Initial Teacher Training
KS3 Physics Objectives and Suggested Acti 7I Energy resources Suggested action QCA sobj Identify fuels as (a) Review student understanding of the word 'fuel', and brainstorm types of fuel sources of heat, and what they are used for. Introduce the definition that when fuels react with light and movement oxygen they produce energy (b) Use a bunsen burner to heat water until it boils. Describe the water and ask where the energy has come from Recall that light, heat and movement are all forms of energy
(a) Demonstrate igniting a bubble of methane. Highlight that the methane has reacted with oxygen and heat, sound and light energy is given off. Discuss whether the explosion could also move objects (b) Students to work in small groups and to think of as many everyday uses of the word 'energy'. Typical answers include the word in many everday contexts eg ' I havent got the energy for this'. Use the answers to discuss and develop the idea that there are different types of energy such as heat, light, movement and sound
Recognise simple energy transfers
(a) Discuss ways in which energy can be stored eg in food, in petrol, by lifting objects up or stored in a spring, and then ways in which energy can be detected ie as heat, light, movement, sound and electricity (b) Consider the energy transfers in a light bulb. What type of energy has gone in (electricity) and what types come out (heat and sound) (c) Use a circus of toys and consider energy transfers in each. Students could identify the type of energy store and what this energy has been converted into.
Identify some fossil (a) Show students pieces of coal and sealed samples of oil. Identify them as being fuels 'fossil fuels' and ask what students understand by the word 'fossil' (b) Students to present a poster on what fossil fuels are, based on information from a video, software or internet resource; Give examples of how we can save fuels
(a) Discuss the fuels of the future, in particular, emphasise the need to use less fossil fuel. What could be done in everyday life and how much would people be prepared to sacrifice eg. smaller car or less flights abroad. Consider whether sacrifices need to be made - think about simple changes of behaviour, such as turning off computers and electrical items on standby, or boiling only the amount of water that is needed rather than a full kettle, running a shower for 1 minute less, walking/cycling rather than driving, etc. (b) Show the students images of various energy sources eg wind turbine, waterfall, bunsen burner and ask to categorise as fossil fuel or not.
Know that fossil fuels are nonrenewable
(a) Demonstrate burning a wooden splint or match. Emphasise that when the fuel is gone we cant use it again. Consolidate by showing a cigarette lighter and asking what use is it when it is empty? Define 'non-renewable fuels' as those that cant be renewed easily and so will eventually be used up (b) Brainstorm what fuels get used up when they burn (all of them!) but then ask which can be replaced within a short time. Identify wood, wax, and alcohol as fuels that can be produced relatively quickly. Highlight that there are other sources of energy than fuel.
Understand why we (a) Students could make a leaflet suitable for Year 6 pupils raising the issues of must conserve fossil using fossil fuels and suggested ways to conserve them fuels (b) Distinguish between 'conserve' used here as something people can do to minimise consumption and 'the principle of conversation of energy' which students will meet later which has a stricter use Know how fossil fuels were formed
(a) Students to make cards with labels for significant eras during Earth's history eg: Formation of Earth, Formation of Oceans; First Life, Jurassic and First Man. Position these to the correct scale around the perimeter of the classroom and emphasise that there has been a very long time for fossil fuels to be made, that the fuels take millions of years to form but that we are using them up at an much faster rate (b) Show a suitable video or animation that shows the formation of fossil fuels, in particular, the time scale and the fact that they were originally made up of living matter
Know that fossil fuels do not last forever
(a) Students to design a pamphlet for younger students summarising the problems about using fossil fuels (they are non-renewable, contribute to global warming and acid rain, and countries are not self sufficient) (b) Analyse data that shows type of fuel, energy it produces per unit volume, cost, and time to replenish
Understand the (a) Demonstrate the use of a photovoltaic device, and allow students to highlight difference between the advantage that no fuel is being used. Identify solar energy as being a renewables and non- renewable source of energy. Brainstorm all energy resources and students to renewables separate into those that are 'renewable' and those that are 'non-renewable' (b) Make a solar panel by heating water left in the sun. Students compete in trying to make their water the hottest by using aluminium cartons and black paper. Ask the question 'Is heating water like this better than using electricity?' and discuss answers. Students may consider electricty as being 'better' because it is percieved as being more efficient but the definition of what is a better fuel could develop wider issues eg debate about environmental concerns. Also note that electricity can be produce by different resources.
Identify renewable energy resources from a list
(a) Students could play snap by using cards with different energy sources draw or written on them. When two renewable energy sources are consecutive we have 'snap' (b) Students create their own wordsearch using a list of renewable energy source and swap with a partner
Explain how energy (a) Students to consider a scenerio (such as SATIS: Ashton Island) where they resources are have to survive on a desert island without fossil fuels. They are to consider renewable strategies for maintaining short and long-term survival (eg how to cook food, forestry of trees) explaining why their suggestions involve renewable energy resources (b) Ask students to invent a useful device for the future. Encourage creative approaches, but based on science, eg wind farms at sea. This workcould be used to generate discussion on pros and cons of renewable energy sources and a comparison of energy resources available to less-developed nations. Know that renewable energy resources are used to generate electricity
(a) Show students a wind up radio or torch. Ask students how it works and why they are so important in less-developed or isolated countries. Try to elicit the response that a small generator converts movement to electricity which charges a battery. Consider ways to turn the handle using renewable energy resources eg falling water, wind, wave (b) Provide students information about contemporary hybrid cars that switch from fuel driven to battery powered. Survey friends and relatives to find to if people would ever consider buying one. (c) Research the National Grid and finding out how much 'conventional' electricity comes from renewable energy sources
Explain how nonrenewable energy resources are used to generate electricity
(a) Show students a model generator or wind up radio. Highlight an energy transfer in the generator where movement energy is converted into electricity. Challenge students to devise ways in which coal, oil or gas could be used to turn the handle on the generator. Try to elicit need for steam turning turbines as efficiently as possible (b) Students to make a model power station using moveable parts eg turbine circle and paper fastener, identifying key energy changes
Know that food is (a) Use custard powder and a candle to blow the lid from a large coffee tin (full the energy resource risk asessments needed). Highlight that the stored energy in the powder and the for animals oxygen has been converted to heat, light and sound (b) Ask students in groups to investigate the energy resource in foods, eg breakfast cereal, crisps, marshmallow by burning them and measuring the rise in temperature of some water. Establish that although our bodies don't 'burn' fuels by lighting them like this, we do burn them in a different way Know that light is the energy source for plants
(a) Compare plants to a laptop. The laptop can run from battery power only but the battery is topped up by plugging it into the mains every now and again. Similarly, plants use energy all the time (respiration) but a good dose of sunshine tops up the sugar levels which is used as an energy resource (photosynthesis). (b) Students to handle molecular models of large sugar molecules, which they can break up. Emphasise that the plant gets it energy by breaking up the molecules but most plants also use sunlight energy to make the sugar molecule up again.
Identify energy flow (a) Students to devise their own food chains that include humans. Question what through food chain happens to the energy contained in our food. Try to elicit the answers: it is used to make us grow (ie some is stored), it is used by us to do things, and some of it is passed straight out of the body. Guess the fraction of energy that is stored at each stage of the food chain considering how much food an animal eats in its lifetime compared to its body mass (b) Look at packets of various foods and find the energy label in kJ or cal. Introduce a calorie as an old fashioned measured of energy and discuss the consequences of eating more or less than the energy you burn Know that a food chain can be extended to show the link to sunlight
(a) Students to devise their own food chains and then asked "where does this get its energy from", pointing at the first card. Keep asking the same question until they conclude that plants get their energy from the Sun. Students to write this conclusion in their notes (b) Students to examine in small groups why wide animals often give birth during the Spring eg many birds. Relate to availability of food and increase in sunlight.
Understand that the sun is the energy source for almost all the Earthâ€™s energy resources
(a) Students to make 16 cards by drawing symbols of their choice on the card. The cards produced will have symbols of : Sun (x4), trees, coal, fire, wind, turbine, electricity, grass, cows, milk, plankton, oil, nuclear. Ask students to arrange cards into 4 energy chains (Sun to trees to coal to fire; Sun to wind to turbine to electricty, Sun to grass to cows to milk; and Sun to plankton to oil Conclude that all energy except nuclear come from the Sun (b) Imagine a scenario when a large volcano has erupted and the entire Earth is covered in a permanent thick dust cloud that sunlight cannot penetrate. How would people survive with no sun when the fossil fuels run out? Encourage imaginative answers that use science eg large solar panels in space but also encourage answers that rely on nuclear and tidal power
Know that different fuels produce different amounts of energy (including foods)
(a) Burn various types of fuel in spirit burners beneath a beaker of water and compare temperature rise. (b) Compare the energy labels on different food products and tabulate which foodstuffs give the most energy per 100g. Keep a diary of foods eaten in a day and total the amount of energy consumed in a day. Students could be provided with a list of activities and their corresponding energy expenditure. They could then work out if they are consuming more or less energy than they use. (c) Research the energy capacity of different fuels, presenting in a display
Know how to use fuels economically
(a) Discuss the statement 'Buses are more fuel economical than cars'. Highlight that buses use more energy than most cars so how can this statement be correct? (b) Research then produce a display comparing how much energy per passenger for cars, buses, trains, planes. Widen the perspective to include other environmental factors such as global warming and ease of use so that students can appreciate a balanced argument (c) Relate to reasons as to why it is considered important not to 'waste energy'
Compare advantages and limitations of energy resources
(a) Brainstorm the advantages of fossil fuels and the disadvantages of fossil fuels. Repeat for the advantages and disadvantages of renewable energy. Discuss differences and what would make an ideal fuel. (b) Match pairs of cards that show name of energy resource and advantages/limitations. A game could be made of this by turning the cards face down and the students have to remember the location.
7J Electrical circuits Suggested action sobj Recognise that a (a) Review students' knowledge and understanding of electrical circuits by asking circuit must be them to complete circuits by drawing on correct connections. Discuss results as a complete to work class or in small groups. (b) Students should construct simple circuits using cells, wires (with insulation) and bulbs or buzzers. (c) Ask students or groups to explain their observations to others. Know how a switch can be used to break a circuit
(a) Students construct (i) burglar alarm, (ii) pressure pad and (iii) steady hand tester. (b) Demonstrate a BIG circuit that circles the room. Students predict whether a bulb will take longer to light if it is further from the battery. Confront the misconception that energy has to travel from the battery to the bulb before it works. Use analogy of a fan-belt or rope loop and demonstrate that if it snaps it can no longer work. (c) Ask students to fix circuits that are not working.
Can construct simple series circuit with given components (using drawings of components not circuit symbols)
(a) Demonstrate how to connect up a circuit using a 12V/24W bulb (car headlamps) with a 12V DC power supply and a large demonstration ammeter emphasing correct procedures. (b) Examine pre-drawn component diagrams and check if students can assemble correctly. (c) Discuss how a torch works. Draw a poster with a moveable part that explains how a torch works.
Can match electrical components (switch, lamp, wire, cell) to circuit symbol
(a) Students match circuit symbols to components using mix and match cards. (b) Emphasise the symbol for a battery of cells, noting that the positive terminal of a standard cell is the long thin line not the short thick line as many students would expect. (c) Use interactive software that allows circuit symbols to be dragged on the screen and relate to real components.
Can construct simple series circuit using circuit diagrams
(a) Students construct circuits using circuit symbol diagrams that are printed on cards. (b) Students discuss and explain the results when more cells are added to a simple circuit that includes an ammeter and a bulb or buzzer, emphasising the difference in circuit diagram. (c) Students make a torch from a circuit diagram.
Can draw diagrams of simple circuits using correct circuit symbols
(a) Demonstrate a simple circuit using 12V/24W bulb, a 12V DC battery (rather than a power pack), a switch and a large demonstration ammeter. Ask students to draw correctly the circuit using symbols and compare, emphasising the need for accuracy. (b) Use software to drag symbols onto a circuit. (c) Students design a burglar alarm using symbols.
Know that an electrical circuit is made from electrical conductors
(a) Investigate which common materials make a bulb light when completing a simple circuit. (b) Emphasise the key words 'conductor' and 'insulator', noting that these words also relate to heat. Define a conductor as a material that easily lets energy pass through. (c) Look closely at the materials that are used to make up an electrical circuit. Discuss which parts of the circuit need to be conductors and where insulators would be useful.
Can identify (a) Demonstrate burning wood from a pencil connected into a series circuit common conductors including a large ammeter (use a fume cupboard or extractor). Note that the and insulators graphite is a conductor because current is passing but the wood catches fire showing energy doesn't pass through it easily. (b) Students design a method of testing which materials are conductors, presenting results to class. (c) Demonstrate copper-plating using electrolysis of copper sulphate solution, showing that liquids can also be conductors. (d) Think about materials that conduct heat: are these materials also good conductors of electricity? Understand how switches work in parallel circuits
(a) Present students with a diagram of a parallel circuit that uses component drawings only. Discuss possible positions of switches and what the effect would be of closing each switch. Students could then try out themselves in small groups. (b) Present students with a circuit diagram of a parallel circuit using symbols that has several switches included. Discuss the effect of closing each switch.
Understand how parallel circuits work using components other than switches (e.g. hairdryer)
(a) Students construct a traffic light that follows the correct sequence (i.e. red only, red and amber, green only, amber only), presenting results to the class. (b) Students construct a 2-speed hairdryer circuit that allows another fan to be incoporated if required. (c) Diagnostic questions designed to probe students' ability to recognise equivalent ways of drawing a circuit with two parallel branches.
Understand that the brightness of (identical) bulbs wired in parallel stays the same whatever the number of components Understand that current is the same at all points in a series circuit
(a) Make a huge set of fairy lights and ask students to predict the effect of adding and removing more bulbs. (b) Use software to predict and test the effect of parallel circuits that have differing numbers of bulbs on each branch. Discuss results. (c) Relate to students' experience of light bulbs blowing at home. Do all the lights go out, do they get dimmer, or do they stay the same? The lights in their homes will almost certainly be parallel wired. (a) Demonstrate using a loop of rope to represent the circuit: the current is represented by the amount of rope that passes through the hands each second. (b) Students predict then measure currents at different points in a simple circuit. Discuss class results. Ensure ammeters are not so sensitive that they cause confusion. (c) Confront student misconceptions, for example, 'Why do kettles only have one lead?'
Understand that current divides in a parallel circuit
(a) Model a parallel circuit using two loops of rope, both being pulled through the hand, which represents a cell. Relate current to the amount of rope that passes a point each second - both loops together means more current. (b) Students work in pairs to build a parallel circuit and to measure the current through the leads and through each bulb. (c) Demonstrate a large circuit with two bulbs in parallel, connect in series with a third bulb. Students predict then test the brightness of each bulb.
Recognise amperes as the unit of measurement for electricity flow
(a) Use a fan-belt or rope loop analogy and demonstrate an electric circuit by pulling the rope around: the amount of rope passing a point each second is the current. Identify an Ampere as a certain length of rope. (b) Use a bingo style game that associates quantities to their units.
Know how to measure current using an ammeter
(a) Identify an ammeter as being like a guard in a train station counting the number of carriages passing through every second. In a model railway, a piece of track may have to be removed and the special station piece has to be inserted instead. In the same way, a circuit must be broken and the ammeter inserted so it is now part of the circuit. (b) Demonstrate how to connect up a circuit using a 12V/24W bulb (car headlamps) with a 12V DC power supply and a large demonstration ammeter emphasing correct procedures.
Understand the difference between current and energy transfer in a circuit
(a) Students relate different quantities to their units using a mix and match card game. (b) Use specialist software where students could be involved in setting challenges or labelling current and charge flow. (c) Use an analogy of supermarket deliveries to explain energy transfer. Ask students to discuss similarities and differences between this analogy and their understanding of electrical circuits.
Can explain the difference between energy and current in a circuit
(a) Discuss the current either side of a motor and relate to where energy is being transferred. (b) Relate to rope loop where the teacher pulls the rope around and a student holds rope between fingers. The student's hands get hot, energy is transferred from teacher to student due to a current. (c) Model the electric circuit as a pump lifting water up, which then flows down a channel, turning a water wheel, only to be lifted up again. Where is energy put in and taken out? The current is the flow of water. (d) Think of a bicycle upside down - it doesnâ€™t take much effort to make the wheels go around fast. Current is the speed of the chain and in this case it is high but the energy transferred is low.
Recall that adding more components to a series circuit makes bulbs (!brighter or !) dimmer
(a) Using a rope loop, pull through one student's fingers and note that the student experiences heat. Then introduce a second student doing the same and note that if the teacher pulls with same force the rope is slowed down and neither student experiences the same initial amount of heat, i.e. energy has been shared. (b) Demonstrate that adding more bulbs into a series circuit means that each bulb becomes less bright. (c) Relate to sharing out a fixed amount of a quanity so if there are more people to share to they recieve less each, and that using this analogy, in sharing the energy from the battery,the more bulbs there are, the less energy each bulb gets, so each is dimmer.
