Get Science See inside


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A preview of chapters in the 11-14 science textbook GetScience. The book is a student companion to the Wikid course.

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Get Science See inside

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  2. 2. Chapters start with ‘understand’ or ‘good’ and progress to the more difficult material in ‘master’ or ‘expert’. Challenging questions have hints to help you – see next page. The number in brackets tells you how difficult the question is. It is the Level in the English National Curriculum. The pictures are as important as the words in helping to explain the Big Idea. Early questions get you to summarise and practise using the idea. The top part of a page connects to what you already know about the topic. Bold words are key scientific terms. To avoid cluttering the page, they are described in the glossary at the back. Later questions test your understanding more. Preview
  3. 3. Get Science Contents The Big Ideas Page Page 1 Explanations Adaptation 6 Forces 53 Behaviour 9 Geological time 58 Cells 11 Magnetism 60 Changing atmosphere 18 Microbes 63 Chemical patterns 22 Models 67 Chemical reactions 26 New life 70 Classification 30 Particles 73 Drugs 32 Solar system 81 Dynamic Earth 34 Theories 85 Electric current 37 Universe 87 Energy resources 41 Voltage 90 Energy transfer 44 Wave energy 93 Food webs 49 Weathering 98 2 Applications Decision making 101 Technology 103 3 Communication Collaboration 105 Interrogator 110 Communicator 107 4 Investigation Safe experimenter 113 Planner 118 Hypothesiser 115 5 Evidence Analyser 120 Reasoner 125 Evidence checker 123 Preview
  4. 4. Y7 Y8 Get Science Contents upd8 units Unit Sequence Page Unit Sequence Page A&E Blood 11 Electromancer Watcher 37 Birth 70 Seeker 60 Machines 103 Weaver 118 Therapy 85 Knower 90 Alien Far-side 53 Extinction Mammoths 18 Contact 120, 125 Apprentice 107 Probe 81 Polar Bears 6 Spore 87 Turtles 30, 9 Cook Hot stuff 44 Forensics CSI files 113 Ice-cream 73 Fake 73 Pancakes 26 Cold case 123 Inside story 67 Abduction 22 Unit Sequence Page Unit Sequence Page Catastrophe Evacuate 105 Pyrotechnics Skycolour 73 Etna 34 Burn 26 Damburst 98 Human torch 113.115 Hobbit 58 Reveal 22 Live & kicking Academy 11 Species at war Disease 63 Mucus 118 Pandemic 67 Wasted 32 Paradise island 49 Expo 123 Big science 103 nViz 2050 18, 85 Studio magic Drummer 93 Music 44 Venue 125 SimEnergy 41 Plug-it 110,107 Leaders 101 Festival 93 Preview
  5. 5. Extras at Cells 1 ...understand upd8 Link A&E > Blood What keeps you alive? Mary (58) pale, no pulse A lungs F skeleto-muscular K glucose drip Dylan (19) back pain, can’t move B intestines G nervous L restart heart Kasia (10) blue, hardly breathing C bone H respiratory N pin bone together Jack (2) weak, keeps being sick D heart I digestive N keep patient still Sam (32) arm broken E nerves J circulatory O clear airways Symptoms System affected Treatment Tissue/organ damaged If your heart stopped, your circulatory system couldn’t move blood through other organs. Delivery of oxygen and glucose would cease and you’d die. With no brain to control your nervous system, you’d be paralysed and unconscious. Without lungs, your respiratory system couldn’t get oxygen into your blood, or remove poisonous carbon dioxide. If your intestines stopped working, your digestive system couldn’t bring nutrients like glucose into your blood, so you’d starve. If the muscles and bones in your skeleto-muscular system seized up, you couldn’t move; and a fractured skull or ribs wouldn’t protect your most vital organs. 1 Summarise: Our bodies are made of many different ___. If any get ___ we could die. 2 Exemplify: Think of an organ system not shown on this page. Why is it important? (L4) 3 Use the idea: Match each casualty’s symptoms to the correct letters from the other columns. Describe how serious each patient’s condition is, and explain why. (L4) Got it? Preview
  6. 6. Extras at Cells 1 ...understand 12upd8 Link AE Blood Inside organs Got it? 1 Summarise: Your organs are made of ___ and your tissues are made of ___. These cells do the jobs that make your ___ work. To stay warm and ___, they need to transfer energy from ___ and ___. 2 Use the idea: Which two students don’t understand the Big Idea of cells? Correct their sentences. (L4) Maria: We have cells in some organs. David: Cells get energy by taking in glucose. Kasia: Each sort of tissue is made of different cells with different jobs. 3 Explain: a When you run, your circulatory system needs to send more blood through your leg muscles. Explain why. (L4) Hint? b How does the composition of your blood change as it flows past your brain cells. (L4) Hint? c Mr Evans had a stroke, which means a clot blocked a blood vessel in his brain. One side of his body is now paralysed. Explain why. (L5) Hint? Yes! Unlike their pictures, real cells are warm and active. 1000s of chemical reactions take place inside them. They convert nutrients from your blood into spare parts for growth and repair. All this takes energy and cells get it by reacting glucose with oxygen. Are cells actually alive? To make this happen, millions of these tiny compartments must make themselves shorter. They are your heart muscle cells.’d see its muscle tissue squeezing. Imagine zooming into your beating heart... In your brain, millions of nerve cells like this pass messages to each other. Cells make your brain tissue active. So you can sense things, think, and decide which muscles to move. glucose and oxygen from blood skin cell carbon dioxide and water Preview
