P2 Student Book Answers

Answers – P2: Physics for your future P2.1 Static electricity

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Insulating materials a Nucleus b Around the nucleus 5, as the positive and negative charges normally balance The polythene now has more electrons than protons, so it has a negative charge. The cloth has more protons than electrons, so it has a positive charge. They are on the outside of the atom. Positive charges are fixed inside the nucleus of the atom and cannot move. All the strands of her hair have the same charge, so they are all repelling each other. If the balloons are both made of the same material, they will both get the same type of charge when they are rubbed on the jumper (this could be positive or negative). As both balloons have the same charge, they will repel each other. A good answer will contain the following points:  Rubbing the comb gives it a static charge.  If this is a negative charge, it repels electrons in the pieces of paper, leaving the sides nearest the comb with a positive charge.  The negative charge on the comb and the positive charge on the pieces of paper attract each other.  (Accept similar answer written assuming a positive charge on the comb.)

P2.2 Uses and dangers of static electricity Student Book 1 2

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Skills spotlight A real atom is much smaller than the atom shown. A real atom is three dimensional. Other differences include: the relative sizes of the nucleus and the overall atom – the nucleus is much smaller than the atom; the particles are not coloured spheres, as drawn here, and they do not have + and – signs on them!

Activity Pack P2.1b Static electricity questions 1 2 3

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From top: electron, proton, neutron, nucleus Electrons Negatively charged electrons have been transferred from the rod to the cloth. The rod now has fewer electrons than it started with. a Repel b Attract c Repel

P2.1c Static charges 1 2

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Diagram similar to Figure B in Student Book. The clothes rub against each other while they are being tumbled, so electrons may be transferred from one item to another. a Electrons from the glass rod have been transferred to the cloth, leaving the glass rod with fewer electrons than it started with. It now no longer has enough electrons to balance the positive charges on all its protons, so it has an overall positive charge. b Attract c If they are made of the same material, they will get the same charge and so will repel. a Electrons from the jumper have been transferred to the balloon. It now has more electrons than protons, so it has a negative charge. b The negative charge on the balloon will repel electrons in the near part of the wall. This leaves the near part of the wall with more protons than electrons, so it has a positive charge. This will attract the negative charge on the balloon, so the balloon will stick to the wall.

a Furniture polish is usually applied by rubbing (or a spray-on polish is then rubbed off with a duster). The rubbing action will transfer electrons between the cloth and the surface being rubbed, leaving the surface with a static charge that will attract dust. b The polish contains a conducting material (such as a special polymer) that is left behind as a very thin layer when the solvent in the polish evaporates. This forms a thin conducting layer that prevents a static charge building up.

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The charge flows through the door to earth. a The spark could ignite fuel vapour in the air. b Any charge built up would be discharged through the bonding line, so there will be no charge to make a spark. c The static charge needs to be discharged before the fuel nozzle gets close enough to the aircraft for a spark to jump across the gap. a They all have the same charge, and like/similar charges repel each other. b The object must have the opposite charge to the paint drops, so that they will be attracted to the object. a The drops of insecticide all have the same charge, so they spread out to provide a more even coverage. b It means there is less wasted insecticide, so costs of spraying are cheaper. It might also mean that it is quicker to spray a given area of crops, so again costs will be less. c If it reduces the amount of wasted insecticide, it means that the insecticide is only going where it is needed and is less likely to harm other wildlife. A good answer will contain the following points:  Static electricity can be dangerous if it causes sparks.  This is particularly so in places where the spark might cause a fire or an explosion.  This danger is avoided by making sure that any static charge is discharged before the spark can occur.  This can be done by earthing the charged object.

Skills spotlight a Advantage: the spray spreads out more, so the insecticide can cover the crop more evenly. Disadvantage: the spray may spread out so much that it gets onto crops/hedges that it is not intended for, or it might be easier for the spread-out spray to be breathed in by people. b Advantage: paint spreads out if it is charged, so it gives a more even coverage, or charged drops of paint are attracted to the object being painted, so less paint is wasted. Disadvantage: a fine mist of paint produced by charging it might be more flammable/easier to ignite than a paint spray that is less spread out.

Activity Pack P2.2a Static and helicopters A–3 d When the helicopter lands its static charge is earthed through the tyres, so it is safe to touch. B–8 c The helicopter will have a large static charge. If a person standing on the ground touches it, that charge will run to earth through them and give them a severe electric shock. C–2 f The helicopter will have a large static charge. If a person standing on the ground touches it, or uses an object to touch it, that charge will run to earth through them and give them a severe electric shock. D–7

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h The discharge wand allows the charge to run through the wand and the wire to earth, without passing through the person. E–6 a The helicopter will have a large static charge. If a person standing on the ground touches the cable, that charge will run to earth through the cable and through them and give them a severe electric shock. F–4 e The discharge wand allows the charge to run through the wand and the wire to earth, without passing through the person. However, as the helicopter is still hovering, it will quickly build up another charge unless the wand is kept in contact. G–1 b This is unsafe because the person will be the first thing to touch the ground, so the static charge on the helicopter will be discharged through them. H–5 g The cable will touch the ground first, so the static charge will run through the cable, not the person.

P2.2b Using static electricity 1

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Your shoes rub on the carpet as you walk. Some electrons are transferred from the carpet to your body. You now have a negative charge. When you touch a door handle, the charge can flow into the door and to earth. You feel a shock when the charge jumps from you to the handle. You are now discharged. The charged drops spread out so they cover more crops. The charged droplets of paint are attracted to the object being painted. The charged droplets of paint repel each other and spread out. A conducting material that allows electricity to flow through it. It earths the aeroplane and the tanker so there are no sparks.

P2.2c Static problems 1

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The answer should include: how static charge can build up, how it can cause sparks when discharged, how sparks could cause a fire if there is fuel vapour around, how a bonding line prevents this by ensuring there is no potential difference between the tanker and the aircraft. The answer should include how charge can build up on a person, and what happens when a metal object is touched. Advice could include changing shoes for ones made of a different material that might not build up such a high charge, or holding a metal object towards the door so the spark jumps from the metal and not from the person's hand. If one of the straps is broken it will not conduct electricity from the person to the casing of the board being worked on, so any static built up on the person could suddenly discharge into one of the components when it is touched. If the strap is working properly the lamp will light as there will be a complete circuit. If one is broken (i.e. not conducting between the wrist strap itself and the clip that is fastened to the equipment being worked on) then it will not conduct electricity and so will not discharge the person using it. Sparks arising from static electricity could damage the circuitry in such items. If the prongs on a chip are all stuck into carbon-filled foam the conducting nature of the foam prevents a build-up of static charge that could harm the component. (Hard drives and new circuit boards are also delivered in anti-static bags.)

Conducting materials have electrons that are free to move around between the atoms. Insulating materials do not. 3 a A direct current always flows in the same direction. In an alternating current, the electrons change direction many times each second. b Cells and batteries (students may also answer power supplies) 4 a Coulombs b Amperes 5 3 A × 30 s = 90 C H6 Time = charge/current = 5000 C / 20 A = 250 s 7 A good answer will contain the following points:  Make a circuit using the wire and a cell.  The cell will cause some of the electrons from the metal atoms to move along the wire.  This is a current.  This will not work with an insulating material.  This is because there are no electrons that are free to move around. 2

Skills spotlight The words for different quantities are often different in different languages, which could cause problems if scientists in different countries are communicating with each other. Symbols are quicker to write, and an agreed set of symbols can be used internationally.

Activity Pack P2.3a Matching symbols A, i, voltmeter, measures voltage B, c, resistor, makes the current in the circuit smaller C, f, ammeter, measures current D, h, open switch, stops current flowing when open E, b, motor, transfers electrical energy into kinetic (movement) energy F, d, lamp or bulb, transfers electrical energy into light and heat energy G, g, cell, pushes electrons around the circuit and gives them energy H, a, variable resistor, can be adjusted to change the amount of current in a circuit I, e, wire, conducts electricity around the circuit J, j, closed switch, allows current to flow in the circuit

P2.3b Currents and calculations 1 2 3 4 5

P2.3c Charges and currents 1

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P2.3 Electric currents Student Book 1

A flow of charge – in a metal these moving charges are electrons.

A direct current always flows in the same direction. An alternating current changes direction. Charge = current × time = 4 A × 20 s = 80 C 3.6 A × 60 s = 216 C Current = charge/time = 750 C/60 s = 12.5 A Time = charge/current = 4000 C/2 A = 2000 s

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a 4.5 A × 20 s = 90 C b 3.6 A × 60 s = 216 C c 22 A × 1800 s = 39 600 C 800 C/4 A = 200 s a 90 000 C/7200 s = 12.5 A b 9000 C/18 000 s = 0.5 A a The hosepipe was empty, so she had to wait until the hosepipe had filled up before water started to come out of the end. b The hosepipe still had water in it. When the tap was turned on, the water going in at that end pushed water out at Jenny’s end. There are already electrons in the wire. When the switch is pressed the electrons ‘going into’ the wire at that end push other electrons along. We don’t have to wait for an electron at the switch to travel all the way to the bulb before the light comes on. 3 metres = 3000 mm. It would therefore take 3000 seconds for an electron to travel from the switch to the bulb, or 50 minutes. a t = Q/I = 1/1.5 × 10-6 A = 6.67 × 105 seconds b t = Q/I = 1/20 × 10-9 = 5 × 107 seconds

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P2.4 Current and voltage Student Book 1

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P2.4d Currents and circuits 1

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H5 1 V is 1 J per coulomb, so 20 C at 5 V is 20 × 5 = 100 J 6 A good answer will contain the following points:  Subtract the reading on A2 from the reading on A1 to get the current flowing through B2.  This works because the current flowing through the main part of the circuit splits up at the junction.  Therefore the sum of the currents through B1 and B2 is the same as the current in the main part of the circuit.

Skills spotlight The boiler and pump represent the cell, the pipes represent the wires, the water in the pipes represents the moving electrons, the heat energy in the water represents the energy transferred by the electrons, and the radiator represents the bulb. An 'ammeter' in the central heating system would measure the volume of water passing a point in the circuit each second. A voltmeter would measure the temperature of the water going into and out of the radiator (or into and out of the boiler).