Recognise that thinner wire adversely affects the brightness of bulbs
(a) Relate resistance to students moving through a narrow corridor: if it is too narrow the flow slows down and the students get hot and bothered. The current drops and less energy is available for the bulb. (b) Demonstrate a simple circuit that includes a bulb and a nichrome wire link. A thinner wire will glow hot and the bulb will dim.
Can identify resistance as a term that means opposing the flow of electricity
(a) Relate to rope loop. If a student lets a rope be pulled through their fingers they will experience heat. If the rope is gripped tighter they give more resistance and the rope slows. (b) Students investigate fuse wire. What is it used for and how does it work? (c) Identify 'resistance' as a key word and ask students to recall its definition as a term that means opposing the flow of electricity. Draw linguistic connection between 'resistance' and 'resist', to put up a fight. (d) Discuss students' experiences of dimmer switches. How do they think they work?
Know that increasing the number of cells or batteries in a circuit can make bulbs shine more brightly
(a) Working in small groups, students investigate the effect of adding more cells in a simple circuit. (b) Relate to workers in a factory: if they get paid twice as much they work twice as hard! How does this compare with electrical circuits? (c) Consider the similarities between a power pack and a battery of cells. Draw a table of similarities and differences.
Know that cells need to be connected in correct polarity to work
(a) Students look at different shapes and sizes of batteries. Consider what features they have in common, emphasising the positive and negative. (b) Demonstrate a simple circuit that includes a battery of cells. Students predict then test the effect of reversing the polarity of one or more of the cells. (c) Relate to a toy car that will not work if the batteries are not inserted correctly.
Know that the voltage of a cell is a measure of the energy available to the circuit.
(a) Demonstrate using a power pack connected to a bulb. Discuss the effect on the bulb as the dial is turned up from 3V to 6V. The bulb gives out more energy as voltage increased. (b) Rub a ruler with a tie and try to pick up paper circles due to the static force. The paper will jump higher if the ruler has more voltage. (c) Demonstrate how a voltmeter measures the energy difference between two points in a circuit. Students predict how a voltmeter is connected into a circuit.
Know that the voltage of a circuit's energy source affects the current and performance of components (qualitative)
(a) Relate a simple circuit to a rope loop pulled by a teacher. If the rope is pulled with more force, the rope moves faster, corresponding to a larger voltage and a larger current. A student lightly holding the rope will experience more heat as the voltage and current increase. (b) Students investigate current readings on an ammeter in a simple circuit including a bulb as voltage of power pack is varied. (c) Think of riding a bicycle. When you pedal faster (increase voltage) the chain turns quicker (increase current) and the bike goes faster (better performance).
7K Forces and their QCA effects sub-objective Suggested action Understand simple (a) To overcome the 'I can't see a force so it isnt there' misconception use cardboard arrows of different length and stick them to everyday objects. balanced and Emphasise that there are forces on static objects but they always cancel each unbalanced forces other out. (in linear (b) Students to make a weighing machine using an elastic band which they have movement) calibrated with hanging weights
Understand unbalanced forces in terms of newtons of force needed to move objects
(a) That moving things need a force to keep them going is a very common misconception. Try to engage in thought experiments where students describe the motion of, for example, dropping a spanner out of a spaceship. Consider the effort needed to push and obect from rest and the effort needed to keep the object moving (b) Use cardboard arrows on a OHP to overlay on acetates of objects. Discuss the size of the arrows when a objects are moved. Students may well introduce gravity and this may present opprotunities to introduce reaction forces (c) Produce a force ladder where the size of various forces is presented on a scale. Introduce a Newton as the weight of an apple
Understand friction (a) Some students seem to think that friction only occurs when an object is as a force that moving or when it is stationary. Emphasise friction is present whenever two opposes motion surfaces are in contact and that it opposes motion (b) Use a trainer or a book on a ramp and a newtonmeter, to investigate: 'How much force needed to move the trainer' and ' What angle does the trainer first move' (c) Draw the forces on a cyclist when he is cycling, coasting, and applying the brakes Identify where friction can be useful (examples)
(a) Discuss with students what it would be like to live in a frictionless world. Draw a cartoon of the 'Adventures of the Child without Fiction!' (b) Compare types of bicycle tyre. Consider why broader tyres give more grip and when they are useful (c) Show a video clip of race cars crashing especially when they lose grip at a corner. Write a statement using the word 'friction' explaining why the cars crash. The car needs to experience friction or else it will continue in a straight line.
(a) Show video clips of Winter Olymics. Discuss why most events try very hard to Identify where reduce friction. Students to select a sport and explain in detail why it is important friction can be a to minimise friction problem (examples)
(b) Discuss with the students their experiences when friction has been a problem eg trying to slide wonky windows or doors, or opening doors on creaky hinges (c) Many students have a problem understanding air resistance, believing air is 'nothing'. Use a pea-shooter to fire at a wall and consider how air can cause a considerable resistance (consider air to be hitting moving objects like millions of tiny pea-shooters)
Recognise some key effects of contact friction (heat and wear) and recognise that a lubricant such as oil can reduce it
(a) Get the students to rub a finger really fast on a desk and note the heat generated. Now repeat but lubricate with a drop of olive oil and compare the feeling. (b) Show containers of engine oil and discuss why a car will grind to a stop if it runs out of oil (c) Demonstrate the effect of rubbing 2 stones together, or sandpaper on wood, then the effect of introducing water or oil between the surfaces.
Can read graphs showing direct relationships, e.g. force required to move objects across different surfaces
(a) It is important that students have practice both plotting and using graphs. Produce a conversion table showing a direct relationship, plot the graph correctly and then use the graph to find an unknown value (b) Students to make bar charts of a prepared table showing weights and ages of students in a school. The students should write their own conclusions and enourage discussion about general trends and linear relationships
Can read graphs showing inverse relationships e.g. less pulling force indicates more effective lubricant
(a) It is important that students have practice both plotting and using graphs. Produce a conversion table showing an indirect relationship eg weight of an object and distance from Earth, plot the graph correctly and then use the graph to find an unknown value (b) Use a card game to match graph shapes with their corresponding statement eg match an inverse graph shape to a statement about pulling force and amount of lubrication. Discuss the answers in detail so that students can relate a graph to visualisation.
Can resolve two unbalanced forces in terms of resultant force and direction
(a) Great care must be taken when drawing force arrows onto objects. Make sure that they are consistently straight, in proportion to the size of the force and the base of the arrow originates from the object. Relate to drawings of real life situations such as a mass on a spring and draw on an arrow for each of the forces that the mass is experiencing. Many students will intuitively know the resultant force will be the vector sum of arrows if they see the force arrow drawings (b) As above but some students may prefer a mathematical approach by giving arrow pointing to the left a negative sign and the arrows to the left a positive sign as that the numbers can be 'added' to give resultant.
Can resolve three (a) Use a tough rubber ring and combinations of students pulling from different unbalanced forces sides. Discuss which students were the strongest and how we could tell from the in terms of resultant direction the ring was pulled. Practice drawing the force arrows on the ring in force and direction
different situations and consider the resultant force in each case. (b) Consider bubbles rising in a bottle of fizzy drink. State that their are three forces acting on each bubble, namely weight, upthrust and drag. Student to draw correct force arrow diagram for the bubble.
Identify gravity as a (a) Find a strong beam in the school and challenge students to dangle for as long force and its effect as they can from the beam. Let them feel the force of gravity, discuss the resultant forces acting and whether or not they all feel the same force of gravity as each other? (No, they are different weights!). The main purpose of this activity is to focus on the everyday phenomemon of gravity and that the study of science is about real life, it also gets the students involved and so provides a reference for later discussion (b) Show animations of the revolving solar system and ask what is the force keeping it all together? Most will state 'gravity' but in which direction does it act?
Identify upthrust as (a) Students to measure the weight of an object with a newtonmeter in air and in water. Challenge the students to conclude for themselves that there must be an a force and its upthrust and to calculate its magnitude effect
(b) Demonstrate to the students lowering a mass into a beaker of water that is placed on a top pan balance. The mass is to be hanging from a newtonmeter. Challenge the pupils to declare whether the reading on the balance will increase, decrease of stay the same. Discuss the results in terms of forces. (c) Students to push a balloon or polystyrene brick/flotation device into a bucket of water so that they can feel the effect of upthrust for themselves. Relate upthrust to the feeling of being supported in water when they go swimming or float.
Can calculate simple balanced forces in floating and sinking
(a) Consider a ship floating on water. Ask questions such as 'Does the ship still have weight?', 'Why isn't it sinking?', and 'Can we explain what we know with force arrows?'. (b) Use an OHP and an acetate of a floating object. Students to come up and select the appropriate cardboard arrows to represent weight and upthrust of the object. Discuss what the resultant force would be.
Can calculate unbalanced forces in floating and sinking
( a) Demonstrate a helium balloon floating to the ceiling. Use cardboard force arrows on a picture of a balloon to show that upthrust is bigger than its weight. When the balloon is released which force will cause it to move and in what direction? (b) Spend some time examining the keyword 'floating', concluding that unlike 'sinking' floating can means staying at the same level as well as moving in the air. Emphasise that care must be used when using common words when explaining the forces and motion of objects.
Understand that when an object floats its weight is equal to the
(a) Consider a ship floating on water. Ask questions such as 'Does the ship still have weight?', 'Why isn't it sinking?', and 'Can we explain what we know with force arrows?'. (b) Use an OHP and an acetate of a floating object. Students to come up and upthrust of the fluid select the appropriate cardboard arrows to represent weight and upthrust of the object. Discuss what the resultant force would be. Understand that when an object sinks its density is more than the density of the fluid
Understand the concept of density and can apply to specific situations
(a) Density is a difficult concept and many students will believe 'heavy thing sink and light things float'. Help to overcome this by letting the students feel a metal coin and a large wooden block, comparing the weights. Drop both objects in water and make sure the students verbalise their own conclusion. Ensure they establish some heavy objects float and attempt to relate to a concept of density (b) A practical investigation could be made into density by measuring the volume of a object by the amount of water it displaces when pushed under water. Then dividing the mass of the object by this volume and comparing results. Floating objects should have a density less than 1g/cm3.
(a) Be clear with the units that density is measured in, and show that the density of water can either be written as 1g/cm3 or 1000g/litres or 1000kg/m3 - its all the same! Students may have problems changing units, commonly believing that there are 1000 cm3 in a m3. (b) Show a large cylinder of water that has a density gradient (possibily using lots of bath salts and allowing to settle). Squirt ink into the cylinder and find where if finds its level. Conclude that the density of the ink lies between that of the salty
water above and the salty water below. Relate to smoke on a still day and clouds that flatten out at a certain height.
State that the greater the applied force on a material the more it stretches (up to a limit)
(a) Show pictures of bungee jumping and ask for students experiences. Consider why there is a maximum weight allowance for bungee jumping (b) Using all the necessary safety considerations, allow the students to heat the middle of a glass rod in a fierce bunsen flame. Pull the ends of the rod apart and the students will produce fine threads of glass
Can interpret (a) Use a cola lace (as from the sweet shop) or horse hair in an investigation to tabular data on measure the extension with varying load. Tabulate results and them to use their force and extension tables to predict the extension caused by an unused load (b) Distinguish between 'length' and 'extension' by using two columns in a table
Can interpret force/extension graphs
(a) Make a weighing machine using an elastic band, metre ruler, and hanging weights. Plot a graph of results and then use the graph to predict the weight of an unknown object, then test the prediction. (b) Plot force/extension graphs from cola laces at different temperatures and ask students to conclude the effect of temperature of the properties of the cola lace.
Recognise mass as a measure of how much matter there is in an object
(a) Concept map using various cards such as: 'Moon', 'Earth', 'Gravity', 'Mass', 'Weight', 'Force', 'Down', 'kg', 'Newton', '10N/kg'. Ask the students to draw links between their cards and explain their choices (b) Spend time explaining why a 'weight of 90kg' is not a correct science statement although it is common in everyday life. Encourage students to switch between everyday and science mode. State that 'mass is a measure of how much stuff there is and is measured in kilograms'. Ask if that would change if the object went into space
Can state that weight is caused by the force of gravity acting upon a mass
(a) Prepare some cereal packets so that they have different weights but look identical. Let the students lift them and state that this what the packets would feel like on different planets which have different gravities. What would they feel like
in space? (b) Show video footage (eg BBC Class Clips) of simulated zero gravity by free falling in a diving aeroplane. The passengers are not really weightless but dont feel heavy. Discuss the forces on a falling person and establish that their weight is constant throughout the fall.
Recall that gravity on Earth has a force of 10N and uses this in weight calculations
(a) Prepare some cereal packets so that they have different weights but look identical. Label each with a big sticker that names the planet they represent. Make sure that the mass is visable but let students weigh them using a newtonmeter. Make the packet that has the Earth sticker weigh ten times the mass (in kilograms). (b) Students draw on forces arrows onto pictures of objects with the mass written next to the object
Understand that mass does not change but weight does in the context of the moon
(a) Prepare 3 cereal packets, looking the same but with different weights inside. One of them is labelled Earth. Establish that gravity on the moon is 1/6 that on earth: which of the other 2 packets represents how the Earth packet would feel on the moon? (b) Show a passage of text relating to the experiences of an astronaut. Set questions comparing his weight on the Moon and Earth eg Why did he have to wear heavy boots on the Moon? (c) Show video clip of life in a spaceship. Students to write a commentary highlighting the features that are different compared to life on Earth
Describe what is meant by speed
(a) 'Speed' is a common word that also has a particular science meaning. Ask students to list as many words as they can that include the word 'speed' (eg: Speeding, Speedo, Speedway) within a time limit, perhaps run as a competition. Discuss the science use of the word 'speed' as the distance travelled in a certain time. (b) Sort cards of objects (eg rabbit, skier, hurricane) into 'speeds'. This helps to appreciate relative scale of speed rather than just accepting some objects are 'fast'.
Recognise the scientific units of speed
(a) There is often confusion with different units used for speed. Show pictures of road signs in the UK and in Europe and ask what they mean. Pay particular attention to the units quoted and if necessary draw and an analogy with different measurements for height. Further work could also discuss why some units are more appropriate than others (eg miles per hour for cars and metres per second in classroom activities (b) Issue the students with a conversion chart of metres/second to miles per hour and convert roadsigns to metres/second. Also speeds with different units could be presented to the students and then challenge them to find the fastest (c) Card matching activity of objects (and animals) to their top speed. Emphasise
the unit when going through the answers which will lead to the idea that speed in a measured quantity.
Can calculate speed (a) Watch short video clips of moving objects such as windsurfer, bobsleigh, tortoise. Issue students with stopclocks and ask them to calculate speed. This should open up discussion about the required distances needed to calculate speed and possibly even a comparison of different units (b) Consider Police Speedtraps. Do students think they are useful? Now consider how they work and try to get students to work it out for themselves using open questioning (speed is calculated using markings on the road) (c) Take the students out in the playground, place them at known distances, and
issue each with a stopclock. On a signal, everyone is to start their stopclock and a student starts to run. The timers stop their clock when the runner passes by. Record the class results and plot graphs. Can calculate (a) Relate average speed to to typical journey where speeds vary. This helps to distance, given dispel the idea that a speed is always constant through a journey average speed and (b) Many pupils will have low confidence in rearranging the speed equation. For time taken
these, try to teach by using sentences about proportion eg If I am moving at 10 m/s, I travel 10 metres in each second. How far do I travel in 2 seconds? etc (c) Circus of toys, trollies, paper helicopters etc. Students to work out ranking of speeds even though distances vary. Discuss how far they would travel in a given time before using maths to confirm.
Can calculate (a) Calculate the average speeds of cars travelling between two points along the journey time, given road. Assume that they keep that speed and discuss how far they would take to average speed and travel 2 km and then confirm using maths distance
(b) Use motion analysis software to predict journey times. An example of suitable free software can be downloaded from http://webphysics.nhctc.edu/vidshell/vidshell.html
7L The solar system and beyond QCA sub-objective Suggested action
Know that the Sun appears to rise in the East and set in the West
a) Present students with a true/false worksheet that poses questions such as: At night time the Sun is covered by clouds, T / F ? Promote discussion within groups of students, perhaps using a triad activity b) Establish which way is north, west and east perhaps by relating N/S/E/W to maps of local area/home/school. Students to write on paper where the Sun rises, where it sets and where it is at midday. Also establish what happens differently during the summer and winter;
Know that the Earth a) To discover student's initial conceptions, ask students to work in pairs. One of takes one year to them is the Earth and is write instructions for how the Sun should move orbit the Sun throughout the course of a year and the other student is the Sun and should write instructions on how the Earth should move throughout a year. Ask them to face each other and act on the instructions for each month; b) Relate to information about the orbit time of other planets and hence deduce the lenth of a 'year' on other planets.
Understand the a) Position a globe (preferably on a titlted stand) near a light source in a dark phenomena of night room. Show the countries and spin the globe emphasising which countries are and day
experiencing night or day b) Question students to relate any experiences they have of the night being at different times in differnt countries (eg 24 hour time zones, long-haul flights, jet lag, sporting events, reality game shows) c) Use diagnostic questions to pinpoint student misconceptions. Common misconceptions are that the Sun is covered by clouds at night, that the Sun goes round the Earth once a day and that the Earth goes around the Sun once a day.