  7. 7. Extras at Cells 1 ...understand upd8 Link AE Blood Long, thin nerve cells like this carry messages from your spine to muscle cells up to a metre away. Why do cells look different? Giant fat cells store nutrients, and add them to your blood when you need them. Tiny, flexible red blood cells squeeze through narrow blood vessels to bring oxygen to every cell. 1 Summarise: Cells have different shapes and ___ so they are suitable for different ___. 2 Deduce: Use the structures of each of these cells to match them to jobs D-F. (L4) 3 Explain: Each of these cells has 100s of tiny hairs on top of it so it looks like a brush. This brush of hairs keeps bending, and sweeping from left to right. What job could these cells be specialised to do? Explain why. (L5) Hint? 4 Solve: Read the description below and decide what job the cells do. (L5) Hint? ‘These cells keep dividing. New cells push older ones upwards and cut off their blood supply. Before each cell dies it turns everything left inside it into a hard protein. As the dead cells pile up, they make a solid plate.’ B This cell produces a jelly which slowly turns hard.A When this cell’s hairs vibrate, it sends a signal to the nerve below it. Specialist jobs D Build bones. E Take nutrients out of your intestines. F Detect sound. C The fringes on these cells let them absorb chemicals quickly. Got it? Preview
  8. 8. Extras at Link AE Blood Inside cells Cells 1 ...understand skin leaf What if cells get damaged? Every cell takes in supplies, carries out reactions and releases energy. Whatever its shape or size, it uses the same structures to do these jobs. Your brain and heart cells can last a lifetime, but skin cells wear out and need replacing. Cells make more cells by splitting into two. Some cells can’t divide, but stem cells keep dividing to replace the damaged ones. 1 Summarise: All cells are ___ from the same components, but plant cells have extra structures to provide ___ and let them make ___. Some cells can copy their contents and split into two ___ cells. Those that can’t, are replaced by ___ cells. 2 Recall: Name the cell parts that do each of these jobs. (L3) a Let in glucose and oxygen. b Make food. c Release energy. d Support a plant cell. (2) e Build new cell parts. (2) 3 Explain: a Jen cut her finger last week, but it looks fine now. How did she get more cells to repair it? (L3) b In diagrams, animal and plant cells are easy to tell apart. With photographs, like the one on the right, it’s more difficult. (L4) i What makes it look like an animal cell? ii What makes it look like a plant cell? iii Suggest why plants might not have chloroplasts in every cell. c Red blood cells have no nucleus and their cytoplasm is full of red protein, which they use to carry oxygen. Suggest why they cannot divide. (L5) Hint? Got it? 14 cytoplasm where chemical reactions make new cell parts chloroplasts which absorb sunlight and let plants make their own food a vacuole for support a cell wall for support a membrane to control what goes in and out a nucleus to store genes, which are instructions for building cells mitochondria where energy is released from glucose and oxygen Preview
  9. 9. Extras at Changing atmosphere 1 ...understand upd8 Link Extinction Mammoths Got it? Why worry about climate? 1. Summarise: The climate is the usual pattern of ___ and rainfall. When the climate changes, living things can find it harder to ___. 2. Exemplify: a Name an animal that has been made extinct by climate change recently. (L3) b Why did the climate change make it harder for the animal to survive? (L3) 3. Recall: The temperature is different everywhere, so scientists work out an average. How has Earth’s temperature changed in the past? (L3) 4. Explain: a Some people think mammoths went extinct because their woolly coats made them too hot. Explain another reason why a warm, wet climate could have made them die out. (L4) b Sabre-toothed tigers were fierce predators. They also became extinct at the end of an Ice Age. Use the ideas about climate change to suggest why they did not survive. (L5) Hint? c Earth has been hotter in the past than it is today. Explain why scientists worry about rising temperatures. (L5) Hint? Around 10,000BC, an ice age ended and the climate got warmer and wetter. That was bad news for this animal. Earth’s temperature is always going up and down. But most extinctions have happened after the climate warmed. Mammoths ate grass, but climate change let trees take over the grasslands. Lack of food pushed mammoths towards extinction. In 2004, golden toads were declared extinct. They had all died. Why? Their forest home became warmer and drier. Ponds dried up and their tadpoles couldn’t hatch. So climate change made them extinct. That’s happened many times before in Earth’s history. Mass extinctions Millions of years ago 500 250 today Temperature Preview
