P1 Student Book Answers.pdf

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© Pearson Education 2010. Edexcel GCSE Science Teacher and Technician Planning GuideThis document may have been altered from the original.

Answers – P1: Universal physics

P1.1 The Solar System

Student Book

1 A model with the Earth at the centre.2 a What is at the centre of the model and the way in

which the planets followed smaller circles in their orbits

in Ptolemy’s model.b Two of: the number of planets; the fixed stars; thecircular orbitsc One of: more planets; dwarf planets; the stars are notfixed; orbits are not circular

3 They show that not everything orbits the Earth, asPtolemy thought.

4 Light waves, radio waves, microwaves5 To get away from pollution/clouds/atmosphere (the

absorption of different wavelengths by the atmosphere isnot required at this stage).

6 The following points should be made:

telescope allowed greater detail to be seen

telescope allowed smaller objects to be discovered

telescope showed that not everything orbits the Earth

photography allowed better data recording some telescopes can detect radio waves/microwaves

detecting radio waves/microwaves allows objects thatare not visible to be ‘seen’

Skills spotlight

By reading Copernicus’s book or talking to otherscientists

By observing the way in which Jupiter’s moons orbitedJupiter, rather than the Earth

Activi ty Pack

P1.1a Beautifu l Space

Students’ own answers, which should include:

What the object is called

What type of object it is (star, planet, galaxy etc.) Where they obtained the image

Any other information such as the name of thetelescope or astronomer that took the picture

The name of anybody who deserves a copyright credit.

P1.1b Comparing astronomical observations

Observation in detail Summaryfor Venndiagram

Naked-eye;Telescope;Photography

In 1610, Galileo discovered fourof Jupiter’s moons

Jupiter’smoons

telescope

In January 2010 NASAannounced that its Kepler spacetelescope had recently found five

exoplanets, those outside ourSolar System

exoplanets photographyand telescope

Every full moon is a public holidayin Sri Lanka

full moon naked eye

On a clear night, Venus may beseen bright near the horizon justafter sunset

Venus naked eye

To protect your eyes, a solareclipse can be viewed by taking apicture of it.

solareclipse

photography

Sometimes collections of meteorsprovide a fiery lightshow as theyfall to Earth.

meteors naked eye

Neptune was discovered by local

observatories following predictions by John Couch Adams and Urbainle Verrier in 1846

Neptune

discovery

telescope

The ancient Mayan Pyramid ofKukulcan was constructed withparts that line up at certain times tocomplex sun and star formations.These formations would havetaken years for their astronomersto measure.

Mayanpyramid

naked eye

Photos of nebulae from theHubble Space Telescope showedwhere young stars are born.

nebulae telescope andphotography

In 2005, NASA’s Cassinispacecraft sent back pictures ofSaturn’s moon called Tethys.

Saturn’smoonTethys

telescope andphotography

Time-lapse photography allowsus to observe the movements ofthe stars across the sky over awhole night. In the UK, the resultis a set of concentric circles withthe North Star at the centre.

apparentmovementof stars

photography

Ptolemy worked out a geocentricmodel of the Universe by looking

up at the sky and noting downwhat he saw.

Ptolemy naked eye

P1.1c New planet discovered

1 The following underlined:It's definitely bigger than Pluto.It is currently almost directly overhead in the early-morning eastern sky in the constellation Cetus,We are 100 percent confident that this is the first objectbigger than Pluto ever found in the outer solar systemEven if it reflected 100 percent of the light reaching it, itwould still be as big as PlutoI'd say it's probably [about] one and a half times the sizeof Pluto, but we're not sure.

2 The following circled:

using the Samuel Oschin Telescope at PalomarObservatory near San DiegoGemini Observatory in Mauna Kea, HawaiiThe three photos were taken about 90 minutes apart.Image credit: Samuel Oschin Telescope, PalomarObservatory.

3 The following highlighted:It's definitely bigger than Pluto.The planet appears to be typical of Kuiper Belt objects--only much bigger.the first object bigger than Pluto ever foundit would still be as big as Pluto"I'd say it's probably [about] one and a half times the sizeof Pluto, but we're not sure."

4 Oct. 21, 2003

5 Less likely to interrupt observations due toclouds/rain/pollution6 14.55 billion km (or 14 550 million km)7 One and a half times the size of Pluto8 A dark realm beyond Neptune where thousands of small

icy bodies orbit the sun.9 a photos using sam Oshin telescope

b That it’s a large object in our solar system;about 15 billion km away;about 1.5 x size of Pluto

10 To ensure that the name had not already been used, ORto make sure that the dwarf planet was real and could beseen by other scientists, OR to make sure that the dwarfplanet only ended up with one name that all scientistsshould use.

P1.2 Refracting telescopesStudent book

1 Two from, for example: air, glass, water



© Pearson Education 2010. Edexcel GCSE Science Teacher and Technician Planning Guide

This document may have been altered from the original.

2 Light/waves change direction when they cross theboundary between two media.

3 The distance from a lens to the point where rays of lightfrom a distant object meet.

4 Hold the lens up in front of a screen, with light coming toit from a distant object. Move the lens back and forthuntil a clear image appears and then measure thescreen-to-lens distance.

H5 a Bend away from the normal

b Bend towards the normal6 Lenses change the direction of light entering and leaving

them. The shape of convex lenses bends rays of light so

that a beam of parallel rays is brought to a focus. In arefracting telescope an objective lens brings parallel raysfrom distant stars to a point. Another convex lens is usedas an eyepiece lens, which magnifies this image.

Skills spotlight

Light rays have arrows showing the direction the light istravelling

Standard outline shape for lenses (2D not 3D; notdrawn realistically)

H Normal line drawn at the interface

H Waves can be represented either by rays (straight

line with arrows) or as straight lines at right angles tothe ray (a wavefront)

Activi ty Pack

P1.2b Refraction effects

1

2

3

4

P1.2c Refraction questions

1

2

3 a Normal lines

b

4 Lens drawn between the window and screen. Labelsshould include an indication that the screen is showing afocussed image of the view through the window, and thatthe focal length is the distance between the lens and thescreen.

P1.2d Refraction Challenge

1

2 Diagram similar to fig D in Student book (page 210). 3 a It slows down

b Air to glass. It slows down more when it goes intoglass than into water.

4 a Normal linesb, c

d As diagram for the answer to P1.2c Q3b.5 Glass; slows; towards; increases; away; refraction

P1.4 Reflecting telescopes

Student Book1 Refraction and reflection (allow change of speed)2 Some light is reflected at the lens so does not contribute

to the image. A mirror uses all the light to make the image.3 A camera picture of the image can simply be turned the

other way up.4 The focusing of rays happens through a reflection within

the telescope. A second reflection means the same spaceis used twice in the focusing of light, nearly halving thelength of tube needed.


Reflectors use a primary mirror instead of an objectivelens – this can allow fainter stars to be seen

Reflectors have a secondary mirror that can block someof the incident light – for small-diameter telescopes thisis a significant problem in terms of light collection

Both use an eyepiece lens to magnify the imageproduced – this allows technology crossover betweenthe two types

Skills spotlight

More distant or fainter stars only send a very smallamount of light to us

Cameras need a minimum amount of light to obtainimages

A larger diameter telescope can collect more light For larger-diameter telescopes, reflectors (mirrors) use

more of the light collected to produce the image (lensesreflect some light away)

Activi ty Pack

P1.4b Refracting and Reflecting Telescopes

1 Light from distant object; Light rays from a very … focusof the lens; The eyepiece lens acts … from the objectivelens;

2 So that the image is not ‘washed out’ by light from othersources.

3 Large lenses improve the magnification, so largertelescopes will give clearer images of distant objects.

4 Reflection from the lens surfaces reduces the amount of

light (large lenses deform under their own weight as theycan only be supported at the edge, distorting the image

– however this idea is not required in the Corespecification.)





5 a Labels as on fig C in Student Book (page 215)b Focus parallel light rays to form an image of thedistant objectc magnify the image produced by the primary (curved)mirror.

6 Mirrors don’t suffer light loss because the reflected lightis used to make the image. The secondary mirrorblocking light is less of a problem with large telescopes.

P1.4c Hamid’s telescopes

1 Colour; upside-down; magnified2 a Produces an image of the distant object

b To magnify the image produced by the objective lens.3 a Concave mirror; secondary mirror (flat or convex);

eyepiece lensb Diagram similar to fig C in Student Book (page 215)

4 Reflecting telescope would be better for viewing veryfaint, distant stars. Some light is reflected at an air/glassboundary (lens), so there is a loss in collected light (eventhough most light passes through). This loss of lightmakes the image fainter. This is not a problem with amirror, so a reflecting telescope can allow fainter stars tobe seen.

5 Their separation should equal the sum of their focallengths.

6 To prevent other light sources affecting the light from theobject.

P1.5 WavesStudent Book

1 All the water would move to the other end2 Longitudinal: sound and some seismic waves

Transverse: two of water waves, light, radio, gamma etc.3 2 Hz4 a 300 000 000 m/s

b 340 m/s

H c 50 m


Diagram as per Figure B (mark for shape, and mark forlabels)

Wavelength is distance from point on one wave to samepoint on next wave

Amplitude is maximum displacement from rest/meanposition

Frequency is number of waves passing a point eachsecond

Speed is how fast a wave moves and can be calculatedby multiplying frequency and wavelength

Skills spotlight

Count the number of waves passing you in (e.g.) 10seconds

Frequency is then this measured number divided by 10

Time one wave travelling from your position to otherend of pier

Wave speed is then 50 m divided by time measurement

Wavelength is wave speed divided by frequency

Activi ty Pack

P1.5a What are waves?

1 a wavesb lightc transversed longitudinal

2 a matterb slowerc transversed longitudinal

3

P1.5b Amplitude, frequency and wavelength

1 wavelength; frequency; amplitude2

3 a i 3m ii 0.25 mb i 0.25m ii 4mc i 8m ii 12m

4 Every second the string produces 440 sound waves.5 3.4m6 5 Hz

P1.5c Wave Speed

1 Words to be deleted: b) least c) transverse d) longitudinale) light f) amplitude

2 1.5; 8; wavelength; 8 x 1.5; 12 m/s3 12 m/s, 250 m/s, 5m/s

P1.5d The wave equations

1 250 Hz has a wavelength of 1.32m; 17600 Hz has awavelength of 0.01875m

2 a f = 4 x 1014 Hzb f = 7.5 x 1014 Hzc difference is 3.5 x 1014 Hz, so 2.5 x 1014 more blue

waves are produced each second.3 0.104 m/s4 11 785 Hz5 a 3500 m

b 0.05 mc 0.12 m

6 a 85 714 Hzb 6 x 109 Hzc 2750 Hzd radio and microwaves transverse; sound longitudinal

7 3.24 m8 a 330 m/s

b Yes in air, as it has the speed given for air travel.9 4 x 10-7 m10 0.0079 m

11 Question 7 waves: 0.0067 s; question10 waves: 6060 s(101 m6inutes)

P1.6 Beyond the v isible

Student Book

1 Most to least: red, orange, yellow, green, blue, violet2 The Sun is too bright to look at safely; the filters would

reduce the intensity to make it safer.3 He could have tested the heating effect further beyond

red and beyond violet. (Accept other sensiblesuggestions.)

4 He may have read about it, probably in a scientific journal, or gone to a lecture.

5 Both transverse; both electromagnetic6 The following points should be made:

William Herschel discovered IR; this is beyond the redend of the visible spectrum, invisible to the human eye;he showed its presence by observing its heating effecton a thermometer

Johann Ritter discovered UV; this is beyond the violetend of the visible spectrum, invisible to the human eye;he showed its presence by observing its effect on silverchloride, which was greatest outside the visible region.

Skills spotlight

If one end of his experiment had been nearer the fire inhis room, this would have affected the temperaturemeasurements and it would not have been a fair test.

The control thermometers were in place to measuresuch other heating effects within the room so these

effects could be discounted.







