General Science Mixed Quiz: Set 48

The correct answer is A, Femto. In the SI system the prefix femto, written f, stands for 10 raised to minus 15. The name comes from the Danish and Norwegian word femten, meaning fifteen. It is the prefix used for the size of an atomic nucleus, which is a few femtometres across, and a femtometre is also called a fermi after the physicist Enrico Fermi. Laser pulses lasting a few femtoseconds are used to watch chemical bonds break. B is wrong because zepto, z, stands for 10 to the minus 21. C is wrong because atto, a, stands for 10 to the minus 18, the step between femto and zepto. D is wrong because yocto, y, is the smaller 10 to the minus 24. Exam tip: learn the descending ladder - milli, micro, nano, pico, femto, atto, zepto, yocto, each three powers of ten apart.

The correct answer is C, Thallophyta. Litmus is a purple dye taken from lichens, and in the classification used in school science lichens are placed in Thallophyta, the group of simple plants whose body is an undifferentiated thallus with no true root, stem or leaf. Algae and fungi belong to the same group, and a lichen is in fact a partnership of an alga and a fungus living together. Litmus is a natural indicator: it stays purple in a neutral solution, turns red in acid and blue in base, and is used both as a solution and as litmus paper. Option A is wrong because gymnosperms are well developed plants with naked seeds, such as pine and cycas. Option B is wrong because pteridophytes, the ferns, are the first plants with vascular tissue. Option D is wrong because bryophytes such as moss and Marchantia are called the amphibians of the plant kingdom. Exam tip: litmus is red in acid, blue in base and purple when neutral.

The correct answer is B, 40 m. Put the values straight into s equal to u t minus half g t squared, taking upward as positive: 30 into 4 gives 120, half of 10 into 16 gives 80, and the difference is 40 metres. Reading it step by step makes the picture clear. The ball rises for 3 seconds, because 30 divided by 10 is the time to lose all its speed, and in those 3 seconds it climbs 45 metres. In the fourth second it falls back 5 metres, so it is 40 metres above the hand at the end of 4 seconds. A is wrong because 50 metres is the total path length, 45 up plus 5 down, and the question asks for displacement. C is wrong because 30 metres only repeats the initial speed. D is wrong because 15 metres is the height gained in the first second alone. Exam tip: displacement uses u t minus half g t squared, while distance adds the upward and downward paths.

The correct answer is C. Ultraviolet light is a transverse wave, not a longitudinal one, so this statement is the wrong one. In an electromagnetic wave the electric and magnetic fields vibrate at right angles to each other and to the direction the wave travels, which is the definition of a transverse wave. Longitudinal waves need a material to squeeze and stretch, and sound is the standard example. Option A is correct because ultraviolet light sits in the electromagnetic spectrum between visible light and X-rays. Option B is correct because electromagnetic waves need no medium and cross empty space, which is how the Sun's ultraviolet rays reach the earth. Option D is correct because ultraviolet wavelengths run from about 400 nanometres down to 10 nanometres, shorter than violet light, and this higher energy is what burns skin and is absorbed by the ozone layer. Exam tip: all electromagnetic waves are transverse; only mechanical waves such as sound can be longitudinal.

The correct answer is B, 32. Work done is force multiplied by the displacement along the force, so F equals the work divided by the distance, that is 480 joules divided by 15 metres, which gives 32 newtons. The formula to hold is W equal to F into s into the cosine of the angle between them; here the push and the movement are in the same direction, the cosine is one, and the mass of 25 kilograms is extra information that the question setter adds to mislead. One joule is the work done when a force of one newton moves a body one metre. A is wrong because 50 does not divide 480 by 15 and would need the work to be 750 joules. C is wrong because 16 halves the right answer, as if the distance were 30 metres. D is wrong because 25 simply repeats the mass in newtons, which is the trap in the question. Exam tip: W equals F into s, so force equals work divided by distance.

The correct answer is C, Avogadro. The statement in the question is Avogadro's law, given by the Italian scientist Amedeo Avogadro in 1811. It says that equal volumes of all gases at the same temperature and pressure hold the same number of molecules, so the volume of a gas is directly proportional to the number of moles in it. This is why one mole of any gas occupies 22.4 litres at standard temperature and pressure, and why the number of particles in one mole, about 6.022 x 10 to the power 23, is named the Avogadro number after him. A is wrong because Charles law links the volume of a fixed mass of gas to its temperature at constant pressure. B is wrong because Boyle's law says that volume varies inversely with pressure at constant temperature. D is wrong because Gay-Lussac gave the law of combining volumes and the pressure-temperature law. Exam tip: Avogadro ties volume to the number of molecules, Boyle to pressure and Charles to temperature.

The correct answer is D, Convex mirror. A convex mirror bulges towards the viewer and always gives a virtual, erect and diminished image, so whatever your distance from it, your reflection looks smaller than you. Because the image is small, the mirror takes in a wide field of view, which is why convex mirrors are fitted as rear-view mirrors on vehicles, at blind corners of roads and in shops as security mirrors. Its focus lies behind the mirror, so it is also called a diverging mirror. A is wrong because a plano-concave surface curves inward like a concave mirror and does not shrink a nearby face. B is wrong because a concave mirror gives a large magnified image of a close object, which is why it is used as a shaving and dentist's mirror. C is wrong because a plane mirror gives an image exactly the same size as the object. Exam tip: convex mirror means always virtual, erect and diminished, with a wide view.