Activity Pack P2.4b Modelling circuits 1

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b The cell pushes the electrons around the wires in the circuit. c The electrons do not get used up, they just go round and round the circuit. d The lamp converts energy from the electrons into light energy. e This produces light. B C

P2.4c Measuring in circuits 1 2

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a Voltmeter drawn across cell, labelled V1 b Voltmeter drawn across bulb, labelled V2 a In series b In parallel

a Amperes (or amps), A b Volts, V a2A b2A c 1.5 A d1A e2A a The current is the same everywhere in a series circuit (or similar explanation). b The current in the branches adds up to the current in the main part of the circuit (or similar explanation).

a2A b2A c 1.5 A d1A e2A a Voltmeter drawn across cell, labelled V1 b Voltmeter drawn across bulb, labelled V2 a The cell b Electrons c The energy carried by the electrons a It increases b More lorries would leave the supermarket each second a Parallel b Each lorry would have to visit all the supermarkets in turn, unloading only some of the bread at each one. a The number of lorries driving round the route is always the same; only the amount of bread they are carrying changes. b The total number of lorries leaving the factory must be the same number as arrive back, and this total number is split between the different routes they have to drive (representing different branches of a parallel circuit). a The potential difference represents the energy transferred by each coulomb of charge. If a lorry represents the charge, then the potential difference is the difference in the amount of bread carried by lorries entering and leaving the factory. b The difference in the amount of bread carried by a lorry as it enters and leaves a supermarket (or the amount of bread left at a supermarket).

P2.6 Changing resistances Student Book 1 It increases 2 5 A × 50 Ω = 250 V 3 Current and potential difference (or voltage) H4 R = V/I = 4.5 V / 0.5 A = 9 Ω 5 a LDR b Thermistor c Variable resistor 6 A good answer will contain the following points:  The resistance of the thermistor will control the current flowing through the circuit.  If the temperature rises the resistance of the thermistor will decrease.  Therefore more current can flow in the circuit.  If the current is higher, the motor driving the fan can turn faster.

Skills spotlight A is the filament lamp, B is the normal resistor and C is the diode. The diagrams show complex mathematical relationships but students should be able to describe the general shape of the graph and use this evidence to draw a conclusion about which component it represents.

Activity Pack P2.6c Components and graphs C, H, B or J, graph labelled light intensity and resistance. M, G, B or J, graph labelled temperature and resistance. A, F, L, graph labelled potential difference (x-axis) and current. N, K, D, graph labelled potential difference (x-axis) and current. O, I, E, graph labelled potential difference (x-axis) and current.

P2.6d Components and resistances 1

a Variable resistor b Filament lamp

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c Thermistor d Diode e Light dependent resistor It will go down/get less. 10 V / 2 A = 5 Ω a Current = 5 V / 100 Ω = 0.05 A b It will go down. c It will go up. a Resistance = 12 V / 3 A = 4 Ω b It will go up. c It will go down.

P2.6e Changing resistances 1

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Potential difference (V) Current (A) Resistance (Ω) 0 0 2 0.38 5.26 4 0.64 6.25 6 0.83 7.23 8 0.98 8.16 10 1.10 9.09 12 1.18 10.17 14 1.24 11.29 It goes up. a Correctly plotted graph. b As the potential difference increases the gradient of the line gets less. That means for each increase in potential difference, the increase in current gets less, so the resistance must be increasing. a 0.26 A b 0.06 A The resistance must be greater when the potential difference is higher, as the 2 V increase in potential difference from 12 V to 14 V has resulted in a much smaller increase in current than it did from 2 V to 4 V. a

a 12 V × 3 A = 36 W b 10 minutes = 600 s Energy = 12 V × 3 A × 600 s = 21 600 J (or energy = 36 W × 600 s) H4 Current = power/potential difference = 25 W/230 V = 0.11 A 5 Energy transferred = 358 800 J Energy = power × time Time = energy/power = 358 800 J/500 W = 718 seconds (to the nearest second) 6 A good answer will contain the following points:  Electricity passing through a resistor (such as the element of a kettle) causes a heating effect.  The power of an electrical appliance can be calculated using the potential difference and current.  For the same kettle, a lower potential difference will mean that a lower current flows.  The power will be much less than with a higher potential difference.  It takes a certain amount of energy to boil a fixed volume of water.  The power is the energy transferred per second.  If the power is lower it will take longer for the same amount of energy to be transferred. 3

Skills spotlight Students will need to draw on knowledge from Units C1 and P1 to answer this fully. Possible advantages include: electric heaters are efficient (very little of the electricity paid for is converted to forms other than heat); they do not produce waste gases that can be toxic; they are easier to start than a wood fire; they can be used sustainably if the electricity comes from renewable resources. Possible drawbacks include: their overall efficiency depends on the efficiency of the power station that produced the electricity, so they may not be as efficient; many people prefer the appearance of flames from a 'real' fire; a wood fire is a sustainable means of heating, as long as the wood is harvested sustainably. Possible risks include: risks of electric shocks as well as burns if the heater (and the electricity wiring in the house) is not installed and maintained correctly.

Activity Pack P2.7a Choosing the wiring 1 b 2

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P2.7b Electrical heating

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P2.7 Transferring energy Student Book 1

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a 500 W b 500 W/230 V = 2.17 A c 1.0 mm2 a 8500 W/230 V = 36.96 A b 6.0 mm2 c Because if another high power appliance was used on the same circuit, the circuit could overload. a 9.6 kW or 9600 W b 9600 W/230 V = 41.7 A c 10.0 mm2

Components heat up when electric current flows through them, and electronic components do not work properly if they get too hot. a Any two useful effects, such as in kettles, electric fires, cookers, electric blankets, tumble dryers, etc. (do not accept microwave ovens or any other electrical appliance that does not involve direct heating). b Any two examples of wasted heat energy, such as TVs, radios, computers.

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a Useful b Useful c Not useful d Useful e Not useful Watt 230 V × 8 A = 1840 W Current = power/potential difference = 90 W/230 V = 0.39 A Joule 1840 W × 60 s = 110 400 J (or 230 V × 8 A × 60 s = 110 400 J)

P2.7c Heating and power H1 a Current = power/p.d. = 90 W/230 V = 0.39 A b 1000 W/230 V = 4.35 A c 2000 W/230 V = 8.70 A H2 a Energy = current × potential difference × time 3 hours = 3 × 60 × 60 = 10 800 s Energy = 0.39 A × 230 V × 10 800 s = 968 760 J

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b 5 minutes = 5 × 60 = 300 s Energy = 4.35 A × 230 V × 300 s = 300 150 J c 2 minutes = 2 × 60 = 120 seconds Energy = 8.70 A × 230 V × 120 s = 240 120 J H3 The electrons collide with the atoms and transfer energy to them. 4 a If it did not, it would melt and break the circuit when the appliance was working normally. b Many appliances use a smaller current than 13 A, so it is safer to use a fuse that melts only just above the normal current. H5 a Current = 0.39 A, fuse = 3 A b Current = 4.35 A, fuse = 5 A c Current = 8.70 A, fuse = 13 A H6 a A higher potential difference causes a higher current to flow. This means that more electrons are passing through the filament each second, and so more electrons will collide with the atoms in the filament. More energy will be transferred to heat energy. b They vibrate more. c The vibrating atoms are more likely to get in the way of the moving electrons (or similar explanation), so the resistance to the current will increase. The higher the potential difference, the hotter the filament and the more the vibrating atoms get in the way of the moving electrons.

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a 1.4 m/s b No, because the direction is different. At C; 500 m a 1000 m b Displacement is distance in a particular direction as the crow flies, not the total journey. a 1400 m b 900 s c 1.6 m/s 3.5 m/s

P2.8d Lane swimming 100 m 0m 0.8 m/s a 0.8 m/s up b 0.8 m/s down; the velocities are opposite as the direction is opposite. H5 80 s H6 3 m H7 23 m H8 15 m 9 Length 1, 2 m/s; Length 2, 1.72 m/s; Length 3, 1.72 m/s; Length 4, 2.17 m/s 10 5 m from David’s end of the pool 1 2 3 4

P2.9 Acceleration

P2.8 Vectors and velocity

Student Book

Student Book

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Displacement is the straight-line distance moved in a particular direction; distance is how far an object has moved. 2 The runner has arrived back exactly where they started. 3 9 m/s 4 Vector quantities such as force and velocity have both a size and a direction. 5 The velocity has changed because the direction is different. H6 350 m 7 a 0.8 m/s b 0 m/s H8 224 m 9 A good answer will include the following points:  A distance-time graph shows distance travelled plotted against time.  The gradient of a distance-time graph gives the speed because speed is distance/time.  A horizontal line shows an object is stationary.  A straight sloping line shows an object with a constant speed.  The steeper the line, the greater the speed.

Acceleration is the change in velocity per second. It is calculated from the equation acceleration = change in velocity/time taken. 2 23.3 m/s2 H3 12 m/s 4 Because velocity is a vector quantity/it has a direction as well as a size. 5 −5 m/s2 H6 70 s 7 A good answer will include the following points:  Negative acceleration means the acceleration is acting in the opposite direction to the object’s velocity (provided the initial velocity is taken to be positive) so the object’s velocity in the original direction will decrease − it will slow down.  If a negative acceleration continues to act, then eventually the object will stop and then start to get faster in the opposite direction.  Positive acceleration acts in the same direction as the object’s velocity so the object’s velocity will increase (it will get faster).  An acceleration of zero will not change the object’s velocity so it will continue at a constant speed.

Skills spotlight

Skills spotlight

Suggestions such as: it is easier to see the change in an object’s motion from a graph, shown as a change in the slope of the line, than just by comparing values in a table.

In a car none of the instruments give the speed in m/s and people are unlikely to understand speed in m/s. Acceleration from 0 to 60 mph uses speed values people understand and gives an idea of how quickly a car can pull away from traffic lights, or accelerate when overtaking or merging on a motorway.