Skills spotlight

The device indicates UV levels at the time

We can protect against skin cancer by reducingexposure to UV

So when the device shows higher UV levels, childrencan move to the shade

Activi ty Pack

P1.8a Electromagnetic dangers

Radio waves Little danger

Infrared Skin burns

Microwaves Internal heating of body cells

Visible light Little danger

Ultraviolet Temporary blindnessCan lead to skin cancerDamage to skin surface cells

X-rays

Gamma rays

Damage to cells in the bodyMutations of DNACan lead to cancer

P1.8b Mr Strawbrain’s suncream experiment

Instruction 1 a Each group could be detecting light from other groups'

lamps or from the window.b Groups could set up their lamps and plastic squares in

cardboard boxes or set up screens around theirapparatus.Instruction 2a Safety – it would be easy for light from a lamp 30 cm

above the bench to shine into someone's eyes. Theamount of light hitting the plastic squares will vary with theheight of the lamp. Different plastics/thicknesses will havedifferent transmission properties, so each group can onlycompare the two suncreams they tested, they cannotcompare their results with other groups.

b Set all lamps to be 10 cm above the bench. This will makethem all the same, and also make it less likely that UVlight will shine into students' eyes.Every group should use the same type and thickness ofplastic.

Instruction 3a The amount and thickness of cream is not defined.b Measure or weigh out the same amount of suncream for

each group. Each group has to smear their suncreamover the same area.

Instruction 4a Different detection systems could produce inconsistent

results. Judging the brightness of a UV pen is subjective(results will vary from student to student).

b Results should only be pooled and compared fromgroups using the datalogger. Other results can becompared but should be treated with caution. Thegroups using the UV pens should use two squares ofplastic, each with one of their suncreams on, so they candirectly pair one with the other. All students in the groupshould agree which of the two is brightest. These results

can be used to rank the suncreams in order, but cannotbe used for a quantitative conclusion.

Instruction 5a The first type of suncream will still be on the plastic.b Clean the plastic squared before applying the 2nd

suncream, or use a new piece (of the same thickness).Instruction 6a Cannot use a bar chart to display comparative results

(from the groups using UV pens).b Ask groups using UV pens to put their suncreams in

rank order.

P1.8c Lead shields against X-rays

1. The curve goes up in an S-shape, with gradientincreasing after 200 kV, but then decreasing again after

600 kV.2 a 25 mmb 45 mmc 50 mm

3 Approximate energies:a 250 kVb 350 kVc 500 kV (depends on students curves)

4 a greater thickness needed with greater voltage/energyb Higher voltage, higher energy, higher frequencyc Higher voltage, higher energy, greater cancer risk

5 a increased exposure increases risk of cancer, so a limitkeeps risk to acceptable level.b To reduce their own exposure to X-rays

6 Visible light reflected is not harmful7 Radio waves pose little potential danger to humans

8 a scientists report facts of potential dangers togovernment.Government chooses level of acceptable riskb Workers’ x-rays exposure should be monitored;compared with acceptable levels; working conditionsaltered if likely to go over the limits; prosecution foremployers failing to protect their employees;

P1.8d X-ray shoe fitting

1, 2, 3 (points to be circled are shown here in italics)The shoe-fitting fluoroscope was used in shoe shops about50-80 years ago. They had a wooden box with a hole at thebottom where you put your feet. When you looked through ahole on the top, you could see an image of the bones of thefeet and the outline of the shoes. This picture was made by anX-ray scanner.The fluoroscope, was an X-ray tube.

X-rays have very highfrequency, so are very high energy and we now know theycan cause cancer after long term exposure. The onlyprotection between your feet and the tube was a 1 mm thicksheet of aluminium. Often there were three differentintensities: the highest intensity for men, the middle one forwomen and the lowest for children.Despite high exposures, there were no reported healthproblems for shoe shop customers. Unfortunately many shoesalespersons put their hands into the X-ray beam to feel the

shoe during the fitting. One saleswoman who had operated a shoe-fitting fluoroscope 10 to 20 times each day over a 10-year period developed a skin disorder. A shoe model receivedsuch a serious radiation burn that her leg had to be removed.These machines were used in Britain until around 1970.

4 50-80 years ago until around 19705 Because of the health hazards6 They used them all the time so had increased exposure7 X-rays are absorbed by the body. The strong one would

be needed to get through a large foot, but that would betoo much for a small foot where no bones would be seenas they wouldn’t absorb enough of the x-rays.

8 1 mm thickness of aluminium absorbs little x-ray energy(and if the filter absorbed too much energy there would notbe enough X-rays going through the feet to form animage).

P1.9 Using electromagnetic radiation

Student Book

1 The bulb emits a lot of UV that is not used for illumination(we can’t see it). The fluorescent material absorbs the UVand re-emits the energy as visible light, so making thebulb brighter.

2 The bush itself emits little infrared, so there is a bigcontrast between the suspect’s thermal image and thebush. Infrared waves pass through the gaps betweenleaves to reach the camera. With visible light, the lightreflecting from the bush masks any light from the suspectthat gets through the leaves.

3 UV kills bacterial cells so can be used to sterilise sewage.4 The gamma rays kill microorganisms in the herbs but the

rest of the herb remains unchanged (and does notbecome radioactive).

5 Killing cancer cells by radiotherapy; gamma scan fordiagnosis (gamma-emitting chemical is injected into theblood and blood flow can then be observed by themovement of gamma emissions around the body);sterilising surgical instruments.





6 The following points should be made, with a briefexplanation of each:

gamma rays: including sterilising food and medicalequipment, and the detection of cancer and itstreatment

X-rays: including observing the internal structure ofobjects, airport security scanners and medical X-rays

ultraviolet: including sterilising water, security marking,fluorescent lamps and detecting forged bank notes

visible light: including vision, photography andillumination

infrared: including cooking, thermal imaging, short-

range communications, optical fibres, television remotecontrols and security systems

microwaves: including cooking, communications andsatellite transmissions

radio waves: including broadcasting, communicationsand satellite transmissions

Skills spotlight

CCTV: keeps a permanent record of events within itsfield of view; can be used in police investigations and asevidence to help fight crime; does not allow people tomove anonymously, which many people would like as afreedom; may shift crime to other areas withoutcameras; saves police resources; reduces employmentas a result

Full body X-ray scanner: can identify contraband anddangerous items being held secretly in a person’sclothing; this can protect against terrorism and help fightcrime; an invasion of privacy, as clothing does notprotect modesty any more; saves resources byreducing need for security officers; reducesemployment as a result

Activi ty Pack

P1.9a Researching the Electromagnetic Spectrum

Students own answers

P1.9b Using radio waves

Use Users Brief description Benefit topeople

Radiostationbroadcast

The public Governments/companies sendmessages to region.Everyone with aradio can receive.

Passesknowledge on;entertainment

Walkietalkies

Public;military;securitypersonnel

Handsets cancommunicate overshort range (fewkm); differingfrequencies preventinterference

Quick shortrangecommunications; increasedsafety (e.g.explorers don’tget lost);improvedoperationalcapability

Remotecontrolledcar

Public Control handsetsends electronicmessages to carwhich control itsmovements; veryshort range (100m)

Entertainment;greater capabilityfor model caractivities

Television Public Governments/companies sendmessages to region.Everyone with a TVand aerial canreceive.

Passesknowledge on;entertainment

GPS Public,emergencyservices,military

Satellites sendsignals that thehandset receives,and works out theposition on theEarth.

People knowwhere theyare/don't getlost.

P1.9c Search the low energy EM spectrum

Yellow highlight: newspaper, watch, view, spotlight, textmessage, purple, lights, sawPink highlight: Search for Extra-Terrestrial Intelligence's bigdish, switched off the radio, Arecibo radio dish, TV (TV can beradio waves or microwaves).Green highlight: microwave, TV, live by satellite, mobilevibrateRed highlight: toaster, remote, electric fire, switched over,thermal imaging camera, heater

P1.10 Ionising radiation

Student Book

1 They can change atoms into particles with a charge(ions); these are very reactive, can damage DNA andmay lead to cancer.

2 Alpha, beta and gamma3 All transfer energy; all ionising radiations4 Alpha are particles, gamma are waves (alpha are also

more ionising, though this is not required).5 Use the GM tube to monitor the sample over time; if it

detects ionising radiation regularly without ever stopping,then this could be said to be ‘all the time’.


gamma, UV and X-rays are ionising, so can damageDNA and lead to cancer

other EM waves are non-ionising so cannot cause this alpha and beta are ionising so can also cause cancer

eventually

Skills spotlight

The country with the gamma bomb could easily win a war withsuch a powerful weapon; other countries do not want thedanger of being beaten in a war by them; so they will developsimilarly devastating weapons. Student's opinions on thedesirability of this may vary, but should be backed up with anexplanation. Opinions may range from 'yes, we need todefend ourselves' to 'no, this only escalates arms races andwastes money/makes it more likely that someone will usesuch a weapon'.

Activi ty Pack

P1.10a Radiation j igsaw reading

Radium1 White2 Alpha, beta and gamma3 They can change atoms into ions4 Energy5 All the time6 It glowsUranium1 Grey2 Alpha3 They can change atoms into ions4 Energy5 All the time6 Can be used in nuclear weapons

Plutonium1 Silvery2 Alpha3 They can change atoms into ions4 Energy5 All the time6 Can be used in nuclear weaponsIodine1 Purple2 Beta3 They can change atoms into ions4 Energy5 All the time6 Can treat thyroid disordersStrontium

1 Silvery2 Beta3 They can change atoms into ions4 Energy





5 All the time6 Can be used to make small nuclear power

supplies/named after the Scottish town Strontian Americium1 White2 Alpha3 They can change atoms into ions4 Energy5 All the time6 Used in smoke detectors

P1.10b Ionising radiation quiz

1 a Alphab Damagec Cancerd Ion

2 a Steriliseb Energyc Betad Kille Radioactive

P1.10c Becquerel’s plates

Students own answers

P1.11 The Universe

Student Book

1 Some nebulae are collections of stars; the Milky Way ismade of stars; discovery of more planets and theirmoons in the Solar System.

2 The Sun3 The Sun and the planets orbiting it (and their moons).

Students may also include dwarf planets, asteroids,comets etc.

4 a Our galaxyb All the galaxies (or all of space and everything in it).

5 Moon, Earth, Sun, Solar System, Milky Way, Universe6 The difference between the large and small

measurements is too big (or similar response).7 A possible answer: Some objects are very faint and/or

very far away. Many of these cannot be seen with thenaked eye, or cannot be seen in much detail. Astelescopes with better magnification were developed,astronomers could make out more detail on nearbyobjects such as planets in the Solar System, and couldtell the difference between clouds of gas and clusters ofstars (galaxies). They could also work out the sizes ofplanets, stars and galaxies and the distances betweenthem.

Skills spotlight

a The approximate diameters of the Earth, Sun and Moon,and the distances to the Sun and Moon.

b Neptune had not been discovered, nor had galaxies, andthe nature of the Milky Way (as one among billions ofgalaxies in the Universe) was not known. Models of theUniverse at the time assumed that stars were muchcloser than they are, so if he had estimated a distance to

Proxima Centauri it would have been far too small (and itwould not have been known then that Proxima Centauriis the closest star to the Sun).

c The distance to the furthest galaxy observed. Astelescope technology improves, more powerfultelescopes and better computer processing may bedeveloped that can detect galaxies even further away.Some students may add that more powerful techniquesmay allow more accurate determination of suchdistances.

Activi ty Pack

P1.11b Nebulae and galaxies questions

1 A cloud of gas.2 Some are gas clouds, some are clusters of stars, and

some are galaxies beyond our own.3 More powerful telescopes (greater magnification), which

allow more detail of distant galaxies to be seen.

4 We can see more stars in some parts of the sky thanothers, and the area with the most stars appears as abright band across the sky.

5

Astronomer

Shapley CurtisModern

astronomers

Size ofUniverse

300 000 lightyears

smaller thanShapley

at least 93 billionlight years

Nature ofnebulae

small gasclouds within

the galaxy

some weregalaxies

beyond ours

gas clouds,clusters of stars,

or galaxiesPosition ofSun

not at thecentre

at the centre not at the centre

P1.11c Nebulae and galaxies cards

Shapley: 300 000 light years across; Universe is a galaxy;Sun is at the centre of the galaxy.Curtis: Galaxy is 30 000 light years across; Universe is manygalaxies; Sun is not at the centre of the galaxy.Hubble: Universe is many galaxies; Andromeda Galaxy is 1000 000 light years away.Modern astronomers: Universe is many galaxies; Sun is notat the centre of the galaxy; Universe is at least 93 billion lightyears across.

