KS3 Science Revision and Exam Questions PDF

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; - Se gg IT oO O es ©.a OD (a4 wheneed a D2 eso ae a 7  Contents Pr ocesses life Processes. and ‘Cells +. scech..- qatar tea tees Variation 2 seer Seer ae ether g aca ee ee 42 Five Specialised! Cells’.:...:....:.coeimee: osnsneee Zz Environmental and Inherited PIARC-OPQANS. cone css ars -nnies cos eter: ee 4 VariagOn £0 ADIRIAlS «.4,.s05.0000%-vzavacsdecestee eee 43 FIGARO GANS YStGI1S Bae ne Fe een oc. 7) Environmental and Inherited Warm-up and Worked Exam Questions........... 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TG GUL ieee vars epee: caveesk 13 Kidneys and Water Regulation.........c.ccccccee 14 Skeleton, Joints and MUSCIES.............cccccccececeee 15 Warm-up and Worked Exam Questions........... 16 VAC APCAN OWS. asd) cnet ie cae. ta cae ee ae eye Exam Questions) ee ee 17 Sustainable Development.........:cccccescescereseseees 55 Growing Up: Sian ee tae recientes eras rae, 18 FOOU- CHAINS cc tate veaet nal ahh aie eee 56 ReproductiveuSy siento aecee rennet atte oe ee 19 FOOCIWEDSt a 4 atten es tucson 57 TheMenstrual GQ¥Glet ene hee eee 20 Pyramids OF INUOC tsa ce tad eee actrees 58 WghAVHOO GAD x.c30: tectren adeeb aah toate eh eh as 21 SURVIVAL 3 a, ot Papettcise are ee ee 59 Warm-up and Worked Exam Questions........... BD Warm-up and Worked Exam Questions........... 60 FEAF COUIOS HONS ca cstelecs cae meena earn, acs 23 EXAM QUESTIONS ncceterc oe re eee Se eee 61 Breathing.....:.2i,Aepeecmemeas Aare Pes) aa 24 REVISIOWSSUUTIAIV rate tehai eaten reset corte 62 RESP ATION: vaccatartnn aneCaae Deceaemats cteee eee 26 SPOR: 4.02.wcyiasiltar ds asset ee tact MENG Re aoe 27 IX — am FSR.) SRM Nr et saprh es Lene ee eater a 28 ssifying Mat FIBMURE ISCAS hts eves oh cee Cee ne mney oo 29 Warm-up and Worked Exam Questions........... By SOlidS :LIQUIOS aNd GaSESe 1.5 ea wear 63 EX@NT! QUESTIONS tes ci insane teas: 32 PACU CIEST CORY ae eee ts oekceent hee 64 REVISION SURPGAGIY 3. ce. MPeaneevonianeecwee deca ate 315) PRYSICQT CHAN GOS red. cles oe seater pone 66 Warm-up and Worked Exam Questions........... 68 Xam) QUESTIONS, x..8is.c.. 0h ae ce 69 ALOTNSPANOMEICINGDIS asta. «1k - arent eee 70 COMPOUNGS: oc.2istadsk:.5.n ie ee 71 Plant Nutrition Naming COmpOUNnGS:..2.:1.5:.. €-100 fm@10(=%-j de) at 2 Roses are Red Ltd. is interested in selectively breeding a new variety of rose to sell. The company has a number of roses with different characteristics available to breed from. Fall number of flowers Disease Resistance oor ood average ood to insects P g g g (a) The new rose must have lots of flowers and be resistant to disease and insect attack. (i) Which two roses should the company choose to breed from? (2 marks) (ii) The cross produces a number of promising roses, but none of them exactly meet the company’s requirements. What should the company do next? (1 mark) (b) Cuttings are taken from the new rose to produce genetically identical offspring. The young plants are grown at various sites. The company notices that the roses grow more quickly at some sites. Suggest two reasons why the roses are growing at different rates. (2 marks) 3 Each of these animals belongs to a different group. sparrow frog starfish mouse lizard Choose an animal from the list above that (a) is an invertebrate (b) is amammal (c) is a reptile (d) is an amphibian (e) is a bird (5 marks) SECTION FOUR —VARIATION, CLASSIFICATION AND. INHERITANCE  Revision Summary Section Four’s fairly basic really, but there are some words which could cause you grief until you've learnt exactly what they mean. ‘Variation’ just means ‘differences’; ‘genes’ are just a ‘blueprint’ for how a living creature is put together; ‘chromosomes’ are those X-shaped things inside cell nuclei which contain genes; etc. etc. These questions aren’t the easiest, but they test exactly what you know and what you don’t. You need to be able to answer them all, because all they do is test the basic facts. There’s no understanding needed for these little jokers — it’s just a matter of learning. You must practise these questions over and over again until you can sail through them all. What does variation mean? What is a characteristic feature? Think of two different species of dog and list three characteristic features for each. Name a characteristic feature which is impossible to spot from looking at the outside of the body. What does inherited mean? What is an environmental characteristic feature? Give three ways that environmental factors could affect identical twins and make them look different. Give four characteristics of animals which are totally unaffected by the environment. Give four characteristics which are influenced by genes and by the environment. 10) Which are usually affected more by their surroundings — plants or animals? 11) List four things which could affect how well a plant grows. 12) What controls inherited characteristics? 13) What is a gene? 14) Where do you find chromosomes? 15) How many chromosomes do humans have in each cell? 16) Why are a person’s characteristics a mixture of the characteristics of their parents? | 17) How many chromosomes do sperm and ova have each? \ “4 1 8)) What happens to a sperm and an egg in fertilisation? 1 9)) What happens to genetic information in the sperm and the egg in fertilisation? 20) Explain how selective breeding can lead to new varieties of plant or animal. 21) ) Give three examples of the results of selective breeding. 22) Why are domestic livestock selectively bred? 23) What do we call selectively bred dogs? 24) What is the difference between a vertebrate animal and an invertebrate animal? 25) Are fungi plants, or animals, or neither? 26) ) Give an example of a mollusc. 27) What do keys help you to do? 28) ) What are the rules for using keys? SECTION FOUR — VARIATION, CLASSIFICATION AND. INHERITANCE 2 / SECTION FivE — LIVING THINGS IN THEIR ENVIRONMENT Adaptation | Se (so no photosynthesis) a v 4. Animals store food Hibernation is a very useful trick There’s a lot of information in the diagram on this page. So look at it carefully, then learn it really well until you can reproduce it without looking. _ The examiners like asking questions about adaptation, so it'll be worth it. SECTION Five — LivinG THINGS IN THEIR ENVIRONMENT  3p) IVES) fare] o)(-WeBY-Y fe) i + + oe & > The particles in a solid have the least energy. The particles in a liquid have more energy. The particles in a gas have the most energy. This particle theory explains all the different properties of solids, liquids and gases... It all seems to make sense | think it’s pretty clever the way you can explain all the differences between solids, liquids and gases with just a page full of blue snooker balls. , Anyway, that’s the easy bit. The not-so-easy bit is making sure you've learnt it all. SECTION Six — CLASSIFYING MATERIALS  Particle Theory There are strong forces of attraction between particles. The particles are held closely in fixed positions in a very regular ' arrangement. But they do vibrate to and fro. > The particles don’t move from their positions, so all solids keep a definite shape and volume, and can’t flow like liquids. Solids can’t easily be compressed because the particles are already packed very closely together. There are