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Activity Pack P2.8b Using distance–time graphs 1 2 3 4 5 6 7 8

4 m/s aC b 10 s aB b 5 m/s aD b The slope is the shallowest so the speed is least. 8 m/s a 55.6 m/s b 36 minutes (or 0.6 hours or 2160 seconds) a 589 m b 1085 m 75 s

P2.8c Country walk 1 2

1.5 m/s 2 m/s

Activity Pack P2.9a Theme park Missing values: A, a = 6 m/s2; B, a = -3 m/s2; C, u = 33 m/s, v = 3 m/s, D, u = 25 m/s, v = 5 m/s, E, a = 9 m/s2; F, a = 6 m/s2

P2.9b Acceleration sentences acceleration: has a direction and so is a vector quantity, has units m/s2, is given by the equation (v – u)/t, is given by the equation change in velocity/time taken speed: does not have a direction and so is not a vector quantity, has units m/s, is given by the equation distance travelled/time taken distance: does not have a direction and so is not a vector quantity, has units m displacement: has a direction and so is a vector quantity, has units m

© Pearson Education 2011. Edexcel GCSE Additional Science Teacher and Technician Planning Guide This document may have been altered from the original.

velocity: has a direction and so is a vector quantity, has units m/s (note that velocity is displacement in a given time – the direction must be given) force: has a direction and so is a vector quantity time: does not have a direction and so is not a vector quantity

P2.10d Velocities and accelerations on graphs

P2.9c Acceleration

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a 5 m/s2 b 1 m/s2, arrow to the right c –2 m/s2, arrow to the left d 2.5 m/s2, arrow to the left a 10 m/s2 b 5 m/s2 c 5 m/s2 d –1.5 m/s2 e –5 m/s2

P2.9d Changing velocity 1

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a a = 1 m/s2, acceleration to the right b 2 s, acceleration to the left c v = 5 m/s; velocity to the right d u = 20 m/s; acceleration and velocity in opposite directions a5s b 14 m/s a 20 m/s b A velocity of 15 m/s upwards – in the opposite direction to the original velocity. c -35 m/s d -175 m/s2 a 1.5 s b 20 m c 11.25 m

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P2.11 Forces Student Book 1 2

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P2.10 Velocity-time graphs Student Book Velocity is constant. aC bB cD 3 A 0.5 m/s2 B 2 m/s2 C 0 m/s2 D −0.5 m/s2 H4 a A 100 m, B 200 m, C 900 m, D 900 m b 2100 m 5 A good answer will contain the following points:  Suitable graph with time on horizontal axis and speed on the vertical axis.  Values of acceleration for the different parts (10 m/s2, 20 m/s2, 7.1 m/s2, −10 m/s2, −6.6 m/s2).  Possible extra information could be: label to show where the greatest acceleration was (from 4 to 16 s); label to show where the Thrust started to slow down (peak of graph). 1 2

A free-body diagram shows just the forces acting on a single object, so they are not confused with the forces acting on other objects.

Activity Pack P2.11a Everyday forces a, squashing force on balloon; b, weight and upthrust on boat; c, weight and tension force on lamp; d, weight and magnetic force on paperclips; e, lift, weight, thrust and air resistance on aeroplane; f, stretching force on chest expander.

P2.11c Forces and diagrams 1 2

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Suitable graph 15–17 s; steepest slope 5–15 s and 17−20 s; horizontal lines on graph 15–17 s and 22–25 s; the line slopes downwards with time Accelerations: 6 m/s2, 0 m/s2, –7.5 m/s2, 0 m/s2, 2.5 m/s2, –6.7 m/s2 75 m, 300 m, 45 m, 45 m, 35 m, 30 m

P2.10c Velocity–time graphs 1 2

a Correct lines drawn b Speeding up into a gallop; steeper slope A, 4 m/s2; B, 0 m/s2; C, 1 m/s2; D, –5 m/s2; E, –1 m/s2

Students’ own free-body diagrams with forces correctly labelled. a Pull of string on the brick/pull of brick on the string; pull of string on the balloon/pull of balloon on the string b Weight of the balloon, pull of string on the balloon c Upthrust from the air d Forces are weight of balloon, upthrust from the air, pull of string on the balloon.

P2.11d Moving in space 1

Activity Pack P2.10a Shooting script

a Upthrust and weight; or drag and push from diver b Push from diver, because the arrow is larger Simple free-body diagram showing downward force arrow from bird labelled ‘weight’ and upward force arrow for reaction labelled ‘reaction from fence post’. The fence post should not be shown. Force of rocket on hot gases and force of hot gases on rocket 53 000 N The force on the rocket would be in a different direction too so it would change its direction of motion. Suitable free-body diagrams – each should only show one object and the forces acting on it. A good answer will contain the following points:  Clear diagram showing push of astronaut on diver and push of diver on astronaut.  The two forces should be shown as arrows in opposite directions.  The two arrows should be equal in size.  Diagram shows forces on two objects, whereas freebody diagrams just show forces on a single object.

Skills spotlight

Skills spotlight Advantages: very easy to compare sizes and sign of acceleration in number form; numbers are quicker to use for calculations; would have to find the gradient to put a value on an acceleration from a graph. Disadvantages: not as visual, so not as easy to compare changes in acceleration over time as on a graph.

A, 4 m/s2; B, 0 m/s2; C, 1 m/s2; D, –5 m/s2 102.5 m E, 1 m/s2; F, 0.4 m/s2; G, –0.2 m/s2; H, 0 m/s2; I, –3 m/s2; J, 2 m/s2. 793.75 m a Graph plotted correctly (straight line sloping down from maximum velocity 30 m/s) b at 3 s c –10 m/s2 d 45 m e 90 m

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a Diagram labelled with weight of astronaut, upthrust from water b Free-body diagram showing forces from part a. Weight of astronaut, upthrust from water, pull of rope on astronaut, pull of astronaut on rope The action force of the astronaut on the rope is equal and opposite to the reaction force of the rope on the astronaut. a Diagram showing weight of astronaut, upthrust of water and pull of rope on the astronaut b As part 1b. a The reaction force pushes on the astronaut and pushes her in the opposite direction – away from the space station. b Sensible suggestions such as using ropes or clips.

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P2.12 Resultant forces Student Book 1 2

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The arrow for thrust is bigger than the arrow for air resistance (drag). Simple free-body diagram with labelled forces lift (upwards), weight (downwards), thrust (to the right) and drag or air resistance (to the left). Sizes of arrows same relative size as in Student Book. 0N 103 N a Because the lift is equal to the weight. b Because the thrust is greater than the air resistance. There is no air resistance in space. A good answer will contain the following points:  No thrust means that there is no forward force.  There is still drag because the craft is moving.  There is a resultant force in the opposite direction to the craft’s motion.  This gives a negative acceleration that slows the craft down in the forward direction.  The lift must be less than the weight.  The resultant force is therefore downwards.  This gives an acceleration downwards, which means the craft loses height.

Skills spotlight Qualitative: The diagram in Figure B uses arrows with different sizes to compare forces. Quantitative: Worked example uses numerical values to show the resultant force.

Activity Pack P2.12a Why do things move? True: A, F, G, H False: B, C, D, E

P2.12b Theories of motion 1

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a An object needed a force to be acting to keep it in motion. b The feather did not have as big a force on it so it moved more slowly. a A moving object did not need a force to keep it moving. It would carry on at a steady speed unless a force acted to slow it down. b The friction force had more effect on the feather so it moved more slowly. a Newton’s first law b Newton also included stationary objects. a By thinking about observations. b By carrying out experiments and by ‘thought’ experiments. c Galileo’s method a All objects need a force to keep them moving. b Resistive forces act to slow the bicycle down. The cyclist must pedal to balance these forces. a Answers may vary. One answer could be no, because the packages are moving in a different direction to the car, so there is no force to keep them moving forward. b Yes. The packages continue to move in the original direction. The friction between the packages and the carpet in the back of the car is not enough to change the direction of motion immediately. c Third law

P2.12c Forces and motion 1

2 3

b Accelerates forward c Slows down (accelerates backwards) d Changes direction a Right b4N a balanced forces; the car will continue forwards at a steady speed b 300 N upwards; the helicopter will accelerate upwards

2

3

P2.14 Forces and acceleration Student Book It will accelerate in the direction of the resultant force. A cricket ball has more mass than a tennis ball so the same force will give the tennis ball a greater acceleration. 3 You would need a much larger force for the lorry, because it has much more mass. 4 The larger catapult will fire the rock faster because it can produce more force, and so more acceleration. 5 4500 N H6 9 m/s2 7 A good answer will contain the following points:  Force = mass  acceleration  To achieve the fastest speed at the start the cyclist needs the most acceleration.  A more massive bike will need more force to give the same acceleration.  A cyclist with more mass needs to produce more force to give the same acceleration on the same bike.  A cyclist can only produce a certain amount of force.  So the lowest mass of bike/rider combined will give the greatest acceleration for the same force. 1 2

Skills spotlight F − stands for force, measured in N m − stands for mass, measured in kg a − stands for acceleration, measured in m/s2

Activity Pack P2.14a Accelerating vehicles 1 Cars matched as: Caterham Super Seven 1.4 0–60 mph in 4.7 s 500 kg (5.5 m/s2)

a 10 N upwards, the bag is lifted upwards b 15 N forwards, the ball accelerates forwards

2750 N

Renault Clio 1000 kg

0–60 mph in 10.2 s (2.5 m/s2)

2500 N

Ford Focus 1500 kg

0–60 mph in 9.3 s (3.0 m/s2)

4500 N

Volvo XC 2000 kg

0–60 mph in 7.2 s (3.5 m/s2)

7000 N

Range Rover 2500 kg

0–60 mph in 12.7 s (2.0 m/s2)

5000 N

? 2

0–60 mph in 6.6 s (4.0 m/s2) Mystery car has mass 550 kg.

P2.14b Force, mass and acceleration 1 2

P2.12d Resultant forces 1

c Friction force backwards, the skateboard slows down d No resultant force, the fish doesn’t move in any direction e No resultant force, the boy doesn’t move in any direction f 16 N in direction the cue hit the pool ball, the ball accelerates forwards g 500 N forwards, the car accelerates forwards a 200 N b Forwards c It will increase the speed and so will also increase the lift, so the aeroplane will accelerate upwards. d The reaction force from the air pushes the aeroplane forwards. a His weight downwards and the upwards push from the floor of the lift. b The upward force is larger than Thomas’s weight. c The resultant force is upwards as Thomas is accelerating upwards.

3

a 50 N b 75 N a 160 N b 160 N c 80 N a Greater b Smaller

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2200 N

4

a Resultant force 8 N, to the left, 4 m/s2 b Resultant force 2 N, to the right, 10 m/s2 c Resultant force 3 N, upwards, 0.75 m/s2 d Resultant force 5 N, upwards, 0.5 m/s2 e Resultant force 100 N, to the right, 40 m/s2 f Resultant force 6 N, upwards, 0.6 m/s2

P2.14c Calculating force, mass and acceleration 1

2

a 60 N b 75 N c 180 N d 180 N e 90 N a Resultant 8 N, to the left, 4 m/s2 b Resultant force 2 N, to the right, 10 m/s2 c Resultant force 3 N, upwards, 0.75 m/s2 d Resultant force 6 N, to the right, 12 m/s2 e Resultant force 26 N, downwards, 0.5 m/s2 f Resultant force 2 N, downwards, 0.002 m/s2

3 Object

Force (N) Mass (kg) Acceleration (m/s2)

sprinter

160

P2.15d Weight and terminal velocity 1 2

3

4 5

P2.15e Safe landing 80

2

charging elephant 1000

1000

1

Formula One car 4500

500

9

cyclist

150

100

1.5

bullet

80

0.002

40 000

0.13

30

hockey ball 4 4 a 180 000 m/s2 b 8100 N 5 a -0.0072 m/s2 b 2160000 N

1

2

3

P2.15 Terminal velocity Student Book 1

2 3 4 5 6

7

Mass is amount of matter in an object; weight is the gravitational force on the object, which depends on the gravitational field strength. a 300 kg b 7500 N The hammer and feather had same acceleration, and there was no air resistance. Terminal velocity Air resistance increases with speed. a 600 N b Acts towards the Earth (downwards) c 600 N d Acts upwards A good answer will contain the following points:  Both crates travel the same distance to reach the ground.  The full crate has greater mass and so greater weight.  The full crate will need a larger air resistance to balance its greater weight.  The full crate will have a larger terminal velocity.  A larger terminal velocity means the full crate will travel the same distance as the empty crate in a shorter time.  So the full crate will reach the ground first.