P1.11d Space wordsearch

1

2 Students' own responses.P1.11e The Universe

1 a Solar Systemb Galaxyc Universed Telescopee Naked eye

2 Moon, Sun, Neptune, Atlair, Andromeda3 Earth 13 000 km; Jupiter 143 000 km;

Milky Way 1 × 1018 km; Moon 3500 km;Sun 700 000 km

P1.11f The changing size of the Universe

1 The atmosphere distorts light from the stars, and on ahigh mountain there is less air above you. Mountain tops

are also sometimes above clouds.2 Any sensible answer – such as it would easily fit within

the orbit of the Earth, or it was about half the size of theEarth’s orbit.

3 a The Earth was at the centre with everything movingaround it, so the stars would always be the samedistance away.b If they were fairly close, the Earth would be closer to aparticular star at some times than at others. Answersshould include a suitable diagram marking differentdistances to stars at different times of year.

4 Better/more accurate telescopes were available.5 61-Cygni was about 10 light years away, and there were

many more stars much further away than that.6 They have more powerful telescopes, and so they can

measure smaller angles more accurately. 7 a He used Cepheid stars, which vary in brightness in a

way that depends on their actual brightness. To estimatethe distance, he compared their true brightness with howbright they appear to be from Earth.





b Dust would make the stars appear dimmer, so the starwould seem to be further away.c Measurements have been repeated with moresensitive and more precise instruments. (In fact, thereare two types of Cepheid variable with differentbrightness/period relationships, which Hubble did notknow about.)

P1.13 Exploring the Universe

Student Book

1 The photograph can collect light over a longer time and so

detect fainter objects.2 Radio telescopes usually have big dishes; visible lighttelescopes have lenses or mirrors. Visual light telescopeshave to be kept inside buildings for protection; radiotelescopes do not.

3 Exploded stars (Figure B); details on the surface of theSun (Figure A).

4 The Earth’s atmosphere absorbs UV and X-ray radiation,which are the wavelengths detected by the Swifttelescope.

H5 a UV, microwave (although some parts of the microwave

spectrum can be detected from the surface of the Earth),IR (though some IR wavelengths can be detected fromEarth).b The atmosphere absorbs some or all of the radiation atthose wavelengths/frequencies.

6 Any three from the following reasons (expressed in shortparagraphs). Astronomers now have much more powerfultelescopes (greater magnification) than Galileo did; theycan use photographic equipment to detect light and recorddata permanently; they can use computers to process andanalyse the data; they can use telescopes that detectparts of the EM spectrum other than visible light.

Skills spotlight

a They can answer questions about the different types ofelectromagnetic radiation that stars and galaxies emit(not just visible light); also the nature of very faint and/ordistant nebulae and galaxies; distances to stars; etc.

b Questions about the nature of the most distant (faintest)objects.

Activi ty Pack

P1.13a Advantages and d isadvantages

A: 3 (advantage), 4 (advantage), 7 (advantage), 10(disadvantage)

B: 1 (advantage), 2 (advantage), 5 (disadvantage), 6(disadvantage), 8 (disadvantage), 9 (advantage)

P1.13b Telescopes and the Universe

1

Statement A B C

a Detects radio waves

b Detects visible light ()

c Launched using rocket

d Can only detect EM that travels throughatmophere

e Can detect EM absorbed by atmosphere

2

DiscoveryDid not

needVisible

lightOther parts ofEM spectrum

Fuzzy patches callednebulae visible

Earth orbits the Sun

Exploding stars giveout X-rays

Some nebulae aregroups of stars

Some nebulae areclusters of stars

Some objects give outradio waves

3 The atmosphere absorbs X-rays and infrared, so atelescope on the ground would not receive any radiationfrom the stars.

P1.13c Radio telescopes and pulsars

1 a Bell had to look at paper printouts. Today the signalswould be recorded in a computer, and probably beanalysed by the computer as well.b Computers can analyse a lot more data than humanscan.

2 Anything that sends out radio signals, such as radiotransmitters etc. Many electrical devices also causesome sort of interference.

3 They did not know of any stars that could producesignals that pulsed so fast.

4 It would be very unlikely that four alien civilisations livingin completely different parts of the Universe wouldchoose to communicate in exactly the same way.

5 a Bell and Hewish checking for interference from Earth-based sources, and checking the rest of the sky forsimilar signals.b The article in Nature.c Other scientists examining their findings and makingtheir own observations.

6 A diagram showing a star emitting light in two narrowbeams (accept one beam, unless students havespecifically been asked to research their answer), andan indication of rotation. The explanation is that radiowaves from the star are only detected when the part ofthe star emitting them is facing the receiver, soobservers on the Earth only sees a pulse as the beamsweeps past.

P1.14 Alien life?

Student Book

1 Water is necessary to life as we know it, so if there iswater on Mars it is more likely that life as we know it mayonce have existed there.

2 A rover3 a They have not found any evidence of life, but they

have not investigated everything they can so they cannotsay that there is no life – ‘absence of evidence is not

evidence of absence’. b They will never be able to investigate all the planets inthe Universe or search for radio signals from alldirections in space.

4 Oxygen usually reacts with surface rocks, removing thegas from the atmosphere. So it would only be detectablein an atmosphere if there were some (life) processproducing it, such as photosynthesis.

5 Stars and other astronomical objects emit radio waves.The SETI projects have not detected any signals thatcould have come from intelligent life.

6 A possible answer: Life as we know it needs liquid water.If the water discovered was frozen, even in the Martiansummer, that means that there is very little liquid waterpresent now (the temperature is too low for liquid water).

The channels on the surface show that there must havebeen liquid water flowing in the past. If life did developon Mars it is likely to have died out when there was nomore liquid water, so we might find remains such asfossils even if we do not find living organisms.

Skills spotlight

Answers will depend on which option students choose. An argument ‘for’ could emphasise that humans need to knowand understand their surroundings, and that it would beinteresting to find out if there is life elsewhere.

An argument against could say that it is more important toimprove the lives of people on Earth, or to protect theenvironment etc.

Activi ty Pack

P1.14a Finding ou t1 Probe – an unmanned spacecraft that goes into orbit

around another planet or moon





Lander – an unmanned vehicle that lands on the surfaceof another planet or moonRover – an unmanned vehicle fitted with wheels and anengine that can move around on the surface of anotherplanet or moon

2 & 3 A: optical telescope on Earth; images of planets, stars or

galaxies; can gather data on many different objects, butlimited by distance and interference from theatmosphere.

B: radio telescopes on Earth; images formed by the radiowaves from stars and galaxies; good for listening for

possible signals from intelligent life, but not a lot of helpin looking for signs of life on planets or moons.

C: camera on space probe; images of the surface of otherplanets or moons; good for getting detailed maps of thesurface, but can only investigate one planet/the moonsaround one planet, and cannot get very close up imagesof rocks/soils/possible life forms.

D: radar on space probe; maps of other planets or moons;not very useful for looking for signs of life.(images labelled C and D can be either way round)

E: camera on lander or rover; close-up images of thesurface of a planet or a moon; good for providingdetailed and/or magnified images for looking for signs oflife, but can only investigate a very limited area.

F: sampler on lander or rover; soil and rock samples; good

for carrying out investigations on rocks and soil, but canonly investigate a very limited area of the planet.

P1.14b Looking for l ife

1 B, E2 B3 B4 B, D, E5 C, D6 a E

b D

P1.14c The Viking experiments

1 The lander scooped up samples of soil.2 a Microbes

b If any larger forms of life existed they would probably

have been seen by cameras on the lander or an orbiter.3 The experiment was trying to detect if any of the

radioactive carbon dioxide had been absorbed bymicrobes in the soil. They would not be able to detectthis if any of the original radioactive carbon dioxide wasstill present.

4 a The sterilised samples were to try to make sure thatany positive results were due to the presence of life, andnot just to chemical reactions in the soil. If the sameresult was obtained with both samples, that wouldindicate a soil reaction.b Heating them.

5 a Plants on Earth give off oxygen when theyphotosynthesise, and most living things give off carbondioxide in respiration.

b Some of the radioactive nutrient would be used bymicrobes, and some of the radioactive atoms would thenbe excreted as a gas.c Carbon atoms from the radioactive gas would havebecome parts of the cells of microbes, and would bereleased again when the microbes were heated strongly.

6 That the results obtained were due to some reaction inthe soil, because the same thing happened with thesterilised and unsterilised soils.

7 The LR experiment, because the labelled gas wasemitted from the unsterilised sample but not from thesterilised one.

8 Although one of the four experiments indicated that theremight be life present, the other three did not, so thebalance of the evidence was not in favour of thepresence of life.

9 Possible answers:GEX: obtain soil sample add nutrients and water take samples of gas above soil sample analyse gasesto see if there is any change.

LR: obtain soil sample add radioactive liquid nutrient take samples of gas above soil sample analysegases to see if there are any radioactive gases presentPR: obtain soil sample add radioactive carbon dioxideand leave for 5 days remove gas from samplechamber heat sample collect and analyse anygases given off to see if radioactive gas is present.

P1.15 Life-cycles of stars

Student's Book

1 Hydrogen

2 A cloud of dust and gases is pulled together by the forceof gravity, becoming denser and denser until it gets hotenough for fusion reactions to start.

3 a A normal star that has used up most of its hydrogen.Its core has collapsed but its outer layers haveexpanded.b A collapsed star in which no fusion reactions happen,so it is cooling down.

4 Red giant

H5 An explosion that happens at the end of the life of a red

supergiant.

H6 It does not have enough mass to go through the part of

the life-cycle that ends in a black hole.7 A possible answer: Gravity pulls the dust and gas in the

nebula together, and compresses them so much that the

inside becomes hot enough for fusion reactions to start.Gravity also pulls the remains of a red giant togetherafter fusion reactions have stopped. This forms a whitedwarf.

Skills spotlight

Astronomers have observed millions of different stars, andnoticed that they form particular types. They have alsostudied the Sun in detail. They have devised models thatexplain what happens inside stars, and used these models tomake predictions that they check against observations.

Activi ty Pack

P1.15a Life Story

1 & 2Gas is pulled together by gravity until … it gets hot

enough for fusion reactions to start.The Sun is in the stable part (main sequence) of its life… which lasts for about ten billion years.The Sun provides … light and heat for the Earth.The Sun has used up most of its hydrogen … andexpanded to about 100 times is current size.The Earth will be too hot for life to exist … and may becompletely destroyed.The Sun throws off a shell of gas … and no more fusionreactions happen.The Sun will cool down for ever … and will eventuallystop shining.

P1.15b Star life cycles

1 Protostar – a hot cloud of gas, not quite hot enough for

nuclear reactions;Shell of gas – gas thrown off by a star when it finishes itsred giant stageNebula – cloud of dustMain sequence star – a stable star using hydrogen infusion reactionsWhite dwarf – a small, cooling star, in which fusionreactions have finished.Red giant – a star that has used up most of its hydrogenand expanded greatly

2 C, A, D, F, B, E3 Gravity4 Fusion reactions5 Red giant

P1.15c A sunny story

1 B – because the Sun is expected to end its life as awhite dwarf.

2 a Ab It would be more massive.





3 a Star in A and B (red giant and red supergiant are alsocorrect answers, but students are not expected to knowthis)b Red giant and red supergiant in A and Bc Neutron star in Ad Cloud and protostar stages in A and Be Protostar in A and Bf Star and red supergiant in A, star and red giant in B.

4 In biology, ‘life-cycle’ refers to a continuous cycle of birthto death and includes reproduction. For stars, there is noreproduction involved.

P1.16 Theories about the UniverseStudent's Book

1 They are moving away from us.2 a Both

b Steady Statec Big Bang

3 Both theories say that the Universe is expanding.4 a Cosmic microwave background (radiation)

b Radiation emitted by the Big Bang, which now has amuch longer wavelength because of the expansion ofthe Universe.