some forces of attraction between the particles. The particles are close but free to move past each other. However, they “i do still stick together. The particles are constantly moving in all directions. Liquids don’t keep a definite shape and can form puddles. They flow and fill the bottom of a container. But they do keep the same volume. Liquids won't compress easily because the particles are packed closely together. Liquids are quite dense, as there are quite a lot of particles in a small volume. = Particles There are hardly any forces of attacton between the particles. The particles are far apart and free to move quickly in all directions. The particles move fast, so collide with each other and the container. Gases don’t keep a definite shape or volume and will always expand to fill any container. Gases can be compressed easily because there’s a lot of free space between the particles. Gases all have very low densities, because there are not many particles in a large volume. Particle Theory isn’t rocket science That's why it’s called particle theory. Learn what's on this page, then cover the page and write down all the main properties of solids, liquids and gases, and why they behave the way they do. Check youranswers, , then coverc rand test te styourself again until you ‘re sure. SECTION Sie — Cure Treen 66 adahYA-) (or-|MmOdaT:late (=t— | Physical changes don’t change the particles — just their arrangement or their energy. / depends on h W. A change of state just means a substance is changing from one state of matter to another. 2) Ata certain temperature, 3) When a liquid is heated, the particles have enough again the particles get even energy to break free from more energy. their positions. This is called melting and the 4) This energy makes the solid turns into a liquid. particles move faster which weakens and breaks the bonds holding the liquid together. we rrr 1) When a solid is heated, its 5) At a certain temperature, the particles gain more energy. particles have enough energy This makes the particles vibrate to break their bonds. This is more, which weakens the forces called boiling and the liquid that hold the solid together. turns into a gas. This makes the solid expand. ee ee, Pee OR A red arrow means heat Is supplied A blue arrow means heat is given out From the sublime to the ridiculous So matter can move from solid to liquid to gas and back again. Learn this, and learn what / happens when it changes state. Write it all down bit by bit. Start with the diagram, | then add the five labels — then try to learn all the details that go with each one. SECTION SIX — Giusarine MATERIALS  lng NVA} (or-] a 9 at-Lale [2 When you increase the temperature, it makes the particles move faster. 2) This has two effects: a) They hit the walls harder. b) They hit the walls more often. 3) Both these things increase the pressure. 1) If you reduce the volume it makes the pressure increase. 2) This is because when the particles are squashed up into a smaller space they'll hit the walls more often. But then that’s pretty obvious, isn’t it? ir particles ©. oO © eet o © fo) © © Smell diffused 's © © o) % ©. a & Seueincne aire. Oo oo ae The smell particles move away from where there are lots of them, to everywhere else where there are only a few of them — but remember, diffusion is always slow. This is because the smell particles keep bumping into air particles, which stops them making forward progress and often sends them off in a completely different direction. Aerosols hold gases under pressure, and when you spray an aerosol, you get to smell diffusion in action. Marvellous. Now cover the page and see how much you can write down. SECTION SIX — CLASSIFYING MATERIALS  Warm-up and Worked Exam Questions There’s a bit too much gas in this section in my opinion. Just tackle the warm-up questions first, — then examine the nice worked example. Name the only state of matter that can be easily compressed. In which state of matter are the particles fixed in a regular pattern? What happens to the speed at which particles move when they are heated? What is sublimation? Why does gas pressure increase when the volume is decreased? 1 An aerosol can of deodorant contains liquefied gas under pressure. (a) The aerosol can is a solid. What are the properties of a solid? Tick two correct boxes. Has a definite volume % Flows easily as Is easily compressed La Has a high density Takes the shape of a its container (2 marks) (b) When the deodorant is sprayed, it changes from a liquid into a gas. Each deodorant particle can be represented by a circle. Carefully complete the diagrams below to show the arrangement of particles in the deodorant, as a liquid and as a gas. Don’t forget that there should gas liquid always be more liquid particles than 3@ Y p gas ones in diagrams like this. ashes a oa Soe eee (4 marks) (c) A student uses the deodorant in the corner of a changing room. After a couple of minutes everyone in the room can smell the deodorant. Name the process involved and explain how it works. (i) Name of the process: diffusion (2 marks) SECTION SIX — CLASSIFYING MATERIALS  Exam Questions Drivers are advised to check their car’s tyre pressures before setting out on a long journey, particularly if the car is heavily loaded. (a) Explain how air molecules inside a car tyre exert pressure on the walls of the tyre. (1 mark) (b) In terms of the gas particles, explain why tyre pressure is increased when a car is heavily loaded. (2 marks) (c) After several hours driving, the tyres feel hot to the touch. (i) What effect will this have on the speed of the air molecules inside the tyre? (1 mark) (ii) In terms of the motion of the air molecules, give one reason why this will lead to an increase in tyre pressure. (17 mark) (d) Tyres at very high pressure can be dangerous. Suggest what might happen to a tyre if the pressure is too high. (1 mark) Jenny boils 2 litres of water in a large pan in her kitchen. After half an hour Jenny cools the water and measures it in a jug. There is 1 litre left. (a) Explain what has happened to the water that is not in the jug. (1 mark) (b) Jenny notices that there are droplets of water on her kitchen window. Name the process that has taken place to form the droplets. (1 mark) (c) Jenny freezes the water in the jug to make some ice cubes. She thinks that the particles will change when they change from a liquid to a solid. Is Jenny correct? Explain your answer. (2 marks) SECTION SIX — CLASSIFYING MATERIALS  Atoms and Elements | ents consist 0 Elements can’t be split up into anything simpler by chemical methods. They only contain one type of atom. There are about 100 different elements (shown below). Each one has a name and a shorthand symbol, e.g. Carbon, C. 4) Everything on Earth is made up of elements. Group O aa mass SG rs |e number H aS Group! Group I! Z Hyd Group Ill Group |1V Group V Group VI Group VI ee Erdeie sly — number ™ reactive transition other non separates metals metals metals metals metals gases from non-metals : Group Names The elements are specially arranged so that every column contains elements with very similar properties. Group 1: The alkali metals These columns of elements are called groups. Group 2: The alkaline earth metals Group 7: The halogens The horizontal rows are called periods. Group 