Look for suggestions where students time muffin cases over consecutive distances, say 0−10 cm, 10−20 cm, and so on. They find the velocity for each distance and see how the velocity changes as the muffin case falls. A constant value would show that the falling muffin cases did reach a terminal velocity.

Activity Pack P2.15a Terminal velocity

2

a i 750 N downwards ii velocity increases b i 500 N downwards ii velocity increases less quickly c i 300 N downwards ii velocity increases less quickly d i 0 N ii constant velocity e i 750 N upwards ii velocity decreases rapidly f i 0 N ii constant velocity Suitable graph

a 259 N b 12 kg c 8.9 N/kg a 6764 N b E (rapid deceleration) c C to D d B to C and D to E e C to D and E to F. At C the parachute opened, and at E the lander hit the planet’s surface. f E to F; steepest line so greatest acceleration, and so greatest force. a On Venus the atmosphere is so thick that the terminal velocity is very low. The atmosphere on Mars is much less dense, so the air resistance would be much less. This means that the terminal velocity will be much higher, even with a parachute. The spacecraft would have to be moving much faster for the resistance force to equal the weight. Without the thruster, it would crash. b Similar to graph for Venus. Thruster rockets applied near end of fall, causing a rapid deceleration. c Any sensible suggestion that the thruster accelerates the spacecraft upwards and so reduces its velocity just before landing.

P2.16 Stopping distances Student Book 1 2 3

4 5

6

Skills spotlight

1

a 700 N b 1610 N a 15 000 N b 13 500 N c 6000 N a B; there is no resultant force as the two forces are balanced. b C; there is no resistance force. b, f, g a In a vacuum, all objects have the same acceleration (or similar). c The terminal velocity does depend on the air resistance of the atmosphere. d When an object reaches its terminal velocity the upward force is equal to the downward force. e The force that accelerates an object downwards is its weight.

In order to leave a safe distance so they do not crash when a hazard appears. 17 m Braking distance plus thinking distance = stopping distance, so if braking distance is shorter but thinking distance is the same then stopping distance will be less. Thinking distance – no change; braking distance – longer Drinking alcohol increases reaction time, therefore increasing thinking distance. This increases stopping distance, leading to more crashes. A good answer will contain the following points:  Thinking distance is increased by:  alcohol; drugs; tiredness; faster speed  Braking distance is increased by:  faster speed; extra weight; worn brakes; lower friction road surface, e.g. mud, gravel, wet, ice

Skills spotlight Faster speed increases both thinking distance and braking distance (the latter significantly). Reducing vehicle speeds reduces the number of accidents, making the roads safer. Also, faster speeds significantly increase kinetic energy, so accidents at reduced speeds are significantly less dangerous.

Activity Pack P2.16b Stopping distances summary 1 2 3

True False If a driver is tired, the thinking distance will be increased. True

© Pearson Education 2011. Edexcel GCSE Additional Science Teacher and Technician Planning Guide This document may have been altered from the original.

False If the road is wet, the thinking distance will be the same. 5 False A car with four passengers will have a longer braking distance than a car with one. 6 False In the rain a driver will need a longer braking distance. 7 True 8 C Stopping distance = thinking distance + braking distance 9 Worn brakes provide less braking force, so braking distance is increased (so stopping distance is increased). 10 Both thinking and braking distance are increased at greater speeds. 4

7

8 9

It is an easy to remember method for making sure drivers have sufficient space to stop safely if the car in front stops suddenly. These make the stopping distance longer. If the car in front is moving faster, it will take longer to stop as well.

P2.18 Momentum Student Book

5

Drunk

1.8

9

2

11

a 14600 kg m/s north b 20 000 kg m/s south 2 Velocity is zero, so mass × velocity is zero. H3 120 kg 4 a 120 kg m/s and zero b 120 kg m/s c To the right d 120 kg m/s to the right e Yes 5 A sleeping cat – not moving so zero momentum. A running dog – moving but it is slower and has less mass than both the others. The meteorite from question 3. A monster truck in a race – in the worked example the monster truck has more momentum than the meteorite and is not going at race speed. 6 A good answer will contain the following points:  Need to know the mass and velocity.  Multiply these to calculate momentum.  Conservation of linear momentum means same total momentum before and after a collision.  So it will be conserved in a crash.  So can work out the velocity of vehicles after crashing.  If you know their mass.

10

Drunk

1.8

18

8

26

Skills spotlight

15

Drunk

1.8

27

17

44

20

Drunk

1.8

36

31

67

25

Drunk

1.8

45

48

93

30 4

Drunk

1.8

54

70

124

P2.16c Stopping distances graphs 18, 32, 51, 73, 100

1 2

3 Speed Conditions Thinking Thinking Braking Overall (m/s) time (s) distance distance stopping (m) (m) distance (m)

1

 Video recording of crash allows qualitative by just looking and describing what happens to each car.  Could use markers painted on road and car to actually measure movements in video, also knowing time for each video frame.  Could datalog speedometers from cars, plus additional sensors like accelerometers or forcemeters.  Qualitative advantage – can produce general conclusion for all crashes (such as head-on crashes are more dangerous than glancing impacts).  Quantitative advantage – can use results to inform design specifically (e.g. bumper strength must be a minimum of…).

Activity Pack P2.18b Explaining momentum conservation 5 Speed Conditions Thinking Thinking Braking Overall (m/s) time (s) distance distance stopping (m) (m) distance (m) 5

Normal

1

5

2.4

7.4

10

Normal

1

10

9.6

19.6

15

Normal

1

15

20.4

35.4

20

Normal

1

20

37.2

57.2

25

Normal

1

25

57.6

82.6

30 6

Normal

1

30

84

114.0

1 2

3 4 5

Gravity speeds it up, so its momentum increases. Momentum is conserved, so if the first ball stops, its momentum is transferred to the far one, which moves off with the same momentum as the first one had. As answer to 2, but the initial momentum is greater, so final momentum must also be greater. As answer to 2, but the initial momentum is greater, so final momentum must also be greater. Gravity is an external force so can change momentum. As one ball swings up at the end, it slows and changes direction, thus changing its momentum.

P2.18c Momentum calculations 1 2 3 4 5 6 7 8 9 10

560 kg m/s 220 kg m/s 33 kg m/s 144 kg m/s 55 kg m/s 0 36 kg m/s 25 800 kg m/s 0.0002 kg m/s 402 kg m/s

H P2.18d Penguin collisions 1

a 66 kg m/s

© Pearson Education 2011. Edexcel GCSE Additional Science Teacher and Technician Planning Guide This document may have been altered from the original.

2

b To the right c Zero d To the right e 6 m/s f Momentum is conserved a 56 kg m/s b -36 kg m/s c They are opposite d You must account for its direction. e -28 kg m/s f 8 m/s g Momentum is conserved.

P2.20 Momentum and safety Student Book This reduces the forces involved. Lower force means lesser injury. 2 On impact, the air bag squashes, reducing the rate of change of momentum and so reducing the force on your head. If your head hits the dashboard it will stop suddenly, reducing the momentum very quickly and so causing your head to connect with great force. 3 On impact, the bubbles squash slowly, reducing the rate of change of momentum, and so reducing the force on the object being protected. 4 a They both squash to reduce the rate of change of momentum, protecting the contents. b The car has designed failure points so it crushes in a designed way. H5 a 600 N b 40 kg m/s/s; 40 N H6 2.25 s 7 A good answer will contain the following points:  Crumple zone  Reduces a car’s momentum more slowly.  This means less force.  Air bag  Reduces a passenger’s momentum more slowly.  This means less force.  Seat belt  Reduces a passenger’s momentum more slowly.  This means less force.  Less force means lesser injuries. 1

air bags bumpers headrests All act in the following way: -large momentum gets smaller via a force that removes momentum -slower change in momentum needs smaller force -large forces hurt people -so all slow down change in momentum to protect people.

P2.20d Forces change momentum All act in the following way:  large momentum gets smaller via a force that removes momentum;  slower change in momentum needs smaller force;  large forces hurt people;  so all slow down change in momentum.  In relation to the equation, they increase value of t, whilst mv – mu is the same, so F is reduced. 2 1400 N 3 33.3 N 4 0.5 N H5 a 7 kg m/s b 10 m/s 6 1500 N H7 13 m/s H8 9.53 s H9 10 m/s 10 New force is 83 333 N (c.f. original of 250 000 N) so reduction is 67% of original. 1

P2.21 Work and power Student Book 1 2 3

4

5

Skills spotlight

Amount of energy transferred a 2000 joules b 5000 J a 420 J b 106 400 J c 4800 J a 210 W b 266 W c 600 W At higher speeds a car has more kinetic energy. The brakes have to do more work to remove all of this kinetic energy. The maximum braking force is constant, so the time taken must be greater if the work done is greater.

Variables to be measured: Independent: number of layers of bubble wrap Dependent: damage suffered by egg Control variables: drop height, egg mass, uniformity of wrapping, landing surface Method: Choose the height, measure it out, and mark drop position. From a large selection of eggs, measure their masses and select several of identical mass. Drop an unwrapped egg from the drop position. Record the damage suffered by the egg. Repeat with a layer of bubble wrap wrapped uniformly around the egg. Record damage. Repeat with an egg with 2 layers and record the damage. Continue repeating, each time with one additional, uniform layer of bubble wrap. Stop when the damage suffered is zero. Repeat entire experiment. If possible, also repeat entire experiment with eggs of a different mass.