5 a Bothb Big Bang

6 A possible answer: In 1900 astronomers did not knowthe distances to any other galaxies. (If students haveused Worksheet P1.11d they may also add that at thetime it was not known whether the Milky Way was thewhole Universe or just a tiny part of it.) Now they knowthat most other galaxies are moving away from us, andexplain this using a model that says the Universe hasexpanded from a starting point called the Big Bang.There is other evidence, such as CMB, that supports thistheory.

Skills spotlight

When stories such as the one in Figure A were told, peoplehad no evidence on which to base their ideas. Theories suchas the Big Bang theory are developed by trying to explainscientific observations, and then making predictions andlooking for further evidence to confirm or reject these

predictions. Activi ty Pack

P1.16a Timeline for the Universe

In order, from the bottom up:Universe forms in the Big BangGalaxies formThe Solar System starts to formThe Sun produces light and heat from hydrogen fusionThe Earth formsThe first life appearsHumans observe the sky with the naked eyeGalileo uses a telescope to observe the stars

Astronomers use other parts of the EM spectrum to makeobservations

The Sun turns into a red giantThe Sun becomes a white dwarfThe white dwarf cools.

P1.16b Different theor ies

1

IdeaSteadyState

BigBang

Space is expanding

Universe started about 13.5 billion yearsago

Matter is continually being created

All matter was created at the beginning ofthe Universe

We can detect radiation from all over thesky that is energy from the beginning of theUniverse

2 When light from distant galaxies is shifted towards thered end of the spectrum.

3 a Away from usb It is expanding

4 a Red-shiftb Bothc Radiation coming from all over the skyd Big Bange Big Bang

P1.16c Discovering CMB radiation

1 It was coming from all over the sky.2 The findings were published in a scientific journal.

Before publication, the article would have been sent outto other scientists to check (peer review). When it waspublished, anyone else who had the right equipmentwould have looked for the background radiation.

3 Observation by Hubble – most galaxies are movingaway from us.Question – why is this happening?Theory – Big Bang or Steady State theoryPredict – there should be some radiation left over fromthe Big BangObservations – CMB discovered (but not by the samepeople who made the predictions!). This is evidence forthe Big Bang.Conclude – Big Bang is the better model (do not accept'the truth' or similar).

4 It often takes some years for it to become clear howimportant a particular discovery is. Sometimes adiscovery appears to be important, but later work showsit to be incorrect. The time delay prevents the prize beingawarded for this kind of discovery.

P1.17 Red-shi ft

Student Book

1 a The frequency is higher as the ambulanceapproaches, and lower as it heads away.b The wavelength is shorter as the ambulanceapproaches, and longer as it heads away.

H c The speed of the wave does not change, so if the

frequency increases the wavelength decreases.2 The shifting of lines in the spectra of stars towards the

red end of the spectrum.

3 Diagram should show that the distance between twostars changes with time, so that light emitted from a starappears (to an observer elsewhere) to have a longerwavelength.

H4 Almost all galaxies we observe are moving away from

us, and the further away they are the faster they aremoving. These observations can be explained by anexpanding universe.

H5 The Sunflower Galaxy – the further away a galaxy is, the

faster it is moving away.

H6 It is supported by the existence of CMB, which does not

fit with the Steady State model.

H7 A possible answer: The light from a newly discovered

galaxy is made into a spectrum and examined for blacklines. The positions of these black lines can be used to

work out how fast the galaxy is moving away from us.The faster the galaxy is moving away, the further away itis, so its speed can be used to work out its distance fromus.

H Skills spotlight

Einstein had thought that space could not be expanding.Hubble's interpretation of his measurements of red-shifts anddistances persuaded Einstein that the Universe is expanding.

Activi ty Pack

P1.17a Binary s tars

1 Light is shifted towards the blue end of the spectrum –i.e. the frequency gets higher and the wavelengthshorter – because the object emitting the light is moving

towards us.2 If the stars are orbiting each other, one must be going

away from us as the other is coming towards us. The lightfrom the one coming towards us would be blue-shifted, sothe other would be red-shifted.





3 a A and D – although they show red-shift and blue-shift,these vary about the zero axis.b D – the frequency of the changes is higher/period isshorter.c B – the frequency of the changes is lower/period islonger.d B and C – the average shift is red.e B – the red-shift is greater.

4 If it was just one star, the red-shift would be constant.When one of the stars is moving away from us (as part ofthe rotation of the binary pair) its red-shift increases abovethe average value. When it is moving towards us its red-

shift is less than the average value.5 In E there would be no red-shift or blue-shift at all,

because the stars are not moving towards or away fromthe Earth.In F there would be some red-shift and blue-shift fromeach star, but less than in G, because part of themovement is not towards or away from the Earth.In G there would be the full range of red-shift and blueshift.

P1.17b Galaxy calcu lations

1 a Correctly plotted graph with line of best fitb No – not all the galaxies on the graph lie exactly onthe line, so there are variations from the numbercalculated (or similar explanation).

2 a The gradient should be approximately 60 km/s/Mpc.b There may be a reason why some of the galaxiesplotted are not moving in the same way as most others,so the data is not representative/this is a very smallsample/some of the distances may have been calculatedassuming a older estimate for the value of the Hubbleconstant.

3 Values here are calculated using 70 km/s/Mpc for theHubble constant.

GalaxyDistance(in Mpc)

Speed(in km/s)

M49 18.4 1288

M51 11.3 791

M65 10.7 749

M95 11.7 819

M99 18.4 1288

4 Values here are calculated using 70 km/s/Mpc for theHubble constant.

GalaxyDistance(in Mpc)

Speed(in km/s)

M66 10.7 749

M96 11.7 819

M81 3.7 258

M100 18.4 1288

M105 11.7 819

5 a M65 and M66 (these are actually part of the Leo Triplet);M95,M96 and M105 (part of the Leo I group); M49, M99and M100 (part of the Virgo cluster).

b Where they are in the sky. If they are close to eachother (i.e. in the same direction as viewed from Earth)they could be part of a group/cluster.

6 a The value is adjusted if new, more accurate data on thedistances and speeds of galaxies is obtained.b That for 2009 – it is likely to have been made using moreinformation, or using more modern equipment.c The journal editor will send the paper out to otherscientists working in the same field, for them to assess it forvalid working methods, correct analysis of the results etc.Once the journal article is published, other scientists willsimilarly check it, and some may try to reproduce herobservations or her analysis.

P1.17c The Doppler effect

1 pitch – how high or low a sound isfrequency – the number of waves per secondwavelength – the distance between one wave and the next

2 It sounds higher-pitched as it comes towards you.It should lower-pitched as it moves away from you.

3 Doppler effecg4 a X

b arrow pointing to the leftc 'low' written to the right of the object in X

P1.17d Moving galaxies

1 The movement of object makes the waves it emits havea shorter wavelength in front of it and a longerwavelength behind. Diagrams could be similar to FigureB on page 240 of the Student's Book.

2 The speed at which a galaxy (or other object) is movingaway from us.

3 a Albefoilb AR348

4 a AR348, NM86B, Albefoilb The closer a galaxy is to us, the slower it is movingaway, and so the smaller its red-shift.

5 The lines have been moved away from the red end ofthe spectrum (or moved towards the blue end). It ismoving towards us, rather than away from us.

6 One far away – the further away a galaxy is, the faster it ismoving away, and so the bigger its red-shift.

7 a Both the Big Bang and Stead State theories.b Big Bang theory – there is more evidence to support it(e.g. the CMB).

8 The galaxy is rotating. This means that on the side of thegalaxy rotating away from us, the stars are moving awayfrom us faster than the galaxy as a whole, so the red-shiftwill be increased slightly. On the other side, the stars aremoving towards us as the galaxy rotates, so this meanstheir speed away from us is a bit less, and the red-shift isreduced slightly.

P1.18 Infrasound

Student Book

1 a The number of waves/vibrations per second.b Hertz (Hz)

2 No. Infrasounds have frequencies below 20 Hz.3 It travels further.4 It is difficult to see any distance in forests because the

trees get in the way, so detecting infrasounds allowsanimals to be detected from much further away.

5 The meteor may explode over the ocean or over anuninhabited area, so a lot of meteor explosions would notbe reported.

6 Infrasounds can be detected at any time, whereas asatellite photo of a volcano may not be taken very often. Ifan eruption starts at night or when there is thick cloudcover, the eruption may not be detected by satellites evenif one is overhead and available to take photos. It mayalso be easier to set up automatic systems to detectcertain sounds than to set up systems to automaticallyanalyse images for signs of smoke or ash clouds.

Skills spotlight

Possible benefits include: cheaper equipment; can beused at any time (as opposed to only getting imageswhen the satellite passes overhead); not limited bycloud cover (although some students may speculateabout the sounds caused by rain/thunder etc. interferingwith the infrasound detection of animals); we mayeventually also be able to work out what the animalsare ‘saying’.

Possible drawbacks include: only detects animals thatemit infrasounds (whereas a satellite image mayprovide information about other animals in the areaand/or what the other animals are doing); can onlyshow the direction of the animals from the detector, notdistance (although some students may suggest thatusing several detectors at different locations may allowtriangulation).

Activi ty Pack

P1.18a Using infrasound A – a/b, f/g; B – c, I, d; C – (none); D – a/b, f/g; E – e; F – h





P1.18b Infrasound questions

1 change: transverse to longitudinal; amplitude tofrequency; metres (m) to hertz (Hz); below 20 Hz toabove 20 Hz, above 20 000 Hz to below 20 000 Hz;higher to lower.

2 elephants and other large land animals, whales3 Infrasounds travel further in air than normal sounds;

Elephants make infrasounds that can be heard manykilometres away.

4 Humans cannot hear infrasound, so we would not beable to hear anything on a normal recording. We needspecial equipment that can detect and record

infrasounds.5 volcanic eruptions, meteors passing through the air

and/or exploding

P1.18c Monitoring volcanoes

1 sounds too low for humans to hear2 some animals (whales, elephants), meteor explosions or

meteors passing through the air3 a so they can study processes inside the volcano and/or

so local people can be helped/evacuated if an eruptionhas occurred.b Infrasounds travel further in air than sound beforebecoming too faint to detect.

4 a Ash and smoke would not be visible at night (althougha satellite with IR sensors might detect an eruption).

b Clouds would block the view of the ground surface.5 An active volcano is erupting, or could erupt at any time;dormant volcanoes have not erupted for some time butscientists think that they could do so in the future; extinctvolcanoes are not likely to erupt again.

6 Infrasounds can be detected from a long way away, soone set of sensors could listen for eruptions from manyvolcanoes. This is cheaper and easier to set up andmaintain.

7 Erupting volcanoes can cause damage to buildings andcrops and cause loss of life, so people need to bemoved out of the danger area if a volcano is likely toerupt. If scientists fail to predict an eruption many peoplecould die. If they predict an eruption that does nothappen, many people will be unhappy at having to moveaway from their homes and farms/jobs for no reason,and may decide not to leave next time the scientistspredict an eruption.

P1.19 Ultrasound

Student Book

1 Sound above a frequency of 20 kHz, which is too highfor humans to hear

2 Bats make noises that are too high for humans tohear/bats make ultrasounds, so the equipment is neededto detect the sound and turn it into frequencies thathumans can hear.

3 Light does not travel very far through water before it getsscattered.

4 a distance = speed x time = 1500m/s x 3 sec = 4500m

b 4500 m/2 = 2250 m5 a Visible light cannot pass through the body, so cannot

be used for making images of the inside of the body.b X-rays can damage cells or cause mutations, soultrasound is safer.

6 A probe touching the skin emits ultrasound waves, whichtravel into the body. These are reflected by the differentlayers within the body (such as a foetus within thewomb). A machine detects the reflected waves andworks out how long the wave has been travelling, andtherefore where the reflecting layer is. A computerprocesses the information into a picture.

7 A loudspeaker sends out a pulse of ultrasound, which isreflected by the sea floor and detected by a microphoneon the ship. A computer works out the depth from the

time the sound took to return. Fish will also reflect someof the sound, so an echo from a depth above the seabed is likely to be fish.

Skills spotlight

Blindfold some bats and see if they can still fly around/catchinsects. If they can, then they are not achieving this byeyesight. Repeat the experiment but this time block up thebats’ ears. If this stops them being able to catchinsects/causes them to bump into things, then it is likely thatthese abilities are connected to their hearing. Ultrasounddetectors could also be used to confirm that the bats are emitting ultrasounds (although detecting the ultrasoundsalone does not show that these are being used to detectobstacles/insects – the sounds could just be forcommunication).