0: The noble gases There’s always a gradual change or “trend” in properties across a period. The block of elements between groups Elements are listed in order of atomic number — this is [iecaeaeemabthem use inall see ateinelelamail ase just the number of protons in the nucleus of the atom. The atoms in an element are all identical. All atoms are really tiny. Atoms are the basic building blocks of all materials. Nucleus made up of protons and neutrons | Atoms have a nucleus in the middle which contains protons and neutrons. Protons are positively charged. Neutrons are neutral. Electrons whizz around the nucleus. Electrons are negatively charged. They’re even smaller than protons and neutrons, and they go really fast. SECTION SIX — CLASSIFYING MATERIALS  Ofe) aa}ered Ulare 1) The particles in a compound are called molecules — formed when atoms join. 2) To make a compound, the atoms must be from different "join" or "bond" elements and the “join” is known as a chemical bond. Een CO: in molecule You need to know the difference between an element, a compound and a mixture. An element ee §6he particles are all the which is made u p , } same and not joined up — it must be an element. of atoms: An element The atoms may be joined, which is made but there’s still only one type, so it’s still an element. up of molecules: Molecules in a Se sanener Here we have different compound: atoms joined together — that’s a compound. A mixture of ee eee! = [his is not a compound different elements: ae | because the elements aren’t joined up — it’s a mixture. SECTION SIX — CLASSIFYING MATERIALS 72 1) A chemical reaction involves two or more chemicals (called the reactants) combining together to form one or more new substances (called the products). 2) The new compounds produced by any chemical reaction are always totally different from the original elements (or reactants). (We sometimes say a new compound is synthesised.) The classic example of this is iron reacting with sulphur as shown below: It reacts with sulphur to make iron sulphide, a totally new substance which is not magnetic: Strong magnetism Not magnetic aus! £ Se SE, I ee ons Se Word equation: Iron + Sulphur a Iron Sulphide In symbols: (Fe + ¢ ‘Fer When elements undergo a chemical reaction like the one above, the products will always have a chemical formula — e.g. H,O for water or FeS for iron sulphide. Compounds can be split up back into their original elements, but it won't just happen by itself — you have to supply a lot of energy to make the reaction go in reverse. Chemical reactions form brand new products | There’s an equation to learn on this page, and a bit of important general information. _ It goes into a lot more detail later on, so make sure you're happy with the basics, and that you understand how compounds are formed. SECTION SIX — CLASSIFYING MATERIALS  \FTaatiale pxOxe)aa)ekeyelavets When elements combine their names often change slightly. Learn the three simple rules. Formula Sodium and chlorine Magnesium and oxygen SODIUM CHLORide — Suen | 2) The current is the same anywhere in this Circuit, as it has no choice of route. Did | tell you current isn’t used up? — well, don’t forget. 3) In series circuits the current is either ON or OFF — the switch being open or any other break in the circuit will stop the current flowing everywhere. | Why don’t you wire your house lights in series? _ It’s pretty obvious, | reckon. If a bulb went, all the lights in a series circuit would go off, leaving _ you in total darkness. So it won’t come as a surprise that there is another type of circuit... SECTION NINE — ELECTRICITY AND MAGNETISM  119 Electric Currents in Circuits Current flows out of the cell and it all flows through the first ammeter A.. It then has a “choice” of three routes and the currents splits down routes 4) Quand. The readings of ammeters A,, A, and A, could be different, depending on the resistances of the components — i.e. the bulbs. The split-up current joins up again on its way back to the cell. So the readings of A,+ A,+ A, added together will be equal to the reading for current on ammeter A, (which will also equal A,). It’s difficult to believe | know, but the current through A, is the same as the current through A, — the current is not used up. (I may have told you that once or twice already.) 5) Parallel circuits are sensible because part of them can be on while other bits are off. In the circuit here, two bulbs are on and the other one is off. | through — — that bulb| Switch 3 Switch 1 Switch 4 So now you know the two different types of circuits Make sure you know which is which — it's vital for exam questions. Parallel circuits are a lot more versatile than series circuits. Andgelusehin case you'd iPigeticn, the current is not used us eee ete — mien, iy ANDey Ne een  120 The circuit is complete when the switch is closed — the bulb lights up. 2) Ammeter reading = 4A. 1) The bulb is twice as bright compared to (1). 2) The two cells provide twice the push for the current, so the bulb shines brighter. 3) Ammeter reading = 8A. 1) The bulbs are dimmer than in (1). 2) With two bulbs in series, and only one cell to “push”, the current is only half as big. 3) Ammeter reading = 2A. It’s tricky to understand why, but if the two bulbs were in parallel, they would both be just as bright as normal. 1) The bulbs are as bright as in (1). 2) The two cells provide twice the ‘push’ compared to (1), but the two bulbs give twice the resistance for it to “push” against. 3) Ammeter reading = 4A. i.e. same current as (1). 1) In the diagram you can see that the current takes the easy route round the bulb and not through it. This is known as a short circuit. 2) It's easier for the current to go through the wire simply Short circuit because the wire gives much less resistance to the flow. (short cut Once the short circuit is in place, the circuit behaves for current) like there’s only one bulb. ; 3) Hence the ammeter reading would be back to 4A as in (1) above. _ What a lot of circuit diagrams They're not too complicated, though. The good thing about physics is that it’s pretty logical. Once you've learned the rules, you'll be OK. SecTION NinE — ELectricity AND MAGNETISM  121 WM ETefatsiay Only iron, steel, nickel and cobalt are magnetic. Bar magnets HAVE to be made using one of these metals. All bar magnets have invisible magnetic fields round them. One end of the bar magnet is called the north pole, and the other end (astonishingly enough) is called the south pole. The field lines always point from the N-pole to the S-pole: Lines of magnetic force Se, cian, Repelling A magnetic field is a region where magnetic materials (e.g. iron) experience a force. You can investigate magnetic fields using either iron filings or a plotting compass: The iron filings The field lines (or ‘lines of force’) will align along always point from north to south. the field lines. 6 The compass will always point from NtoS along “ the field lines, wherever lron filings are sprinkled onto a piece of it’s placed in the field. thin card which is covering the magnet. SECTION NINE — ELECTRICITY AND MAGNETISM  127 | Repulsion is the | 1) The only true test of whether or not a piece of metal is a permanent magnet is to get repulsion, because you need two magnets to get repulsion. 