  10. 10. Extras at Changing atmosphere 1 ...understand upd8 Link Extinction Mammoths Got it? Past, present, future 1. Summarise: Carbon dioxide is a ___ gas. It helps keep the Earth at a suitable ___ so that life can exist. By studying past changes, we can ___ what might happen in the future. 2. Recall: The amount of water vapour in the atmosphere varies. List the other gases in the atmosphere with the one there is most of first. (L3) 3. Deduce: a How have temperature and carbon dioxide levels varied in the past? (L5) Hint? b How similar are the changes in temperature and carbon dioxide levels? (L5) Hint? c Explain why James Hanson is worried about present carbon dioxide levels. (L5) Hint? d Explain how scientists measure past levels of carbon dioxide. (L5) Hint? Scientist James Hansen believes that his grandchildren face climate chaos if we keep putting more carbon dioxide in the atmosphere. His argument is based on past climates. Scientists discover past carbon dioxide levels by digging out ice buried for thousands of years. Trapped air bubbles show what the climate and atmosphere were like when the ice formed. Carbon dioxide is a very small part of the atmosphere, but very important. It’s one of the ‘greenhouse gases’. Without them, Earth would be too cold to live on. Argon 1% Carbon Dioxide 0.04% Oxygen 21% Nitrogen 78% 400 200 0 Thousands of years before now carbon dioxide temperature Present carbon dioxide levels The graph shows that carbon dioxide levels are higher now than they have been for the past 400,000 years. Preview
  11. 11. Extras at Changing atmosphere 2 ...understand upd8 Link nViz 2050 Got it? Out of balance? 1. Summarise: Carbon dioxide is added to the ___ by both natural and ___ activities. 2. Exemplify: Describe how natural and human activities affect atmospheric carbon dioxide. (L4) Hint? 3. Explain: a Calculate the total carbon dioxide human activities release each year. (L4) b How much do natural sources release? (L4) c Why do scientists worry more about CO2 from human activities? (L5) d What consequences could there be if CO2 levels continue to rise? (L5) In this toy, many things work together to keep the balance. It’s the same with the carbon dioxide in the atmosphere. But it only takes one change to cause problems. Animals breathe out CO2 and volcanoes add more. Plants absorb CO2 and use it for photosynthesis. Human activities like deforestation and burning fossil fuels release extra carbon dioxide. Until recently, the CO2 going in and out of the atmosphere was balanced. Now we have upset the balance. Earth’s oceans can absorb part of the excess, but not forever. Temperaturerise (°C)carbon dioxide CO2 To predict future climates, scientists use computer models. They show that extra greenhouse gases, like carbon dioxide, methane and water vapour, will cause global warming. Preview
  12. 12. Extras at Changing atmosphere 2 ...master upd8 Link nViz 2050 Got it? The greenhouse effect 1. Summarise: To stay at the same temperature, Earth must emit as much energy as it ___. Solar ___ can get through the ___, but some of the ___ Earth emits is absorbed by ___ gases. 2. Deduce: Sam beamed infra-red radiation into a jar of air and a jar of carbon dioxide. An hour later the carbon dioxide jar was much warmer. Explain why. (L5) Hint? 3. Explain: a Explain why Earth’s temperature doesn’t usually change much. (L5) Hint? b Use a model to explain how CO2 can make Earth’s temperature rise. (L6) Hint? c The amount of CO2 we release is rising faster than ever. Explain why. (L6) Hint? d Roger doesn’t understand how a little bit of extra CO2 could warm the Earth. Write a step by step explanation that he can’t fail to understand. (L7) Hint? If you’re warm, you take your jacket off and cool down. Earth has a jacket too – the greenhouse gases in the atmosphere. That jacket is getting thicker every year - and we can’t take it off. Earth could soon get very uncomfortable to live on. Greenhouse gases are spread all through the Earth’s atmosphere. The more we add, the more energy they trap... Earth absorbs more than it emits, and its temperature rises. Deforestation means less carbon dioxide is absorbed. So levels are rising faster than ever. As Earth’s population increases we use more energy, burn more fossil fuels and release more carbon dioxide. greenhouse gases solar energy in energy absorbed and emitted energy trapped infra-red radiation out atmosphere warms Preview