The correct answer is C, Stomata. Stomata are the tiny pores on the surface of a leaf through which a plant takes in carbon dioxide and gives out oxygen and water vapour, so the exchange of gases takes place through them. Each stoma is bounded by two bean-shaped guard cells that swell to open the pore and shrink to close it, and this is how the plant controls its water loss. Most stomata lie on the lower surface of a leaf, so less water is lost to direct sunlight. Transpiration also happens largely through these pores. A is wrong because the cell membrane controls what enters and leaves a single cell, not the gas exchange of the whole plant. B is wrong because the nucleus carries the genetic material and directs the activities of the cell. D is wrong because guard cells only open and close the pore, while the exchange itself happens through the stomatal opening. Exam tip: stomata do the gas exchange and transpiration, guard cells only open and close them.

The correct answer is A, 400 m/s. The speed of any wave is its frequency multiplied by its wavelength, so here 200 Hz times 2 m gives 400 metres per second. Frequency is the number of complete waves that pass a point each second, measured in hertz, and wavelength is the distance covered by one complete wave; multiplying the two therefore gives distance per second, which is speed. In a given medium the speed of sound is fixed by the medium itself, so when the frequency rises the wavelength must fall in the same proportion. Sound travels at roughly 343 m/s in air at 20 degrees Celsius, about 1,500 m/s in water and about 5,000 m/s in steel, because particles in a denser and more elastic medium pass the vibration along faster. Option B is wrong because 200 is the frequency copied without multiplying. Option C is wrong because 80 does not follow from these numbers at all. Option D is wrong because it divides the frequency by 2 instead of multiplying. Exam tip: speed equals frequency times wavelength, and in air sound moves at about 343 m/s.

The correct answer is B, In the same direction. In a class 3 lever the fulcrum is at one end, the effort is applied in the middle and the load sits at the far end. Since both the effort and the load lie on the same side of the fulcrum, the beam turns one way and they move in the same direction. The effort arm is shorter than the load arm, so the mechanical advantage is less than one and more effort is needed than the load; what such a lever gains is speed and a wider sweep of movement. The human forearm, a pair of sugar tongs, a fishing rod and a stapler work this way. A is wrong because effort and load move oppositely in a class 1 lever, where the fulcrum lies between them, as in a see-saw or scissors. C is wrong because a lever turns about a fixed point and its two ends never move at right angles to each other. D is wrong because the size of the load changes the force needed, not the direction of motion. Exam tip: class 1 has the fulcrum in the middle, class 2 the load, class 3 the effort.

The correct answer is B, 10 ohm. For resistors in parallel the reciprocals add, so one over R equals one over 20 plus one over 20, which is 2 over 20, and R comes out as 10 ohms. A short cut worth keeping is that when two equal resistors are joined in parallel the result is half of one of them, and when n equal resistors are joined in parallel it is the value divided by n. The supply of 40 volts is not needed for the resistance; it only tells you that the circuit draws 4 amperes. A parallel joining always gives a resistance smaller than the smallest branch, because the current now has more than one path. A is wrong because 40 ohms is what the two would give in series. C is wrong because 25 ohms follows from no rule of combination. D is wrong because 20 ohms is the value of one resistor alone. Exam tip: series resistances add, parallel resistances add as reciprocals.

The correct answer is C, 1.6 sec. Time period is the time taken for one full oscillation, so it is the total time divided by the number of oscillations: 64 divided by 40 gives 1.6 seconds. Frequency is the reverse quantity, the number of oscillations in one second, which here is 40 divided by 64, or 0.625 hertz; period and frequency are always reciprocals of each other. For a simple pendulum the period depends only on the length of the thread and on the acceleration due to gravity, through T equal to 2 pi times the square root of L by g. It does not depend on the mass of the bob, nor, for small swings, on how wide the swing is. A pendulum about one metre long has a period of close to two seconds. A is wrong because 0.6 second would give more than 100 oscillations in 64 seconds. B and D are wrong because 6 and 16 seconds are far too long for 40 swings in just over a minute. Exam tip: time period equals total time divided by the number of oscillations.

The correct answer is A, 11. The atomic number of an element is by definition the number of protons in its nucleus, so an atomic number of 11 means 11 protons. The mass number is the total of protons and neutrons, so this atom has 23 minus 11, that is 12 neutrons. In a neutral atom the number of electrons also equals the atomic number, so there are 11 electrons as well. Atomic number 11 identifies the element as sodium, written as Na. The atomic number fixes an element and never changes for it, while the mass number differs between isotopes because the neutron count differs. Option B is wrong because 23 is the mass number, the protons and neutrons counted together. Option C is wrong because 12 is the number of neutrons in this atom. Option D is wrong because 22 is merely twice 11 and means nothing here. Exam tip: protons equal the atomic number, and neutrons equal mass number minus atomic number.