2) There are two possible reasons why an unknown piece of metal will be attracted to a magnet: a) It might actually be a magnet, or b) It might only be made from a magnetic material (iron, nickel etc.), but not actually be a magnet. |Pre-magnetised paper clip -Repulsion Non-magnetised Pre-magnetised steel paper clip S steel paper clip N S |Same effect in both cases — attraction | Get hold of some magnets and experiment The best way to remember this stuff about magnets is to play around with them for a bit and do some of these experiments, until you've convinced yourself that it’s all true. / SECTION NINE — ELECTRICITY AND MAGNETISM  123 Electromagnets Electric current also creates magnetic fields. We can use this effect to create powerful electromagnets. TASES VIED SORTER EE SEALS 1) A current going through a wire causes a magnetic field around the wire. 2) A solenoid is just a long coil of wire. Its magnetic field is the same as that of a bar magnet. Magnetic fiel i lines Wire witha current in it. An electromagnet 1) More current More turns on 3) Acore of soft iron in the wire. the solenoid. inside the solenoid. ES More wigs Soft iron Ry: core Soft iron has to be used for the core to make it perform as an electromagnet should — i.e. turning on and off when the Current is turned on and off. If a steel core was used, it would stay magnetised after the current was switched off — which would be no good at all. SECTION NINE — ELECTRICITY AND MAGNETISM  124 Electromagnets 1) When the switch is operated, the current flows through the coil and the electromagnet attracts the hammer. 2) As the hammer moves, it not only clangs the bell but also pulls the contacts away, and the circuit is broken. This turns off the electromagnet, which releases the hammer and it springs back to its original position. 3) This turns the electromagnet back on which again attracts the hammer, which again clangs the bell... TC: Relay 1) Asmall current in one circuit is used to switch on a much larger current in another circuit. 2) When the small current is switched on the electromagnet activates and the iron lever is attracted to it. This makes the lever rotate. 3) As it rotates, the other end of the lever pushes the contacts together which turns on the other circuit. | Electric magnets... whatever next | You can have a lot of fun with electromagnets. Honest. Electromagnets are used in power | stations to generate electricity and they also turn up in loads of handy gadgets, like hairdryers. SECTION NINE — ELECTRICITY AND MAGNETISM  N29 Warm-up and Worked Exam Questions There’s a good mix of warm-up questions to get you started, then you can launch yourself into the nitty-gritty of circuit diagrams and magnetism. What a great way to spend an evening. What is an insulator? Give an example. Draw the circuit symbols for a) a cell b)abulb —_c) an ammeter. Why is a parallel circuit more useful than a series circuit? Which elements are magnetic? What is a solenoid? How can the strength of an electromagnet be increased? Stella wraps a piece of copper wire around a plastic tube and connects it to a simple circuit. Plastic tube Copper wire AUC (a) When Stella switches on the circuit she finds she can pick up three steel paper clips using the wire coil. Suggest one change to the apparatus to make the coil pick up more paper clips at once. She could also increase the number of coils inthe (1 mark) wire, or increase the current by adding another cell. (b) Stella tries to pick up a small silver earring with the coil, but it doesn’t work. Explain why the coil will attract steel paper clips but not a silver earring. (2 marks) (c) Stella places a small compass at one end of the coil. The needle points into the coil. ss Remember — a compass needle always points from N into S along the field lines of a magnetic field. ACCC) Where will the needle point if she connects the battery the other way around? (1 mark) SECTION NINE — ELECTRICITY AND MAGNETISM  126 Exam Questions 2 When a key is turned in a car ignition, ore a small current flows in the ignition circuit. Using a relay, this switches on ct | Tine the starter motor to start the car. as ae: starter motor ignition circuit —: motor circuit (a) The relay is an electromagnet. (i) Give the name of the most likely material to be used for the core of the electromagnet. (1 mark) (ii) Give the name of a suitable material to use for the rocker. (1 mark) (b) Explain how the relay works to switch on the starter motor. (3 marks) Abby is building-amodelecar = «© — 4 She has designed a circuit to control. the electric motor and headlights. Switchon Headlights Switch B (a) Copy and complete the table to show how the switches can be used to control the motor and headlights. Switch A| Switch B| Is the motor working? | Are the headlights on? closed closed a open open ia closed open — —| open closed (4 marks) (b) Abby wants to add a switch to the circuit that will allow her to turn the headlights on when the motor is off. On the circuit diagram above, label a suitable place for the switch with an ‘S’. (1 mark) (c) Abby now wants to add a light in parallel that will come on when switch A is closed. On the circuit diagram above, draw a bulb and connecting wires to show how she could do this. (1 mark) SECTION NINE — ELECTRICITY AND MAGNETISM  Ezy Revision Summary Phew. Electricity and magnetism — it’s no holiday, that’s for sure. There are certainly quite a few grisly bits and bobs in this section. Then again, life isn’t all bad — just look at all these lovely questions I’ve cooked up for your delight and enjoyment. These are very simple questions which just test how much stuff you've taken on board. They're in the same order as the stuff appears throughout Section Nine — so for any you can’t do, just look back, find the answer, and then learn it good and proper for next time. Yep, that’s right, next time — the whole idea of these questions is that you just keep practising them time after time after time — until you can do them all effortlessly. 1) Give the name of the most common group of conductors. 2) Give the names of five insulators. 3) What is needed for electricity to flow? 4) Cana bulb light if electricity doesn’t get to the bulb? 5) What is a circuit diagram? Why don’t we draw out the real thing all the time? 6) Sketch the circuit symbol for all of these: a)abuzzer b)abulb c)abattery d)aswitch (open) e) a cell. 7) Current is the flow of what? 8) What job does a battery do in a circuit? 9) What instrument do we use to measure current? What are the units of current? 10) What happens if there is a break in a series circuit? 11) Which type of circuit allows part of the circuit to be switched off? 12) In parallel circuits current has a choice of what? 13) What is not used up in a circuit? 14) In a series circuit, what happens to the current if you double the cells present? 15) In a series Circuit, what happens to the current if you increase the number of components in the circuit? 16) What is a short circuit? Why does the electricity flow through this route? 17) What are magnets always surrounded by? Name three magnetic materials. 18) ) Draw a labelled diagram of a bar magnet. What are the lines around it called? 19) ) What is a magnetic field? In which direction do field lines always go? 20) ) Show the lines of force for two magnets that are a) attracting —_b) repelling. 