200 000 200 000 20 5000 40 7 A good answer will contain the following points:  Braking changes kinetic energy into heat.  If you brake hard, so that this heat is generated faster than the brakes can cool, they will get hot.  Heat can damage the brakes.  So if they overheat the brakes may fail.  Braking more suddenly uses more force.  Braking more suddenly generates heat more quickly.  So brakes are less likely to cool quickly enough.  This makes them more likely to overheat and fail.

Activity Pack

Skills spotlight

P2.20b Momentum changes and road safety

Example answers: If the amount of energy used was an important cost factor, then the appropriate power could be chosen using the quantitative information. If only certain machines are available, then knowing which are more or less powerful will allow an appropriate change of machine when one is found to be lacking.

1 2

Ticks: A, C, D, F, G Crosses: B, E, H A3; B4; C8; D1; E7; F6; G2; H5

P2.20c Momentum and car safety seat belts crumple zone

H6 Initial velocity (m/s)

Initial kinetic Work done Braking Braking energy (J) to stop (J) force (N) distance (m)

5

12 500

12 500

5000

2.5

10

50 000

50 000

5000

10

15

112 500

112 500

5000

22.5

© Pearson Education 2011. Edexcel GCSE Additional Science Teacher and Technician Planning Guide This document may have been altered from the original.

Activity Pack P2.21b Warehouse work 1

2 3 4

Students’ own answers. Examples as in the picture (from top left): jerry cans: 240 J each; water tanks: 320 J each; 5.5 kilo cartons: 110 J each; wood bundle: 200 J; sand bags: 810 J each; oil drum: 1125 J; paving slabs: 350 J each; crate: 382.5 J; paint tins: 60 J each. E.g. oil drum cannot go more than 2.8 m at a time, so would need to go to 2 m shelf first and then up to top shelf. Students’ own answers, combining answers to 1 and 2. E.g. paving slabs from floor to 4 m shelf is 560 J so 112 W, so SLOW LIFT.

H3 10 m/s H4 0.2 m 5 The kinetic energy is converted into heat. 6 A good answer will contain the following points:  GPE = mass × height × gravitational field strength  So need to know m, g and h  This is transferred into KE as it falls  Because h (and hence GPE) is reducing  KE = ½ × mass × (velocity)2  So need to know m and v

Skills spotlight  Work = force × distance  GPE = mass × gravitational field strength × height  Equations allow scientists to make quantitative statements.  This allows design to be informed by a need to use specific numerical values.  For example, lifting against gravity is doing work, so F×d=m×g×h  So F = m × g  So a crane would need to be designed to provide a force equal to the weight of anything it needs to be able to lift.

P2.21c So much work 1 2 3 4 5 6 7 8 9

1500 joules 3300 J 13 200 J 600 J 3000 J 50 J a 5500 J b 367 W a 3740 J b 1870 W a 50 000 joules b 6250 W

P2.21d Work and power and work to stop cars 1 2 3 4 5

6

50 J a 5500 J b 367 W a 3740 J b 1870 W a 50 000 J Hb8s a

b The relationship is almost linear. The slight variation from direct proportionality indicates the slight variation in maximum braking force in real-life situations. c Work done in joules: 10400 41600 88400 161200 249600 364000 H d Times in seconds: 0.14 0.58 1.23 2.238889 3.47 5.06 Kinetic energy is directly proportional to velocity squared.

P2.22 Potential and kinetic energy Student Book 1

2

a 20 J b 96 000 J c 30 000 J a4J b 2240 J c 98 000 J

Activity Pack P2.22a The car catapult 1 Rubber Start Kinetic Vertical GPE band velocity of energy (J) distance car gained (J) 2 stretch, d car (m/s) KE = ½ mv moved (m) GPE = mgh (cm) 2

1.0

0.2

0.04

0.16

4

1.2

0.288

0.07

0.28

6

1.6

0.512

0.12

0.48

8

2.0

0.8

0.16

0.64

10

2.1

0.882

0.20

0.8

12 2

2.3

1.058

0.23

0.92

3 4 5 6

The greater the kinetic energy at the start, the greater the GPE at the end. a Elastic potential energy to kinetic energy b KE to GPE Energy losses such as friction Yes. The fourth result, starting at 8 cm, appears slightly off the pattern of the other points.

P2.22b Mars Rovers energy transfers Rockets – Chemical potential to kinetic and (wasted) heat and sound Airbag landing – GPE to kinetic (falling) to heat and sound (on impact) Movement up a hill – electrical to kinetic and gravitational potential and (wasted) heat and sound Solar panels - light to chemical potential to electrical Laser signalling system – chemical potential to electrical to light Radioisotope heaters – nuclear potential to heat

P2.22c Sports day energy transfers 1

When this girl falls back down, her GPE will be transformed into kinetic energy. This moving girl has kinetic energy.

© Pearson Education 2011. Edexcel GCSE Additional Science Teacher and Technician Planning Guide This document may have been altered from the original.

2

Because it is up in the air, the shot has gravitational potential energy. To find the GPE of the javelin, we need to know its mass, the gravitational field strength and its height. m = 72 kg, v = 5.5 m/s. What is the KE? KE = ½ × 72 × (5.5)2 = 1089 J. m = 7.2 kg, v = 14.0 m/s. How would you calculate the kinetic energy? KE = ½ × 7.2 × 142 = 705.6 J m = 80 kg, h = 2.2 m, GPE = 1760 J m = 2 kg, v = 3.8 m/s, KE = 14.44 J m = 1.2 kg, h = 11 m, GPE = 132 J The pole vaulter will have 1760 J when hitting the crash mat as the GPE will all be converted into kinetic energy.

P2.22d Sports day energy calculations 1

2 3 4

High jumper, mass, height and gravitational field strength. Girl running on the track, v = 5 m/s Shot, h = 3.3 m Javelin, GPE = 78 J Boy on long jump run up, v = 5.5 m/s Hammer, m = 7.2 kg Discus, KE = 72 J Pole vaulter, m = 80 kg Dog, KE = 14.44 J Hat blowing away, m = 0.2 kg Hovering bird, GPE = 132 J GPE to KE to heat and sound on impact Mass = 80 kg; on impact KE = (starting GPE =) 1760 J gives v = 6.63 m/s The same percentage improvement is a smaller amount, and there will be a limit on the possible record, so as we get closer to this, improvements become more and more difficult.

P2.23b Isotopes Atom

Atomic Mass Number of Number of Number of number number protons neutrons electrons

1 1H

1

1

1

0

1

2 1H

1

2

1

1

1

3 1H

1

3

1

2

1

6 3 Li

3

6

3

3

3

7 3 Li

3

7

3

4

3

12 6C

6

12

6

6

6

14 6C

6

14

6

8

6

24 12 Mg

12

24

12

12

12

25 12 Mg

12

25

12

13

12

26 12 Mg

12

26

12

14

12

2

3

a Atoms with the same number of protons but different numbers of neutrons. b Three c Proton number (and number of electrons) d Mass number and number of neutrons Nucleons: The sub-atomic particles in the nucleus of an atom. Nucleon number: The number of protons and neutrons in the nucleus of an atom. Proton number: The number of protons in the nucleus of an atom.

P2.23 Isotopes

P2.23c Are they isotopes?

Student Book

1

1 2 3 4 5

The number of protons in the nucleus The total number of protons and neutrons 4 2 He

6 7

8

A

a 4 protons b 5 neutrons a 4, 5 and 4 b Beryllium and boron c

10 4 Be

a Atom

,

10 5 Be

and 94 Be

19 9F

No, isotopes have the same number of protons but different numbers of neutrons so they actually have different mass numbers. A good answer will contain the following points:  Isotopes contain the same number of protons but different numbers of neutrons – they have the same atomic number.  All three isotopes of hydrogen contain one proton.  Hydrogen-1 does not contain any neutrons.  Hydrogen-2 contains one neutron  Hydrogen-3 contains two neutrons.

2

C

3

7

6

5

5

a 94 Be 31 15 P

c

40 18 Ar

d

27 13 Al

e

39 19 K

Activity Pack P2.23a Find the isotopes

4

6

D 5 6 5 b Same proton number and same number of electrons. c They have different numbers of neutrons and the mass numbers are different. d Yes, they have the same number of protons but different numbers of neutrons, so they are isotopes of the same element. b

3

Number of electrons

5

Sensible suggestions such as so that these do not depend on the language spoken by scientists; so that any scientist will understand the shortened way.

Cards 1 and 13, cards 2 and 20, cards 3 and 16, cards 4 and 19, cards 5 and 17, cards 6 and 23, cards 7 and 18, cards 8 and 21, cards 9 and 14, cards 10 and 22, cards 11 and 15 Cards 1, 2, 3, 13, 20 and 16; cards 4, 5, 19 and 17; cards 6, 7, 8, 18, 21 and 23; cards 9, 10, 11, 14, 15 and 22 Beryllium (proton number 4), boron (proton number 5), carbon (proton number 6) and nitrogen (proton number 7)

Number of neutrons

B 7 6 7 b The mass number is the same. c They have different numbers of protons, neutrons and electrons. d No, because the proton numbers are different. a Atom Number of Number of Number of protons neutrons electrons

Skills spotlight

2

Number of protons

4

f 24 12 Mg Atoms that are isotopes and that are electrically neutral always have the same number of electrons, as they have the same number of protons. However, an atom can lose or gain electrons to become an ion, in which case isotopes of the same element could have different numbers of electrons.

© Pearson Education 2011. Edexcel GCSE Additional Science Teacher and Technician Planning Guide This document may have been altered from the original.

P2.24 Ionising radiation Student Book 1 2 3 4

An atom with an electrical charge –1 4 A few millimetres of aluminium or a smaller thickness of lead To stop gamma rays

5 6 Alpha particle

Beta particle

3 4

P2.24d Alpha, beta and gamma radiation 1

Gamma ray

equivalent to the electron emitted nucleus of a helium from nucleus atom – contains 2 protons and 2 neutrons

electromagnetic wave

charge of +2

charge of –1

not charged

stopped by a few cm of air or a few sheets of paper

stopped by a few mm of aluminium

stopped by a few cm of lead or many metres of concrete

2

most ionising type moderately ionising least ionising form of radiation of radiation 7 Its mass number goes down by 4 and its atomic number goes down by 2 – it becomes a different element. 8 A good answer will contain the following points:  Radioactive source emits ionising radiation (e.g. alpha particles, beta particles or gamma rays).  Ionising radiation collides with oxygen atom.  Collision knocks an electron out of the oxygen atom.  Charge in the nucleus is now not balanced by the charge on the electrons.  The atom has a net charge and so is an ion.