  13. 13. Extras at Got it? Dynamic Earth ...understand Journey to the centre of the Earth In a famous story, a scientist falls down a volcanic pipe, and finds prehistoric life. In reality, the Earth is solid. But if you could fall through the planet, you would travel through three different layers. A volcanologist predicts eruptions and whether they will send out lava, gas or ash. Summarise: Earth has 3 layers: the ___ , ___ and ___ . The core is hot. Convection carries ___ up through the ___ towards the crust. In places, the mantle melts to form ___. If this breaks through the crust, it becomes ___. Compare: Which is hottest, the core or mantle? (L4) How do magma and lava differ? (L4) How do ash, gas and lava differ? (L4) Deduce: Why does magma solidify faster if it flows into a lake? (L5) Hint? No-one can stop a volcano erupting. How do volcanologists reduce the number of deaths volcanoes cause? (L5) Hint? A volcanic eruption often affects more than one country. Suggest why. (L5) Hint? Food crops grow well in soil that contains volcanic ash. Suggest a possible problem that could cause. (L5) Hint? upd8 Link Catastrophe Etna 34 1. 2. a b c 3. a b c d High temperatures and huge pressures make the solid rocks flow like liquids. They carry heat upwards by convection and make volcanoes possible. Crust 1) The crust passes by quickly. It’s just a thin skin of rocks. 2) Most of your journey is through the mantle. The temperature is unbearable - over 3000o C. Some rocks have melted, to form magma. This lies just below the crust, ready to shoot out of the Earth as lava. Mantle 3) Finally, you reach the source of Earth’s heat, a core made of molten iron. Its temperature is over 5000o C Core Preview
  14. 14. Extras at Dynamic Earth ...understand 35upd8 Link Catastrophe Etna Rock detective Got it? Summarise: Volcanoes bring magma to the surface to form ___ rocks. The size of their ___ tells us how fast they cooled. ___ rock forms when heat and ___ change existing ___. Compare: Describe the differences between: The crystals in granite and basalt. (L4) The crystals in granite and slate. (L4) Igneous and metamorphic rocks. (L4) This is where rocks are born, out of the fire of a volcano. By examining a rock carefully, you can deduce how it formed. This is basalt. It has tiny crystals. This means it turned to solid quickly. It must have formed on the surface, where it could lose heat quickly. Deduce: What sorts of rocks are these? Gneiss – dense and hard, with layers. (L5) Obsidian - non-porous with microscopic crystals. (L5) Gabbro – has large, attractive crystals. (L5) Explain: Why does granite cool slowly? (L5) Hint? What makes a rock metamorphic? (L5) Hint? Why are metamorphic rocks non-porous? (L5) Hint? 1. 2. a b c 3. a b c 4. a b c Igneous rocks, like basalt and granite, have interlocked crystals, which makes them hard. Water can’t get through, so they are non-porous. Deep underground, limestone and mudstone were heated by ris- ing magma and squeezed, which changed their structure. Marble and slate are dense and hard, and slate has layers. They were not made by cooling lava. They are changed or metamorphic rocks. slatemarble limestone mudstone HEAT PRESSURE This is granite. It has large crystals. They form slowly, so it must have taken longer to cool. It solidified inside the crust, insulated by rock. Preview
  15. 15. Extras at Low Density High Density Gas bubbles break up erupting magma, to form huge ash clouds. upd8 Link Catastrophe Etna 36 Dynamic Earth ...master Countdown to disaster Got it? Summarise: Volcanoes erupt when molten _____ rises up through the ____ and breaks through to the surface. Ash, ____ and ___ escape and can change the appearance of the ____ . Explain: What makes magma rise? (L5) Hint? Why do gases escape? (L5) Hint? How is volcanic ash made? (L5) Hint? Deduce: What can you tell about the lava that produced this volcano? (L6) Hint? Explain: In the past, a giant volcanic eruption killed most plants and animals on Earth. How could it affect every continent? (L6) Hint? Why is the rock on the sides of a volcano in layers? (L6) Hint? Why do volcanologists need to know how viscous new lava is? (L6) Hint? Predict: When magma cools suddenly it shatters like glass. When water boils it produces clouds of steam. Imagine a volcano erupting under a glacier. Suggest what damage the volcano could do. (L7) Hint? What signs might indicate that a volcano was about to erupt? (L7) Hint? It looks innocent from above, but this volcano is about to erupt. 1. 2. a b c 3. 4. a b c 5. a b Dissolved gases explode out of the pipe, like fizz from a bottle. Magma is less dense than solid rock, so it rises. Lava flows Runny lava flows fast and travels a long way before it solidifies. It forms gently sloping cones. Thick, viscous, lava flows slowly. It forms a steep cone. The pipe feeds magma to the surface through a weak spot in the crust. Preview
  16. 16. Extras at Forces ...understand upd8 Link Alien Farside Got it? What can forces do? 1. Summarise: Forces can make an object change its shape, ___ or ___. We use ___ to show their ___. 2. Use: A skateboard is sliding downhill. You try to stop it. Sketch the skateboard and add an arrow to show the force you applied. (L4) 3. Predict: Suppose Venus hit the ball even harder. What difference would that make to the racket and the ball? (L4) Hint? 4. Deduce: When this carriage got to the bend it changed direction. A force from the track made it turn. Which arrow shows the force correctly? (L4) 5. Compare: How does the distance from Earth affect a satellite’s speed? (L5) Forces can slow things down too. The arms of the tackler pull backwards to stop the player in his tracks. Instead of changing speed, a force from the side makes the female skater change direction and move in a circle. Venus Williams is one of the fastest servers in history. The strings of her racket push the ball with great force. It speeds up to an amazing128mph (206km/hr). Not all forces rely on contact. The invisible pull of gravity is what makes the Moon circle the Earth. Gravity keeps any satellite in a circular orbit, if its speed and distance are right. fast slow medium gravity a force towards centre of Earth pull Preview