Recognise that the tilt of the Earth remains constant as the Earth orbits the Sun during one year
a) Position a light source in the middle of a large room and introduce a globe, emphasising that the axis will always point to one corner of the room. Move the globe to the other side of the light, keeping the axis pointing at the same corner. Ask the students to relate amount of sunshine to months of the year. (b) Show long exposure photographs of nightime sky and of weather systems. Discuss whether or not this evidence that the Earth is spinning.
Can name luminous (a) List some shiney objects and consider it they could be seen at night time. and non-luminous (b) Relate experiences of total darkness (eg in caves) and conclude that even sources in space shiney object could not be seen if it was really dark (not even cats could see!) (c) List some objects in space and decide which ones are hot enough to give off their own light (ie they are 'luminous') and which just reflect light.
Can use the words a) Discuss the following observations and argue whether they support the idea luminous or nonthat the Moon is luminous or non-luminous: the moon cannot be seen during luminous in context
the day; not all the moon is visible; men have landed on the moon; it is possible to read in moonlight etc; (b) Consider where the word 'luminous' has been met before. Note that 'glow-inthe-dark' toys and watch hands are luminous because they give off their own light but a mirror-ball is non-luminous because it reflects light
Know that the Moon (a) Show animation of Moon orbiting Earth and ask students whether they agree orbits the Earth with this model, and if they do, ask how long do they think the moon takes to go every 28 days
Can identify simple a) Position a light source in the corner of a dark room. Ask a student to hold up a phases of the Moon, ball and describe what they see from their view point. They are to rotate on the full, new and quarterspot, describing what they can see every quarter turn; disc
b) Students to rearrange pictures of the phases of the moon into the correct order;
Can describe a (a) Show a video clip of a solar eclipse. Discuss student ideas as to the cause of partial solar eclipse such of a phenomenon and then ask students to model with balls. from Earth (b) Consider the question: ' Why are solar eclipses rare?' because many students will think they should occur every month. The answer to this comes from an appreciation of scale and it is worth modelling with the Earth as a football, the moon as a tennis ball, and positioning them 6 metres apart. The angle of the plane of the Moon varies and rarely is in line.
Know that a total (a) Model the Earth and Moon by using a football and a tennis ball and a light solar eclipse is source as the Sun. Draw attention to the remarkable coincidnce that the Moon sunlight blocked by and Sun appear to be the same size from Earth and that when they all align at is the Moon
possible to get a total eclipse from some parts of Earth. (b) Show a video clip of the last total eclipse in 1999, simultaneously modelling the alignment (c) Ask students to explain a partial eclipse in their own words, comparing to a total eclipse
Understand how the phases of the Moon make the Moon appear to change shape from Earth
a) Position a light source in the corner of a dark room. Ask a student to hold up a ball at arms length in the light. The student holding the ball describes what they see from their view point. They are to rotate on the spot, describing what they can see every quarter turn; b) Show photograph of the Earth from the Moon. Discuss whether phases of the Earth would be seen from the Moon. c) Use diagnostic questioning to highlight student misconceptions. The common misconceptions regarding the question 'Why does the moon change?' are that the moon's appearance is due to: the shadow of the Earth, clouds covering the Moon, the shadow of a planet on the Moon
Knows that a lunar eclipse is when the Earth blocks sunlight to the Moon
(a) Model the Earth and Moon by using a football and a tennis ball and a light source as the Sun. Discuss what the moon would look like as it moves into the shadow of the Earth (b) Show a video clip of a lunar eclipse, simultaneously modelling with balls. Emphasise that this is rare event because the angle of the plane of the Moon through the Earth varies.
Know that the Sun appears lower in the sky in winter than in summer
(a) Relate to pictures showing shadows during the summer and the winte. Model shadow length using a lamp and a toy figure, showing that shadow length is longer when the Sun is lower in the sky. (b) Discuss where the Sun is in a winter sky compared to a hot summer day.
Understand that the tilt of the Earth as it orbits the Sun makes days in the UK longer or shorter
a) Position a light source in the middle of a large room and introduce a globe, emphasising that the axis will always point to one corner of the room. Rotate the globe on its axis and highlight when a particular country is in day and in night. Move the globe to the other side of the light, keeping the axis pointing at the same corner. Again rotate the globe about its axis and ask students to now descibe the day and night time. Discuss the corresponding months of the year and how in summer months we have longer days and shorter nights b) Model using a tilted Earth and a light source. Use a ruler parallel to the light rays that hit the Earth and ask students to describe why the Sun is never completely up overhead in the UK
Can relate the position of the Sun or the Earth to the changing height of the Sun in the sky
a) Position a light source in the middle of a large room and introduce a globe, emphasising that the axis will always point to one corner of the room. Move the globe to the other side of the light, keeping the axis pointing at the same corner. Use a ruler parallel to the rays from the Sun to show angle is greater during summer; b) As above, but also translate hoe the Sun would look in the sky as the Earth spins on its axis.
Know that the tilt of the Earth gives us changing seasons
(a) Ask students to brainstorm all the differences between summer and winter. Pull out temperature, daylength, height of sun in sky. Draw anecdotes about it being winter in Australia when it is summer in the UK. Pool student reasons why we get seasons. (b) Use an overhead projector and an acetate with dark bars across it. Put a globe with tilted axis into the light and note that the bright bars are more spread out towards the poles i.e. energy covers a large area. Rotate the globe so that the axis is now pointing at a different corner of the room and discuss the difference this has made to any particular country. (c) Produce posters of the seasons we would experience if the Earth had a different angle of tilt (eg if tilt angle = 0)
Understand that the tilt of the Earth gives us the four seasons (on level of longer days heating area for longer)
a) Highlight that 'spin', 'orbit', 'rotate', 'revolve' are words with similar meaning and that they may be a source of confusion. 'Spin' is about an axis and 'Orbit' is about a body. Agree with students what is meant by each word. b) Use diagnostic questioning to highlight student misconceptions about seasons. The common misconceptions about seasons are: clouds stop heat from the Sun, the Sun gets closer to the Earth, and in the summer, the Sun is on 'our side'.
Understand why the a) Lift hands up to feel the heat from a fire. Most heat is felt when palms are tilt of the Earth gives perpendicular to rays. Relate to winter when the Sun is low (fingers pointing at us the four seasons
fire) and colder days. Similarly, when the Sun is more overhead the palms get more direct rays; b) Confront misconceptions about the Earth getting closer to the Sun during the summer by discussing experiences of an Australian Christmas or reality game shows or sporting events;
Recall that our solar system consists of our Sun, planets, asteroids and natural satellites that orbit the planets and can describe how they behave
a) Concept mapping in groups three or four. Students to link 'concept' cards displaying terms such as planet, sun, star, gravity, meteorite, orbit, rotate, etc into a poster and discuss why they have made their links b) Produce a leaflet 'Guide to the Solar System' showing the names, positions and characteristics of the different bodies
Know the order of the first four planets nearest the Sun
a) Write a travel brochure for space tourists. What would it be like to go on a criuse to the Inner Planets and how long would it take to reach each destination? b) Discuss how astronomers obtain evidence of planets and other bodies in the solar system by using telescopes but before only the closest planets could be seen with the naked eye. Relate planets to Roman and Greek mythologies c) Create wall display of the four inner planets with groups of students taking responsibilty fro drawing and describing their planet (d) Devise a useful mnuemonic such as Mean Vegatables Eat Man! to remember the four inner planets
Know the correct order of all the planets
a) Model solar system using fruit. Nine pupils hold cards showing the planet they represent and use a pumpkin for Jupiter and a pea for Pluto b) Devise a mnuemonic such as My Very Eccentric Mate Jumps Suddenly Up Near Policemen to order planets, and then draw a cartoon of their mnuemonic;
Know that conditions on a planet (ie hot/cold) depend mostly on its distance from the Sun
a) Use planetary data, that is commonly available from textbooks or the internet, to produce graphs or charts that show trend of surface temperature against distance from Sun (Venus is exceptional) b) Present students with a spreadsheet containing planetary information such as: , distance from the Sun, length of year, length of day and sort data to produce a graphical representation of trends
Know that the planets take different times to orbit the Sun, depending on distance
a) Use planetary data, that is commonly available from textbooks or the internet, to produce graphs or charts that show trend of orbit time against distance from Sun; b) Take students onto a playground or field. Instruct them to to lap around a centre point at differnt radii and ask them why planets take differnt times to orbit the Sun
Know that the brightest stars are closest to Earth
a) Show some pictures of constellations such as Orion and The Plough. Note that sometimes these stars are accompanied by another wandering star and seems to move from one constellation to another. Explain that the wandering star is not actually a star at all but a planet. Ask how can a planet look like a star and relate to luminous/non-luminous objects. b) Use a card sort game to order in size: an asteroid, a planet, a star, a solar system, a galaxy, a universe.
c) Show some images of galaxies and nebula and note that some stars are brighter than others because they are bigger and sometimes stars look dimmer because they are so far away
Have some understanding of the distances between objects in our solar system
a) Model solar system along a corridor. Students to cut out circular discs to scale of the first four planets and label; b) Show 'Powers of Ten' video clip (available from the internet) c) Write a travel brochure for space tourists. What would it be like to go on a criuse to the Wonders of the Solar System and how long would it take to reach each destination? (a useful resource is Bill Bryson's 'A brief History of Everything')
Understand that a light year is a measurement of distance not time
a) Emphasise that a light year is used as a measurement of distance not time and that nothing, according to Einstein, can travel faster than light b) Students are often fascinated by large numbers. To travel around the world is about 36 000 km, to the moon is about 15 000 000 km and to the nearest star is about 40 000 000 000 km. Calculate how long it would take to travel theses distances in a spacecraft travelling at 50 000 km/hr. c) Set students to calculate the number of times light travels around the Earth in each second d) State that when we look at our nearest star we are look back 70 years in time and ask students to explain that statement
Unit 8I Heating and cooling QCA sub-objective Suggested action
Know about the Celsius scale of temperature used in science
(a) Feel warmth of water and measure using thermometer; suggest temperatures and compare. (b) Discuss holidays and typical temperatures that students would have experienced or would have heard on weather reports. Mention negative temperatures and ask what is the coldest temperature they have experienced. (c) Highlight the symbol oC as meaning 'degrees Celsius' and ask if they have heard of any other temperature scales. State that 'degrees Centigrade' is the same as 'degrees Celsius' and ask it anybody has heard of 'degrees Fahrenheit'.
Know some typical temperatures and the freezing point and boiling point of water
(a) Measure the temperature of ice and boiling water using a Celsius thermometer and plot on a large visible scale. Ask the students to use thermometers to measure the temperature of the air inside and outside the classroom, the temperature of their hand and the temperature of a nice cup of tea. Plot these values on the scale. (b) Research the hottest and coldest places on Earth and display on a world map. (c) Challenge students to explain why, on holiday, the temperature was over 'a hundred degrees!' but the water in my body didnâ€™t boil. The answer, of course, is that two different temperature scales are used (boiling point in the Fahrenheit scale is 212 degrees). Relate key temperatures (freezing and boiling points of water, room temperature and body temperature) between Celsius and Fahrenheit scales.
Know that there are (a) Demonstrate different types of thermometer, especially show the common different kinds of glass/alcohol and compare with a temperature probe. Show that they record the thermometer same temperature for a cup of tea and consider the advantages and disadvantages of each. (b) Show pictures of hot furnaces and consider why a typical glass thermometer would not be suitable. Similarly think of the problems in recording a large number of temperatures over a long period of time, especially when the person doesnt want to sit there all day and night recording the temperatures in a book. In these cases, other kinds of thermometer have to be used. (c) Demonstrate a thermocouple connected to a suitable ammeter. Use this to show what is meant by the key word 'calibration', ie it is possible to use any quantity that varies with temperature as a thermometer as long as it is consistent.
Know that temperature is a measure of how hot things are.
(a) 'Temperature' is a measure of the average movement energy of particles. Imagine people shopping in a supermarket - some people potter around and others whizz around as quickly as they can. 'Temperature' is like a measure of their average speed - it doesn't measure how many people are in the supermarket. Whereas 'heat' is a measure of the number of people times the average speed, ie the total energy. (b) Still using the supermarket analogy, there are times of the day when people come home from work and lots of them just want to get the shopping done as quickly as possible and go home. In this case the average speed goes up. If the average speed of particles increases then the thing is hotter and the temperature is higher. (c) Role play air particles on a cold day. Here the students walk slowly in straight lines in an enclosed space, bouncing off the walls and each other. Instruct them that the temperature is getting even colder and that they should walk even slower. Eventually, it gets so cold that they stop - this represents temperature of Absolute Zero (-273oC), the temperature of deep space.
know the difference (a) Consider a sparkler and a cold bath. Ask if it sparkler were put out in the between heat and bath, whether the temperature of the water would be hot enough to bathe in? temperature
The answer is 'no', because the bath has many more particles and so the energy has to be shared around so much that it hardly makes any difference. (b) Similarly, consider a hot bath and a sparkler - which has more total energy? Its the bath because, although the sparker is made up of bits of white hot metal, there are so few particles compared to a bath (actually even a cold bath of water has considerably more total energy than a hot sparkler). (c) Role play air particles on a cold day. Here the students walk slowly in straight lines in an enclosed(!) space, bouncing off the walls and each other. Gradually let more and more people become involved with the role play. A constant temperature means that they all walk around slowly, no matter how many people, but the total energy goes up because everybody who joins the game brings their own energy along.
recognise heat as energy.
(a) In groups, ask students to write down as many expressions as they can that include the word 'energy' on postiks and then try to organise their expressions into groups with common features. Use this work as a basis to explain that in science, everyday words often don't help understanding. It is useful to think of energy as 'the ability to do something' (and, importantly, it is possible to quantify energy, eg. this object has twice as much energy as this one). (b) Many students believe that heat is a substance, reinforced by expressions such as 'heat rises' or 'don't let the heat out!'. Consider expresssions involving the word 'heat' and ask the students to define what they actually mean by 'heat'. State that in science it is possible 'to heat something' and that 'heat' is also used as a measure of the amount of energy an object has. (c) Consider the expression 'the flame has heat' with the students and try to rewrite this in terms of particle movement eg. 'the partcles near the flame are moving faster'
know that temperature change involves energy flow
(a) The word 'heat' is common in every day use but its connotations are varied and often misleading. Energy is stored in hot bodies and this energy can be shifted to other stores, but energy is energy and there aren't different types of energy. Introduce this idea to students, asking them to list, instead of types of energy, ways in which energy can be stored up 'waiting' to be used. (b) Introduce a 'thermal store', and a 'chemical store' as ways of storing energy consider when a match burns, before the match is struck energy is stored in a 'chemical store', afterwards the air has more stored energy (more particles are moving faster) - we say the air has more energy stored in its 'thermal store'. (c) Role play particles in air on a cold day, where the students walk in random directions in straight lines, bouncing off each other and the walls. One student hides behind a chair and represents the Sun. As the Sun appears the particles move faster and as it goes away they slow down again. The Sun is giving the particles energy via electromagnetic radiation (and the particles lose their energy by warming the land and sea when they hit them)
understand that heat flows as a result of temperature differences.