21) ) Sketch a diagram showing how a plotting compass points around a bar magnet. 22) Show a) two poles attracting —_b) two poles repelling. 23) ) How can you test if a material is magnetic? 24) What's a solenoid? What do the field lines around a solenoid look like? 25) ) What's an electromagnet? List three ways to increase the strength of one. SECTION NINE — ELECTRICITY AND MAGNETISM  128 SECTION TEN — FORCES AND MoTION This line means A formula J» divided by or me clare & d aie. shared by (+). Time 1) Speed is simply how far you've travelled in a certain time. 2) The formula triangle is definitely the best way to do speed calculations. 3) Use the word SIDOT to help you remember the formula: Remember SIDOT.: Speed Is Distance Over Time 4) There are three common units for speed, as shown below. You should realise that they’re all kind of the same: i.e. distance unit per time unit: metres per second — m/s (or even ms") miles per hour — m.p.h. or miles/hour / kilometres per hour — km/h Always use units. To work out speed you need to know the distance travelled and the time taken. EXAMPLE 1: A sheep is running down a farmer's track. It takes exactly 10 seconds to move between two fence posts, 10 metres apart. What's the sheep’s speed? Answer: Put your finger over ‘S’ in Step 1) Write down what ou know: the formula triangle — distance,d=10m_ time, t= 10s which leaves d/t Step 2) We want to find speed, s (i.e. d=0). From the formula triangle: s = d/t Speed = distance + time = 10 + 10 = 1 m/s Speed questions are a doddle if you just learn the formula triangle EXAMPLE 2: A van drives down a road and travels 15 miles in 30 minutes. What's its speed? Answer: Step 1) Write down what you know: distance, d= 15 miles time, t = 30 minutes = 0.5 of an hour. Step 2) We want to find speed, s — From the formula triangle: s = d/t Speed = distance + time = 15 + 0.5 = 30 miles/hour (mph) For the answer to be in mph you need the distance in miles and the time in hours, so the 30 mins had to become 0.5 hrs. Don’t be scared by this formula Speed is a pretty simple idea really. Mind you, that doesn’t stop people getting muddled up _ about it. Learn the formula, the units, and go through the examples until you're sure. SECTION TEN — FORCES AND MoTION  £29 Force and Movement a a iS TOTO Forces can’t be seen, but the effects of a force can be seen. 2) They are measured in newtons —N. 3) They usually act in pairs. an 4) They always act in a certain direction. ) A newton meter is used to measure forces. Speed up] / Slow Down wo ; ©. bia ih es — like hitting a ball with a bat. diesionos | vu Do; C aN ACE SPANNER — like turning a spanner. turn} Changing shaneWe J aaa j Sst a EB Bending — like stretching, twisting, compressing, bending. Learn these two important statements: Table produces an ¢- [1g m@lU(-s-) 4(0)pt There are quite a lot of calculations to get to grips with here. Go back over the ones you get wrong until you’re confident about how to do them. How is speed calculated? What are the units of speed? A girl cycles for 30 seconds at 5 m/s. How far has she cycled? Why does a parachutist fall at a steady speed for most of his jump? What is the rule about levers and turning forces? If a girl weighing 500 N balances on one ice-skate (area: 20 cm?), how much pressure does she exert on the ice? Give the units. A tennis player tosses her ball in the air before serving. (a) As she waits for the ball to fall, the tennis player is not moving, although there are forces acting on her. What does this tell you about the forces acting on the tennis player? If something isn’t moving, then the The forc are es balanced, toesaed On le (1 mark) (b) As the ball begins to fall back towards her, she strikes it with her racket. Suggest two ways in which the force of the racket acts on the ball. SU eee A OCU ew a CC eS uae Cire? Siti a aie Noe NTnGt tos POCO NOG) IIe WO CIRaC IRC IIC CIC irICR Pe tue (2 marks) (c) The ball leaves the tennis player’s racket at a speed of 50 m/s and travels a distance of 20 m before bouncing. (i) Calculate how long it takes the ball to travel this distance. HITE = Algvance/ ¢ PEER SUL BACT ORR... tas hescasent Make sure that you're using the right units — (1 mark) in this case the answer should be in seconds. (ii) The actual time taken for the ball to travel this distance is slightly longer than you have calculated. Suggest a reason why. SECTION TEN — Forces AND MoTION  t37 =plan @lurst-j ale) ats 2 Stuart is using a single hole-punch. Force applied As he presses down on the handle, the cutter presses down on the paper, making a hole. (a) Calculate the moment (turning effect) of the 6 N force Stuart applies to the handle. Give the units. (2 marks) (b) This moment makes the cutter press down on the paper. Calculate the force with which the cutter presses down on the paper. (1 mark) (c) The area of the edges of the cutter is 0.1 cm*. Use your answer to (b) to calculate the pressure of the cutter on the paper. Give the units. (2 marks) Martin is sliding on a polished wooden floor in his socks. (a) When Martin is sliding, he usually stops moving after a couple of metres. Name one force that is acting to slow Martin down. (7 mark) (b) When Martin takes his socks off, he doesn't slide as easily. Suggest a reason for this. (1 mark) (c) Martin’s mother wears shoes with a pointed heel. After she has walked across the floor, Martin notices that her heels have left dents in the floor. Martin weighs 700 Newtons and his mother weighs 600 Newtons. (i) Explain why his mother has dented the floor, even though she weighs less. (2 marks) (ii) One of his mother’s shoes has an area of 60 cm? Calculate the total pressure that his mother is putting on the floor when she is standing on two feet. Show your working. (2 marks) SECTION TEN — FORCES AND MOTION 138 Revision Summary Section Ten is all about forces and motion. It’s all pretty straightforward stuff really, and the questions below will just test whether you've learnt the basic facts. If you can’t answer any of these then you haven't learnt the facts. Don’t start kidding yourself that it’s too difficult for you to “understand” — sit down and learn it instead. If you’re having trouble learning the stuff, try taking just one page on its own. Start by learning part of it, then covering it up and scribbling it down again. Then learn a bit more and try scribbling that down. You'll find this “grown up” method is about 100 times more effective than the usual 14 year-old revision technique, namely: “Errm, | think just reading it through once will be OK, won't it?”. Yeah right. — ) What exactly is speed? Write down the formula triangle for speed. 2) ) How does SIDOT help you remember what speed is? 3) ) A mouse runs 5 m in 2 seconds. Calculate the speed of the mouse. 4) ) On sports day you run 100 m in 20 seconds. Can you move faster than the mouse? ) When a car is going at 40 mph, how far will it travel in 15 minutes? eon Oy ) Can forces be seen? How do we know they’re there? a ) What are the units of force? What would you use to measure force? ee)) What are the five different things that forces can make objects do? O) What do balanced forces produce? What do unbalanced forces do? 10) What is air resistance? What's the best shape for avoiding air resistance? 