  17. 17. Extras at Forces ...understand upd8 Link Alien Farside Got it? Combining forces 1. Summarise: If the forces on an object are balanced it will stay at the same ___. If they are ___ its speed will change. It gets faster if the forward force is ___and slower if the ___ force is bigger. 2. Exemplify: a Draw this airship and add arrows to show the forces that make it move at a steady speed. (L3) b Add another pair of arrows to show that it is also rising at a steady speed. (L4) c On a second airship, draw forces that would make it go faster and faster. (L4) 3. Use: A boat is crossing a lake. The wind pushes with a 500 N force, but there is 300 N of friction. a Sketch the boat and forces. (L4) b What is the resultant force? (L5) c If you want to go faster you need a bigger resultant force. Describe 2 ways you could make the resultant force bigger. (L5) Hint? 4. Explain: You ride a bike. There is 150 N of friction, and your driving force is 200 N. What is the resultant force, and what effect will it have? (L5) Hint? In a clash between a car and motorbike, the bike usually loses. It’s best for the rider to avoid a collision. But how do bikes speed up or slow down, and what decides their maximum speed? It all depends on the resultant force when all the others combine. The rider twists the throttle. He makes the forward force bigger than the backwards force, so his speed increases. The bike’s speed makes friction increase. The forces are now equal, so the speed stays the same. The rider eases back on the throttle. The forward force is smaller, so the speed decreases. Unbalanced forces friction 1000 N driving force 2000 N resultant force 1000 N speed increases Balanced forces driving force 2000 Nfriction 2000 N resultant force 0 N speed unchanged Unbalanced forces. resultant force 1000 Nspeed decreases friction 2000 N driving force 1000 N Unbalanced forces Preview
  18. 18. Extras at Forces ...understand upd8 Link Alien Farside Got it? Lose weight in space 1. Summarise: Mass is the amount of ___ an object is made from. Weight depends on mass and on the strength of ___. An object’s weight changes when ___ changes, but its mass always stays the ___ unless you ___ some of its atoms away. 2. Recall: a How does weight change as you get further from the surface of the Earth? (L3) b How would your weight change if you went to a planet with a bigger mass like Jupiter? (L3) c Astronauts can jump much higher on the moon than on Earth. Suggest why? (L5) 3. Use: At the Earth’s surface, an astronaut weighs 500N. Show how she can calculate her mass. (L4) Hint? 4. Explain: An astronaut eats a meal on the Moon. Her mass and weight both change. Explain why. (L5) Hint? 5. Predict: You are returning to Earth in a space elevator. Explain how your weight changes as you get closer to the surface. (L5) Hint? In the future, tourism could be very different. The space elevator could take you 40,000 km up, and then it’s off to the Moon. Going into space would be an easy way to lose weight. Weight is the force of gravity, pulling towards the centre of the Earth. On the surface it is strong and he weighs a lot. As the elevator rises further from the Earth, gravity decreases and he weighs less. Celebration on the Moon. Gravity is much less than on Earth because the Moon has less mass. A force meter works in a similar way to scales. The bigger the weight, the more the length of the spring inside it changes. Bigger weights make the spring longer. Mass Unfortunately, his mass stayed exactly the same for the whole trip. Mass is the amount of stuff (atoms) he’s made of. The scales actually measure weight in Newtons and then convert it to kilograms. The gravity at the Earth’s surface is 10 N/kg. The weaker the gravity the smaller the number you divide by. mass in kilograms = weight in Newtons 10 Preview