(a) Show histograms showing temperature against volume of water for two different samples. The area under the bar is an indication of heat energy. Mix the volumes of water and record the resulting temperature. Investigate using different proportions of hot and cold, predicting what the new temperature will be. (b) Students often believe that if things are heated up for the same time, their temperature will go up by the same amount. In fact the final temperature of an object depends on energy supplied, mass and material. Design an investigation to find the factors that effect the final temperature of an object. (c) Imagine being at a crowded rock concert (like Glastonbury). People at the front start bouncing up and down, knocking onto the people behind. The people at the front (high temperature) get slowed down a bit because ethey keep hitting the people behind and the people behind move a bit faster than they did a kind of average is obtained. Explore this analogy of temperature difference and energy transfer with students.
know that heat flows more easily through good thermal conductors
(a) Touch different materials and discuss which ones feel hotter. Imagine putting your bare feet on ceramic tiles and a woolen rug - which one feels warmer. Inform the students that the tiles and the rug are at the same temperature - so why do they feel different? The answer is that the tiles are better at moving the energy away from the body, so it loses energy quicker and feels colder. (b) Consider the keyword 'conductor'. In groups or pairs, students write down sentences that include the word 'conductor'. Sort into scientific uses and others. Students will probably recall electrical conductors from earlier work, but it is important that they appreciate that 'conductors' let energy pass through them easily. Compare with lightning conductors and emphasise that they let energy pass through them easily . (c) Concentrate on the keyword 'thermal'. Brainstorm where the term is used (eg thermal underwear, thermal springs, thermal gloves), concluding that it is an alternative to 'heat' in many instances.
know that most (a) Discuss situations where students have touched metal when it has been a metals are good cold day. The body temperature is higher than that of the metal and the metal thermal conductors moves the energy away very quickly so it feels cold to the touch. (b) Demonstrate the conductivity of metal rods compared to glass rods by putting them both in a beaker of hot water and feeling the other ends of the rod. Pieces of thermal paper could be stuck to the ends of the rods and the colour changes could be compared. (c) Students to think of practical examples of why metals are used in certain situations. In particular, the properties of mercury could be considered. Why is mercury used as a switch in situations where the device has to be level eg in devices uded in surveying?
know that heat flows less easily through poor thermal conductors
(a) Discuss cooking utensils and, in particular, the reasons why a saucepan is metal but with a non-metal (wooden, Bakelite, etc.) handle. Suppose what would happen if it were the other way around! (b) Demonstrate temperature gradient along rods of different material, e.g. copper and steel. This can be done by fixing drawing pins to the rods using blobs of petroleum jelly and heating one end of the rods. As the energy travels down the rod the pins fall off, so giving an indication of rate of travel. Use this demonstration to show that there is a range of values of conductivity - from those that allow the energy to pass through very quickly to those that don't seem to allow energy to pass through it at all. (c) Recount situations where students have noticed the apparent difference in temperature between materials eg. cermic tiles and woolen rugs or metal handlebars and rubber grips. Emphasise that body temperature is higher than the objects and that they feel warm or cold depending on the rate that energy is moved away from the body.
know that liquids (a) Demonstrate poor of conducitvity water using ice cube at bottom of a boiling and gases are poor tube which is being strongly heated at the top. Temperature sensors could be thermal conductors
used showing the difference in temperature at top and bottom of the tube. (b) Investigate double glazing or thermos flask. Students need to appreciate that there is air (or partial vacuum) involved in keeping the room or drink warm and to develop reasons as to why they work. (c) Research highly effective clothing that is used in extreme weather conditions. Focus on air pockets or water layers that are an integral part of their design.
know that poor (a) Brainstorm sentences which use the word 'insulation' or 'insultators'. thermal conductors Encourage students to write 3 sentences of their own that correctly use these are called insulators
words. (b) Separate a box of materials into 'good thermal conductors' and 'poor thermal conductors'. Introduce the word 'Insulators' as an alternative to 'poor thermal conductors'. (c) Compare with electrical insulators, which is a term students may have come across previously. Students to compare and contrast the similarities and differences between electrical insulators and thermal insulators in their own words.
know that insulation can reduce unwanted energy transfer
(a) Discuss ways to reduce energy loss from a house. Include loft insulation, double glazing, carpets and wall paper. This is an opprtunity to assess if students have the misconception summarised by 'Shut the door - you'll let the cold in'. Many students have felt cold draughts and believe that The Cold is an entity that has to be prevented from coming in. Encourage students to write in open prose by themselves and then try to emphasise that it is a matter of keeping a place of high energy just that - a place of high energy. (b) Investigate the effect an insulating material. Use a film cannister with hot water and a temperature probe inserted through the lid. Wrap a thin layer of insulation around the cannister and record the time to drop a certain temperature. Repeat with more and more layers and compare. (c) Challenge students to use everyday materials such as bubble wrap and cotton wool to keep a hot object as warm for as long as possible. Make it into a competition - Who can keep my soup warmest?
know that radiation (a) To most students, the key word 'radiation' is linked with 'radioactivity' and to energy can travel a lesser extent 'radiators'. It is important that 'radiation' is assosociated with through a vacuum light and that there is a whole spectrum (or colours) of light, most of which our eyes can not see! (b) Heat strongly a wire gauze until it glows red hot. Watch it as it cools. Establish that objects cool down by giving off radiation. (c) Recall the energy can be transferred by particles but that there are no particles between the Sun and the Earth. Challenge the students to expain why the sun warms us up.
understand that hot (a) The sihouette of a candle flame or a bunsen burner flame in a bright light fluids rise and cool should show a turbulent shadow rising upwards. A spiral 'snake' can be made to ones sink rotate if it is put in this upstream of air. Establish that it is an image of moving air that is being seen not an image of 'heat'. (b) Use computer images to establish what is meant by 'convection currents'. Establish that hot material rises to be replaced by cooler material and circular currents are obtained in a closed system. Relate to hang-gliding and convection currents in the Earth's mantle. (c) Consider and research weather systems. Ask the students to explain why we get wind and they could conjecture why there are ocean currents like the Gulf Stream. Here, differences in global warming cause areas of hot fluid and areas of cold fluid, resulting in currents.
understand that expansion of a material reduces density
(a) Demonstrate a metal ball that can just pass through a hoop or gap at room temperature, but is unable to do so when hot. Consider the key word 'density'. Ask the students if there is any more 'stuff' or matter given to the metal and establish that there is the same amount of matter it is just more spread out. Students to describe this themselves using the word 'density'. (b) Show ice cubes floating on top of a glass of water. Ask students to explain why the ice floats using the expression 'density'. Consider why ice cubes have less density than water (ice occupies more space for given mass compared to water).
know that materials can change state when energy is added or removed
(a) A class practical where a beaker of ice is heated over a bunsen burner until it melts and then boils should show clearly that a constant input of thermal energy causes a change of state. Consider what would happen to steam and then water as energy is removed. (b) Elicit ideas that cold days have less energy from the Sun and that is why we
get ice and snow. (c) Heat a boiling tube of wax until it has melted, insert a temperature probe and alow to freeze. Note the temperature fall and the students could write in their own words what is happening to the wax in terms of its stored energy.
know that these changes are reversible
(a) Consider what is meant by the key expression 'reversible change' and establish that with a reversible change you can get back to exactly what you started with. Ask the students to come up with some examples of non-reversible change (such as frying an egg, or striking a match) and of reversible changes. (b) Use ICT simulations to show the effects of heating on particles. Discuss what the effect will be if the particles loose energy and try to expand the model to explain complications of non-reversible changes (ie the partcles have reacted with each other). (c) Research cryogenics. Establish the idea that living material can be frozen and then unfrozen so that it is living again - do the students believethis is possible and what are the moral implications?
know that changes (a) Students to independently heat boiling tubes of wax, insert a temperature of state occur at probe or thermometer and record the freezing temperature. A comparison of fixed temperatures. different results should show that the freezing temperature is same for everybody. It is worth establishing that freezing temperature is the same as melting temperature, as students can think that these are different. This can be demonstrated by now heating the boiling tube of wax again in a water bath and comparing the melting temperature with others. (b) Research melting/freezing points and boiling points of water at standard pressures of different substances and plot them on a large scale. This can be an important exercise as many students will have difficulty with negative numbers and they need to appreciate -200oC is colder than -100oC for example. (c) Students to consider the word 'evaporation' which, like boiling, converts liquid to vapour but at a lower temperature.
understand that particles move further apart with increasing temperature
(a) Demonstrate expansion of air by placing sealed syringes in hot water or the expansion of liquid in a capillary tube as one end is warmed. Relate to simple thermometers and obtain suggestions how the devise can be used to measure temperature. Ask the students to consider particles and for their ideas as to what is happening to them as they are warmed. (b) Show an ICT simulation of particle movement in fluids at differnt temperatures eg http://www.walter-fendt.de/ph14e/
explain conduction (a) Role play conduction. Here, students for a conga line with both hands on the using the particle shoulders of the person in front to represent bonding in solids. As the person at model one and pushes backwards and forwards, the energy is transmitted down the line. Repeat but this time the students only use one hand, representing liquid they are then asked to explain why conduction is not as good in liquids. (b) Show an ICT simulation of partcle movement during conduction eg Institute of Physics' Supporting Physics Teaching (11-14), Energy CD. (c) Introduce to students that, in metals, conduction is also due to free electrons. How would students model electron conduction using role play? For example, a ball could also be thrown down the line.
explain convection (a) Imagine a really busy concert or dense crowd of people. Now imagine a group of people getting more and boisterous and dancing about. Within the crowd there in terms of the is a place where there is more space between the people. This is meant to particle model illustrate that in a crowd of gas particles, ubbles or pockets of lower density are possible.
(b) Ask the students to push an air-filled balloon into a bucket of water and let them experience the upthrust. Relate to a helium filled balloon and brainstorm why the balloon rises in air. Relate now to a hot air balloon and ask for student ideas as to why it rises. (c) Show pictures of hot-air balloons and ask students if anybody has experience in riding in one. Ask what the heater does and how the pilot makes the balloon go up an down. The students are to describe, in their own words or in pairs what is happing to the particles in the balloon as it goes on a journey.
understand that movement of particles increases with increasing temperature
(a) Ask students how they would role play particle movement in gases to younger children. Ask what would happen if they were given more energy and how that could be demonstrated. (b) Heat a conical flask that contains a little water. Then plug the opening with a pickled egg. As the air inside cools, the particles more less slowly, and because some of the particles were evacuated during heating there are less particle than before. The result is that the is an imbalance of pressure inside and outside the flask and the egg gets pushed in. Students could draw a cartoon strip of the various stages.
be able to use the particle model to explain changes of state
(a) Role play changes of state. Here the students put both hands on the shoulders of another student to represent 'solid', one hand on a shoulder to represent 'liquid', and no hands to represent 'gas'. Discuss the model with the students and how it could be improved to represent ice turning into steam. (b) Use an ICT computer simulation of particles movement during the three phases of matter and ask students to identify the features that are different in each state. (c) Research how changes of state are dependent of the surrounding pressure. Students to explain, using particle theory, why you can never get a nice cup of tea on top of a mountain.
Unit 8J Magnets and electromagnetism QCA sub-objective Suggested action (IoP activities in bold)
Can state that a magnet attracts magnetic materials but not others
(a) Highlight that most everyday materials are a mixture of different elements. Show a Periodic Table and explain that this is a list of the different ingredients that we now about. Pick out iron and state that this element is special because a magnet sticks to it! Use a magnet and a sample of iron to show that it is magnetic. Issue a magnet to students and they investigate what things contain iron (b) Investigate objects that a fridge magnet will or will not stick to, including something like copper pipes or silver jewellry (ie something that is metallic but not magnetic). (c) Students to find magnets around their own home and say why they are useful, emphasing the key words 'attract' and 'iron' (d) Hanging with magnetism (hovering paperclip)
Identifies which materials are magnetic. Pupil Challenge 1: All metals are magnetic!
(a) There is a very common misconception that all metals are magnetic. The classification of materials into electrical conductors in primary school suggests to children that metals are special when it comes to electricity. Therefore, it is not surprising that the same classification is transferred in childrenâ€™s thinking into the topic of magnetism. Metals are expected to be magnetic and non-metals are expected to be non-magnetic. In fact, most metals are not magnetic. The most common magnetic metals are iron, steels with a high iron content, nickel and cobalt. Elicit the student's starting point by testing labelled substances. (b) Get some samples of iron and pure copper. Which is magnetic? Now, investigate which coins are magnetic. Conclude that new copper coins must contain iron (or some other magnetic materials). (c) Referring to the Periodic Table, find and take time to pronounce Iron, Nickel and Cobalt. Indentify these as magnetic materials and that any substance that contains these will be magnetic to some extent. Refer to the word 'steel' and explain that steels contain iron and so are magnetic. (d) All materials are magnetic to some extent - show 'floating strawberry/frog' and/or 'magnetic oxygen'
Is aware that magnets have 2 poles n & s:
(a) Look at different types of permanent magnet inc. bar magnet, horseshoe magnet, flat magnets. Let the students play with them - which ends stick together and which ends push away? Try to push two repelling magnets together - who is the strongest person here? Ask how is a bar magnet turned into a horseshoe magnet (by bending it around). (b) Magnets have places where their 'magic' seems to be concentrated - these are called 'poles'. Pose the question ' What happens when a magnet is cut in half - does it have one pole and one end without magnetism?'. Discuss their ideas and demonstrate if possible. Tell them that even the greatest scientist that have ever lived have never found a pole on its own - they always come in pairs. (c) Show students compasses (especially walker's compasses) - what do they notice about them? Where would compasses be useful? Show the effect of different ends of a magnet on a compass needle.
Magnetism is much (a) Hang increasing amounts of weight from a neodymium magnetic hook. The stronger than gravity students should be amazed at how strong magnetism is! (b) State that if the Earth was a magnet the strength of the field would be 10^40 times greater than gravity (ref: Particle Physics book I have). Discuss this - what does this mean? In particular size and strength of magnet are not necessary the same. (c) Investigating the magnetic force
the strongest part (a) Cover a bar magnet in a thin clear plastic bag and dip into iron filings. Note that of a magnet is at the the majority of iron filings cluster at the ends. poles (b) Place a bar magnet on an OHP and use plotting compasses to construct lines
of force. The lines of force are more concentrated at the poles which is indication of a stronger field in that region and more force. (c) Race some ball bearing along a table by using a strong magnet underneath to pull them along. Ask the students what they did to make the balls move fastest, especially concentrating on the orientation of the magnet.
Knows that all magnetic materials have a North seeking and a South seeking pole Pupil Challenge 7: The magnetic N & S of the Earth
(a) There is a common misconception that gravity is related to magnetism. Children know that magnets are associated with a magnetic force and that there is magnetism associated with the Earth. When a mechanism is sought to explain gravity, magnetism therefore becomes an obvious candidate. Discuss the students' ideas with them and identify with them that gravity and magnetism are fundamentally different types of force. (b) Hang a bar magnet in a sling, taking care that there are not any magnetic materials near by that it may be attracted to. Consider what direction the magnet is pointing and what would happen if you kept on following the magnet north. Identify one end of a magnet as 'north-seeking' and the other as 'south-seeking. (c) Many students think that the Earth's magnet must be special because a north pole of a compass is attracted to the North Pole of the Earth. Emphasise that the Earth's magnet is â€˜upside downâ€™ and that fundamentally unlike poles attract. It can be demonstrated that the North pole of a walker's compass is attracted to the South pole of a bar magnet. (d) Finding North (e) The Earth's magnetic field
Recognises the shape of a magnetic field around a bar magnet Pupil Challenge 4: The magnetic field is those iron filings around it! Pupil Challenge 5: Drawing magnetic field lines
(a) It is common to show the shape of a magnetic field using iron filings, however, a magnetic field is a theoretical idea invented by physicists that is useful. There is nothing to see or touch around the magnet. When pupils first come across the idea of a magnetic field it is not surprising that many think the field is the iron filings they see. The magnetic field is the space around the magnet where it will attract or repel and the shape is best shown by first placing a bar magnet on a OHP and using a small plotting compass to gradually construct a 'line of force', and then another, each time discussing what is happening (b) A 3-D field viewer. Show that a magnetic field is in 3D space by using chopped iron wool in caster oil. The iron pieces align to point towards a pole and it shows that the magnetic field is all around the magnet not just flat on the paper. (c) Compare the fields of two magnets repelling each other to two balloons
being pushed together. Emphasise that the magnetic fields try to restore their original shape and so push the other magnet away. (d) Exploring a 3D space (using gimballed probe)
Knows that like poles repel & unlike poles attract. Pupil Challenge 2: Magnetism and Gravity are related!
(a) Explore a magnetic travel chess set. Which magnets are the same way up? This can be tested by trying to push their bases together - some will stick together and some repel each other. Students to write up their own conclusions. (b) Suspend a bar magnet from a stirrup. Bring another magnet near, showing the effects of different ends of the approaching magnet on the bar magnet. When is
the magnet pushed away? Repeat with a metal bar - note that it is not possible to make the magnet repel. (c) Emphasise the key word 'repel', and practise using it in sentences to replace 'push away from'. The sentence 'like poles repel but opposites attract' is a key one and students should be encouraged to remember it, perhaps by using analogies with personalities. (d) The magnetic force and the magnetic field (trains pushed together)
Magnets can work in a vacuum Pupil Challenge 3: magnets need air to work!
(a) Some students believe magnets need air to work. Challenge this misconception by demonstrating the effect of a magnet on a piece of iron that is inside a bell jar. Ask the students to predict what will happen as air is evacuated from the flask and then demonstrate that air is not needed for magnetism to work. (b) The magnetic force requires no medium to act-at-a-distance. The concept of a field is quite an advanced one and many students struggle with the idea that a force can be exerted without something being in contact with it. Compare magnetic force with gravitational force, listing the similarities and the big difference that it is possible to push something away with a magnet but not with gravity. Emphasise the fundamental importance of this difference - nobody anywhere ever has ever been able to work out why! (c) Obtain data about magnetic fields of planets and how far their magnetism extends into space. Point out that the magnetic fields do not depend on whether the planet has an atmosphere or not.
Understands that the magnetic field weakens over distance Pupil Challenge 6: The magnet sends out electricity!
(a) Use a force meter to measure how much force it takes to pull a bar magnet away from a retort stand base. Investigate the effect of placing thin sheets of card between magnet and base, concluding that the further the magnet is from the base , the easier it is to pull them apart. The effect of the actual card as opposed to air in the gap is minimal. (b) Use a magnet beneath an exercise book to magically move a metal object above. Challenge the students to guess how many pages are needed before the trick no longer works and then test it out. (c) Carefully observe two attracting magnets at different distances. Note the movement gets faster as the magnets get closer. Role play this observation.
