General Science Questions and Answers

Answer: C

Epoxy resins are used as adhesives, and also as coatings and casting materials.

They are supplied as two parts - resin and hardener - that cross-link on mixing into a rigid solid, bonding strongly to metal, glass and ceramics.

Answer: D

Optical fibres are used mainly for communication. A signal is sent as pulses of light along a glass fibre, kept inside it by total internal reflection.

A single fibre carries far more information than a copper cable, over much greater distances, and is immune to electrical interference. Submarine fibre cables carry almost all intercontinental internet traffic.

Answer: A

Paraffin wax is the petroleum wax, obtained from the heavier fractions of crude oil during refining.

Carnauba wax comes from a Brazilian palm, jojoba from a desert shrub and beeswax from the honeybee - all three are natural rather than mineral waxes.

Answer: D

Cotton fibres are almost pure cellulose - about 90 per cent of the dry fibre.

Cellulose is a polymer of glucose whose chains lie parallel and are held by hydrogen bonds, which is what gives cotton its strength and its ability to absorb water.

Answer: A

Antidiuretic hormone makes the walls of the arterioles contract and stimulates the reabsorption of water from the kidney tubules, so less urine is passed and blood volume rises.

It is made in the hypothalamus and released from the posterior pituitary when the blood becomes too concentrated. Its other name, vasopressin, refers to the same vessel-constricting effect.

Answer: B

Gonadotropic hormone (GTH) is secreted by the anterior pituitary.

The gonadotropins are FSH and LH, which act on the ovaries and testes to control the production of eggs, sperm and the sex hormones. Their release is itself directed by the hypothalamus.

Answer: C

People with blood group O negative are called universal donors.

Their red cells carry neither A nor B antigen, so they provoke no reaction in a recipient of any group. Group AB is the universal recipient for the opposite reason: it has no anti-A or anti-B antibodies in the plasma.

Answer: D

Sugar is the most soluble of these in water - about 200 g dissolve in 100 ml at room temperature, far more than common salt's 36 g.

Sucrose is so soluble because its many hydroxyl groups hydrogen-bond to water. Camphor and sulphur are non-polar and essentially insoluble.

Answer: C

Eucalyptus is the fastest growing of the trees listed, adding two to three metres a year in good conditions.

That speed is why it is planted for pulp and fuelwood, though its heavy water use makes it controversial in dry regions.

Answer: C

Electric current is measured with an ammeter, connected in series with the circuit so the whole current passes through it.

Its resistance is made very low so that inserting it barely changes the current. A voltmeter, by contrast, has a very high resistance and is connected in parallel.