  19. 19. Extras at Forces ...master upd8 Link Alien Farside Got it? Air resistance 1. Summarise: As an object’s speed increases, its air___ goes up too. When the resultant ___on the object is cut to ___, its speed can’t increase. ___ is a force that also ____ motion. 2. Explain: As you walk, friction stops one foot sliding while you push the other forward. Skaters vary this friction by angling their blades. Explain when they need low friction and when they need high friction. (L6) Hint? 3. Use: Before his parachute opened, Mark was falling at a constant speed. a Sketch him and his parachute and show the forces on them. (L5) b Mark’s parachute opens. Sketch the forces now and describe their effect. (L7) Hint? c How will the air resistance change as he continues to fall? (L6) Hint? Friction As the jumper falls he’ll get faster. But if he drops far enough his speed will eventually stop increasing. Why? He takes off. The only force acting is gravity, so he quickly gains speed. Friction is a nuisance for Kasia. Her pushing force isn’t big enough to move the sledge. As he falls, air pushes back on him. This air resistance opposes gravity. It cuts the resultant force, so his speed increases more slowly. The faster he falls, the bigger the air resistance. When it balances gravity, he stays at the same speed. Friction always tries to stop one surface moving over another. Eva makes use of friction. It stops her sliding on tight turns. gravity gravity gravity air resistanceair resistance pushing force friction no movement pushing force friction pushfriction Preview
  20. 20. Extras at Forces ...master upd8 Link Alien Farside Got it? Speed 1. Summarise: The average speed is the total ___ divided by the total ___. The more steep a distance-time graph is, the greater the ___. 2. Exemplify: a A runner took 10 seconds to run the 1st 50 metres of a race and 20 seconds to run the last 200 metres. Did his speed change? (L5) Hint? b During which part of the race would his distance-time graph be steeper? (L5) Hint? c A driver travels 100 km in 2 hours, stops for an hour and then travels 200 km in 2 hours. Draw the distance-time graph. (L6) 3. Explain: A sprinter and cyclist set off at the same time. Describe what happened during the 1st 10 s and explain why. (L7) Hint? Why was Bolt slower? A distance-time graph can solve the puzzle. The relay team ran 400 metres (m) in a time of 37.10 seconds (s) average = 400 m = 10.78 m/s speed 37.10 s The Jamaican crowd had plenty to cheer about. Bolt took the 100 metre world record in 9.58 seconds. Then the relay team took gold with a speed that was even faster. Don’t believe it? You calculate average speed with this formula: average = distance speed time in metres per second Bolt’s average speed = 100 metres (m) 9.58 seconds (s) = only 10.44 m/s In the relay, only the first runner had to speed up. The others were running before they took the baton, so their average speed was faster. Distancerun(m) Time (s) distance(m) 0 10 0 5 40 80 100 cyclist sprinter The arrows show the times Bolt took to run each 10m. As the times get shorter, his speed increases and the graph gets steeper. Time after start (s) The 4th and 5th arrows are the same length and the graph is a straight line. His speed has stopped increasing, so he now has a constant speed. Preview
  21. 21. Extras at Models ...understand upd8 Link Cook Inside story How can we explain the invisible? Ice-cream becomes a runny liquid when it warms up. Why? Replacing something difficult to think about (particles) with something easy and familiar (an audience) is called using a model. It’s not easy to answer. You can’t see what’s happening inside. Ice-cream particles are far too small. Imagine ice-cream particles are like an audience. In the solid form, the people stay in their places. Heating gives the audience (ice cream) energy. The people (particles) start moving around and they spread out. So that’s why the ice-cream becomes runny. Got it? 1. Summarise: Models help scientists explain scientific ideas. They use something ___ to represent ___ we cannot see, like particles. Physical models use ___. Thinking models use ___ and computer models show how things ___ or change with time. 2. Exemplify: Use a model to explain why chocolate goes runny when you heat it. You could draw the model (L3) or describe it. (L4) 3. Recognise: Three students wrote about models. Which one doesn’t understand what they are? (L4) Jay: they are not completely realistic but they explain how real things behave. Kuba: they can be objects, animations or analogies that help explain things. Karen: they are exact 3D copies of things. 4. Use: Emma uses models to explain why her cake tastes so good: i Gas bubbles in the cake mix blow up like balloons as it bakes. ii The sponge shows what her cake is like inside. a Which is a thinking model? (L3) b Which properties of Emma’s cake could her second model explain? (L4) Hint? c Emma’s dad smelt the cake as soon as he opened the front door. Draw a particle picture to explain how the smell got from the cake to his nose. (L4) Hint? d In part c you used a model. How does it make the job of explaining easier? (L5) Hint? Thinking models use analogies e.g. solid particles are like people in an audience. Physical models use objects e.g. Lego bricks, to represent particles. Computer models show how things move or change with time. Preview