States how magnetic materials can be made into magnets
(a) Firstly demonstrate that a steel rod is not magnetic then rub the length of a steel rod continuously and methodically with the same end of a magnet, taking care to only stroke the magnet in one direction (a bit like stroking a cat!). Test the rod to see if it is magnetic. (b) Place an steel rod in a solenoid (tunnel of wire coils) carrying a DC current. Test the rod to see if it is magnetic. (c) Repeat these procedures but use a soft iron rod instead on an steel one. The idea here is to show that it is easier to make a magnet out of steel than soft iron because the steel seems more capable of retaining the magnetism.
Knows how magnets can be demagnetised
(a) A strong magnet (such as rare earth magnets which are now readily available) can be used to hold coins. Heat the magnet strongly and the coins will drop. (b) Place a magnet in solenoid with AC current. Show that the magnet has lost its magnetism after a short time in the solenoid. (c) Get a magnet an hit it continually with a big hammer (usually there are no shortage of volunteers). Show that the magnet soon loses its magnetism.
Magnetism is reduced when the internal magnets in a material become disordered
(a) Many students feel that magnets do wear out because the magnets 'use up power' - perhaps sending out 'magnetism' and eventually it all runs out. To gain an understanding of demagnetism it is helpful to consider the magnet to be made up of internal mini-magnets. When the mini-magnets are aligned the overall effect is a magnetic bar but when they become disordered and out of alignment with each other, then effectively they cancel each other out. In real life, â€˜permanentâ€™ magnets do wear and lose their magnetism this is because the mini magnets gradual get out of alignment. (b) Demonstrate the idea of mini magnets lining up by using as many small magnets as are available. Discuss what the overall effect would be and compare to a situation where some of the magnets are not lined up. (c) Role play this idea by asking all of the students to point out of the window (hopefully they will all point in the same direction) and then ask them to point to where the Headteacher is at the moment - hopefully they will point in more random directions.
Describes the function of an electromagnet at a car recycling plantcar crusher Pupil Challenge 1: It's different kind of magnetism
(a) Students sometimes believe that bar magnets are different from electromagnets and that it is a different kind of magnetism. Discuss student starting points and emphasise that permanent magnets and electromagnets give rise to the same kind of magnetic force. It doesn't matter how a magnet is made, its magnetic properties are the same as another magnet. (b) Use a BIG electromagnet to demonstrate how strong an electromagent can be. Gradually add small weights at first and the kilograms at a time, amazing the students with just how much wieght it is possible to hold. (c) Demonstrate with an electromagnet that is suspending a load, the effect of cutting the current. Discuss why this different to a bar magnet and where this ability to switch magnetism on and off would be useful. Relate explicitly to a car
Recalls the use of electromagets in domestic electrical apparatusetc
(a) Demonstrate an electric doorbell. Here, a springy strip of metal (eg a hacksaw blade) is attracted to an electromagnet and one end hits a bell. It needs to be set up so that the strip is part of the circuit, and by moving it breaks the circuit and springs back, only for it all to start again. It is better if the students themsevlves construct this circuit and identify clearly each stage as it works. (b) Show students a modern 'fuse box', like they will have at home. Show the RCB switches that will cut out the electricity to different pats of the building and make it clear that each switch contains an electromagnet. Challenge students to explain how they work. (c) Start with the statement ' Electromagnets are often used as a safe way to turn on dangerous circuits' and let the students working in groups develop ideas. Would they dare to turn on a switch in a live national grid with 100 000's volts? I wouldnt - I'd use an electromagnet, but how? For example, a car has a start up current of 30A but a key is turned to complete a smaller circuit, that activates a magnet, that in turn completes the 30A circuit.
Describes how to make an electromagnet
(a) Students to construct their own electromagnets using insulated wire and a power supply that gives a high current (eg Westminster Power Supplies). Take care not to use a steel former instead of an iron one, because the steel former retains some of its magnetism when the current is switched off - which is detrimental to the key points about electromagnets. (b) Students to write an advertisng leaflet, explaining the key advantages of electromagnets, where they could be used how they are made. (c) Use internet resources to explore the commercial manufacture of electromagnets.
Recognises that wires carrying current produce an electromagnetic field
(a) Demonstrate Oersted's experiment. The secret here is to generate some of
the surprise and interest that Oersted experienced when he witnessed this phenomenon. Place a plotting compass on an OHP and agree that it is pointing North-South. Bring a wire near and note that nothing happens until a current of at least 5A is passed through the wire, when the compass will change direction. Conclude that a current carrying wire must generate a magnetic field. (b) A card with a loop of current carrying wire cutting perpendicularly across it is very much worth investigating as plotting compasses show a circular magnetic field around the wire. Next a card with a series of loops should show the magnetic field around a solenoid. (c) Students could construct their own solenoid by wrapping wires around a broom handle (or similar) and then removing the dowell and then investigate the effect on a plotting compass as the current is switched on and off. Mapping the field of an electromagnet
The strength of an electromagnet can be increased by the presence of an iron core Pupil Challenge 2: The core has a current in it
(a) Some students believe that the electric current flows through the coil of wire and into the iron and that the electric current then turns the iron core into a magnet. Actually, there is an electric current in the coils of wire of the solenoid and this creates a magnetic field, magnetising the iron core. There is no current in the iron core. Discuss this with students to ascertain their starting point (b) Students could construct their own electromagnet by wrapping a few turns of current carrying wire around a long iron bar (perhaps a retort stand), noting that the far end of the iron bar behaves like magnet. Compare the effects of using a wooden rod instead. (c) Use internet resources to investigate the manufacture of commercial electromagnets
Knows that the strength an electromagnetcan be increased by greater current Making Stronger electromagnets
(a) Use a simulation package, such as Focus Science Investigations that allows
students to model the magnetic effect of increasing current, in terms of the number of virtual paper clips the electromagnet can pick up.
(b) Students can perform an investiagation where an electromagnet is connected in series with an ammeter and a variable voltage power supply. How many paper clips can the electromagnet lift at different currents. (c) As (b) but card or beer mats are placed between the electromagent and a paper clip. What is the 'drop current' at different thickness of card. This investigation can be related to car manufacture because a similar technique is use to see if the correct thickness of paint has been applied.
QCA sub-objective Know which materials are transparent or opaque
Suggested action (a) Provide a range of materials that are either transparent or opaque. Ask the students to sort into materials that it is possible to see through and those that it is not. Introduce the keywords 'transparent' and 'opaque', paying particlular attention to 'opaque' as it is an uncommon word and label the two groups of materials. (b) Give the students a spelling test, introducing the words 'transparent' and 'opaque' and then ask them to produce a wordsearch containing these, and other keywords. An extension activity is a wordsearch or crossword with clues to the keyword. (c) Write the words 'opaque' and 'transparent' on 5 posticks each. Students to go around the classroom correctly sticking the postiks on transparent and opaque objects and then try to locate the postiks of other students.
Know that when an opaque object blocks a path of light a shadow is formed
(a) Produce a puppet show 'the Opaque Players', using silhouettes of figures on sticks in a dark room with a bright light source. Write a play where the words 'transparent', 'opague' and 'shadow' have to be included. (b) Place a large flipchart paper on a wall and illuminate a students profile. Draw around the shadow and afterwards, cut out, mount on black paper and make a wall display. The students are to explain what they have done using the word 'opaque' and 'shadow' and even 'silhouette', emphasing that light has been blocked out to form the shadow and that a shadow is formed due to the absence of light. (c) Using a ray box without a lens to it forms a wide beam, produce shadows by putting objects in the way. This helps students to identify that light comes from a source. Then ask students to spot other shadows at home or around the school, and try to find the light source in each case. (d) Compare shadows by using sources of differing intensities shining on an object from different directions.
Know that we can see clearly through transparent materials but not transluscent
(a) Introduce the keyword 'translucent' as being a substance that lets some light through. Provide a range of materials for students to sort into transparent, translucent and opaque groups by shining a light through them or holding up in front of a projector. (b) Use a data-logger and light sensor to compare the amount of light that is transmitted through different materials and tabulate their results. (c) Pose the question 'is it possible to get a suntan when swimming?' and discuss ideas and experiences. Imagine deep sea and describe what it is like - cold and dark because the light doesn't get down that far really. Introduce the idea that water looks transparent but it is translucent if deep enough and so the words 'transparent' and 'translucent' depend on the dimensions of the medium not just the material.
Know about luminous and nonluminous objects
(a) Consider with the students the keyword 'luminous', what do they think it means? Introduce some examples of objects that give off their own light eg a lit torch, candle or match. Define luminous objects as those that give off their own light and ask if they agree that everything is either 'luminous' or 'non-luminous'. (b) Use a yellow highlighter pen to colour-in all the luminous objects in a picture of a room. (c) Students play a pairing cards game, where the names of a variety of objects are on upside-down cards, some of the objects are luminous and some are nonluminous. The students are to turn over two cards and remove them if they are both luminous or non luminous. If they fail to pair up two then the cards are returned faced down and another person has a go.
Know that we see non luminous objects because they reflect light to our eyes
(a) Elicit students' ideas about how we see things. There are three basic misconceptions: eg "Light filled the room" i.e. the light is just there, "throw glances" i.e. the 'active' eye gives out something like a spotlight, "light goes into our eye so we can see" i.e. the light goes straight into the eye. Discuss these misconceptions drawing pictures to identify what they mean. (b) Consider how we see objects by constructing the path from the 'source', to the 'object', and into the eye through a 'medium'. Note that light travels to an object and then is reflected off non-luminous obejects in all directions but some of this reflected light goes into the eye. (c) Students should experience being totally in the dark - or at least as near as possible, use a bright torch to light a circle and ask the students to explain how it is possible to see objects, emphasising that that light is travelling into the eye.
Know that shiny objects reflect more light than dull objects
(a) Some students may believe that light is only relected off mirrors and find it difficult to comprehend that dull surfaces including people, walls, rocks, wood etc., are reflecting light. Reinforce the idea that light comes from a source or luminous object and goes into the eye, often by bouncing off objects first. Locate objects on a scale of reflectivity from mirrors at one end of the scale to black matte paint on the other. Students could be shown schematic diagrams or electron micrographs of ultra smooth vs 'bumpy' surfaces to see why (smooth) shiny things reflect light so much better and therefore seem shiny. (b) Introduce the idea of diffuse reflection by discussing snow and skiing holidays. Often sunglasses have to be worn because of the glare but it is not possible to see a reflection of yourself in the snow. (c) Survey lighting at home, listing the room, type of bulb, type of fitting, power, colour. Importantly, ask if the lighting is direct or indirect i.e. does the light go directly to the person or is it ambient lighting that reflects off walls and ceilings. Comment on the wall colour and the light level in the room, comparing the reflectivity of gloss and matte paint.
Know (qualitatively) how light is reflected at plane surfaces and describe reflected images
(a) Introduce reflection using a torch in a darkened room. Ask the students to predict where the reflected light rays go. Emphasise that light comes from the source and is reflected from the objects in the room, some of this reflected light will enter the eye and some will scatter off the objects elsewhere in the room. Some of this scattered light will enter the eye eventually as it reflects off the walls etc, giving the impression that the whole room is dimly lit to some extent. Draw a ray diagram of a several parallel rays incident on rough a surface, showing the reflected rays bouncing off at random directions. (b) Draw several parallel light rays incident on a plane mirror. Note that they all reflect off so that they still remain parallel and compare with scattered light. (c) Arrange two mirrors so that it is possible to see the back of your head. Students are to draw the ray diagram from the back of the head to the eye. Ask where the source of the light is and ask them to put this ray onto the diagram.
Know that an image formed in a plane mirror is laterally inverted
(a) Introduce the idea of the nature of a mirror image produced in a plane mirror. Ask students how such an image differs from the object viewed, and explore their explanations of why this happens. Students in pairs, to role play a person in a mirror, where one person pretends to be the mirror image of the other. (b) Ask students to explore the symmetry of images by predicting and testing which capital letters or words are symmetrical and by attempting to write words in 'mirror writing'. (c) Students could compare a photo of their reflection in a mirror with a photo taken front-on - in photos we look the wrong way round because we're used to seeing the inverted reflection in the mirror
Understand that light travels in straight lines
(a) Show the students a sequence of photographs of beams of light eg light shining through clouds, light rays in a mist, and spotlight beams where straight lines are clearly visible. (b) Show pictures of sharp shadows eg skiing pictures or sundials. In a dark room cast a shadow onto a screen using a bright light source, encouraging students to explain the phenomena in terms of a sequence beginning with light leaving a source, travelling through a medium and hitting the object. Students to draw a diagram explaining shadows - a ruler is essential, and to be clear that the shadow is formed when light is blocked. (c) Use a laser in a dark room to produce a spot on the wall. Then, sprinkle talc or chalk dust in the path of the laser beam and a straight line can be seen. Discuss why the dust enables us to see the beam. Emphasising that the only reason is that light is scattering off the dust into the eye.
Know how to represent the path of light by rays
(a) The first point to make clear to students is that a ray diagram is a simplication of a real event in order to only study information that is relevant. Also a light ray is a theoretical construction rather than something real (we should not refer to rays of light travelling away from a lamp) and that there are countless possible rays that could be chosed and it is our task to pick the key ones that are most useful to what we are trying to say. By making these points clear to students they should use ray diagrams to explain and predict events rather than go through the motions because the teacher tells them to. (b) Show how a specific ray diagram is constructed making clear to the students all the thinking behind the various stages. Use the examples of constructing a ray diagram for a shadow and for a pin hole camera image. Make sure that the diagrams are drawn in pencil, all rays are drawn with a ruler, and all rays carry an arrow showing the dirction of light travel.
Know how to identify the correct reflected ray from a plane mirror
(a) Roll a small ball on the floor so it hits the wall and bounces off at about 45 degrees. Repeat this for a number of different angles, without comment, and ask the students what they notice about how the ball bounces away and then to predict the direction that the ball will bounce off at. Consider what is meant by the term 'angle' and to predict the angle of relection of the ball Make the point that the aim of the activity is to think about light reflecting not bouncing balls. (b) Locate a projector in the middle of a room so that it casts a narrow beam of light across the lab. Switch off the lights and locate the beam. Ask students to predict where a mirror will reflect the beam to on the wall and then try out. Repeat with different mirror angles, establishing the idea that the more the angle is turned the greater the angle of relection. (c) Students working in pairs with ray boxes establish the idea that the 'angle going in is the same as the angle coming out' by using relection of the ray in plane mirrors and measuring with a protractor. Measure the angle from the mirror to the rays before and after the reflection.
Know how to apply understanding of angles of incidence and reflection
(a) Introduce the keyterms: 'incident ray' as the ray before reflection,'reflected ray' as the angle after reflection, 'the normal' as a theoretical line perpendicular to the mirror, 'angle of incidence' as the angle between the normal and incident ray, and 'angle of reflection' as the angle between the normal and the reflected ray. Concentrate on discriminating between these angles and those between the mirror and the rays. (b) Demonstrate the correct ray diagram construction of a reflection in a plane mirror on an OHP, but pause before drawing the reflected ray. Ask the students to predict the angle at which it should be drawn, refering to any earlier work with bouncing ball etc. Elicit from them that "the angle of reflection must be equal to the angle of incidence" and test using a ray box on the OHP that the theory is correct. (c) Students to work in pairs using ray boxes with slits to check if their predicted ray diagrams are correct.
Know about applications of reflection two mirrors
(a) On a piece of plain paper, students to draw the predicted reflected ray of two plane mirrors, and then test out their predictions using a ray box and slit. (b) Tell the students that they are going to use their knowledge of the law of reflection to invent their own device that uses muliple mirrors eg a device for looking over high walls around football grounds. Ask them to make a careful drawing of the invention, showing each of the mirrors, and to draw a single ray of light to show how it passes around the mirrors and into the eye. At each of the mirrors be sure to include the normal line and mark the angles of incidence and reflection. (c) Using a prepared worksheet showing the cross section of a periscope, students to show the path of light. Test them to see if they put the arrows on correctly and use the angle of relection correctly.
Know the effect of a (a) A shallow cookery dish, filled with water, and placed on an OHP, usually casts prism on white light a 'rainbow' on the wall. Examine the colours - how many are there and in what order are they in? Relate to a rainbow. (b) Demonstrate a of a beam of white light incident on a traingular prism in a darkened room. Make a poster, carefully drawing the colours and develop a mnemononic for remembering the order of the colours of the visible spectrum eg Richard Of York Gave Battle In Vain. (c) Research the work of Issac Newton on Light, especially on his attempts to further split the colours of light. This last point is important because white light is made up of the superposition of fundamental colours.