11) When a parachutist first jumps out of a plane, what happens to their speed? 12) As the person moves faster, what happens to the air resistance? 13) What happens to air resistance when the parachute opens? 14) Does the speed then change? When does the person’s speed become steady? 15) What might happen if the ground didn’t provide an upward force to equal the person's weight? 16) Give four good points of friction. Give two bad points of friction. 17) What is a pivot point? Give another name for it. 18) What is a lever? How can a lever help you roll a rock over? 19) What important rule must you learn about levers and turning forces? 20) Draw out and label five examples of levers, and put in the effort and load arrows. 21) What is a moment? Give the formula for a moment. 22) What does “balanced moments” mean? 23) ) A force of 100 N is put 1 m away from the middle of a seesaw. What distance from the middle should a force of 50 N be applied to balance the seesaw? 24) What is pressure? Give the formula for calculating pressure. 25) Explain how an elephant can walk on dodgy sand but a car would sink. 26) A force of 200 N acts on an area of 2 m?. Calculate the pressure. 27) A force of 200 N acts on an area of 10 cm?. Calculate the pressure in N/cm? 28) Why do stiletto heels damage wooden floors? (NB - Answers to questions 3-5, 23 and 26-27 can be found on page 165.) SECTION TEN — FORCES AND MOTION  SECTION ELEVEN — LIGHT AND SOUND 139 Properties of Light 1) The light travels in a straight line from the sheep to the tracing paper screen through the pinhole. Because the hole is small, only one ray gets in from each point on the sheep. 2) bithe image | ofthe sheep seen by the eee | ee farmer is upside down and crossed over. This is because the rays of light cross over inside the camera, as shown: dows are Place. 2 Transparent means “see- through’i Opaque means “not see-through”. Beir shee Light travels in straight lines from the bulb to the cA screen — but leaves a dark area (i.e. a shadow) where it can’t go through the Opaque object. The shadow is the right way up (upright) and gets i bigger as the object gets nearer to the light source. Smaller shadow > Gjaht travels very ae — each eal faster than sound. When a starting pistol is fired (some distance away), you see the smoke first — and hear the bang afterwards. This is because the light reaches you before the sound does. 1) Light is produced by ito: nee Eien as the CGP Top Value Revision Book Sun, candles, light bulbs, flames, and glow worms. Light reflects off non-luminous objects, in other words, everything else, e.g. the Moon, planets, you, me, sheep, books, etc. Reflects off Light reflects off these objects and into our eyes | epee) ea and that, my friend, is how we see. Light travels atabout 300,000 km/s... now that’s fast. You don’t need to learn this fact — | just thought it was interesting. However you do need to learn userestee ble Egon — aaa Gass Oe. — it write it down ugar SHEL Gacneh ee _ ae AND ae 140 Reflection : Being teenagers you'll be familiar with mirrors. Well, reflect on these facts: Light travels in rays which reflect off mirrors and most other things. 2) Mirrors have a very smooth shiny surface which reflects all the light off at the same angle giving a clear reflection. 3) Rough surfaces look dull, because the light is reflected back in lots of different directions. This is called a diffuse reflection. Not shiny Learn the Law of Reflection: Angle of incidence = angle of reflection Angle i = angle r Shiny side Dull side of mirror _|f//|_of mirror , eps J ightGorey ray Ve Z 7,(Normal Make sure you draw straight lines and get the angles the same when drawing these ray diagrams — get yourself a protractor. 1) Checking that you're still beautiful. 2) Rear-view mirrors in cars, etc. 3) Periscopes — used in submarines. eC » The Law of Reflection is a useful one to know | It’s really worth learning the stuff on this page. Learn the diagram as well, because | they’re quite leh to ask you to draw an angle:of reflection in the exam. RET ELEVEN — LiGHr: AND SOUND  141 eX Vigsleqdte)al tion iis s when Li 1) Light won’t travel through opaque material, bia will goceaibitain Beek ransparent. 2) When light travels from one transparent material to another, it bends or refracts. 3) Any substance that light travels through is called a medium. (The plural is media.) (...things that carry information) LEARN When light goes from a LESS dense medium to a MORE Example: THESE dense medium: Light bends TOWARDS THE NORMAL air to glass. REALLY WELT: When light goes from a MORE dense medium to a LESS Example: dense medium: Light bends AWAY FROM THE NORMAL glass to air. Light bends — like a car hitting sand at an angle. The right wheels get slowed down first and this turns the car to the right — towards the normal. 2) Leaving the sand, the right wheel speeds up first and this turns the car to the left — away from the normal. 3) If both wheels hit the sand together they slow down together, so it goes straight through, without turning. Light rays do exactly the same. |, This wheel Incident ray Leecontinues to aS move fast Ray bends towards the normal Normal Refracted ray es pay. | Wheels all slow |- fe. | or speed up at | dade time | Not refracted Don't get reflection and refraction mixed up If you learn one thing from these pages, learn the difference between reflection and refraction. Learn the Robie actingstale learn theeailiapranianeandfeud‘Il soonBinaye it sorted out. Gane er — Ricca,ANDsee 142 Colour | Bit of a shocker, | know — but white light is actually a mixture of colours. This shows up clearly when white light hits a prism or a rain drop. It gets dispersed (i.e. split up) into a full rainbow of colours. The proper name for this rainbow effect is a spectrum. s == Se para FT eT Se IE red Learn the order that the colours come out in: A prism orange ‘ A spect Red Orange Yellow Green Blue Indigo Violet. Se yN ax Oe yellow rite lignt Remember it with this historical jollyism: green Richard OfYork Gave Battle In Velcro. blue Violet is bent the most indigo violet cata foured Filters a They 1) A filter only Aico one 2 iteeatee abet a lightto to go Se 2) All other colours are absorbed by the filter — so they don’t get through. Red Red | Red Orange 3 (Orange| Orange 3 |Orange| 4 |Vellow |B | Yellow | g L Green White Green S Green White Green 0 White i O 7 Blue Blue $ light piven R Blue light| —T light. Indis B ; 'B ty Indigo |£ > 2 Indigo. Violet 5 Violet |D Violet > [Violet |P Violet > 1) Blue jeans j are> blue pacauce they reflect wee Blue ete ane absorb all the spies colours. 2) White objects reflect all colours. 3) Black objects absorb all colours. Objectss seem toChi n IN WHITE LIGHT! WE GREEN LIGHT| Green SS — oP 5 light SS ~ 1) The boot looks red — it reflects red © 1) The boot looks red 1) The boot looks black light and absorbs all other colours. — it reflects the red light. — it has no light red to reflect and it absorbs the green light. 