3

4

5

Skills spotlight Use the GM tube to measure the activity of a source. Put a sheet of paper between the source and GM tube. If the count rate drops to almost zero, it is an alpha source. If not, replace the paper with an aluminium sheet a few mm thick. If the count rate drops to almost zero, it is a beta source. If not, it is a gamma source.

Activity Pack P2.24a Ionising radiation Alpha particles: largest form of ionising radiation; stopped by paper; contains two protons; has a charge of +2. Beta particles: can travel through paper but not a few millimetres of aluminium; has a charge of –1 Gamma rays: smallest form of ionising radiation; is not made of any particles; can travel the furthest distance through air; can travel through a few millimetres of aluminium; an electromagnetic wave; does not have an electrical charge Beta Alpha Alpha Alpha Beta Gamma Gamma Gamma Alpha Gamma Alpha Alpha

a Alpha b Alpha c Gamma d Beta e Gamma f Beta g Alpha h Gamma If alpha particles cannot reach you then they cannot cause damage to the cells in your body as they would be absorbed by skin cells on the skin’s surface (or by the air before they reached your skin). a A, C and D b B and E c Beta particles are less ionising and so travel further than alpha particles. d No, because they are emitted in a random process. e The particles in the tracks in the cloud chamber lose electrons and become ions. Radioactive sources may emit alpha, beta and gamma radiation. Lead will stop all three types of radiation, which is why it is used. (Using aluminium would not be any good because gamma rays can pass through aluminium and could cause damage to the body.) Jennifer would still be irradiated and contaminated by the air that she breathed in and the food and drink that she ate. It is not possible to be completely protected from radiation as it is present inside your body. Also, you can never be sure that all gamma radiation from a source has been stopped by the lead.

P2.25 Nuclear reactions Student Book 1 2 3 4 5 6

7

P2.24b Types of radiation 1 2 3 4 5 6 7 8 9 10 11 12

b They are not as ionising and so have fewer collisions with other atoms. Alpha particles Unstable; random; decay; ions; loses; gains (last two in either order)

Neutron Two daughter nuclei (barium-141 and krypton-92) and three neutrons Mostly kinetic energy and some thermal energy. By other materials absorbing neutrons so that only one from each fission goes on to cause another fission. Because there are many fissions in an uncontrolled chain reaction. a Uncontrolled chain reaction b No chain reaction c Controlled chain reaction A good answer will contain the following points:  Two or three neutrons are produced in each fission.  Each of these neutrons can be absorbed by other uranium-235 nuclei.  The uranium-235 nuclei then become unstable and split up.  Some of these neutrons need to be absorbed by other materials.  Only one neutron should go on to cause another fission.  The reaction will then continue at a steady rate.

Skills spotlight One neutron: 10 atoms; two neutrons: 1024 atoms; three neutrons: 59 049 atoms

Activity Pack

P2.24c Radiation penetration

P2.25b Nuclear fission jigsaw

1 Radiation Blocked by

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Penetrating Ionising

alpha

skin, paper, a few cm air

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a few mm of aluminium

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gamma thick lead 2 a Alpha, beta, gamma

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The pieces should make a diagram showing the fission of uranium-235 and the fission products xenon-143 and strontium-90. a Proton number 40; mass number 99. b Correctly labelled diagram similar to Figure B on page 256 of the Student Book.

© Pearson Education 2011. Edexcel GCSE Additional Science Teacher and Technician Planning Guide This document may have been altered from the original.

P2.25c Nuclear chain reactions 1

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a Neutron b It becomes unstable. c Nuclear fission a Daughter nuclei b Neutrons c Energy a Only one of the three neutrons released goes on to cause the fission of another uranium-235 nucleus. b The other neutrons are absorbed by another material.

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P2.26c Nuclear power station 1

P2.25d Nuclear reactions 1 2

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a Controlled chain reaction b The other neutrons are absorbed by another material. a The chain reaction becomes uncontrolled. b A nuclear/atomic bomb c There is no chain reaction/the reaction will stop. One of the nuclei produced when the uranium-235 nucleus splits up. Any sensible suggestions. The proton numbers of the two nuclei should add up to 92. The mass numbers of the products (including two or three neutrons) should add up to 236. a The reaction will gradually die away until it stops altogether. b The reaction will gradually increase – it is uncontrolled.

P2.26 Nuclear power

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Nuclear energy to thermal energy To maintain a steady rate of fission – if this does not happen, the reactor could explode like a nuclear bomb. a To absorb neutrons b To slow down neutrons Don’t store too many of them together and keep them a reasonable distance apart. Flow diagram should include the following stages: nuclear energy → kinetic energy → thermal energy → kinetic energy → electrical energy Raise the control rods to increase the rate of the chain reaction. The moderator A good answer will contain the following points:  The rate of reaction needs to be maintained at only one neutron from each fission going on to cause another fission.  If the reactor core is cooling down, the rate of reaction needs to be increased.  Control rods are raised to increase the reaction rate and hence the temperature.  If the reactor is heating up too much, the rate of reaction needs to be decreased.  Control rods are lowered to reduce the reaction rate and hence the temperature.

Skills spotlight Sensible suggestions including effect on jobs, site needs to be outside major population centres, local population may have worries about having a nuclear power station nearby, potential hazards in areas that are prone to earthquakes.

Activity Pack P2.26a Control rod feedback loop 1

Labels going clockwise from top left: control rod, moderator, turbine, generator, heat exchanger, shielding, nuclear reactor Lines should be drawn connecting the part with what it does as follows: nuclear reactor: where nuclear fission takes place heat exchanger: where water is boiled to make steam turbines: large blades which rotate to drive a generator generator: produces electricity when it spins shielding: stops radiation and neutrons escaping from the reactor control rod: controls the rate of the chain reaction moderator: slows down neutrons

P2.26d Parts of a nuclear power station 1 2

Student Book 1 2

Reactor core: nuclear energy to kinetic energy and thermal energy; kinetic energy to thermal energy. Heat exchanger: thermal energy to kinetic energy. [Turbine: kinetic energy to kinetic energy] [Generator: kinetic energy to electrical energy] Some students may also include some of the wasted energy transfers, e.g. in the generator, kinetic energy is also transferred to thermal energy and sound energy.

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A: control rod, B: moderator, C: turbine, D: generator, E: nuclear reactor, F: shielding, G: heat exchanger a To absorb neutrons and slow down the chain reaction. b Without them, all of the neutrons could go on to cause more nuclear fissions – the reaction would then be uncontrolled and the reactor could explode. a To slow down the neutrons so they can be absorbed more easily. b The neutrons are travelling very fast when emitted and are not absorbed by the uranium-235 nuclei. The control rods should be raised slightly to increase the rate of the chain reaction. This will produce more heat energy to keep the temperature of the super heated water at the correct level. The thermal energy is used to convert water into steam. The steam has kinetic energy, which is used to transfer kinetic energy to the turbine. The turbine is connected to the generator, which transfers kinetic energy to electrical energy. The fission products are radioactive and the shielding absorbs any radioactivity coming from the reactor. No, the pump should be left switched on. It will take a little while for the chain reaction to stop, so fission is still happening and producing thermal energy. The fission products are also producing thermal energy.

P2.27 Fusion – our future? Student Book 1 Nuclear fusion of hydrogen 2 Helium and neutrons H3 Hydrogen nuclei do not have enough energy to overcome the electrostatic force of repulsion. H4 The pressure is much greater in the Sun (so nuclei are closer together). H5 Nuclei split up in fission but join together in fusion; fission can take place at normal temperatures and pressures but fusion needs high temperatures and pressures; fission creates radioactive waste from fuel while fusion does not (but in both processes containment vessels become radioactive). H6 Other scientists could not get the same results when they repeated the experiment. 7 A good answer will contain the following points:  Very high temperatures and pressures are needed to overcome electrostatic forces of repulsion.  Very difficult to sustain the high temperatures and pressures.  So far none of the experimental reactors have produced more energy than was put in to heat up the hydrogen nuclei and contain them.

© Pearson Education 2011. Edexcel GCSE Additional Science Teacher and Technician Planning Guide This document may have been altered from the original.

Skills spotlight

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Sensible suggestions including: Fleischmann and Pons did not go through the validation process; other scientists were not able to carry out the experiment and get the same results; they did not produce a paper that was subjected to peer review.

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Activity Pack P2.27d Fission and fusion 1

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a False. A uranium-235 nucleus splitting into two daughter nuclei is an example of nuclear fission. b True c False. Both nuclear fission and nuclear fusion make the reactor radioactive. d False. Nuclear fusion is the reaction that is the source of energy in stars. e False. Uranium-235 splits up to form two daughter nuclei and two or three neutrons are released. f False. In nuclear fusion, smaller nuclei are joined together to form larger ones. g True A good answer would include some or all of the following: fusion involves joining two nuclei, whereas fission involves splitting one nucleus. Fusion involves conditions that are currently difficult to achieve, whereas fission conditions can be achieved relatively easily. Fusion to generate energy is still experimental, whereas fission is a major source of the generation of electricity. A suitable answer including the words, e.g. Their claims needed to be validated by writing a paper that was then peer reviewed before it was published. Other scientists needed to be able to carry out the same experiment and get the same results.

Skills spotlight They knew that it could burn the skin and, from Becquerel’s earlier work, that it could ionise gases. They did not know that it can also cause ionisation in cells that can lead to mutations and cancer.

Activity Pack P2.28a Handling radioactive sources The sets are: boxes 1, 6 and 10; boxes 2, 5 and 12, boxes 3, 8 and 11, boxes 4, 7 and 9.

P2.28b Radioactive discoveries timeline 1 2

H P2.27e Fusion reactions 1

2 3

4 5 6

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Fusion involves joining two nuclei, whereas fission involves splitting one nucleus. Fusion involves conditions that are currently difficult to achieve, whereas fission conditions can be achieved relatively easily. Fusion to generate energy is still experimental, whereas fission is a major source of the generation of electricity. The nuclei cannot overcome the electrostatic force of repulsion. A fusion reactor has one reaction that starts with deuterium and tritium and ends up with helium and a neutron. The Sun has several reactions that start with hydrogen nuclei and finish with helium nuclei and neutrons. The temperature in a fusion reactor is about 10 times hotter than the Sun. To overcome the electrostatic force of repulsion. a Stage 2 b 32 He The theory needs to be validated by writing a paper that is then peer reviewed before it is published. Other scientists need to be able to carry out the same experiment and get the same results. It is very difficult to reproduce the conditions of the Sun. Also, the rate of the reaction in the Sun is 1000 times lower than that in a fusion reactor.