Know about simple refraction effects
(a) Some students only associate refraction with something that occurs with rectangular glass blocks. Research other refraction effects such a diamonds twinkling, mirages in the desert and 'bent pencils' in water. An interesting demonstration is to make a test tube invisible by putting it in a beaker of glycerol here the light travels the same in both media and the glass boundaries cannot be seen. (b) Demonstrate careful ray diagram construction of refraction on a OHP or using a PowerPoint presentation. Discuss student experiences of swimming pools appearing to be shallower than they actually are, and construct a ray diagram to explain why a fish appears to be swimming at a shallower depth. (c) Set up the 'reappearing coin in a cup of water' demonstration and ask pupils to explain how it works. Here a coin is placed in a cup and the eye is lowered until it is just hidden by the ridge of the cup. As water is poured in the coin can be seen again!
Know that the dispersal of white light to give a range of different colours is a form of refraction
(a) Research information about know speeds of light in different mediums. Tell students that if you look at the 'small print' the speeds are for light of one colour. Ask reasons why the small print is there - the answer is that different colours travel at slightly different speeds in different media. The values most often stated are for the speeds of yellow light. (b) Confirm that students are aware that white light is the overlapping of the seven visible colours. When white light hits another medium, the colours disperse because the seven visible colours travel at different speeds in the new medium. Demonstrate this by performing refraction experiments with glass bocks and a ray of coloured light. Different colours should be bent by varying amounts given the same angle of incidence. (c) There are several challenging questions that students could research and present their findings to the rest. The challenging questions include: Why is the sky blue?, Why are fog-lights monochromatic? Why do diamonds twinkle?.
Know about changes in the path of light when refraction occurs .
(a) Provide students with a range of glass or perspex blocks of different shapes, including retangluar and semicircular, and ask students to investigate their effects on a single ray of light produced by a ray box. Ask them to look for patterns in their observations and to note light rays bend towards the normal in the glass. (b) In contructing a ray diagram for refraction, firstly a normal is drawn perpendicular to the boundary at the point where the incident ray hits the boundary, i.e. four quadrants are made. Make it clear to the students that any refracted ray must emergy in the opposite quadrant. (c) There is an analogy with go-karts rolling down grassy hills that helps to explain refraction. Running along the bottom of the grassy hill is a tarmac road - surely the go-kart will be crushed by traffic!! Only refraction can save it now. If the go-kart hits the tarmac at an angle, one of the wheels momentarily moves faster than the other which is still on the grass, consequently the go-kart alters course. Emphasise that if a light beam enters a medium where it travels faster, it will bend away from the normal.
Know what effect colour filters have on white light
(a) Ask students to explore how coloured filters affect light by producing a spectrum and allowing this to pass through filters of different colours. (b) students investigate passing white light through one filter and then through a second filter. (c) Discuss how 'black' can be formed. Introduce the key concept that black is the absence of colour. Materials can look to have a black colour if all the colours of light are absorbed by it and none of them are reflected.
Know that coloured filters absorb some colours and transmit others
(a) Some students believe that a filter gives colour to white light rather than removing the other colours of the spectrum. Students use data-loggers and lightlevel meters to investigate the intensity of light as it passes through a filter. The intensity should drop indicating that some the light has been removed by the filter. (b) Produce a poster where the seven visible colours are incident on a filter as distinct bands of colour of equal thickness. The transmitted colour is only a seventh of the total width, indicating that other colours have not made it through the filter. (c) Discuss the effect of placing two differnt coloured filters behind one another. The results should be black as the result of no light passing through.
Know that we see objects as coloured because they absorb some of the colours of white light and reflect others
(a) Inform students that when light hits an object three things can happen: light is either transmitted through, reflected back or absorbed by the object (making it hotter). Demonstrate refelection and transmission by making a white light ray incident on a glass block - some is refracted (transmitted) but there is also a weak reflected ray. Now, remind students that white light is made up of a spectrum of colour and that propose the theory that in most objects the different colours are transmitted, absorbed or reflected. Discuss how this theory may make objects look in normal light. (b) Ask the students what is meant by the term 'white light'. Inform the students that white light is an expression for normal light. (c) Produce posters explaining how light interacts with objects and why objects are seen as different colours. The thickness of the transmitted, absorbed and reflected rays varies depending on the material and colour of the incident ray but always the total width of the three resultant phenomena is equal to the thickness of the incident ray.
Know how primary colours can be combined to form secondary colours
(a) Put a drop of water on a television set and observe closely. The individual primary colours should be seen. Alternatively on an old tv or colour monitor, a powerful magnet near the sreen distorts the colours and bands of green, blue and red light can clearly be seen. (b) Many students will have experienced mixing of primary colours together in art lessons and will be confused that light does not behave in a similar way. especially mixing more pigments together makes a darker colour. Emphasise that with light, this is not the case and actually added more light of any colour will make light more intense. Students to produce wall displays comparing colours in science and art. (c) Coloured light sources can be superimposed in a darkened room and the results recorded. Alternatively, software images showing mixing of colours of light are common and could be projected up so that students can see for themselves the mixing of light
Know the effect of different coloured light on coloured objects
(a) 'Colour' is considered by most people as an inate property of obects: "Light just lets you see the colour". Look at different colour objects in different colour light by using coloured filters on a bright projector in a darkened room. Tabulate results and discuss possible conclusions (b) Make a brightly coloured garden gnomes trousers disappear by rigging up different colour lights. The trousers will only be visible when light of the same colour is incident. (c) Research 'green-tinting' which is a way that television studios using a green background and superimpose weather maps when that colour is removed from the recieving spectrum.
8L Sound & hearing QCA sub-objective
Know that sounds are created by vibrations
(a) Show examples where vibrations are easily seen eg tuning fork and polystyrene ball, loudspeaker and grains of sand. (b) Provide familiar sound sources or pictures, eg musical instruments, and ask students to identify which parts vibrate to make the sound. (c) Students to make a musical instrument by folding tissue paper over a comb and blowing through the paper. The instrument make a noise and students can fell vibrations on their top lip.
Know a range of sources of sound/vibrations
(a) "If you hit a cymbal it vibrates to make a sound. If you drop a spoon on the kitchen table it just makes a noise". Students need to know all sounds are produced by vibrations. Where the vibration is less obvious, they tend to revert to ad-hoc explanations for the generation of sound, often focussing on human action eg ' the stones are making that noise because you are rubbing them'. With the students identify what could be vibrating for every sound they hear. A microphone connected to an oscilloscope with the time base off, will be deflected up and down for all sounds and noises. (b) Students could twang a ruler that is overhanging a table and held tightly at the other end against the table. By adjusting the length of the overhang different pitches can be heard. Students to describe in their own words the experience. (c) Students to research how humans can sing, including the function of vocal chords and the air boxes of the lungs and nasel cavities e.g http://www.voiceproblem.org
Know how notes of a different loudness are produced in musical instruments, eg the bigger the vibration the louder the sound
(a) Demonstrate how a musical instrument can make notes. Identify that there are distinctly two different qualities - pitch and loudness. Elicit that louder sounds are make by blowing or plucking harder whereas pitch is caused by faster vibrations. (b) Demonstrate a Rolf Harris 'wobbleboard' using a sheet of thin plywood or such like. Note that louder sounds can be made if the 'wobbleboard' has large amplitudes and also that more energy has to be put in to make the loud sound. Confront the student misconception: "With bigger vibrations it will sound higher" by eliciting that the sound produced is the same pitch and that louder sounds are formed with bigger vibrations. (c) Connect a signal generator to a large speaker. Make it clear that the frequency control is not being altered but loudness can be be adjusted by only altering the volume control. Close inspection of the paper cone of the speaker should show that quiet sound have low amplitudes.
Know how notes of a different pitch are produced in musical instruments
(a) Students can make a musical straw by flattening the end of the straw and cutting off corners so that it makes a rudimentary reed. By blowing into the straw the newly made flaps vibrate and the straw makes a 'kazzoo' sound. By cutting the straw whilst it is being blown into shorter lengths the pitch can be distinclty heard to increase. (b) Demonstrate two Rolf Harris 'wobbleboards', one large and one small. The two boards give off a different pitch note no matter how hard they are vibrated. (c) Connect a signal generator to a large speaker. Make it clear that volume is not altered by when the frequency dial is altered the sound changes pitch. Students can gently touch the paper cone through a range of frequencies. Introduce the term 'frequency' and ask what the students think it means, concluding that it is the rate that the speaker vibrates and that the pitch of the sound is related to frequency..
Understand that sound travels as vibrations which push particles to make a wave
(a) There is a student misconception that "Sounds come down the cable". Sound is not 'stored' on a CD, sound only comes after the loudspeakers and students have to identify 'sound' as a particluar type of energy transfer. Follow the path how live music gets from a studio to a living room, through sound wave to electrical signal to radio wave back to electrical signal and to sound wave again. (b) Imagine the largest 'jelly cube' in the world. Imagine putting your ear to one side and somebody else kicking the opposite side. Pose the question "would it be possible to 'hear' the kicks through the jelly" and discuss student perceptions. Show a Newton's cradle and ask what relevance has this to hearing sound - the idea is to show that particles can transfer energy to each other. (c) The BBC 'Class Clips' KS3 DVD has some excellent short clips and animations that will help students to visualise sound waves.
Know how changes in pitch and loudness of sound relate to changes in traces on an oscilloscope
(a) There are two big dangers of using an oscilloscope - sound is a longitudinal wave rather than a transverse wave and second, it is tempting to point to the wave on a screen and identify a wavelength as distance between crests. Actually the horizontal axis is time. It is important to explain to students that what they are seeing is actually a picture or representation of sound and that it may be benificial to start with the time base set to zero so the point vibrates about the same spot. (b) Connect up a microphone to an oscilloscope and whistle into the microphone. Can the students notice the difference in the signal? Alter the time base so that the frequency variations can be seen. Draw different frquencies for the same time base and relate to the pitch that can be heard. (c) Look at the insides of a microphone. Identify a vibrating membrane that sends out an electrical signal to the oscilloscope.
Know how traces on (a) Connect up a microphone to a oscilloscope and also a signal generator to a an oscilloscope large speaker. Ask the students to describe in their own words what would be relate to amplitude seen on the screen if the frequency dial constant is kept constant but the volume is changed. Test out predictions. (b) Identify 'amplitude' as a keyword and relate to loudness. (c) Provide representations of different sound waves and ask pupils to indentify, eg the loudest, lowest. Relate to sea waves crashing on a beach - big waves mean loud waves, but lots of quick waves means high frequency (or pitch).
Know that sound cannot travel in a vacuum
(a) There is a student misconception, summarised by: "I had turned my radio on very loud and music just filled the house". Here, the problem is could be that they donâ€™t appreciate that sound travels through a medium rather than an entity that flows into a room. Cosisently stress the need for a source-medium-detector model when considering different sounds. (b) Many students do not really have a conception of what a vacuum is, even Space requires quite an imagination. Discuss with students what is between air partcles and what is left in a gas jar when the air is pumped out. (c) Show conflicting TV footage (spaceships, superman etc) where explosions are clearly heard as well as seen. Ask what is wrong with the footage and what should 'sound' sound like in Space. This is of course, a trick question, as sound cannot be heard in Space.
Know how sound (a) There are two levels here: appreciating that light is faster than sound and that travels much slower light is x1000000 faster than sound in air. The second level is an important step than light as students begin to appreciate scale. Even the first level is not an everyday experience for most people because most things seem to make a sound straight away. Discuss student experiences of seeing fireworks and jet planes before they hear them. (b) Experience echoes by taking students to a large wall and clapping wooden blocks together. Ask the students why echoes can be heard and then why a time delay is never noticed if you look in a mirror or shop window. (c) Use the internet or other resource to find the values of the speed of light and the speed of sound in air. Ask the students to calculate how many more times light is fater than sound.
Know that sound travels at different speeds in different types of material
(a) It is important to realise that young students would never have experienced or noticed sound travelling at different speeds through different materials. Firstly establish that sound can travel through solids and liquids by asking questions such as "Can you hear through closed doors? Can animals hear underwater?" and demonstrate that it can by listening to sound through a wooden bench or by making a string telephone. (b) Consider the theoretical model of particles and how they transmit sound. Show a Newton's cradle and discuss what would be the effect if the balls were further apart so they can to swing a bit before they hit a neighbour. Conclude that if the particles are close together, like in a solid, sound will travel faster. (c) Research the speed of sound in different material and present on a class bar chart.
Know about energy (a) There is a student misconception that "Sounds run out as they get further away transfer involving from the source, and eventually stop". Sounds "die away". The answer is that the sound energy of the particles is more spread out as there are more and more particles involved -like ripples spreading out on a pond. Discuss the analogy of circular ripples on a pond and how it compares to sound, emphasing that sound propagation is in 3D. (b) Using a sonic ruler to measure distances around the room and then draw an accurate floor plan. (c) Show images of unborn babies using ultrasound and students to research the reasons for a gel between mother and reciever; and the limitations of using ultrasound eg it cant be used for images of lungs.
Understand how particle theory can explain how sound travels through materials
(a) There is a student misconception that "The air just in front of loudspeaker is pushed into your ears" Sound is not a packet that travels from source to ear. A good counter argument is that sound travels through solids.Students to put their ear on a table and listen to sounds coming though the table. This may help the students appreciate that sound is getting to them through wobbles in the table. (b) Students to draw a poster, showing how sound travels through a medium from a source to a detector. Encourage students to show sound spreading out from a source and not just a single straight line. Ask students why sounds are quieter further from the source. (c) Use hand held sound meters to investigate 'sound shadows' ie. areas behind obstacles where the volume of sound should be less. Research why sound shadows are less definate than those of light.
Know why sound travels faster through solids and liquids, using particle theory and understanding of energy transfer
(a) The key here is to explain that if the particles are closer, they knock into each other quicker. The particles have shorter distance to travel and so hit a neighbour more quickly. Role play sound propagation at arranging students so they stand half a meter apart. One student starts rocking gently back and forth, from one foot the the other. As he/she touches their neighbour they start rocking and so on until the 'sound' moves down the line. Now position them closer so that they are almost shoulder to shoulder. This time the sound should propagate down the line quicker. Discuss the relevence of sound travelling in solids, liquids and gases (b) Students to listen closely with an ear to a metal railing that is tapped some meters away. Inform the students that sound travels five times faster in metal than in air and ask them to pictorially explain why.
Know that the effects of vibration to the eardrum are transferred to the brain Know that sound makes the eardrum vibrate and this is how we hear
(a) Elicit ideas from students about how we hear sounds. A model eardrum, eg balloon material stretched over a large beaker, can be used to demonstrate the how vibrations can lead of changes of air pressure in the ear (beaker). Discuss experiences of ears 'popping' (e.g. at height, on a plane, under water) and relate hearing to air pressure changes. (b) Describe the scenario of shouting to somebody on a really windy day and ask the students to explain why they cannot hear you. (c) Demonstrate a large speaker showing the paper cone moving up and down in response to electrical signals. Tell the students that the ear works like this in reverse - like a microhone. Ask the students to write in their own words the energy energy transfers associated with an ear.
Know that animals & humans have different hearing ranges (including different hearing ranges in humans)
(a) Use an audio signal generator to generate a range of sounds of different pitch. Clearly demonstrate that the volume control has not been altered. Ask the students to all raise a hand and lower it again when they can no longer hear the sound. Establish an upper and lower range and discuss why a teacher often can't hear the same range as young people. (b) Software such as Multimedia Sound can provide a spectral analysis of sound. Here, the whole range of superimposed frequencies from a sound are shown graphically. Inform students that there is a window of sound which it is possible to hear and that many sounds go unnoticed by the eardrum. (c) Discuss with students what they know about the hearing range of animals eg long-distance communication in whales, ultrasonic echo location in bats, and dog whistles. Demonstrate the use of a dog whistle
Know how the ear works (including describe translation of sound waves into electrical signals which are transmitted to the brain)
(a) Show them an anatomical model of the ear, illustrating the relative sizes of the parts and how they are connected. Explain how the eardrum vibrates as a result of sound entering the ear, and the transmission of vibrations to the inner ear. In the inner ear, vibration is changed into electrical signals that are sent to the brain via the auditory nerve. (b) Students to produce a leaflet "How we hear", intended to be shown to parents at an open evening. (c) Students to investigate whether two ears are bettter than one in detecting direction of sound by blindfolding a volunteer and asking to point to the source of sound, then repeating but with an ear plug in one ear.
Know ways in which (a) The BBC's Class Clips DVD shows footage of the function of auditory cells hearing can be and because they die off, people's hearing range naturally deteriorates with age. impaired Contrast sound to light, in terms that it is possible to determine with sound individual frequencies whereas with light a superposition of frequencies leads to a new colour. Consequently, the range of sound that people can hear can change with age, whereas the range of colours people see generally does not. Students to explain why music could actually sound different to older people. (b) Students to research the ways hearing can be impaired interms of loss of auditory cells, hardening of eardrum, or problems with ear bones. They could present their work to other students using OHP and flipcharts to other students. Encourage students to compare their own presentations with those of others and to identify good and bad points in them. (c) Research Hearing Aids and how they have become more advanced but still do not fully replicate a healthy ear. Investigate hearing cones made out of rolled up paper and whether or not they do improve hearing.