2) The lace looks green — it reflects 2) The lace looks black — it has green light and absorbs no green light to reflect and it 2) The lace looks green — all other colours. absorbs all the red light. it reflects the green light. Rainbows happen when light is dispersed through raindrops It’s worth getting to grips with the stuff on this page, because you’re very likely to get questions on it in the exam. For example they might ask why a blue anorak looks odd in a disco. SECTION ELEVEN — LIGHT AND SOUND  143 The ringing can be heard through the jar because the vibrating vibratin ( oo bells make the air inside vibrate. This makes the jar vibrate, ; which in turn makes Can hear air (alarm clock the air outside vibrate __ — and then we hear it. Now the alarm can’t be heard because even though the bells are clanging, there’s no air in the jar to carry the ey hee vibrations. If there’s Paar ee cn nothing there to vibrate, a. = aap then sound can’t travel. ’ ——-_ ~ ‘yyy ) ) ) ) i Sound needs a medium to travel through because something has to pass on the sound vibrations. 2) Sound carries energy — as the glass shows. 3) It can be reflected and refracted just like light. ATR. An echo is sound being reflected from a surface. \ \ 4) Sound travels much more slowly than light. al Learn the headings and you’re halfway there So make sure you do that first, then learn the diagrams and scribble them down from memory. Then do the same with the details. If you do that for five minutes, it might just help. SECTION ELEVEN — LIGHT AND SOUND 144 1) If sound is seen on an oscilloscope it looks like this — a wave. ) The amplitude of a sound is the height of the wave. © 3) The amplitude shows how much energy the sound has. ) A large amplitude means the wave has lots of energy. ) A large amplitude also means the wave is louder. So a wave with more energy has a bigger amplitude and is louder. | 6) A whisper has a low amplitude — a shout has a large amplitude. Quieter Louder — Sore ee corer BOLERO. 1) The frequency of a sound is the number of complete waves that pass a point per second. 2) It’s a measure of how high pitched the note is. 3) A high frequency means a high pitched note. 4) A high frequency also means more vibrations per second. More waves per second means the sound gets HIGHER PITCHED. 5) A mooing cow produces low frequency sounds, whilst screeching teenagers produce high frequency sounds. ‘Frequency=number leseaSper second | of th Lower pitched Higher pitched _ Make sure you're familiar with oscilloscopes | You need to learn the difference between frequency and amplitude, because chances are they’re going to test you on it in the exam. Get to know these wave patterns now. SECTION ELEVEN — LIGHT AND SOUND  145 Hearing Vibrations of ruler passed to air particles = 00008 0 00000000 @ dada SOB NN \A Ear bones Hairs vibrate Object CN Ear drum ! Ear bones in the cochlea, vibrates vibrates vibrates Melts sending a message to the brain. Audible Range of | Some people can’t hear higher pitched sounds. 2) Poor hearing like that is caused by: a) Wax blocking ears. b) Nerve damage. c) Damage caused by illnesses and infections. kee d) Old age and general deterioration. 3) Dogs, bats and dolphins can hear much higher frequencies than humans, as the chart shows. But then you Raney, eae knew that. 2) Loudness is measured in decibels, (dB). 3) Young people tend to hear quiet sounds much better than older people. 20dB 4048 60 dB 110 dB =p Ear damage likely 4) Someone with good hearing has a good audible range. Hearing can be damaged by too much loud noise such as noisy machinery, or loud music. There's a fair bit of biology on this page The thing is, you still have to learn it. Remember, we hear things because the air carries the ens ogee into our ear. Learn the Sn! about audible ranges for eel and jue es too. Sean eee _ hee ANDAISISINE 146 Warm-up and Worked Exam Questions 3 Have a bash at these questions, and see how far you get. There’s a worked example to get you into the swing of things. You won’t be surprised to find that it involves someone with really bad fashion sense in a disco — examiners seem to love that sort of thing. It’s probably best to do the warm-up questions first, for practice. Which travels faster: light or sound? Name three luminous objects. Name two uses of mirrors. What does the term refraction mean? Name one thing that sound can’t travel through. What does the term ‘amplitude’ of a sound wave refer to? What units do we use for measuring the volume of a sound? Tyrone had his favourite green t-shirt and blue jeans on for the school disco. He also wore red boots with white laces. (a) When he got to the disco there were red spotlights on the dance floor and green ones in the seating area. Complete the table below to show what colour Tyrone’s clothes seemed to be: Tyrone's clothes | colour in red light colour in green light : t-shirt This type of question is common. black green They can ask you about different black black situations, but don’t gSt confused — all you need to do is apply the rules you've learnt in this section ewe | red to the question. (4 marks) (b) At the end of the disco the DJ put the main lights on, so that everybody could see and leave the school safely. (i) What colour did Tyrone’s jeans now appear to be? (1 mark) (1 mark) SECTION ELEVEN — LIGHT AND SOUND  147 Exam Questions 2 The diagram below shows a cross section of the ear. Ear bones Cochlea Ear flap Ear drum Sound waves enter the ear at the ear flap and move towards the ear drum. (a) What happens to the ear drum when a sound wave hits it? (7 mark) (6b) Which part of the ear generates electrical signals to send to the brain? (1 mark) (c) Jim is playing his stereo in his bedroom. He turns the volume down, making the sound quieter. (i) What effect will this have on what’s happening to his ear drum? (1 mark) (ii) The next track on his CD has a much lower pitch. What difference will this make to the way that Jim’s ear drum moves? (1 mark) (d) Jim’s Gran doesn’t notice the noise of the stereo very much because she has poor hearing. Give three possible causes of her poor hearing. (3 marks) SECTION ELEVEN — LIGHT AND SOUND 148 Revision Summary Section Eleven tells you everything you need to know about light and sound. There are quite a few long words in there — and some pretty important diagrams too. Science is never easy of course, and you're bound to find some of the facts hard to learn. But, (as somebody famous once said) “Nothing can take the place of persistence” — in other words, if you want to achieve anything worthwhile or difficult, there’s no other option than to keep on slogging away at it. ‘Tis just the way of the world. 1)) How does light travel? ) Sketch a diagram of a pinhole camera. ies) ) Use a diagram to explain why the image is upside down and crossed over. ) What does opaque mean? ) What does transparent mean? Oo ) Which travels fastest, light or sound? Give a piece of evidence which shows this. 7) What do luminous and non-luminous mean? ) Describe how light gets from the Sun to an object and then to our eyes. ee) 9 ) Name three things that produce light. Name three things that reflect light. ] 0 ) What is a mirror? 11)] ) What is meant by a diffuse reflection? 12) What is the law of reflection? 13) Give three uses of mirrors. 14) What is refraction? 15) ) What does the word “medium” mean? 16) ) What happens when light goes from a less dense medium to a more dense medium? 17) ) What happens when light goes from a more dense medium to a less dense medium? 18) ) Explain in your own words why light “bends” as it enters a glass block. 