The correct answer is D, Neon. When electricity is passed through a sealed tube holding neon at low pressure, the gas atoms are excited and give out a bright orange-red glow, which is why advertising signs are still called neon signs. Neon is a noble gas discovered in 1898 by Ramsay and Travers; it is chemically inert, forms no ordinary compounds, and is also used in voltage testers, high-voltage indicators and lightning arresters. Every gas glows in its own colour in a discharge tube, and that colour is the fingerprint of its atomic energy levels. Option A is wrong because helium gives a pale pinkish-white glow and is better known for filling balloons and airships. Option B is wrong because argon glows a pale violet-blue and is used to fill electric bulbs and to shield welding. Option C is wrong because nitrogen glows bluish, and its common uses are as an inert packing gas and as a liquid coolant. Exam tip: neon gives red light in a discharge tube, while argon is the gas that fills ordinary electric bulbs.

The correct answer is D, Both the statements are true. Reduction means the loss of oxygen or the gain of hydrogen, so each statement states one half of the same definition. In the older oxygen-hydrogen sense, a substance is oxidised when it gains oxygen or loses hydrogen and reduced when it loses oxygen or gains hydrogen. When copper oxide is heated with hydrogen, the copper oxide loses oxygen and is reduced while the hydrogen gains oxygen and is oxidised, which is why the two always happen together in a redox reaction. The modern electron view says the same thing in another way: reduction is the gain of electrons and a fall in oxidation number. A is wrong because both halves of the definition are standard school chemistry. B is wrong because gaining hydrogen is also reduction, as in ethene turning into ethane. C is wrong because losing oxygen is the oldest test of reduction of all. Exam tip: remember OIL RIG - Oxidation Is Loss, Reduction Is Gain of electrons.

The correct answer is D, Gustatory receptors. The receptors that pick up taste are called gustatory receptors, and they sit inside the taste buds on the tongue. They respond only to substances dissolved in saliva, which is why a dry tongue tastes little, and they report five basic tastes, sweet, sour, salty, bitter and umami. From the tongue the signal travels along cranial nerves to the brain, where taste and smell together give food its flavour. A is wrong because sensory receptor is the broad name for every receptor of the body, including those for light, sound, touch and pressure. B is wrong because chemoreceptor is the wider class that covers both taste and smell, so it does not name the taste receptor in particular. C is wrong because olfactory receptors lie in the lining of the nose and detect smell. Exam tip: gustatory means taste, olfactory means smell, auditory means hearing.

The correct answer is A, the epiglottis. It is a leaf-shaped flap of cartilage at the root of the tongue that swings down and covers the opening of the windpipe every time food is swallowed, so that the bolus is guided into the oesophagus instead of the trachea; when it fails we choke and cough. Option B is wrong because the larynx is the sound box that houses the vocal cords, and although it lies just below the epiglottis it does not perform this closing action. Option C is wrong because the pharynx is the common chamber behind the mouth and nose through which both air and food pass, not a valve. Option D is wrong because the pleura is the double membrane wrapping each lung and its fluid only reduces friction as the lung expands and contracts.

The correct answer is A, William Harvey. The English physician William Harvey showed by experiment and measurement that blood is not made afresh and used up in the tissues, as was then believed, but moves in a closed circuit, driven by the heart acting as a pump, and he published this in 1628 in his book on the motion of the heart and blood. Option B is wrong because Karl Landsteiner worked out the ABO blood groups at the beginning of the twentieth century and later helped identify the Rh factor; he explained the kinds of blood, not its movement. Option C is wrong because Edward Jenner introduced vaccination against smallpox using cowpox material and is called the father of immunology. Option D is wrong because Robert Koch identified the bacteria causing tuberculosis and cholera and gave the postulates that link a germ to a disease. A related name worth remembering is Christiaan Barnard, who performed the first human heart transplant.

The correct answer is B, the brain. The brain is the organ that interprets pain, but its own tissue has no pain receptors, so cutting or pricking it causes no sensation; the covering membranes, the blood vessels and the scalp do have receptors, which is why a headache hurts. This is the reason brain surgery can be performed on a patient who is awake and talking, with only the scalp anaesthetised. Option A is wrong because the skin is the richest field of pain receptors in the body and a needle prick there is the standard example of a painful stimulus. Option C is wrong because the heart has pain receptors and signals its distress as the crushing pain of angina, often felt in the left arm as referred pain. Option D is wrong because the cornea of the eye is among the most sensitive tissues of the body, which is why the smallest speck of dust in it is unbearable.

The correct answer is C, because the enzyme in saliva that acts on starch is salivary amylase, also called ptyalin, and not a lipase. Amylase breaks starch into the sugar maltose; a lipase works on fat, and saliva carries no significant lipase, so the statement pairs the right action with the wrong enzyme. Option A is a correct statement, since partly digested food leaves the stomach as chyme and enters the small intestine through the pyloric opening. Option B is correct too, because the digestion of all three major nutrients is completed in the small intestine with bile from the liver and the trypsin, amylase and lipase of pancreatic juice, and absorption follows through the villi. Option D is correct, as the oesophagus carries swallowed food from the pharynx to the stomach by peristalsis.