  22. 22. Extras at Models ...understand upd8 Link Cook Inside story Using models Why does a runny egg turn solid when you cook it? To explain something using a model, follow these 3 steps: Explanation: “Eggs turn solid as they cook because their particles unwind and tangle.” What happens next? “The particles tangle up into a solid lump.” Characters: “Let’s use balls of string to represent egg particles.” Action: “When they get hot, the string unwinds.” Got it? 1. Summarise: Models use ___ to represent real things and actions to ___ what they do. To use a model, choose the characters and ___. Play the model in your ___, like a ___, and ___ what happens next. Then match the model to the real thing and use it to ___ what happens. 2. Use: Pancackes contain egg, flour and milk. a Why are egg particles like balls of string? (L4) Hint? b Eggs go solid when heated. How does the model make this easier to understand? (L5) Hint? c If you don’t add the egg, pancakes fall apart. Use the model to explain how egg particles hold flour and milk particles together. (L5) Hint? 3. Explain: Ben’s dentist showed a model to explain how cola harms teeth. He dropped acid onto a piece of marble. The solid dissolved. a One character in the dentist’s model is the acid. What is the other one? (L4) Hint? b Suggest why the dentist chose acid to represent cola. (L4) Hint? c What makes marble a good model for a tooth? (L4) Hint? d How does the model make tooth decay easier to explain? (L5) Hint? e Sugar has no effect on marble but it causes severe tooth decay. Use the model to suggest what happens to sugar in your mouth. (L5) Hint? 1. Choose characters to represent the real thing and actions to show what they do. 2. Decide what happens next by playing the model in your mind, like a movie. 3. Match the model to the real thing and use it to explain what happens. Preview
  23. 23. Extras at Models ...master upd8 Link Species at war Pandemic Is your model good enough? Karen wants a model to understand her immune system. How does it fight off microbes to keep her healthy? To decide if the model is ‘good enough’ we need to see what it can explain. A. There are more macrophages in the organs that microbes enter more easily, like your lungs. Observations to explain... B. When scientists destroyed the macrophages, in a tissue, it filled up with microbes. C. Macrophages don’t have eyes but they recognise microbes. D. Macrophages can destroy microbes. If it has too many weaknesses we can change its characters or actions to improve it. Got it? 1. Summarise: To decide if a model is ‘good’ ___ , we see how many observations it can ___. Every model has it strengths and ___ . 2. Exemplify: Ben uses a thinking model to describe what macrophages do. “My macrophages are like piranhas. When they detect any microbes, they attack them ferociously.” 3. Recognise: Jen uses a model based on Karen’s. “This is how macrophages guard my body. They scan the surfaces of microbes for chemicals that normal body cells don’t have.” Which of observations A to D, does this model explain? (L5) 4. Explain: Which of these do you agree with? Explain why. (L6) a Simple models can be ‘good enough’ to explain ideas. b Models can be improved by changing their characters or actions. c Models aren’t useful unless they are totally realistic. 5. Predict: Carl uses a different model to explain how macrophages work. “Macrophages are like blobs of slime. They don’t have fixed shapes, so their cytoplasm flows around things.” Extend Ben’s model to explain how macrophages could trap microbes. (L6) 6. Solve: Karis used a high-powered microscope to look at macrophages. She saw tiny bags of fluid in their cytoplasm. These are lysosomes. They contain enzymes to break down fats, carbohydrates and proteins. Use this new information to extend Carl’s model. Explain how macrophages could destroy microbes. (L7) Karen’s model Skin is a tough barrier. It keeps most microbes out. If any break through, your immune system deals with them. Its security guards are cells called macrophages which patrol the tissues beneath your skin.4 4 8 8 Preview
  24. 24. Extras at Particles 1 ...understand upd8 Link Forensics Fake Why are materials so different? Everything is made up of particles. Air, water and rock feel different because their particles have different amounts of energy. In a solid like rock, the particles have less energy. A force of attraction keeps them in place. They can only vibrate. In a gas like air, the particles have most energy. They break away from their neighbours, and move around very quickly. In a liquid like water, the particles have more energy. They are still held close together, but they can move around. Got it? 1. Summarise: Everything is made from moving ___. Solids, liquids and ___ are different because their particles have different ___ of energy. Solid particles have least energy, so they can only ___. Gas particles have most ___ so they ___ around freely. 2. Use: Say whether each of these is a solid, liquid or gas: wood, steam, milk (L4), toothpaste, jelly and a sponge. (L5) 3. Explain: Use ideas about particles to explain these observations: a Rock is hard, strong and heavy. (L4) b Rock and water cannot be squashed, but air can. (L5) c Cooking smells can spread to fill the whole house. (L5) Hint? d Boats can move through water but not through ice. (L5) Hint? e Dry sand contains the same particles as rock, but flows like a liquid. (L5) Hint? Hard Rock Moving Air Flowing Water Preview