19) ) Explain what is meant by dispersal of light. 20) ) How could you show that white light is not just one colour? 21) What is the jollyism for remembering the order of colours in a spectrum? 22) Which colour is bent the most through a prism? Which one is bent the least? 23) What colour of light will a red filter let through? 24) When white light hits a blue filter, then a red filter, no light gets through. Why not? 25) Why does something blue look blue in white light? 26) What happens to all the colours in white light when they hit a black object? 27) In white light red boots look red. What colour will they look in red light and why? 28) ) What does ‘audible range’ mean? 29) Why can’t you hear a ringing bell in a vacuum? 30) What does amplitude mean? 31) ) What does frequency mean? Explain the difference between high and low frequency sounds. SECTION ELEVEN — LIGHT AND SOUND  SECTION Twelve — THE EARTH AND BEYOND 149 That's what a day actually is — one complete 2 =" rotation of the Earth. AN, Se remmae 2) The Sun doesn’t really move, so as the Earth rotates, Day|| : > any place on its surface (like the UK, say) will timel| | mg time sometimes face the Sun (daytime) and other times G face away into dark space (night time). ole Seasons are ES ae 1) The Earth takes 365 4 days to orbit once around the Sun. That’s one year of course. (The extra % day is sorted out every leap year.) Each year has four seasons. 2) The seasons are caused by the tilt of the Earth’s axis. This tilt has two effects which both alter the heating effect of the Sun ina big way: Summer for the UK Winter for the UK March 21st - spring | ; Papamoa, Mid-winter patna e e = December 21st ~ Sun's rays spread | over alarge area | of land aN A fi ~~ Midsummer June 2)st September 22nd — autumn | 1h The north is tilted towards the Sun. 1) The north is now tilted 2) Look carefully and you'll see the northern away from the Sun. half of the Earth spends more time in 2) The north now spends less time sunlight than it does in darkness, in sunlight so days are shorter i.e. days are longer than nights. than nights. 3) Not only that, but the Sun’s rays cover 3) Also, the Sun’s rays cover a larger area a SMALL AREA of land, as shown. of land so the heat is more spread out. 4) So it gets warm and we have summer. 4) So it gets colder and we have winter. SECTION TWELVE — THE EARTH AND BEYOND 150 patti ek e Sun and Stars dor 1) The Sun “rises” in the EAST every morning. (Hence ‘Japan - land of the rising Sun’.) 2) The Sun “sets” in the WEST every evening. 3) The Sun is highest in the sky at midday. (12.00 noon in winter, but 1.00 pm in British Summer Time.) 4) So shadows are always shortest at midday. 5) In summer the Sun gets very high in the sky. 6) That’s why shadows are so short in summer. tg ine Be Star Pole This picture is like a long exposure taken over several hours at night time. It shows that the stars seem to move in circular paths around the night sky. The Pole Star in the north of the sky stays ‘fixed’ and the other stars ‘rotate’ slowly around it. This is all simply caused by the rotation of the Earth. (Stars are there day and night — but are just too dim path ofa star to see in daylight.) ' It's weird to think there might be life on other planets As physics goes, I‘d say this stuff isn’t too boring. It is a bit tricky to get your head round though, so it’s worth spending some time learning it all properly. SECTION TWELVE — THE EARTH AND BEYOND  (51 Satellites SRO TESS = Moons are “natural satellites” — because they’r Diagram not : é 3 to scale natural objects which orbit around planets. 2) Our Moon orbits the Earth in 28 days. It goes anticlockwise — that’s the same direction as the Earth spins. 3) The Moon appears to change shape as it goes through a full orbit of the Earth (over a 28 day period) as shown in the diagram. 4) This is because we only see the part of the Moon which is reflecting light from the Sun. 5) We see different amounts of the Moon’s sunny side as _____ View from | it orbits the Earth — that’s why it seems to change shape, because you can’t see the dark bits. Anything with mass will attract anything else with mass. In other words, everything in the Universe is attracted by the force of gravity to everything else. (But you only notice it when one of the things is really big, like a planet.) 2) The Earth and Moon are attracted by gravity — that’s what keeps the Moon in its orbit. 3) The heavier the object (or body) — the stronger the force of gravity (so big planets have high gravity). 4) The further the distance between objects — the weaker the gravitational attraction becomes. Zs SSS EIR STAI OTS Communication and Navigation Radio, TV and telephone signals are relayed round the world. 2) Monitoring the Weather Weather systems are observed to help weather forecasting. 3) Observing the Earth Spy satellites have military uses and satellite photos help to map the land. 4) Exploring the Solar System E.g. the Hubble telescope orbits the Earth. From there it gets a clear look at the Universe, unhindered by the atmosphere. This page is jam-packed with fascinating facts There’s a lot to learn on this page, so you might like to try the mini-essay method. Scribble : down a mini-essay that covers all the details on this page. Then check to see what you missed. SECTION Twelve — THE EARTH AND BEYOND 152 Solar System You need to know the order of the planets — do it by learning this little jollyism: Mercury, Venus, Earth, Mars, (Asteroids), Jupiter, Saturn, Uranus, Neptune, Pluto (My Very Energetic Maiden Aunt — Just Swam Under — North Pier) A planet is something which orbits around a star. 2) The Sun (at the centre of our Solar System) is a small star. The Earth is one of nine planets which orbit the Sun. 3) The Sun is really huge compared to the planets, and has a big mass — so its gravity is really strong. The pull from the Sun’s gravity is what keeps all the planets in their orbits. 4) The planets all move in elliptical orbits (elongated circles). 5) Planets don’t give out light but the Sun and other stars do. The Sun gives out a massive amount of heat and light. Just think of all those other planets out there None of the others look quite as suitable for living on as dear old Earth though. Mind you, most of them are so far away there’s no way of knowing about them. Scary. SECTION TWELVE — THE EARTH AND BEYOND  153 _ Solar System ortant In rn You don’t need to learn every last detail in this table. What you do need to do is get a good overall idea of how the planets compare to each other, e.g. biggest, smallest, farthest, nearest, etc. _ PLANET (eg.cm—incaseyou (numberof | — Wanttodraw them) Earth masses) op) es) oO MERCURY VENUS = — or i oO Sc EARTH iS MARS fo s “juerrer |: ‘ | SATURN Ee} PLUTO 1) Most of the stars you see at night are in our own galaxy — the Milky Way. 2) The Universe is made up of millions of galaxies. The others are all so far away they just look like small fuzzy stars. Other galaxies You are here in fig ‘ Loe : ae my the Milky Way —ris : : Know the difference between a planet, a star and a It sounds obvious, but you really need to get a feel for how these things fit together. You don’t have to learn the table, but the more stuff you know about the planets, the better. SECTION TWELVE— THE EARTH AND BEYOND 154