Activi ty Pack

P1.19a Ultrasound scans

1 B - jelly, C - woman's body2 a 99%

b 1%c 0.1%d 99.9%e The jelly stops most of the ultrasound energy frombeing reflected before it enters the woman's body. Thisleaves plenty of energy to be reflected by various partsof the fetus. If the scanner is not touching the jelly, mostof the ultrasound energy will be reflected when theultrasound reaches the jelly, as it will then be passinginto the jelly from air.

3 a time = distance/speed = 0.30 m/1580 m/s = 0.000 19 sb It assumes that the ultrasound is only passing throughmuscle, whereas it is likely to pass through manydifferent tissues, all with slightly different properties thatwill affect the speed of sound.

P1.19b Ultrasound in industry

1 a The machine sends an ultrasound pulse into thematerial, and detects the sound reflected from the backsurface of the sheet. It uses the time between the pulseand the echo to work out the thickness.

b thickness = (0.27 cm/s × 3.6 s)/2 = 0.486 cm.2 a too thick; the sound has taken more time to travel than

it should.

b thickness = (0.27 cm/s × 3.8 s)/2 = 0.513 cm. Error

= 0.027 cm.3 Shorter. If the sheet is thinner, the ultrasound has a

shorter distance to travel, so it will not take as long.

4 a thickness = (0.59 cm/s × 2.2 s)/2 = 0.649 cmb There may be a crack within the steel that is reflectingsome of the sound. The depth of the crack from the top

surface is (0.59 cm/s × 0.5 s)/2 = 0.1475 cm.5 Reflections from the bottom of the steel, the bottom of

the polythene and the bottom of the aluminium.

6 thickness = (0.59 cm/s x 8 s)/2 = 2.36 cm.

P1.19c Ultrasound questions

1

Name Type of sound Frequency

ultrasound too high for humans to hear below 20 Hz

infrasound too low for humans to hear above 20 kHz2 a Bats, dolphins

b Any from: communication, finding their way about(note, only communication between animals is requiredby the specification, not echolocation or detectingobstables/prey).

3 They can check the baby is healthy/developing properlyi.e. all organs normal (or to measure the size/rate ofgrowth of the baby) – any explanation of amedical/diagnostic nature (rather than ‘to see the baby’or to find out its sex).

4 a distance = speed x time = 1533 m/s x 2 s = 3066 mb 3066 m/2 = 1533 mc 1493 md It needs to calculate the distance from the time, so it

needs to know the correct speed of the ultrasound wavein water. The speed is different in fresh water and saltywater (and also if the temperature of the water varies).





P1.19d Using ultrasound

1 Similarities: all are longitudinal waves that need amedium through which to travel. Differences: we canhear sound waves, ultrasound waves are too highfrequency for us to hear, infrasound waves are too low infrequency.

2 a 1533 mb 1493 mc It needs to calculate the distance from the time, so itneeds to know the correct speed of the ultrasound wavein water. The speed is different in fresh water and saltywater (and also if the temperature of the water varies).

d They could be echoes from shoals of fish beneath theboat. The first will be 38.3 m beneath the boat, and thesecond 536 m below.

3 a A machine sends ultrasound waves into the body.Some of the ultrasound energy (or wave) is reflectedeach time it passed into a different material. Themachine detects the echoes, and a computer processesall the times between sending the signal and receivingthe echoes into an image.b The speed of sound in the jelly is similar to the speedof sound in skin/water, so not much ultrasound energy isreflected as it passed through the jelly into the body. Thespeed of sound in air is very different to that in the body,so if the jelly were not used most of the ultrasoundenergy would be reflected before it got into the body.

c Ultrasounds would be reflected by the air in thebubbles. These would appear on the screen (or wouldmean there was not much energy going into the body tobe reflected).d The speed of sound in metal is different from thespeed of sound in body tissues, so ultrasound isreflected when it reaches the metal object.

4 If the speed of sound is 1533 m/s, the time for the signalto travel to the sea bed and return would be 8 000m/1533 m/s = 5.22 seconds.

A 1% error in the speed of sound would be 15.33 m/s. Ifthe speed of sound is actually 1548 m/s (1533 m/s + 15m/s), then a 5.22 second time would imply a depth of1548 m/s x 5.22 s = 8080 m. The error in depth wouldtherefore be 80 m (overestimate). (The error in depth

would be 78 m, an underestimate, if the speed of soundis 1% lower than that assumed.)

P1.20 Seismic waves

Student Book

1 a A wave or vibration in the Earth.b A machine that detects seismic waves.

2 Earthquake, explosion3 P waves are longitudinal, S waves are transverse.

P waves travel faster than S waves (or arrive before Swaves).

4 Reflection and refraction

H5 a The properties of rocks change gradually within the

Earth and this changes the speed of the wave. Changesof wave speed cause refraction.b A sudden change in the properties of rocks (e.g. alayer of a different type of rock), which causes a suddenchange in wave speed.

6 Seismometers all over the Earth detect seismic wavesfrom earthquakes and explosions. Scientists use acomputer to model the estimated depths of layers of rockwithin the Earth and the estimated speed of waves in eachof those layers. They then compare predictions of thetravel times of reflected and refracted waves made usingtheir model with those of the seismic waves detected afteran earthquake. Interpreting the data tests their hypothesis(the structure in the model). If the structure in the model(depth of boundaries where the seismic speed changes)fits the data, the model is good (even though othermodels/hypothesis/assumptions may also fit the data!).

Skills spotlight

Trucks: Advantages – easy, cheap and safe to use;vibrations can be produced whenever the scientists wantthem. Disadvantages – only useful on a small scale, as

there would be little energy in the waves so they couldonly be detected at fairly short distances.

Explosions: Advantages – can be set off where the scientistsneed vibrations, allowing scientists to focus theirinvestigations on a particular area they are interested in;more energy than the truck, so can be used toinvestigate larger-scale/deeper structures.Disadvantages – need to be very careful with explosivesfor safety reasons; not enough energy to investigate thestructure of the Earth as the waves would not haveenough energy; explosions on land may unwittinglycause damage to the foundations of buildings or harm

animals that live underground or that use infrasound tocommunicate (as with marine seismic surveys, which arecontroversial in areas where dolphins and whalesgather).

Nuclear explosions: Advantages – lots of energy so waveswill go a long way; can be set off when and where thescientists need them. Disadvantages – expensive andillegal, and potentially extremely dangerous if anythinggoes wrong.

Earthquakes: Advantages – varying amounts of energy, withthe most powerful earthquakes producing waves thatcan be detected around the world. Disadvantages –unpredictable (scientists have to wait until one happens);don’t always allow scientists to find out more about apart of the Earth’s interior that they are interested in.

Activi ty PackP1.20a Wavy words

A Incorrect – students might apply this to reflection, butlight can be partially reflected by a boundary betweentransparent materials.

B Reflection.C Reflection or refraction.D Refraction.E Incorrect – light does not change direction if it arrives

along a normal or if there is no difference in the speed oflight in the two materials

F Incorrect – reflection/refraction can happen to any kindof wave.

G Reflection or refraction.

H Incorrect, both can happen in opaque materials as well,depending on the type of wave.I Incorrect, it travels at different speeds in different

materials.J RefractionK Refraction

P1.20c Seismic waves

1 S-wave, transverse, slowerP-wave, longitudinal, faster

2 a P waves are the low-amplitude waves in the centralsection, S waves are the larger amplitude waves on therightb P waves travel faster than S waves, so they arrive first(note, answers should not refer to amplitude).

3 P waves: A moves up/down, B moves sideways

S waves: A moves sideways, B moves up/down

P1.20d Seismic wave questions

1 a P waves, as this is showing a longitudinal wave, and Pwaves are longitudinal (the particles in the material moveback and forth (oscillate) in the same direction in whichthe wave is travelling)b sketch of a transverse wave

2 a 95 seconds, 158 secondsb The P waves always arrive first (faster than S wavesin the same medium).

3 P waves will make A move up and down, and make Bmove from side to side.S waves will make A move from side to side, and makeB move up and down.

4 a The properties of rocks change gradually with depth,making the speed of seismic waves change andtherefore causing refraction.





b The wave should be shown curving gradually upwardsin both layers, with a sharp change of direction as itcrosses into layer 2.

5 a The seismic waves 'bounce' back from the boundarybetween the crust and mantle.b between the mantle and core

6 The wave should bend towards the normal as it crosses

into layer 2, but should then start to curve upwards again(as the speed will again increase with depth in layer 2).

P1.22 Detecting earthquakes

Student Book

1 P waves2 a Aid agencies can work out where to send help; a

tsunami alert can be issued if the earthquake is underthe sea.b They compare the arrival times of the first P and Swaves to arrive at many different seismometers, and usethe time difference to work out how far away from eachstation the epicentre of the earthquake was.

3 If only two seismometers are used, there could be twodifferent locations for the earthquake (or, the curvesdrawn marking the distances from two stations cross intwo places).

4 The movements between plates that form the surface ofthe Earth.

5 California is on/near a plate boundary, so they have/arelikely to have earthquakes. The UK is not near a plateboundary and so does not have many earthquakes.

6 Time = distance/speed = 1000 000 m/220 m/s = 4545seconds = 75.75 minutes, or approximately 1 hour 15

minutes.7 Seismometers can only be used to locate an earthquake.

Not all earthquakes that happen beneath the sea causetsunamis. If there are too many false alarms, people maystop believing the warnings and may not move to safetywhen there really is a tsunami (other reasons may includethe possibility of looting/theft while people are evacuated,which is likely to be seen as an acceptable risk in theevent of a tsunami, but not if it is a false alarm).

Skills spotlight

The article should include reference to plates and explain thatmost earthquakes happen on plate boundaries, caused by theplates moving past one another. This allows scientists toidentify areas likely to have an earthquake. The article should

explain that forces build up until they overcome frictionbetween the plates, but as scientists cannot measure theforces or the friction, they cannot predict when the movementwill occur.

Activi ty Pack

P1.22a Find the focus

1, 2 A – 86 – 52 s = 34 s, 294.1 kmB – 62 s, 536.3 kmC – 36 s, 311.4 km

5 The focus should be approximately 280 km north of A,and 60 km east (allow for some variation in the timesread from the graphs).

6 a There are likely to be differences from slightdifferences in reading the S wave arrival times from the

graph, and errors in drawing the arcs.b Their results for the position of the earthquake are lessaccurate.

P1.22b Animals, earthquakes and tsunamis

1 This evidence identifies a possible link between animalbehaviour and earthquakes. However pet owners aremost likely to recall unusual behaviour that issubsequently followed by an earthquake, and may notrecall or report such behaviour if there is no particularreason (such as an earthquake) to take note of it/reportit.

2 a They could regularly monitor the behaviour of variousanimals and note any changes in behaviour. If anearthquake occurs they can try to match up anyrecorded changes of behaviour that only occurred just

before an earthquake.b Anywhere near a plate boundary (such as California)where there are likely to be earthquakes (compared tosay doing the research in the UK where there are fewearthquakes).

3 Earthquakes are not predictable, so researchers wouldhave to continuously monitor the behaviour of theirchosen animals for many years (or even decades)before an earthquake happened. Not all animals are saidto react to earthquakes, so they may have chosen ananimal that would not show any behavioural changes.There are other possible explanations for manybehaviours, such as barking or acting scared, and it willbe difficult to rule out other causes (including soundsand smells that humans cannot detect, but which have

non-earthquake causes).4 There is a possible mechanism (detection of

infrasound/seismic waves) whereby animals may detectthe approach of a tsunami (infrasound travelling in theair) or earthquake (seismic waves travelling through theground). Animals may be able to detect minute fracturingof rocks a few milliseconds before a quake shockreaches the surface, or they may be able to detectinfrasound waves in the air before a water wave(tsunami) has arrived, since the speed of tsunamis indeep water is less than the speed of infrasound waves inair from the same source.

P1.22c Waves and the Earth

1 a Seismic (earthquake happening on the sea bed helpspredict a tsunami) b Infrasoundc Seismicd Infrasound

2 C, B, E, A, D3 a A, E

b They are at places where the plates join. Earthquakesare caused by plates moving past each other.