  25. 25. Extras at Particles 1 ...understand upd8 Link Forensics Fake Particle explanations Solids turn into liquids if you heat them enough. This is a change of state. Sugar cubes dissolve in tea. The smell of perfume reaches your nose. Moving tea particles hit the sugar and separate the particles. Individual sugar particles are too small to be seen. Got it? 1. Summarise: The idea of particles explains many observations. Changes of state are caused by changes in the amount of ___ particles have. Dissolving is different. It happens when particles ___. 2. Use: Draw a particle picture to show: a What would happen to the particles in molten gold if you continued to heat it. (L4) b What would happen if a small piece of silver was dropped into the molten gold. (L4) 3. Deduce: Use the data in the table below to find: a The temperature at which gold becomes a gas. (L4) b The temperature at which mercury melts. (L4) c Whether mercury is a solid, liquid or gas at 0°C. (L5) d The state gold is in at 900°C. (L5) metal melting point (°C) boiling point (°C) gold 1100 2856 mercury -39 357 Some liquid particles have more energy than others. The most energetic particles escape and mix with the air – they evaporate. Heating adds energy, so the particles in the gold bar vibrate more. Eventually, they break free and form molten gold. Preview
  26. 26. Extras at Particles 1 ...understand upd8 Link Forensics Fake Separating mixtures There are only water particles in distilled water, so it is pure. We can separate substances if they have different properties: Got it? 1. Summarise: You can separate the substances in a mixture if they have different properties. If their boiling points differ use ___. If they have different solubilities use ___. If one substance has large, insoluble particles, use ___. 2. Use: Name the methods that could be used to separate each of these mixtures: a Tea leaves from tea. b Water from ink. c The food colourings in a sweet. d Water from salty water. (L5) 3. Explain: Salt is often found mixed with sand. a Explain how you could use water to separate sand from salt. (L5) Hint? b What difference between sand and salt makes this possible? (L5) Hint? c Draw particle pictures to show the sand and salt at each step in your method. (L5) Hint? d Explain how you could separate water from a mixture of salt and water. (L5) e What difference between water and salt makes this possible? (L5) Hint? Pure water, or is it? Bottled water contains dissolved substances. It is a mixture. Distillation works because the particles with the lowest boiling point leave the mixture first. Filtration separates liquid particles from large insoluble ones. Chromatography works because the most soluble particles move further. solvent X Filter paper traps sand but lets water through.The particles in red and yellow ink separate as the solvent moves them upwards. alcohol water and alcohol Preview
  27. 27. Extras at Glossary 127 A Absorb Acidic Actions Adaptations Addictive Air resistance Alcohol Alert Alkaline Alveoli Ammeter Amphibian Amplitude Angle of incidence Angle of reflection Antibodies Atoms Attract To take something in e.g. lungs absorb oxygen. A solution with a pH less than 7. In a model, the actions are what the characters do. The physical features or behaviours that make an animal or plant better suited to their environment. Something that changes your brain in a way that makes it difficult for you to stop taking it. The force produced when air pushes against a moving object. It increases as the object’s speed increases. A legal drug found in beverages like beer and wine. Wide awake and ready to react quickly. A solution with a pH greater than 7. Tiny air sacs in the lungs. Their large surface area, thin walls and good blood supply allow blood to absorb oxygen quickly. A device that measures the size of an electric current in amps. A group of cold blooded vertebrates that lay their eggs in water and have smooth, moist skin. The size of the vibrations that produce a sound or the disturbance a wave causes. On an oscilloscope trace it is half the height of a wave. The angle between the incident ray and the normal. The angle between the reflected ray and the normal. Molecules made by B-cells which lock onto specific pathogens and make them easier to destroy. The smallest particles in an element. They are different in each element and cannot be broken down into anything simpler. Pull towards each other like the opposite poles of a magnet. 16 22 68 6 32 56 32 32 22 15 37 31 95 96 96 64 76 60 Preview
  28. 28. GetScience is different to most textbooks in lots of ways - to help you learn better Don’t get stuck – get science! The book was written by many teachers and writers: Main authors: Gemma Young, Ben Rogers, Alison Dennis, Pam Large and Tony Sherborne With Sophie Boles, Gary Talbot, David Hinchley, Nigel Heslop, Ed Walsh, Lucy Austin and Joanne Porter Scholio Educational Research Publishing The Big Idea is clear on every page 4 Pictures help you ‘get it’ so there are fewer words 4 The questions are about science, not writing 4 The pages are easy to read 4 You can understand the science and it’s interesting 4 Preview