Longer-term effects such as mutations that lead to cancer (and other effects such as sterility and blood disorders) became more obvious as time went by. A good answer will contain the following points:  Handle sources with tongs, which increases the distance between the source and your body, so less ionising radiation reaches your body.  Do not point sources at people, which means less ionising radiation will reach their body.  Keep sources in a lead-lined container, as all but the most penetrating ionising radiation is stopped by a few millimetres of lead.  Wear gloves and eye protection to reduce the chances of getting radioactive materials on your skin.

The correct order is: 3, 5, 1, 4, 2 The hypotheses are: 1 The activity of a source depends on the mass of the source. 2 Sources give out different types of radiation that can be stopped by different materials. 3 Uranium gives out ‘invisible rays’. 4 Different types of radiation are stopped by different materials. 5 The ‘invisible rays’ given out by uranium can charge the particles in the air.

P2.28c Safe use of radioactive sources 1 2 3 4 5

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Incorrect. E.g. you should not touch radioactive sources because they can burn your skin. Correct Correct Incorrect. E.g. the hazards of handling radioactive sources are increased by pointing them at people. Incorrect. E.g. scientists did not realise at first that cancer and other health problems could be caused by ionising radiation. Incorrect. E.g. radioactive sources are kept in lead-lined containers because most ionising radiation is stopped by a few millimetres of lead. Incorrect. E.g. mutations are caused by smaller amounts of ionising radiation over a long time. Correct. Incorrect. E.g. regulations are now in place to prevent radioactive materials being added to products, although at the beginning of the 20th century radium or thorium was deliberately added to such items. (Students could argue that the statement is correct, due to background radiation.)

P2.28 Changing ideas

P2.28d Marie Curie in the laboratory

Student Book

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a Radioactivity – the emission of ‘invisible’ rays that came from uranium, which penetrated through solid materials. He also discovered that these rays exposed photographic plates. b Some materials emit more (ionising) radiation than others. a Ionises atoms in cells b Causes tissue damage, such as skin burns, and damages DNA, leading to mutations. Some mutations can lead to cancer. (And if mutations are formed in a gamete-producing cell, the resulting child may have a deformity.) They did not know about the long-term effects.

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Answers should include:  Keep the radioactive source in a lead-lined container, not just in a drawer.  Handle sources with tongs, not with the hands.  Not lift the source close to the eyes.  Wear gloves and eye protection.  Not carry sources close to the body (as Gustave does). For all answers: because radioactive substances emit ionising radiation that ionises cells and causes tissue damage, and possibly cancer.  Most ionising radiation is stopped by a few millimetres of lead.  This increases the distance between the source and the body, so less ionising radiation reaches the body.  As above.

© Pearson Education 2011. Edexcel GCSE Additional Science Teacher and Technician Planning Guide This document may have been altered from the original.

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 Alpha radiation will be stopped by the material of the gloves or glasses; also prevents small particles of the radioactive substance being transferred to the skin or eyes where they could continue to decay and emit radiation.  The closer the source is to the body, the more damage it can do; there is also the risk of the glass tube breaking (or the seal leaking) and the contents contaminating the pocket. Marie Curie has reddened skin on her hands. Although she did not know about the hazards of ionising radiation to living things, she could have used the damage to her skin as evidence that handling radioactive sources was harmful and so they should not be applied directly to the skin (in cosmetics) or swallowed (in food).

Disadvantages: The waste products of nuclear reactors are radioactive; high level waste is radioactive for many tens of thousands of years; the public perception is that nuclear power is dangerous; if an accident does happen at a nuclear power station, radioactive materials could be spread over a large area; nuclear waste needs to be stored in a place that is secure for many tens of thousands of years; a lot of energy is used to make the materials used to build the power station; some low level waste is allowed to be discharged into the environment, because the activity is very low; the waste stored must be safe from being damaged in earthquakes and other natural events; exposure to radioactive substances can cause mutations in cells, which can then cause cancer; mining and transporting nuclear fuel produces carbon dioxide emissions; it is very expensive to clean up old nuclear power stations.

P2.29 Nuclear waste

P2.29c Nuclear power and nuclear waste

Student Book

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Fission products, i.e. used nuclear fuel They both remain radioactive for tens of thousands of years. HLW produces large amounts of ionising radiation while ILW produces a smaller (but still significant) amount. Inside thick concrete and steel for temporary storage and transport, and then sealed in glass. Geological stability of site, number of people living near the site, access for transporting waste to the site. a Does not produce carbon dioxide when it is generating electricity. Does not use up fossil fuels. b Because of the risk of accidents like Chernobyl, where radioactive material was spread over a large area (and the subsequent risk to human health of drinking/eating/ breathing in contaminated water/food/air). A good answer will contain the following points:  It needs to be stored safely for many tens of thousands of years.  It takes many tens of thousands of years for the levels of radioactivity to decrease to safer levels.  The materials it is stored in have to last all this time.  The building structure also has to last for many tens of thousands of years.  Any materials that leak have to be contained so they do not get into groundwater etc.

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P2.29d Storing and disposing of nuclear waste 1

Skills spotlight Answers could include the following points: Firing into space: once the waste is in space it cannot contaminate the Earth if it leaks; there is lots of radiation in space from the Sun, so putting the waste into space is not making the solar system any more dangerous than it already is (although this argument ignores the possibility of actually colliding with the waste). Dumping at sea: the oceans contain a huge amount of water, so any waste that leaks will be diluted and not likely to cause harm to people (this argument ignores any effects on wildlife in the area of the dumping) Storage underground: any radiation leaking from containers will not be able to get through rock to harm people; the earth naturally contains radioactive elements, so putting waste here will not be making it any more dangerous (this ignores the fact that the waste is likely to be far more concentrated than any naturally radioactive substances in rocks)

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Activity Pack

4

P2.29a Advantages and disadvantages of nuclear power Advantages: No carbon dioxide is produced by a nuclear power station when it is generating power; nuclear power does not contribute to global warming; fossil fuels are not used as the source of energy; there are skilled jobs available in a nuclear power station; the risk of an accident happening is very low; the amount of fuel needed is much less than for a fossil fuel power station; over the last 50 years, scientists have started to become worried about releasing carbon dioxide into the atmosphere.

a Advantage b Disadvantage c Disadvantage d Advantage a Radioactive material could get into the wider environment, e.g. the water supply. b The rock absorbs the ionising radiation and therefore prevents it reaching the surface; also the deeper it is the more likely it is to remain isolated from humans and the environment for a very long time (for example isolated from near-surface groundwater). c It must have a low risk of earthquakes/ground movements that would create routes for air or water to travel from the radioactive waste to the surface. d Barrels in the sea can be corroded by the sea water; it is easier to monitor the waste in this store. Any two suitable answers, e.g. risk of accidents that would destroy the reactor and hence cause leaks of radioactive materials; if there is an accident, radioactive material could be spread over a large area, with risks to health of workers or people living in the ‘fallout’ area; target for terrorists; mining for uranium also has health risks due to toxic waste; radioactive waste is difficult to store safely.

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The waste is radioactive for many tens of thousands of years. a Rock absorbs any radiation coming out of the store and so prevents any radiation reaching the surface; also the deeper it is the more likely it is to remain isolated from humans and the environment for a very long time (for example isolated from near-surface groundwater). b So that the store is not damaged if there is an earthquake, otherwise radioactivity could be released if ground movements create routes for air or water to travel from the radioactive waste to the surface. a Containment – placing in a container or other method of storage; dispersal – spreading into the environment, dilution in air/water to reduce the concentration. b The one where liquids and gases are released into the environment. c Sensible suggestions, e.g. people think it makes the environment more radioactive; it can damage plants and animals in the environment; we don’t know fully what happens to the radioactivity when it is released. So that if one method fails or cracks, developing a leak, there is another method of containing the radioactivity. It is much more radioactive and so safer storage processes need to be in place if it is to be safe. a Students’ own opinions b Because of public perceptions about the risks to health and the environment from potential leaks. Sensible suggestions, e.g. knowledge about the site could be lost, entrance could become overgrown, the containers may still break down over tens of thousands of years.

© Pearson Education 2011. Edexcel GCSE Additional Science Teacher and Technician Planning Guide This document may have been altered from the original.

P2.30 Half-life

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Two nuclei The time taken for the activity to decrease by half, or the time taken for half the undecayed nuclei to decay. 30 years a One half-life b Two half-lives c Four half-lives d 0.5 half-lives a 5 million b 2.5 million c 1.25 million d 7.5 million Source A: about 5 seconds; source B: about 20 seconds A good answer will contain the following points:  Activity of a source is given in becquerels.  One becquerel is one nuclear decay per second.  An unstable nucleus is one that will undergo radioactive decay.  When an unstable nucleus decays it may become stable.  The more stable nuclei a substance contains, the lower its activity.

Skills spotlight Measure the activity (for example using a Geiger counter to measure the count rate in counts per second) of the material, for a period such as 1 minute. Then measure the activity again over further time periods. The half-life is how long it takes for the activity to decrease by half. (Students may comment on how frequently you should measure the activity, based on preliminary results and the rate at which the activity is decreasing. Students may also comment that you should plot a graph of the activity against time and take several pairs of readings from the graph in order to get a mean value for the half-life, to show that the half-life is constant.)

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P2.32 Background radiation Student Book 1 2 3 4 5 6

Activity Pack P2.30a Half-lives from graphs 1

2

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a 70 seconds b 70 seconds c 70 seconds They are all the same – in each case it is the time taken for the radioactivity to halve. It is the half-life of the source. Graph 1: 6 hours; graph 2: 30 years

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P2.30b Calculating half-lives 1

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a 70 seconds b 6 hours c 30 years d 3.8 days a Correctly drawn graph b 28.9 years c Two half-lives

P2.30c Half-life of carbon-14 1

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a One nuclear decay per second b It decreases by half. c About 5700 years a They have decayed. b ¼ or 25% c ¼ or 25% d2 e 11 400 years a 1/8 or 12.5% b 1/8 or 12.5% c About 17 000 years (17 100 years)

P2.30d Radioactive dating 1

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a One nuclear decay per second b The activity of carbon-14 decreases by half in 5700 years, or half of the unstable nuclei decay in 5700 years. a 12.5% b Three half-lives c 17 100 years 22 800 years ago

2850 years is an acceptable answer at this level (although it is not perfectly accurate because the mathematical relationship between activity and time is exponential not linear). 710 years is an acceptable answer at this level (although it is not perfectly accurate because the mathematical relationship between activity and time is exponential not linear). Take it as being one-eighth of the way towards one half-life. At 710 years old, it cannot have been a part of Christ’s cross. 11 400 years 75 000 years is 13.15 half-lives. Take this as 13. Divide 40 000 by 2 13 times (divide by 213) to give the answer of 9.15 Bq, so a suitable range would be 0–10 Bq or similar (i.e. sensitive enough to distinguish between readings of 100, 10 and 1). A GM tube does not detect all of the ionising radiation entering it; a radioactive source emits ionising radiation in all directions while the GM tube is only detecting the radiation emitted in one direction; the count from the GM tube also includes background radiation.