4 C, D5 A is wrong – most earthquakes happen on plate

boundaries.

P1.22d Seismic waves and earthquakes

1 a About 6.3 minutes (or 6 minutes 20 seconds)b About 11.3 minutes (or 11 minutes 20 seconds)

2 Time difference = 6 minutes. From the graph, this

corresponds to a distance of approximately 4400 km.3 a their locations

b The difference in P and S wave arrival times is workedout for each station, and circles drawn with that radiuscentred on the station. Where the three circles intersect isthe epicentre.

4 a movements of the plates that make up the surface ofthe Earthb As most earthquakes are caused by plate movements,they are most common where the plates slip against eachother.

5 They can predict the places because they know thatearthquakes are likely to occur along plate boundaries.They cannot predict the time, because that would requirethem to be able to measure the forces pushing the plates

and the friction between them.6 a If an earthquake occurs on the sea bed it may cause antsunami, and seismometers can be used to find out if anearthquake was located on the sea bed.





b Not all earthquakes on the sea bed cause tsunamis(movement of water). A network of pressure sensors candetect whether or not a tsunami wave has formed.

7 a time = distance/speedFor P-waves, time = 4000 km/5.6 km/s = 714.3 secondsFor S-waves, time = 4000 km/3.4 km/s = 1176.5 secondsb P-waves take 11.9 minutes to arrive, S-waves take 19.6minutes

8 a From the graph, it would take P-waves 7 minutes toarrive (420 seconds) and it would take S-waves 12.6minutes (756 seconds). The times from the graph aremuch shorter than the calculated times.

b The wave speeds in this region could be faster than theaverage, which would explain why the calculated times(based on average speeds in the Earth as a whole) arelonger.In addition, an average speed is not realistic. Wavespeeds change with depth. Overall there is an increase inseismic wave speed with depth into Earth and waves thathave travelled deeply spend more of their travel path inareas of higher seismic wave speeds. These waves arerefracted and follow curved paths upwards. So the simple‘one layer, average speed’ model will not give accuratepredictions for travel times.

P1.23 Renewable resources for electricity

Student book

1 They do not produce carbon dioxide (a greenhousegas)/pollution; they will not run out.

2 a Solar cells to convert solar energy directly intoelectricity; or using heat from the Sun to turn water intosteam, which turns turbinesb Build a barrage across an estuary with turbines in it,which turn when water is let in and out; or put turbinesunderwater in places where tidal currents flow

3 a Geothermal, hydroelectricityb Tidal powerc Geothermal, hydroelectricity, tidal (and wind, but this isless limited by location than the other resourcesmentioned here)d Solar, wind, waves

4 a Geothermal – we have no volcanic activity so there are

no hot magma chambers underground (note thatgeothermal energy from areas such as Cornwall, where therocks contain naturally occurring radioactive elements, canbe used to provide heating in the UK, but the ‘hot rocks’ arenot hot enough to produce steam for electricity generation).b Solarc Wind, waves

5 A possible answer could be: The only renewableresources that can be used to generate electricity all thetime are geothermal and hydroelectricity. We do not haveenough suitable sites in the UK to produce enoughelectricity using these resources. Other renewableresources such as tides can generate electricity only atcertain predictable times, while others, such as solar andwind, depend on the weather.

Skills spotlightSuggestions include:

the population size and its energy needs

the types of resource available in the area – e.g. waveor tidal power cannot be used in inland areas and ariver in a valley is needed for hydroelectric power

data for the amount/consistency of wind or number ofsunny days

where they could be located

how much they would cost to build

whether a wind farm or other buildings needed couldaffect wildlife or habitats

what the local population will think about it – e.g. theeffect on scenery or tourism

how the electricity can be transferred from thegenerators to users, etc.

anticipated social, economic and environmental effectsmay influence decisions, and public opinion and themedia can influence acceptance

Activi ty Pack

P1.23b Fair Isle

1 a 16 hours – accept answers near this if students haveestimated from the graphb There are fewer days in February

2 October – this is when the amount of energy from windincreases by a large amount

3 a Most wind energy is available in the winter monthsb The number of hours each day is also greatest in thewinter months

4 Information for a whole year with both turbines operating

(or for more than one year) because data for just one yearmight not be representative5 a About 60% of the time – accept anything between 50%

and 70% if students have estimated from the bar chartson the worksheetsb No – most onshore sites would be sheltered from thewind from some directions

6 About 60% over a whole year – accept anything between50% and 70% if students have estimated from the barcharts on the worksheets. Energy provided by windturbines is approximately two-thirds of the total electricitysupplied.

7 We would need a lot of wind turbines to provide asignificant proportion of our electricity. Most of the windysites for these will be in scenic locations where there arelikely to be objections to building them. These are alsoplaces where we would need new connections to send theelectricity to users. Putting wind turbines out at sea costsmore in building and maintenance.

P1.23c How much electrici ty do we get?

1 A – solar energy: it is available only during the day, and ishighest when the weather was sunniestB – wind: graph is highest in the afternoon and evening,when it was windiestC – waves: no electricity when the sea was calm, but risesas the waves increase in the late afternoonD – tidal: two periods of high energy correspond to thetwo high tidesE – hydroelectric: not affected by the weather

2 Hydroelectric: Advantage - energy is available all the time;

Disadvantage – mountainous areas and dams andreservoirs are needed.Solar: Advantage - can be used in small solar cells orlarge power stations; Disadvantages – only availableduring the day, amount available reduced by bad weatherTides: Advantage – available at predictable times;Disadvantages – not available all the time, needsbarrages built across river estuaries which can harm theenvironment, or underwater turbines which could beexpensive to maintain.Waves: Advantage – can be located at sea;Disadvantages – only available in countries with access tothe sea, only available when there are waves on the sea,installations at sea might affect shipping or wildlife,installations on the coast would not look attractive.

Wind: Advantage – available via small wind turbines orlarge wind farms; Disadvantages – many people thinkthey spoil views and harm birds; installations at sea aremore costly to build and maintain, only available when thewind it blowing; not available when the wind is too strong. B – wind energy is only available when the wind isblowing

3 Hydroelectric and geothermal

P1.23d Tidal lagoons

1 Sluice gates are shut at high tide when the lagoon is fullof water; they stay shut while the tide falls outside; whenthere is enough difference in the water levels the wateris allowed to run out through turbines; the gates are shutnear low tide, and the water rises outside the lagoon;near high tide, water is allowed to run into the lagoon

through the turbines.; the turbines will be used to drivegenerators





2 a Lagoons are likely to have less effect on wildlifebecause they will not block off the whole river – they willnot prevent fish migration, will not have much impact onmud flats (which are habitats and feeding grounds forbirds)b Lagoons will create less disruption to shipping, whichcan sail round them rather than having to go throughlocks specially built in the barragec Lagoons need a lot more aggregate than the barraged The visual impact of the lagoons is likely to be less –they will be almost invisible at high tide; the visual impactof the barrage could be said to extend up the river as far

as it affects the tidal flow in the river3 a If all the planned lagoons are built, they will generate

more electricity than the barrage (about one-third more)b Electricity from the lagoons will be cheaper thanelectricity from the barrage

4 a The electricity from the barrage will cost more.b It needs to have locks incorporated to allow ships tosail up the Severn – these will have to be very big totake full-sized ships

5 It has a very high tidal range (the difference in heightbetween high and low tide); other possible sites includethe Conwy Estuary, Liverpool Bay, Morecambe Bay, theSolway Firth and the Wash.

P1.24 Non-renewable resources

Student book1 They produce pollution (carbon dioxide, a greenhouse

gas, and gases that cause acid rain and ash/dust); andthey use fuels that will run out.

2 Produces less pollution (no ash/dust and no sulfur soless acid rain); and produces less carbon dioxide perUnit of electricity generated.

3 a Does not produce carbon dioxide during operation.b May produce radioactive waste pollution; veryexpensive to decommission.

4 a Have to be built very carefully so that no radioactivematerials escapeb Have to make sure any radioactive material from thepower station is stored safely for a very long time tocome.

5 Radioactive material from the blast can be blown toother countries by winds and then rain can bring it downthere.

6 A possible answer could be: Fossil-fuelled powerstations produce cheaper electricity than solar powerstations, and they can produce it all the time. However,fossil-fuelled power stations produce polluting gases andtheir fuel supplies will run out one day.

Skills spotlight

Arguments for (the benefits) include: the lack of carbondioxide emissions; the low fuel costs; the fact thatelectricity is available at any time (cf. wind or solar); itreduces reliance on finite supplies of non-renewablefossil fuels.

Arguments against (drawbacks and risks) include: thepossible hazards of a radiation leak; the cost ofdecommissioning; uranium is also a finite resource.

Public opinion and the media can influence acceptance,and there may be bias in the evidence gathered to findout whether or not nuclear power is safe.

Activi ty Pack

P1.24b Health ri sks from nuclear waste

1 a He was examining counties with coasts on the IrishSea; he wanted an inland county for comparison.b As a control/to check that the effects he found in thecoastal counties were due to being near the Irish Seaand not effects that applied throughout Wales

2 a When a scientist’s findings are reviewed by other

scientists to check that they have used a valid methodfor their investigationb To make sure that any experiments or investigationshave been done properly

3 a Works for an environmental organisation, that may(not stated but this could be discussed) campaignagainst nuclear power; so he might want to find an effectb Appointed by the government, who subsidise nuclearpower (not stated but this could be discussed); whomight not want to find an effect

4 a If Dr Busby found an effect of radiation, it would helphis organisation to campaign against nuclear powerstations. If there was an effect, the Government mighthave to pay compensation claims, or may have tosubsidise nuclear power stations to install better safetymeasures.

b All the data they used, and the methods they used toanalyse it, could be made available to the public, so thatanyone could check the conclusions.

P1.24c Fuels for electricity

1 a Coalb Natural gasc Gas produces less carbon dioxide/less pollution

2 a 7%b 6%

3 a Biomass fuelsb 1.5%c Produce less pollution/carbon dioxide (and will not runout)

4 Wind5 a One from: they do not produce carbon dioxide; the fuel

will last longerb One from: there is a risk of an accident/radioactivepollution; they cost a lot to decommission

6 a Any sensible answers showing a smaller % of fossilfuels and a higher % of renewables (and possibly morenuclear)b Any sensible explanation

P1.24d 'Carbon-free' electricity?

1 a Water vapourb Produces only water, not carbon dioxide or otherpolluting gases

2 Carbon dioxide is also produced when the hydrogen ismade from natural gas; splitting the methane in naturalgas into hydrogen and carbon dioxide takes energy,

which was probably obtained by burning fossil fuels3 a Be able to sell the electricity generated by burning

hydrogen in the power station, and it will get more oil outof the oil fieldb Be seen to be reducing overall carbon emissions (andhence not contributing further to the greenhouse effect)because the carbon in the fossil fuel does not reach theatmosphere as carbon dioxide

4 Pumping the carbon dioxide into the oil field will allowmore oil to be extracted; this will add carbon dioxide tothe atmosphere when it is burned

5 It is only economical when there is a convenient oil fieldnearby to pump the carbon dioxide into – most gas-firedpower stations are not near oil fields

6 a Grant or deny, based on sensible arguments.

Arguments for might cite the reduction in overall carbondioxide emissions for the electricity produced; argumentsagainst might refer to the increase in oil obtained fromthe oil field, which will cancel out some of the benefits ofthe schemeb Possibly including the need for some quantitative datain order to make a decision, and/or information about howsecure the 'carbon storage' in the oil field is

P1.26 Generating electricity

Student book

1 Use a coil with fewer turns; use weaker magnets; movethe wire/coil/magnet slower

2 a Downhillb Bicycle is likely to be going faster downhill, so the

dynamo will be spinning faster.3 Advantages: no batteries to run out; no cost of buying

batteries.





Disadvantages: less light when cycling slowly; no lightswhen stopped at junctions etc. (more able students mayalso point out that the dynamo will make it harder to ridethe bike as there will be some resistance).

4 Direct current always flows in the same direction. Thedirection of an alternating current changes directionmany times each second.

5 They are cheaper when very strong magnets areneeded.

6 It will flow in the same direction: moving the wiredownwards will reverse the current; swapping the polesof the magnet will change it back again.