Know how to relate (a) Present students with information about hearing impairment, eg among hearing impairment different age groups, and ask them to suggest possible reasons, eg exposure to to possible causes loud sounds at work, exposure to loud sounds when young, inherted deafness. Help students evaluate possible explanations and to think of reasons for supporting and rejecting them. (b) Use some accounts of people's experience of temporary deafness or tinnitus to discuss with students what excessively loud sound can do to hearing. Use a model or diagram of the ear to discuss what might cause the problems.
recalls that the loudness of sound is measured in decibels
(a) Introduce Alexander Graham Bell, who is credited with inventing the telephone, and that the measure of loudness is named after him - the bel, and that one tenth of a bel is a decibel. It is a complicated scale, a bit like the Richter Scale that measures scale earthquake magnitude, but it ranges from 0 dB, which is the threshold of human hearing to 140 dB, which is a billion times greater. (b) Students to research decibel values of aircraft noise, rock concerts etc., draw a picture of the source and plot on a large scale for all to see. (c) Use portable dataloggers to measure decibel values around the school.
Know that loud (a) Raise issues of noise pollution eg near airports, due to traffic and listening to sounds can damage loud music. Relate to a model or diagram of the ear and ask how either the hearing excessively loud events or prolonged exposure can possible damage parts of the ear. Discuss any experiences of ear damage due to noise pollution. (b) Research current law regarding workers rights to noise pollution and present to other students. Use sound-level meters to compare the levels that they are exposed to during the course of a day. (c) Use a sound-meter to measure the rate at which sound diminishes from a source and graph the results.
Know ways in which to reduce noise pollution
(a) Investigate the effectiveness of spongy materials and rough surfaces as sound insulation, eg with a clock in a box filled with different absorbent materials. (b) Research anechoic chambers used in, for example, concert halls, recording students and even car research plants. These are chambers where ambient noise is reduced to a minimum so that only sound eminating directly from the source is recorded, as opposed to also recording echoes off walls. The chambers are characterised by very irregular walls made of spongy material - ask the students to explain way. (c) Consider ways in which people who exposed to loud noise as part of their daily work are protected from noise pollution (ear phones, ear plugs, exposure restrictions) and how hearing capablility can be tested.
Unit 9I Energy and electricity
Sub-objective Know that energy is converted from one form to another to be useful
(a) Energy is not a physical quantity that makes things happen, it is an abstract quantity that can be calculated in many ways. Relate Energy to an amount of cash - the quantity that you have limits what you can do but does not compel you to do anything. Introduce the currency of energy to be a Joule, rather than a ÂŁ or $. (b) 'My auntie used to keep money in different pots around her house and sometimes take money from one pot and put it in another', in a similar way energy is stored in different ways and shifted from place to place. Recall some of the names of the various 'energy pots', eliciting answers such as 'kinetic', 'heat', 'potential', 'sound' . Draw a picture of an auntie moving energy around her house from one pot to another.
Know that energy transfers and transformations are involved in useful energy changes
(a) It is often not useful to think of types of energy but it is better to think of energy being the same, wherever it turns up. However, energy shifts from one store to another. Provide the students with cards with 'types' of energy store labelled on them, which are consistent with their experience of energy teaching in previous years eg 'gravity', 'elastic', 'thermal', 'sound', 'kinetic' and 'chemical'. (b) Explore an energy circus with a range of toys and devices, asking the students to pick the energy store before and after. (b) Things get done when energy changes from one store to another but it is important to point out that sometimes things 'get done' without there being any shift in energy. Consider various situations where things are happening, such as: car driving along a road, rockets taking off, a cannonball falling back to earth, spacemen drifting through space, the Moon orbiting the Earth, an object on a spinning planet - and ask which of this situations involve energy change (the first three) and which do not (the last three).
Classify devices on the basis of type of energy input or output
(a) Ask students to explore a circus of toys and devices, eg battery operated vehicles, clockwork toys, electric bell and a yo-yo. In each case they are to identify the source of energy and the principle output. Group the devices together in terms of a common input or output and add some other examples not seen. (b) Provide the students with cards with 'types' of energy store labelled on them, which are consistent with their experience of energy teaching in previous years eg 'gravity', 'elastic', 'thermal', 'sound', 'kinetic' and 'chemical'. Show the students devices that convert energy from one source to another eg a steam engine and ask the students to place cards on either side of the device to show input and output energy. (c) It is difficult to label 'electricity' as an energy source because it really is a method of transferring from energy stores. Consider the generation of electricity using a generator or dynamo and identify that the original store of energy is chemical.
Know the advantages of using electricity as a way to transfer energy
(a) Electricity is not a thing but a means of transferring energy from one store to another. Consider the big picture that electricity has made it possible to tap into the stored energy in coal, oil and wind, so that the energy can be brought to our homes. Think about lifestyles before electricity eg gas-lamps, only live music etc. Ask the students to sum up the impact that electricity has had on lifestyles in a few concise sentences. Elicit ideas that life would be dirtier, less-convenient and that there would be far less communication around the world. Electricty has changed everybody on the planet, forever. (b) Brainstorm with the students devices around their home that 'use electricity' and ask them if they had to choose, which one would they get rid of. Discuss that we are as a society, dependent on electricity and think about the future. What new inventions are their going to be? What is the world going to be like in 50 years? When batteries and solar panels get more advance, what kind of clothing will we have? http://youtube.com/watch?v=Yd99gyE4jCk .
Know about energy transfers in everyday changes
(a) Identify the energy in certain foods from the packaging and calculate the energy consumed by a student in a day. Consider where that energy has gone and the effects on the body of eating too much or too little. Emphasise that a person's body requires a certain amount of energy to keep warm and functioning. (b) Compare a standard light bulb with an energy efficient one. Ask the students to touch the bulbs - careful, the standard one is hot! Consider the energy going in and coming out of the bulbs. Do we want light bulbs to get hot? Why does the energy efficient light bulb use less electricity in the same time? Elicit from students ideas that many devices transfer energy to forms that are not useful
Recognise ways (a) Define 'fuels' as chemicals that can be burnt to get things done. in which energy is Brainstorm types of different fuels including food. Fuel is a physical thing stored associated with an energy store but ask if other situations can be associated with a storing energy. Elicit ideas about objects held high up have an energy store, as do springs under compression, hot objects, and even moving objects have a store of energy. (b) Students need to develop the idea energy stores often depend on more than one object eg fuel-plus-oxygen and object-plus-Earth are the energy stores.
Understand that transducers can give out energy when put in an electrical circuit
(a) Indroduce the term 'transducer' as any device that gives out energy and challenge the students to name ten transducers in 30 seconds eg light bulb, TV, cooker. Inform the students that a more limited definition is that a 'transducer' conversts a signal to one form to another and includes gramophone pick-up's, piezoelectric crystals and Geiger-Muller tubes (make a clicking noise when radiation present). Ask the students to name some transducers using this narrower definition, but only to help them clarify their thinking to electrical circuits. (b) Energy boards such as those from the Science Enhancement Programme (http://www.mutr.co.uk/prodDetail.aspx?prodID=394) are a useful resource to show various types of transducers on a board. For each devices, students to name the type of energy outputs (c) Discourage any ideas that electricity is a thing at moves from point A to B. Instead encourage a model that electricity is more like a bicycle chain transferring energy from one store to another.
Know that an (a) Study the work of Ampere to give a context that the ammeter is named ammeter after a famous scientist. (b) Introduce different types of ammeter that measures current students may come across in science including an digital and analogue meter and recall that it is used to measure electric current. Emphasise that all ammeters have got a postive and negative terminal. Ask the students to imagine that there is a 'little helper' inside each ammeter with a counting stick in one hand and a watch in the other. The helper counts the number of electric charges that pass in front every second and displays the value on a screen. So how should we connect the ammeter so the helper can do its job? Elicit ideas that the ammeter has to be part of the circuit - put in as you would put in a new piece of track on a model railway. (c) Challenge students to correctly insert ammeters into circuits. Use simple circuits with one or two bulbs and ask them to measure current at various points in the circuit.
Understand how (a) Demonstrate using a rope loop to represent current. Here, the rope is current behaves pulled around by the teacher and is held by a student. If the student holds in a simple circuit tighter than it is harder for the teacher to pull the rope i.e. there is more resistance. Introduce the idea that the current is the amount of rope that passes a point each second. Discuss the speed of rope at various points in the circuit - it is the same! In the same way current is the same at all points in a simple circuit. (b) Ask the students to measure the current using an ammeter at apoint in a simple circuit. Challenge students to predict the currents at various other points eg after the bulb or between two bulbs, and then to check out their predictions. As many students are not yet certain of the significance of decimal points, it is advisable, to use ammeters that are not too sensitive. Digital ammeters that measure to 2 dp may give readings of, say, 0.48V and 0.49V. There is no relevant significance in the difference but can confuse students.
know that a (a) Show the students various types of voltmeter (analogue, digital), voltmeter emphasising that they come in different shapes and sizes but all have two measures voltage terminals and all measure in 'volts'. Draw comparisons with how ammeters look, pointing out any differences such as location of terminals or coloured shunts. (b) Imagine two corridors of students moving from one class to another. It is possible to say that one corridor is much busier compared to the other. In the same way, a voltmeter compares the energy between two points in a circuit. One terminal is connected to one place and the other is connected to another place and the difference in the energy between the two places comes up on the screen. It may be useful to introduce an alternative term for voltage as 'potental difference'.
Understand the link between energy and voltage using a simple model
(a) Model 1: A rope loop is pulled by a teacher through the fingers of a student. The students fingers get hot because of the work done by the teacher. If a second student is added to the circuit, the teacher has to work harder to heat up bothe their hands. The energy in is now spread out over two people. A voltmeter could measure the amount of energy transferred across each person in the circuit (b) Model 2: The battery in a circuit relates to a ski lift. The bigger the voltage of the battery the higher the ski lift. As charges 'ski' back down to the bottom, they lose gravitational potential energy. When they have descended half way they have half the original stored energy ie half voltage. (c) Model 3: A fleet of bakery vans continually drop off loaves of bread at a supermarket. The voltage is the voltage corresponds to the number of loaves dropped off. If there is a second supermarket and the bakery cannot increase production, then each gets some of the loaves and so the voltage across each drops.
Understnd how energy is transformed between a cell and a circuit
(a) The term 'cell' is often introduced without explaination. Enquire of the students whether they have heard of a 'battery of solidiers'. In the same way, what is commonly called a 'battery' is a collection of electrical 'cells' working together. The cells are more obvious in a car battery. (b) Show some pictures of simple series circuits and identify the cell (or battery) as the engine in the circuit. Demonstrate pulling a rope loop through the fingers of students. The engine is pulling the rope and the student is feeling the effects because their fingers are getting hot. In the same way a battery pulls a current around a circuit and the effects are shown in the components eg light bulbs. Another useful analogy is to use a steam engine turning a fan belt that operates say, a loom or printing press. The engine's energy it transferred elsewhere because of the fan belt, just as the cell's energy is transferred elsewhere because of the current.
Understand that cells can produce diferent voltages depending on the reactivity of the metals used as electrodes
(a) Research the conflict between Luigi Galvani and Alessandro Volta, leading to the first battery in 1800. Modern cells consist of two electrodes of differing metals in an ionic solution. The solution is more obvious in a wet cells such as a car battery, but dry cells contain an 'ionic' paste. Draw a picture of a rudimentary cell labelling the component parts. (b) Experiment with a simple electrical cell made with a lemon. To prepare the lemon, gently squeeze it to soften it up, and the insert clean pieces of copper and zinc (5mm X 40mm) into the fruit, close together but not touching. After a few minutes a votlatge can be measured with a sensitive galvanometer. Recall from chemistry, that metals can be placed in a reactivity series and ask the students to predict and investigate different combinations of metal. Lemon cells can also be connected in series with each other to make a battery that can light an LED.
know that some devices use more energy than others.
(a) Devices convert different amounts of energy in the same time. Emphasise this by discussing microwave ovens that have two power settings. The directions on a microwave food packet provide cooking times at different settings (eg 4.5 mins at 650W, 3.5 mins at 750W). Use sets of figures such as these to help students grasp the idea that high power electrical devices can transfer a lot of energy in a shorter period of time. (b) Relate to battery powered toys and devices that students have at home. In their experience, which ones use the batteries up quickest? Elicit ideas that moving toys go through batteries quickly, whereas a radio seems to last for ages without changing the batteries. (c) Students could collect some information from older neighbours and relatives about the appliances that they had in their homes some 30-40 years ago. Use this information to highlight how many more appliances are now more common, and that although modern machines are less wasteful of electricity, there is a lot more strain on resources.
know which appliances use more energy than others
(a) It is a very useful exercise for students to investigate the power outputs of electrical appliances in and around the home. By collecting the figures and grouping them according to size, students can find out that appliances with the biggest power outputs are those that have some kind of heating function. (b) Encourage the students to locate and look at their electricity meter at home. If possible, the students could relate how quickly the dial goes around when an electric cooker or heater is turned on. Compare with normal rate when the heavy heating appliances are not on. Does turning the TV on make much difference to the speed of the dial?
Understand that some appliances transfer more energy than others in a given time.
(a) Ask the students, working in groups, to identify as many expressions as they can that use the term 'power'. Isolate the term as having a particular and distinct meaning in science ie how much energy is transferred each second. Many students will have already come across the unit of power, the watt, outside school. This may be buying light bulbs, choosing hi-fi systems or adjusting the microwave. Consider experiences of using a 40W instead of 100W and use other links to demestic appliances that help students to undersatand that power is related to energy in a given time. (b) Introduce the term 'kilowatt hour' and ask the students to infer what it measures. It actually is a direct measure of energy used (1 kWh = 3600000 Joules) and it is the amount of energy used if a kiloWatt fire is on for 1 hour.. Sometimes is is called 'a unit'. Relate to an electric bill - how much is charged for each kWh? What could be done to reduce the electricity bill?
Understand how electicity is generated from a range of energy resources.
(a) Brainstorm the students' initial ideas of sources of energy. Elicit sources such as nuclear, coal,oil,gas , wind, water, waves and the sun, distinguishing between sources and devices that drive electrical current, such as generators, wind turbines and solar panels. List the sources and ask for each how electricity is obtained from them. Link the source to a device ie nuclear, coal,oil,gas, wind, wave to a generator and the sun to photo-electric panels. (b) Look at a diagram showing how a power station works eg http://www.uic.com.au/uran.htm. Emphasise that the energy store is released to heat water to turn turbines to drive a generator. Ask students what other fuels could be used to heat the water..etc. Elicit any ideas about burning rubbish, getting methane from cows, etc. (c) Discuss the student experiences of photo-electric solar panels. Have they seen them on houses or calculators or spaceships? Imagine all the possibilities of improved panels. Emphasise that solar panels do not need a generator to make electricity but do need to charge up batteries if they are to be used at night.
Know the structure of a simple electricity generator
(a) The key feature of almost every electrical generator is circular motion. Demonstrate a dynamo connected up to a large demonstration ammeter, set up so that a twist of the dynamo gives a flick on the ammeter. Demonstrate a wind-up radio that give a pulse of radio reception if the handle is rotated a couple of turns. Ask the students how to get electricity all the time? The answer to keep rotating the dynamo. What do students consider ways to keep this turning as much as possible? Elicit ideas to put a propeller or turbine on the shaft. If possible, demonstrate a rotating turbine in the steam from the spout of a boiling kettle. (b) Emphasise that dynamos and generators can come in all sizes. There is an alternator in a car, generators for camp-sites, and huge generators in power stations but they are all similar in design. Use a model generator to show the copper turns that rotae with the shaft.
Understand that electricity can be made to flow by causing movement in an electrical generator
(a) Move a thin copper rod in a the magnetic field of strong horeshoe magnet. A sensitive ammeter connected across either end of the wire will show a flick of electric current. Note that when the wire is stationary there is no current and movement is essential. Also, note that the faster the wire is moved the bigger the flick on the ammeter. Demonstrate that the same effect is noted if the magnet is moved relative to the wire. This is the work of Michael Faraday. Ask the students working in groups, to design a way to make it easier to move the wire in the magnetic field. Discuss their designs and show a cross-section of a dynamo or starter motor, highlighting the coils of wire neatly arranged around the shaft so that they move when the shaft is rotated. Note that the magnetic field is often not made by a permanent horseshoe magnet but it is produced in another set of coils instead (but that's another story...). (b) Use a wind up radio to investigate how long the reception lasts for a certain number of turns of the handle and/or turning rate.