The low level of ionising radiation that is around us all the time 168 counts per minute From rocks in the ground If radon is breathed in, alpha particles emitted from the radon gas can damage the lungs. Plants and animals take in radioactive isotopes from their environments. People in aeroplanes receive more cosmic rays than people on the ground because the atmosphere has absorbed fewer cosmic rays at that height. As there are more high-energy particles during a solar storm, there are more cosmic rays reaching the Earth, so aeroplanes should fly lower to reduce the amount of cosmic rays received by people in them. A major part of background radiation comes from radon gas, and radon gas comes from the decay of uranium isotopes in rocks. Different rocks contain different amounts of uranium. The rock types and building stones vary in uranium content in different parts of the country. A good answer will contain the following points:  Recognition of difference between ionising and nonionising radiation.  Majority of background radiation comes from natural sources.  Human-made ionising radiation mainly comes from medical sources such as X-rays and radiotherapy treatment.  Only a very small proportion of background radiation comes from nuclear power stations/nuclear waste.  The biggest part of natural sources is radon gas.  Radon gas can be dangerous if levels build up and it is breathed in.  So it is more likely that natural radiation will hurt you but human-made radiation won’t.

Skills spotlight Need to measure the background count in many different places and over a long period of time to account for regional variation in radon levels and time variation in differences in cosmic rays. Would also need to collect data on the food people eat, the number of X-ray scans they have had (and also any radiotherapy treatment) and their occupations (for example pilots, doctors and workers in nuclear power stations will have varying levels of exposure at work).

Activity Pack P2.32a Interpreting background radiation 1

a Percentage of background radiation from radon gas is much higher than the UK average. Percentage of background radiation from all other sources is lower than the UK average.

© Pearson Education 2011. Edexcel GCSE Additional Science Teacher and Technician Planning Guide This document may have been altered from the original.

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b Percentage of background radiation from buildings and soil and cosmic rays is higher than the UK average; percentage of background radiation from medical and food and drink is about the same as the UK average; and percentage of background radiation from radon gas is lower than the UK average. The amount of radon gas that comes out of the ground varies depending on the rock type in the area. a Food and drink, buildings and soil, cosmic rays and radon gas. Buildings are a natural source because the stone used to make them is naturally radioactive. b Medical a One person may have lots of dental or bone X-rays and/or radiotherapy for cancer, whereas someone else may not have any X-rays, etc. b People working in radioactive environments; fallout from nuclear accidents or weapons testing. Students’ own opinions, with sensible reasons.

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P2.33 Uses of radiation Student Book 1

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P2.32b Monitoring radon levels 1

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Radon can be dangerous. When you breathe in, alpha particles from radon can be absorbed by the lungs, which can lead to an increased risk of cancer. Radon gas builds up inside a house not outside it (radon can build up as more seeps in through the floor, but cannot disperse unless there is good ventilation). a Provide a continuous read-out of radioactivity levels; can trigger an alarm if activity from radon gets too high. b Much cheaper; provide a record of the total amount of activity from radon over a period of time. a More expensive than devices that are left in the house; don’t necessarily provide a record of the overall amount of activity from radon. b Can’t trigger an alarm if activity from radon gets too high; have to be sent back to a laboratory for radiation levels to be calculated.

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P2.32c Background radiation 1

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a 11.5% b Animals and plants take them in from their environment (soil, air, water). c One person might have a job that involves more exposure (e.g. pilot, medical technician) or they may have had more medical treatments such as X-rays or radiotherapy. Cosmic rays – Sun and other stars; radon gas – uranium in rocks in the ground; medical – radiotherapy treatment and X-rays; food – radioactive isotopes in the environment All except cosmic rays Levels of radon gas from rocks in the ground vary due to the different rock types in different places. a Cosmic rays, because all of the others come from the Earth (and there is no atmosphere to act as a shield). b The proportion of background radiation from cosmic rays is higher in space (no shielding by atmosphere), the proportion from ground and buildings, radon gas and medical is lower, but the proportion from food and drink is likely to be similar.

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Nothing can be said to be ‘completely safe’. Even low activities/amounts can be potentially harmful to cells. They compare the activity with the background radiation activity. If they are similar, the source is ‘safe’. The amount would be classified as safe as it is the normal average amount that people in the UK are exposed to. Since no harm comes to most people from this level of radiation, it would be deemed ‘safe’. Any three from: rocks, buildings, food, medical techniques like X-rays, cosmic rays from outer space. a Ionising radiation from outer space b No, the value depends on altitude. For example, people travelling on a plane are exposed to more cosmic rays than people at ground level (due to less protection from the atmosphere). Yorkshire, Aberdeen and Cornwall Rocks, which contain small amounts of uranium-238 and thorium-232, for example.

Radiation from alpha and beta sources inside the body would be stopped by the body so could not be detected outside it. Also, alpha particles emitted inside the body would cause a lot of harm to cells and tissue, whereas gamma rays tend to pass through the flesh without being absorbed. The use of ionising radiation to treat diseases like cancer by targeting and killing the cancer cells. a To reduce the risk of infection by microorganisms b Some heat-sensitive instruments (e.g. plastic) cannot be sterilised using heat. Benefits: kills bacteria in food; food can be stored for longer before going off; kills pests such as insects that may be in the food. Drawbacks: public acceptance; perceived risks (also danger that food may already have deteriorated before the food was treated, e.g. that toxins may already have been produced by microorganisms). The food is exposed to gamma rays A good answer will include the following points:  Should not all be absorbed by the body – should have some penetrating power.  Some tracers should be absorbed by certain parts of the body but not by others.  Should have a short half-life, of the order of hours, so that the body is not exposed to too much radiation.  Should have a low activity level – as above.  The radioactive isotope, or the decay product, should not have toxic side effects unconnected with the ionising radiation.

Skills spotlight Students’ own answers, but should include the following: Benefits: public will know if food has been irradiated or not and can make their own choice. Disadvantages: people may avoid safer food because they don’t want to consume irradiated food (they may not be aware of all the facts). Ethical issues: it might be unethical not to irradiate food since it makes it safer to eat (ethical responsibility to make food safer); alternatively it may be unethical to distribute irradiated food because not enough is known about the effects, e.g. on vitamin content, or because the motive behind it is for profit (to increase shelf life), not for health reasons. The ethical treatment of the environment might also be considered.

Activity Pack P2.33c Radiotherapy 1

P2.32d Sources of background radiation 1

Our bodies have an activity of, on average, 5000 radioactive decays per second. Houses were much more draughty 100 years ago, so the air in the room changed more often and levels of radon gas did not build up as much.

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a Lung b Ovaries c Breast a WI; CR; SD; VG (other answers possible) b QF; SH; DO; NC (other answers possible) c DN; SK; RJ; PH (other answers possible) Large amounts of ionising radiation can damage the skin by burning it.

P2.33d Radioactive wordsearch 1

a Cosmic ray b Radon gas c Irradiate d Sterilisation e Radiotherapy f Becquerel g Activity h Count rate i Background j Half-life k Mutation l Gamma ray

© Pearson Education 2011. Edexcel GCSE Additional Science Teacher and Technician Planning Guide This document may have been altered from the original.

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P2.33e Other uses of gamma rays Because the gamma rays can penetrate up to 15 cm of solid steel. 2 Not very, because most of the truck is showing grey/white. 3 They are absorbing some of the gamma rays. 4 If there were discrepancies between what the documentation says and what you can see on the image. 5 Black 6 No, because the gamma rays from the cobalt-60 source will penetrate solid steel up to 15 cm thick. 7 Yes, because metals will absorb some gamma rays so the guns would make a dark image. 8 GM tube and other sensible suggestions 9 Students’ own answers 10 a Hidden rooms, e.g. in a pyramid b Need to be able to get to both sides of the structure as the source has to be on the opposite side to the camera; object cannot be too big otherwise gamma rays will not get through at all. 1

P2.34 More uses of radiation Student Book 1 2 3 4

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Alpha particles Count detected by monitor decreases, so computer increases pressure applied to the rollers. Alpha particles would be stopped by the paper. The half-life is much greater than the life of the product, so the radioactivity of the americium will remain approximately the same while the smoke alarm is in use. Use same method as for paper, as described in Student Book.

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Flow chart should have three feedback loops showing what happens when: the paper is too thin; the paper is too thick; the paper is the right thickness. A good answer should include the following points:  Long half-life  Gamma emitter so that it can get to the detector through the ground  Low activity level so that it does not damage any living things  Not poisonous to organisms  Increases the background count

Skills spotlight I would need data on the number of people whose lives have been saved in a fire because a smoke detector woke them up or warned them and allowed them to get out of the house in time. I would also need information about the risks of smoke detectors. For example, has anyone become ill because of the radiation emitted by them. This is not likely to happen when the smoke detectors are mounted properly, as alpha particles do not travel far through air. However there may be information about harm caused if they are not disposed of properly, or if people take them apart. If more people have been helped by smoke detectors than have been harmed by them, then the benefits outweigh the risks.

Activity Pack P2.34b Choosing radioactive sources 1

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Americium-241 because an alpha emitter is needed to produce the ionisation current and the activity needs to stay approximately the same for the life of the product. Strontium-90 because a beta emitter is needed (to pass through the thin material) with a long half-life. Technetium-99m because a gamma emitter is needed (to pass through the body) with a short half-life.

P2.34c Choosing the correct radioactive sources Students’ answers may vary – examples are given here. 1 Cobalt-60 because a gamma emitter with a half-life of more than a few days is needed to detect slow leaks. 2 Cobalt-60 because a gamma emitter with a long half-life is needed. 3 Technetium-99m because a gamma emitter is needed with a short half-life. 4 Americium-241 because an alpha emitter is needed and the activity needs to stay approximately the same for the life of the product. 5 Strontium-90 because a beta emitter is needed with a long half-life. 6 Cobalt-60 because a gamma emitter with a long half-life is needed. 7 Cobalt-60 because a gamma emitter with a long half-life is needed. 8 Activity of the source, how easy is it to obtain, cost.

© Pearson Education 2011. Edexcel GCSE Additional Science Teacher and Technician Planning Guide This document may have been altered from the original.