7 A possible answer is: as one side of the coil moves upthrough the magnetic field, a current is induced; thesame side of the coil then moves down through themagnetic field as the coil spins; so then the current isinduced in the other direction; the direction of theinduced current keeps changing as the coil spins;producing an alternating current.

Skills spotlight

The wind-up radios mean that people can listen to theradio even if they have no electricity supply or access tobatteries (or cannot afford to buy electricity or batteries).

Radio broadcasts can be an important source ofinformation and education, particularly in remote areas.

Activi ty Pack

P1.26b Electricity from movement

1 a Opposite direction; the magnet is being moved in theopposite directionb Same direction; the magnet is reversed but it is alsobeing moved in the opposite direction, so the twochanges will cancel each other outc Opposite direction; the magnet and coil are movingaway from each other instead of towards each otherd There will be no current; the two objects are moving atthe same speed and there is no relative motion betweenthem

2 a It goes into the coil; then comes out of it againb It will increase as the magnet starts moving; thendecrease as it comes to a stop inside the magnet; it willincrease in the opposite direction when the magnetstarts to move out; and decrease to zero when themagnet is right out of the coil and stops movingc

P1.26c Generator designs

1 a B, A, D, Cb B has no core, only one magnet, and has only 50turns in the coil;

A is missing the core and a magnet, but has 100 turns;

D has two magnets and 100 turns on the coil, but no ironcore;C has 100 turns on the coil, two magnets, and an ironcore

2 Turn it faster; put even more turns of wire on the coil;use stronger magnets

3 a Goes into the coil; then comes out of it againb Increases as the magnet starts moving; thendecreases as it comes to a stop inside the magnet;increases in the opposite direction as the magnet startsto move out; decreases to zero when the magnet is rightout of the coil and stops movingc & d Position of straight line for part d is not important,as long as it is horizontal and non-zero.

4 From the Student Book: a power station generator useselectromagnetsFrom extrapolation: a power station generator has biggercoils with more turns on them; produces a much higherpotential difference

5 Students may mention other differences, such as havingmore than one coil of wire in the generator (generatorsproduce three-phase AC); or details of bearings (neededto support the heavy weight and allow high rotationspeed); filling of the generator space with hydrogen toreduce friction and assist cooling etc.

P1.27 Transmit ting electricityStudent book

1 25 000 V, 400 kV, 33 kV, 11 kV, 0.23 kV (33 kV and 11kV may be in any order)

2 It wastes less energy.3 A is step-up; B and C are step-down.4 Answers could refer to the lower voltages being safer for

homes and to the fact that domestic appliances aredesigned to run on 230 V supplies.

5 Some of the equipment will have high voltages; childrenmay get electric shocks if they touch it.

6 Fishing rods may touch overhead power cables; theperson carrying the rod may get an electric shock as alarge current will flow through them; electric shocks canseriously injure or kill people.

7 Vp = Vs x Np/Ns = 75 V x 5/10 = 37.5 V 8 Electricity is generated in power stations at a voltage of

25 kV and then sent to step-up transformers to bechanged to a voltage of 400 kV. It is transmitted aroundthe country at this high voltage because less energy iswasted. Transformers step down the voltage to 33 kV or11 kV for factories, and a further set of transformers stepthe voltage down to 230 V for houses.

Skills spotlight

Advantages include: more efficient transmission – lessenergy wasted, so cost of transmitting a certain amountof power to our homes is reduced.

Disadvantages include: the dangers of very highvoltages – high voltage transmission line increases the

hazard of an electric shock; the current that would flowthrough you is very high.

Activi ty Pack

P1.27c Transmitting electricity

1 It wastes less energy2

Startingvoltage

Final voltageStep-up

transformerStep-down

transformer

25 kV 400 kV

400 kV 33 kV

33 kV 230 V

3 a One of the railway lines may be carrying electricity;anyone touching (or going near it) could get a shock/be

injured/be killedb The fishing rods could touch the wire and give them ashockc The kite string could touch/go near the wires;electricity would then flow through it and the children andkill them

P1.27d National Grid questions

1 a Transmitting electricity at high voltages wastes lessenergy as heatb Step-up transformerc Domestic equipment only needs low voltages; highervoltages would be dangerous in situations where thereare peopled Safety rules can be enforced in factories; the risksfrom high voltages are less; factory machinery may needhigher voltages to run





2

3 a There is no voltage difference between their feet, sono current flows through themb There would be a big voltage difference between thewire and the ground (through the kite string and you), soa current would flow

4 V stands for voltage (potential difference), N stands fornumbers of turns, p refers to the primary coil and s to thesecondary coil.

5 a Vs = Vp x Ns/Np = 230 V x 400/250 = 368 Vb Ns = Vs x Np/Vp = 150 V x 250/230 V = 163 turns

6 Vs = Vp x Ns/Np = 230 V x 250/400 = 143 V7 Advantages: they are cheaper; do not need to be

insulatedDisadvantages: they are more likely to be damaged bybad weather; many people object to the visual pollutionthey cause

P1.28 Paying for electricity

Student book1 The amount of energy transferred each second.2 a Power = current × voltage = 2 A × 9 V = 18 W

H b Energy = power × time = 18 W × (60 × 60) s = 64 800

J (or 64.8 kJ)3 1 kilowatt-hour; the amount of electricity transferred

when a 1 kW appliance is switched on for 1 hour.4 Cost = 3 kW × 3 h × 14p = 126p (or £1.26)5 Electricity used = 23 200 − 22 600 = 600 kW h

Cost = 600 kW h × 7.5p/kW h = 4500p (or £45)

H6 a current = power / voltage = 4800 W / 230 V = 20.9 A

b cost/kW h = cost / (power × time) = 350p / (4.8 kW × 4h) = 18.2p per kW h

7 The meters in D show only the total number of Unitsused, whereas the smart meter in A shows how much

power is being used at the moment and how much it iscosting them. It may help people to cut down on theamount of electricity they use if they know how muchthey are using at any one time.

Skills spotlight

Posters should include: an explanation of the power of anappliance and how to find it; the meaning of a Unit (kW h);then how to work out the cost based on the price of a Unit, thepower and the time for which the device has been switchedon.

Activi ty Pack

P1.28b Day and n ight rates

1 a Between about 0700 and 2100 (7 a.m. to 9 p.m.). Accept 1600– 2100, because answering this questiondepends on what level students choose to use to define'most'b 0700–2100 – this is the time when people are awake,making meals, and lighting and heating homes, offices,schools etc.For the evening answer – this is the time when mostpeople have their houses heated, are cooking the mainmeal of the day, and watching TV

2 a Between about 2330 and 0630; again between 0830and 1130 (times are approximate due to the scale of thegraph)b Too much; pumped storage power stations pumpwater uphill using surplus electricity, so if they arepumping then too much electricity is being generatedelsewhere

3 There is surplus electricity at night; electricity companiesare trying to persuade people to use more electricity atnight instead of during the day; to use some of thissurplus electricity and reduce the demand during the day

4 A pumped storage power station needs two reservoirs,one above the other; they have to be built inmountainous country; there are not enough suitable sitesin the UK

P1.28c Power, energy and cost

1 Power = 4 A × 20 V = 80 W2 Power = 0.1 A × 230 V = 23 W3 10 minutes = 600 seconds

Energy = 23 W × 600 s = 13 800 J4 Cost = 3 kW × 2 h × 12 p = 72 p5 a 2000 W

b 2 × 60 × 60 = 7200 sc Energy = 2000 W × 7200 s = 14 400 000 Jd 2 kW he The numbers are too big if watts are used

P1.28d Electricity and standby

1 Power = 4 A × 20 V = 80 W2 a Power = 0.1 A × 230 V = 23 W

Energy = 23 W × 600 s = 13 800 J3 a Cost = 3 kW × 2 h × 12 p = 72 p

b Energy = 2000 W × 7200 s = 14 400 000 J4 a TV: cost = 0.09 kW × 7 h × 12 p/kW h = 7.56 p

DVD: cost = 0.019 kW × 2 h × 12 p/kW h = 0.46 pSet-top box: cost = 0.01 kW × 7 h × 12 p/kW h = 0.84 pTotal cost per day while watching = 7.56 + 0.46 + 0.84 p= 8.86 p

b Cost per year = 8.86 p × 365 days = 3233.9 p (or£32.34)c They watch the TV or a DVD for the same length oftime each day

5 Cost per day: TV: 0.002 kW × 17 h × 12 p/kW h = 0.41 pDVD: 0.002 kW × 22 h × 12 p/kW h = 0.53 pSet-top box: 0.007 kW × 17 h × 12 p/kW h = 1.43 pTotal = 2.37 pCost per year = 865.05 p (or £8.65)

6 a 25 000 000 × £8.65 = £216.25 millionb That all households had the same viewing pattern

P1.30 Reducing energy use

Student book

1 They cost less to run; less carbon dioxide is produced ingenerating the electricity they use.

2 85 kW h × 15p = 1275p (or £12.75)3 They might save the extra cost in lower electricity bills

(although this is unlikely, given the answer to question2!); they might think that producing less carbon dioxidefrom the electricity used is more important than saving alittle money.

4 a It wastes less energy; it cooks things faster so it needsless energy overall.b Benefits: they use less energy and cook thingsquicker. A microwave oven is also smaller than a normaloven.Drawbacks: food does not go brown/does not look asattractive when cooked in a microwave oven.

5 a Draughtproofing

b Double-glazing; it will save the most energy (shown bythe money saved) per year.

6 a Cavity-wall insulation: 3.5 years; loft insulation: 1 year;double-glazing: 17.5 years; draughtproofing: 3.3 years;hot water tank: 4 years; solar panel: 50 yearsb Loft insulation

7 Adding insulation reduces the amount of heat energytransferred from the building to the surroundings and soreduces the amount of energy used to heat the house;reducing energy use is better for the environment andcan also cut bills; loft insulation is not cheapest method,but it is the most cost-effective – it pays for itself withinone year due to the energy savings, so it might be donefirst.

Skills spotlight

Manufacturers are likely to develop new kinds of lightbulbs in order to sell more and so make more profit.

People may buy them because they look attractive orare fashionable.





People might also want to use low-energy bulbs to savemoney (they are more efficient) or to reduce carbondioxide emissions.

LED lights do not break when they are dropped, likefilament light bulbs.

Drawbacks may include the cost of replacement andhence the payback time.

LED lights are also only useful for lighting downwards.

Activi ty Pack

P1.30a People and energy

2 False – House E uses less energy

3 Don’t know – House D has two teenagers and usesmore energy than House C, with only one teenager.However there are also fewer adults in House C, so itmay have been the number of adults that made thedifference. You would need to compare two houses thathad the same number of adults and children with onlythe number of teenagers being different.

4 Don’t know – the number is obtained by comparingHouses A and B, where this appears to be the onlydifference; however, the people in the houses may haveused energy for other things

5 Probably true – House D, with two teenagers, uses moreenergy than Houses A and B, which both have threechildren; so it would seem that two teenagers use moreenergy than three children

6 Don’t know – this is the energy difference betweenHouses C and E, which both have only one adult; butthere is also the fact that House C uses an immersionheater for water, which may account for some of thedifference

P1.30b Saving energy at home

1 a i The amount of time it takes to save the money thatwas spent on the insulationii How much you save compared to the amount youspendb If you cannot afford to install all the different types ofinsulation, calculating the payback times will show youwhich ones will pay for themselves the fastest, and sohelp you to decide which ones to use.

