science GK Questions with Answers – Page 22

At the boiling point, water turns into vapour inside the liquid itself, and these pockets of steam are the bubbles that rise and burst at the surface.

Light travels fastest in vacuum and almost as fast in air, so in any material medium it moves more slowly than in air, and the ratio of the two speeds is greater than one.

Power is the reciprocal of focal length in metres, and 50 cm is 0.5 m, so the power is 1 divided by 0.5, which is +2 dioptre.

In the light reaction of photosynthesis, water is broken up; its hydrogen is used to make food and its oxygen is given out.

Sulphur vapour turns straight into solid sulphur on the cooler rocks without first becoming a liquid, and a direct change from gas to solid is called deposition.

Almost all the world's ammonia is made by combining nitrogen and hydrogen directly in this process. In the Haber-Bosch process, nitrogen from the air and hydrogen, usually obtained from natural gas, are made to react in the ratio 1 to 3.

Nitrogen has five electrons in its outer shell and needs three more to complete an octet, so its valency is 3.

Breaking lead nitrate into lead oxide, nitrogen dioxide and oxygen needs a steady supply of heat, so the reaction absorbs energy and is endothermic.

Sleeping sickness, or African trypanosomiasis, is caused by the protozoan parasite Trypanosoma brucei, which is spread by the bite of the tsetse fly.

At about 6 to 7 metres in an adult, the small intestine is by far the longest part of the alimentary canal.

A Lewis acid is a species that accepts a pair of electrons, and all three of these can do so.

Hydrogen shows 0, +1 or -1 depending on what it is bonded to. In the free element H2 its oxidation number is 0, as for every element in its uncombined state.

A rainbow forms because raindrops split white sunlight into its seven colours, and this splitting of light into colours is dispersion.

Isobars are atoms of different elements with the same mass number, and 18 + 22 gives a mass number of 40, the same as calcium.

A direction in space needs two angles, one in the horizontal plane and one in the vertical plane, and declination and inclination supply exactly these.

This is the fluid mosaic model of the cell membrane given by Singer and Nicolson in 1972. Each phospholipid has a water-loving (hydrophilic) phosphate head and two water-fearing (hydrophobic) fatty acid tails.

Dalton held that the atom is the smallest, indivisible particle of matter, so his theory cannot explain particles inside the atom.

For a swinging pendulum, the component of the bob's weight along its path always pulls it back towards the lowest point, so gravity acts as a restoring force.

A shoot grows upward, away from the pull of gravity, so it is negatively geotropic. A tropism is a directional growth movement of a plant part in response to a stimulus: towards the stimulus is positive, away from it is negative.

An object floats when its average density is less than that of the liquid and sinks when it is greater.