2 Range of costs £500–£10 000; payback 2.5–50 years3 a 3 years

b It has quoted a price for installation based on a verysmall home, where the energy savings would also bequite small; but it has quoted savings for a much largerhome for which it will cost a lot more to install double-glazing

4 Yes – because you would want to know if it was worthdoingNo – because kitchen foil is cheap and the job is nothard to do, so it is worth doing even if the payback timeis quite long

5 a The house may be heated by gasb Insulating the house would cut down the gas bill, somoney would still be saved; less carbon dioxide produced

P1.30c Cost of using a washing machine1 a 104

b 104 × 1.55 kW h × 12 p = 1934 p (or £19.34)c 104 × 2 kW h × 12 p = 2496 p (or £24.96)d £24.96 − £19.34 = £5.62

2 a 365 × 2 kW h × 12 p = 8760 p (or £87.60)b 365 × 1.55 kW h × 12 p = £67.89; saving = £19.71

3 a £60/£5.62 = 10.7 yearsb £60/£19.71 = 3 years

P1.30d Running costs and payback time

1 a 104 × 1.55 kW h × 12 p = 1934 p (or £19.34)b 104 × 2 kW h × 12 p = 2496 p (or £24.96)c £24.96 − £19.34 = £5.62

2 a 365 × 2 kW h × 12 p = 8760 p (or £87.60)b Cost = 365 × 1.55 kW h × 12 p = £67.89; saving =£19.71

3 a £60/£5.62 = 10.68 yearsb £60/£19.71 = 3.04 years

c How much washing it could do at once; how long awashing cycle takes; how noisy the machine is etc.

4 You would need to buy 10 incandescent bulbs to last thesame time as 1 low-energy bulb.Cost of incandescent light bulbs = 10 × 60 p = £6Cost of 1 low-energy bulb = £8Incandescent bulbs electricity cost = 0.1 kW × 10 000hours × 12 p/kW h = 12 000 p (£120)Low-energy bulb electricity cost = 0.02 kW × 10 000hours × 12 p/kW h = 2400 p (£24)Total cost for incandescent bulbs = £6 + £120 = £126Total cost for 1 low-energy bulb= £8 + £24 = £32

Saving over lifetime of low-energy bulb = £94

P1.31 Energy transfers

Student Book

1 Input energy = output energy, since energy cannot becreated or destroyed.

2 chemical energy input, converted to electrical energy,then light and heat energy

3 a (chemical potential energy, for mains electricitygenerated from fossil fuels or for a battery, to) electricalenergy to sound energy and heat energyb electrical energy to light and sound and heat energyc gravitational potential energy to kinetic energy toelastic potential energy to kinetic energy and heatenergy to gravitational potential energy

4 400 J of heat energy plus student’s own diagram(Edexcel do not require scaled Sankey diagrams but thisis good practice and could be encouraged).

5 a Energy transfer chains should start with chemicalpotential energy (in a battery) or electrical energy. Theyshould also include heat as a wasted form of energy.b All diagrams should include energy wasted as heat.

6 Students’ own answers. Six points to be included:

Total energy in = total energy out

So sum of various forms before and after must be equal

An arrow diagram drawn to scale

Can follow the changes in energy form

Without losing any energy

So energy is conserved

Skills spotlight An energy conversion diagram is quantitative so it gives

more information. You can ‘account’ for all the energytransfers during changes by checking they all add up.

It highlights the conservation of energy as the arrowsfor energy output are of the same total width as theone(s) in.

There is a visual clue as to how much energy is beingused usefully or otherwise – the relative amounts ofenergy transferred by each process.

A scale drawing also assists with calculations of energyoutputs.

(More able students may jump ahead to: There is animmediate visual clue as to how efficient processes are,or for comparing different processes or devices.)

Activi ty Pack

P1.31c Energy conversion diagrams 1

1 a electricalb 27 Jc students’ own answers

2 a students’ own answersb It heats the kettle itself and most is then transferred tothe surroundings.

3 cuckoo clock: gravitational potential becomes kineticspring clock: elastic potential becomes kinetic

P1.31d Energy conversions diagrams 2

1 a chemical (potential)b kinetic (plus light, sound, heat in some situations, e.g.

headlamps)c heat, soundd student’s own answers

2 a gravitational potentialb kinetic (+ sound + heat)





c diagram showing chemical potential (muscles) tokinetic to gravitational potential (plus heat in each stage)

3 a electricalb light + soundc heatd students’ own answer – need arrows to scale for 100 =85 + 5 + 10e students’ own answer – need arrows to scale for 100 =85 + 5 + 10 followed by half of this 10 J arrow splitting offinto 4 J heat + 1 J light

P1.32 Efficiency

Student Book1 a Chemical potential becomes kinetic, sound and heat

(and maybe light)b Kinetic useful (plus possibly light, heat and sound)c Heat and sound wasted

2 They wasted too much heat/energy.3 Old-style = 9%; energy saving = 45%4 Amounts of energy stored in petrol; amount of kinetic

energy produced, plus amounts of heat and soundwasted

5 a 45 Jb 10%

6 Six points to be included:

Rating gives an indication of the efficiency

Which depends on how much of the electricity it uses istransferred usefully

Efficiency is calculated from (useful out/total in) × 100%

Higher % is A-rated.

A-rated is more efficient so wastes lower proportion ofenergy supplied, for same job.

Which means it is likely to be cheaper to run

Which makes this useful information for people trying todecide which kind of fridge to buy.

Skills spotlight

To calculate efficiency we need to know the usefulenergy output and the total energy input.

Use electrical means to measure the energy input(either a joulemeter or a voltmeter–ammeter–timingmethod).

Measure the increase in water temperature (plan shouldmention start and finish temperatures).

This indicates the useful energy produced (no furtherdetail about the link between temperature and energy isexpected).

Control variables are: volume of water; roomtemperature (may also mention mains power supplyand start temperature).

Activi ty Pack

P1.32a Efficiency ratings labels

1 fridge–freezer: efficiency = 900 000/3 000 000 = 30% –D rated

2 television: 18/200 = 9% – G rated

3 washing machine: 2500/5000 = 50% – B rated4 computer: 12/60 = 20% (assumes all sound energyproduced is useful) – E rated

5 kettle: 67/90 = 74% – A ratedNote that the energy ratings are worked out by putting theappliances in order of efficiency and then comparing thesewith the energy rating labels given on the worksheet.6 It can be very difficult to (capture and) measure all the

wasted or useful energy.It is difficult to decide how to compare the differentfunctions of each device to make a fair comparison togive an alphabetic score, e.g. it is impossible to make aTV as efficient in percentage terms as a kettle, so shouldno TVs be A rated? This means that the rating is onlywithin an appliance class, but even then there are manysuch differences. Comparing a small screen TV with alarge one, possibly with different screen technologies, isunfair. (However, note that commercial bias is thebiggest influencing factor on the methodologiesemployed by manufacturers.)

P1.32b Testing kettle efficiency

1 112 s2 Use a measuring beaker or measuring cylinder (rather

than just the line on the kettle).3 stopwatch4 The time until automatic cut off would be the best (most

comparable) way; observations of boiling are subjectiveand not as repeatable.

5, 6 students’ own answers7 a more than the theoretical value

b energy wasted in heating the surrounding air/kettlecase – not all the electrical energy is transferred to the

water as heat; hot water/kettle case radiates energy asheat

8, 9, 10 students’ own answers11 Measure mass, time to boil kettle more accurately.

Repeat procedure or take a mean of class results.Measure or control start temperature so that it matchesthe value in the theoretical calculation.

12 Whenever a measurement is made, there will always besome uncertainty or doubt about the result obtained,including the random effects of ‘unseen’ influences onthe measurement. Repeating measurements using thesame equipment under same conditions should produceconsistent results (low variability). If the variation is lowwe can take a mean and this will reduce the uncertaintyfor the mean.

P1.32c Energy transfers and efficiency of electricaldevices

Card groups:7, 1 (or 11), 10, 13 (or 14)19, 11 (or 1), 2, 1712, 6, 15, 58, 3, 9, 13 (or 14)16, 20, 18, 4

P1.32d Efficiency questions

1 efficiency = useful energy transferred / total energytransferred

2 a False b True c False d False e False f True3 Statement a is wrong because heat energy is not the

useful output.

Statement c is wrong because it does not use chemicalenergy.Statement d is wrong because the total energy input isnot 18 J.Statement e is wrong because an inefficient appliancewastes more energy than an efficient one.

P1.34 The Earth’s temperature

Student Book

1 It must absorb the same power that it radiates.2 a 175 W – as 51% is absorbed

b 20.6 W (note that it is 6% of the total incoming solarpower)c The Earth/atmosphere would get warmer.

3 Power absorbed and radiated must be equal, astemperature is constant.4 The Earth would reflect more of the Sun’s radiation so

the Earth and its atmosphere would absorb less powerfrom the Sun.

5 White, as this colour reflects heat better than, forexample, black.

6 Six points to be included:

A system can absorb radiation and warm up.

Warm objects also emit radiation and cool down

If power absorbed = power radiated, temperatureremains constant.

If more radiation is received, the object will warm up

But then it will also radiate more

Eventually the power radiated will increase enough to

balance the higher incoming radiation And the system will stabilise again at a higher

temperature.



Skills spotlight

Students should have included at least one point in favour ofthe model and one point against before deciding whetherit was a useful model.

Points in favour: it represents that the power absorbed (fromthe heating element) needs to be the same as the powerradiated. By turning the thermostat you can change thepower and so change the final temperature.

Points against: it doesn’t show that the energy absorbed isnot the same as the energy radiated by the Earth; theenergy lost by the Earth is in all directions but the energylost by the water in the water bath is mainly from one

direction; the thermostat will click on and off to keep tokeep the temperature constant, and so you can’t modelthe addition of greenhouse gases (anything you add toabsorb energy will be countered by the action of thethermostat).

Conclusion: Despite being simplified this is a useful modelbecause it helps us to think about the overall process ofpower input having to match power output.

Activi ty Pack

P1.34b Radiation increases and decreases

1 The temperature inside is very high as the black body ofthe car is a good absorber of radiation.

2 A white surface reflects more of the radiation falling on itthan a black surface.

3 A black surface is a good emitter of radiation so thiswould be the best colour.

4 Under similar conditions different materials transfer heatat different rates depending on their colour: dark mattsurfaces are good emitters of radiation; white/shinysurfaces are poor emitters of radiation.

5 If the Earth emits more radiation than it receives from theSun… it will cool down.If the Earth receives the same amount of radiation as itemits … its temperature will stay the sameIf the Earth emits less radiation than it receives from theSun ….it will warm up.

P1.34c Constant temperatures?

1 Inside the cars – No

Sun’s radiation absorbed inside car. Less radiation isemitted than is absorbed, so temperature rises. Whenthe doors are opened, more heat energy escapes than isabsorbed so the cars cool down.

2 Underfloor heating – NoWhen the heating is switched on, the room heats up as itabsorbs more power than it radiates. As it warms up, theroom starts to radiate more heat, until the absorbedpower equals the radiated power when the temperaturewill remain constant.

3 Fish tank – YesKept at a constant temperature as the energy in =energy out.

4 Hot drink – NoThe drink is absorbing little heat energy but giving off alot, so it will cool down.

5 Inside an oven – NoThe heating element will provide a lot of energy, morethan the oven emits, so it will heat up.

6 A radiator – YesThe heating system gives the radiator energy, but itradiates as much as it absorbs.

P1.34d Temperature o f sys tems

1 The water heating system would supply exactly thesame power as was radiated.

2 The Earth is constantly radiating the same power as itreceives, so its temperature remains constant.

3 a The atmosphere absorbs radiation emitted from theground. This warms the atmosphere. Then theatmosphere starts radiating. This means that thetemperature is higher as heat is trapped on Earth, butthe temperature will be constant when the emitted powerequals the power absorbed.b More heat would be trapped so the temperature wouldbe higher. Again, the temperature will be constant (but ata higher level) when the emitted power equals the powerabsorbed.

4 When the Sun is not shining on one side of the Earth,that side radiates more power than it absorbs so itstemperature falls.

5 a

Planet Distancefrom Sun(AU)

Proportionof Sun’sradiationreceived(comparedto Mercury)

Atmosphericcarbondioxide

Average

temp ( C)

Mercury 0.435 100 % None 420

Venus 0.7 25% 96% 460

Earth 1 16% <1% 14

b From the distances and hence amounts of sunlightreceived, we would expect the temperatures to be in the

order of Mercury hottest, then Venus, then Earth. Mercury

has no atmosphere to trap heat. Earth has a small amountof carbon dioxide so is a bit warmer then expected.However, Venus has a large amount of carbon dioxide sois much hotter than it should be.

6 The temperature does not vary, even though the nightsare so long. This is likely to be because the densecarbon dioxide atmosphere traps heat and effectivelyinsulates the planet.

Documents

P1 Student Book Answers.pdf