Understand that electricity cannot be stored and is generated on demand
(a) Ask the student what electricity is. 'Electricity' has no particular meaning in science, but it is important that students do not think of it as being used up like a pile of money. In that case their would be no need for a circuit. It isn't possible to have an 'electricity store of energy', it just is a way of transferring energy from store to store. It is, however, possible, to have an 'electro-magnetic store of energy' of which batteries and capacitors are two examples but both of these devices are only viable for small scale storage. It is not possible to store excess energy on a large scale by charging capacitors and batteries. (b) Explore what is meant by the National Grid and how it store energy using hydro-electric power. Inform the students that the demand for electric current varies. At what time of day and year is there the most demand and why? During times of high demand, water is let out of dams to drive hydro-electric plants.
know the difference between useful energy and wasted energy
(a) Recall that most power stations work using steam. The steam of made by using fuels. Consider what happens to the steam after it passes the generator and show pictures of cooling towers. Inform the students that in times of low demand the generators can be switch off and all the heat goes up the chimney and heats up the air. Ask the students if they consider this to be wasted energy. Elicit ideas that it is wasteful because the energy that goes up the chimney is not useful to anyone. (b) What are the students' experiences of patio burners? Do they consider these to be wasteful for energy and discuss whether it is important to worry about wasting energy? (c) Sometimes energy can be wasted because it is not in the form that you want it. Can the students think of any examples? Demonstrate a filament light bulb and note that it is hot, ask what is the useful form of energy and the wasteful form.
know that during energy transfers energy may go to waste
(a) Use a BIG pendulum, suspended from the ceiling and a volunteer. Pull the pendulum bob of the nose of the volunteer and let it swing. Despite the fears of the volunteer, the bob will not swing back onto their nose but it's swing will progressively diminish in amplitude. Establish with the students that some of the energy has been lost from the system with each swing, it is 'wasting' energy each time and less and less is useful to make it swing.(b) Energy efficient light bulbs often state the equivalence to filament bulbs eg 'this 20W bulb is equivalent to a normal 100W bulb'. Ask the students what the other 80W are doing in a filament light bulb. Encourage ideas that the light bulb is 'wasteful' because it gives off heat. Draw Sankey diagrams for the two bulbs where an arrow splits to show the proportion of the output energies. Consider other devices that transfer energy and where they may produce wasteful energy.
Understand ways in which energy waste can be reduced
(a) Provide information about the major energy loses in a home and their proportions of total loss, eg through roof 35%, through windows 20% etc. Discuss what could be done to prevent heat loss in each case, eg loft insulation, curtains etc. Also provide information about the cost to install these energy saving measures and their annual payback. Calculate which are the most cost effective. Produce a leaflet, giving impartial advice about what people could do to save fuel bills. (b) Broaden the issue to looking at use of energy in different ways, eg ask pupils to consider how environmentally friendly electric cars really are. (Although electric motors are three times as efficient as internal combustion engines, the electricity has to be generated first.) Compare battery-powered cars (recharged at the mains) with fuel-cell powered models. Compare the energy required to make a car with the energy needed to run it (ratio is approximately 10:1). Is the real issue about replacing old, inefficient cars with new, more energy-conserving ones?
Understand that when energy is transferred none is lost
(a) A pendulum swing will gradually diminish and many students think that this is evidence that energy is not conserved. Similarly, if methylated spirits is burnt, after a while it has gone. What must be emphasised is that, in both cases, the air has got hotter ie there is an increase in the stored energy of the air. The total energy, including the wasteful energy, is the same before and after an event. (b) There is a conflict between the sentiment 'to need to save energy' and the law of conservation of energy which can cause confusion amongst students. Brainstorm with the students ways to save useful energy around the home eg double glazing, turning off lights etc. but emphasise that what is being attempted is to obtain a greater proportion of useful energy. Illustrate using a Sankey diagram, that the total energy is constant but that there is a split between useful and wasted energy.
9J Gravity & space Sub-objective
Know that gravity is an attractive force acting on the earth towards the centre of the planet
(a) Some students believe objects fall simply because thay are heavy. Practice drawing situation diagrams where students draw straight arrows, proportional to weight, for various objects. Encourage students to also draw the earth, so that they can see that gravitational forces point to the centre of the earth, rather than just vaguely 'downwards' (b) Emphasise that gravity is an at-a-distance force rather than a contact force by asking them to hang from a beam and 'feel the force of gravity'. (c) "I throw an object into the air. Are there any forces acting on it after it leaves my hand?". This is a probing question that reveals that many students commonly cant accept that gravity acts consistently down throughout the motion. Consider a basketball shot at stages during its flight. Ask the students to draw force arrows, emphasising that their is only one arrow, representing gravity, at each stage.
Know that the gravitational pull of the Earth is strongest nearest the surface
(a) Ask the students to draw gravity arrows on aeroplanes and ask how high the plane would have to fly before gravity no longer acted on the plane. Inform them that it would have to 'fly' much further than the Moon before the arrow would be too small to draw. Show a graph of gravity strength per kilogram mass against height to show the gravitional pull drops off with height exponentially. (b) Some students believe that gravity must get stronger away from the Earth because objects that are dropped from higher up fall with more 'force' i.e. a louder bang. Indentify students that have this misconception by asking diagnostic questions involving force arrows at different heights.
Know that the amount of gravity a planet exerts depends on its mass.
(a) Show cereal packets that appear to be unopened but have actually had weight inserted. Students are to lift the normal packet and the heavier ones are what the packet would feel like on Saturn. Discuss why objects will feel heavier on Saturn, eliciting any ideas that it is because Saturn is more massive. (b) Some students believe that there is no gravity on the Moon, because objects 'just float around'. Confront this misconception by showing clips of astronauts walking on the moon or of objects falling on the moon, emphasising that the Moon does exert a gravity but it is less than that on Earth. (c) Use secondary sources to find out the weight of 1kg on other planets. Produce a phamplet advertising 'Loose weight - travel to Mars!' and discuss if such a phamplet could be produced for other planets.
Know that mass & (a) There is a conflict between everday language and scientific language, weight not the same summarised by 'my weight is 55kg', which needs to be addressed. Inform students that this is one of the times that science language is different from everyday language, and that in science weight is not correctly measured in kilograms or stones but because it is a force it is measured in Newtons. (b) Equate to property prices - the cost to build a house is much the same everywhere but how much it is worth depends on its location. It's the same with mass and gravity. The mass of an object is the same everywhere but how much it weighs depends on its location. (c) Students to correct everyday tables that show 'weight' expressed in kilograms, for example tables that relate amount of pet food to a pet's 'weight'. Ask students why they think so many things are incorrectly labelled, concluding that some things have become established already and it is easier just to remember to convert them whenever it is necessary.
Know that weight is (a) Some students believe that gravity only applies to falling objects. Confront caused by the force this misconception by drawing force arrows on objects in static situations such of gravity acting as books on tables, emphasising that on Earth all masses are subject to a force upon a mass.
due to gravity. (b) Ask students to lift masses of a known value and feel the attractive force of the Earth's gravity pulling them down. Emphasise that nobody understands why gravity exists - it is one of the great mysteries of the Universe. (c) Show pictures of spiralling galaxies and discuss Black Holes as regions in space where gravity is so large that everything near gets pulled towards it. Write a descriptive passage of what it would feel like to enter a Black Hole.
know that on Earth, 10N of gravitational force is experienced by each 1kg of mass
(a) Use a spring balance, calibrated in Newtons, to measure the force exerted by the Earth's gravity on known masses. Tabulate results and discuss a conclusion. Consider what would happen if this experiment was carried out in deep space or on the moon. (b) Students to measure the weight of volunteers using bathroom scales measured in Newtons and convert back to calculate their mass measured in kilograms. Use a conversion chart that converts Newtons to the imperical measures of stones, pounds and onces. (c) Produce a large wall display showing pictures of objects such as cars and animals, with their mass, in kilograms, written next to them. Pin on cardboard arrows representing weight onto the pictures. Use a consistent scale eg 1N = 1cm.
Know that mass (a) It is acceptable to state that mass is the 'amount of stuff in an object'. does not change but Imagine floating in deep space and ask the students if they weigh less and then weight can.
ask them if there is any less 'stuff' in their bodies. Draw diagrams of spacemen on Earth and in deep space, arrows may be drawn to represent weight but mass is a scalar quantity that has no direction associated with it. (b) Show video clips of spacemen floating in space eg www.esa.int/spaceflight/education. Ask the students if they are closer to the Earth than the Moon is? The moon is pulled around in an orbit due to gravity, so how come the spacemen appear to be weightless? The answer is that they are not in fact weightless but appear to be weightless because they are constantly falling. (c) Ask students to sketch, on a mini-whiteboard, to draw a graph of mass against distance from the centre of a planet. It should be a straight horizontal line. Ask if a graph of weight against distance from the centre of a planet would look similar.
Understand that distance is a factor that influences gravity.
(a) Look at video clips of the Space Shuttle lifting off from Earth into space. Consider where the rocket seems to burn most fuel and inform the students that when in space, it doesnâ€™t use fuel at all. Discuss why the rocket needs less and less fuel as it gets higher, eliciting ideas that its weight becomes less. (b) Some students believe that gravity must increase with distance because the distance to far away planets is so big that it must need a bigger force to keep them in orbit around the Sun. Confront this misconception by asking the students diagnostic questions, such as drawing force arrows on the planets due to the Sun's gravity. Emphasise that even a small force acting over a long period of time can pull a planet in an orbit. Relate to light intensity that gets less with distance from a source. (c) Introduce the concept of a 'field' ie any region in space where the effect of gravity is felt. The field strength rapidly decreases with increasing distance but astronauts are still in the Earth's gravitational field even on the moon (as indeed is the Moon itself).
Tides are produced because of the influence of the Moon's gravitational field
(a) Many students believe when it is low tide in the UK, it is high tide on the East Coast of the USA. Draw contour lines of the height of the Atlantic Ocean when there is a full moon overhead. The mass of water gets pulled up in the middle, and the tides on both sides of the atlantic are low. Empahasise that it is similar to pulling up table cloth in the middle. Confirm this by comparing tide times on both sides of the Atlantic, correcting for time zone changes. (b) Draw a picture of the Moon over an ocean of jelly. Draw on a straight force arrow from the ocean upwards towards the Moon. Label this arrow 'force of gravity due to the moon'. Consider what will happen to the ocean, eliciting ideas that it would bulge towards the Moon. Consider if the Earth only was made of ocean, with no land. In groups, the students could draw how the bulge moves as the Moon orbits the Earth. (c) Project work with titles such as 'where are the biggest tides in the world?', 'what effect do tides have on fishing?', 'do other planets effect the tide?', 'does astrology have any basis in science?'
Know that the Earth was thought to be the centre of the universe
(a) Using secondary sources, investigate the contributions of Nikolaus Copernicus, Giordano Bruno and Galileo Galilei in shaping our view of the Universe. Illustrate the struggles they had in having their views recognised. (b) Before satellite pictures, evidence for our position in the Universe came from studying the motion of stars and planets. Complicated models of motion are possible to explain the motion of the stars and planets with the Earth at the centre, eg Ptolemaic universe, but a sun centred model is much more simplistic. Consider why powerful authorities such as governments and religions insisted on an earthcentred model
Know that the Earth (a) Some students when asked to draw the Earth will draw a circle and will draw was thought to be people and clouds correctly, but when asked to draw rain and hair they will fall flat
to the bottom of the page - although they will tell you the Earth is round they do not actually believe that gravity acts towards the centre of a planet but instead it acts downwards. Ask students to draw force arrows for objects in Australia to elicit their starting point. (b) The horizon at sea seems flat unless it is viewed from a considerable height. Write a passage descirbing the bravery of explorer's like Christopher Columbus who set off to sea, with many believing he would sail off the edge of the world. (c) Use an time line to show the historical breakthroughs in thinking including the lifetimes of Ptolemy, Copernicus, Galileo and Columbus
Know how our (a) Research the Ptolemaic theory of predicting the motion of the planets. It was understanding of the very accurate but the Sun-at-centre or 'solar system' theory displaced it because solar system essentailly it was a much simpler, less convoluted theory. Appreciate that that developed
science from ancient times is not neccarily crude in its content and approach. (b) Show satellite photographs of the solar system and of artist's impressions of planets. Inform students that looking at Pluto is like trying to study a dust particle half a mile away, and that information about planets is still sketchy. It is important that students appreciate the huge scale of the solar system and that our understanding of the solar system will remain incomplete. Even travelling at 50000 mph it would still take 50000 years to reach the very edge of the solar system. (c) Research the objectives and data returned from Mariner satellites around Mars, and more recently the Cassini-Huygens probe around Saturn and the Galelileo probe around Jupiter. Consider the enoromous cost of such programmes and discuss whether the expense is justified.
Know that the moon (a) Agree that the Moon orbits the Earth in a circle but question who thinks it is a is a natural satellite satellite? The definition of a satellite is any object that moves around another of the Earth object, so the Moon and Metosat (the weather probe) are satellites of the Earth, and the Earth is a satellite of the Sun. Ask the students to list other examples of satellites and what they orbit around. (b) Consider the spelling of the keyword 'satellite', inventing a mnuemonic to help remember.
Know that the orbits (a) Demonstrate swinging a bucket of water around in a circle. Ask: 'What is the of planets/moons direction of the force?', concluding that there is nothing pushing the bucket are roughly circular
around, only the tension in the rope pulling it around. Many students believe that: 'something must keep satellites going. Donâ€™t thay have big rockets that push them around their orbit?'. Highlight this as a misconception and that the only thing keeping a satellite going around is the force of gravity. (b) Draw the solar system using drawing compasses. Emphasising that the scale between the planets cant be consistent, or else the circles for the outer planets would be way off the page. Sketch on the elipitical orbit of Neptune and of comets to highlight that some orbits are not circular. (c) Use an animation to show the simultaneous motion of Earth orbiting the Sun and rotating at the same time, and of the Moon orbiting the Earth and rotating at the same time. Emphasise the difference between 'orbiting' and 'rotating' or 'spinning' about an axis.
Know what an (a) Discuss with the students what they consider to be 'artificial' satellites - they artificial satellite is. are man made. Refer to Arthur C Clarke, the science fiction writer, who first proposed the idea. Research the history of Sputnik 1 and Telstar, trying to give an idea of the competitiveness between the USA and the USSR at the time. (b) Consider with the students this statement: 'something must keep satellites in the air because they are heavy - after all, aeroplanes have big engines and wings donâ€™t they!'. In fact, Sputnik was about the size of a basketball, but none of the satellites require engines. Demonstrate this by swinging a bung around on a string, so that it goes around in a circle. The bung does not have any engines but it is going in a circle. Satellites are pulled around in a circle by gravity, the speed of the satellite has to be just right so that it neither spirals into the Earth or is lost in space. (c) Research how many artificial satellites are in space. Consider what is to be done with them when they are no longer any use - do we have a responsibility to tidy up our space rubbish?
Interpret simple data about satellites
(a) Satellites have to orbit in a great circle about the Earth i.e. the plane of their orbit must pass through the centre of the Earth. Orbiting above the Earth in a kind of halo orbit is not possible. To emphasise this draw a satellite orbiting the Earth, without drawing motion arrows, and consider the force arrows on the satellite. There is only one and that is towards the centre of the Earth. Since satellites do not have engines, their speed is fixed depending on their height above Earth. Satellites that orbit closer to the Earth move faster. (b) Some satellites take pictures of the Earth and so the data that they transmit will depend on the resolution of the camera. Compare the resolution of digital cameras from a catalogue - what does 'resolution' mean? (c) Research 'Galileo', 'Cassini' and 'Megallan', which are artificial satellite around other planets. What information are they gathering?
Understand the use (a) Find examples of how satellites are used now in communications, weather of satellites in forecasting, business, agriculture, resource management transport and science simple contexts by clipping relevant articles in magazines and newspapers or from a collection of website addresses (ESA and NASA). Start a satellite wall display showing why satellites are considered to be increasingly more useful to mankind. (b) Model how GPS systems work by positioning three stationary students in corners of the classroom, representing satellites, and a forth student representing a car. By calculating the time for a signal to travel from the satellite to the car, and by knowing how fast the signal travels, it is possible to calculate the distance between the a satellite and the car. Use a fixed length of string from one of the 'satellite' students to the 'car' student. Show that the car could be anywhere on the radius. By combining with distances between the other 'satellite' students and the car it is possible to fix its position. (c) Show Google Earth. Zoom in to locations of interest, emphasising that the images have been made from satellite photography.
Know that satellites have different orbits depending on their function
(a) The two most useful orbits are geostationary and polar orbits. Geostationary orbits are positioned above the equator and are at just the right height to keep above the same spot on the Earth. There is only one possible distance for a geostationary orbit and this is getting full. The other useful orbit is polar where the satellite crosses above both poles and so can not be above the same point on the Earth. Demonstrate the two orbits with a globe and table tennis ball. Note that stellites in polar orbits will travel faster if they are closer to the Earth so the images it produces are of less resolution than a geostationary satellite and there are times when it is on the other side of the world. (b) Refer to old fashioned flash photography where the subjects had to remain stationary for a few moments and explain that as much light as possible had to enter the camera. Emphasise that the same is true of the digital camera and discuss what is needed for high resolution satellite images.
Know that the Sun is large & exerts a very large gravitational force keeping the planets in orbit
(a) Show that the gravitational effect of the Sun is felt over huge distances by researching the Oort Asteroid Belt, which is considered to be the edge of the Solar System. In particular the huge distance it is from the Sun, but emphasise that asteroids still orbit the Sun due to its gravity. Consider what the Sun would look like from these distances. Similarly, consider Halley's comet, which travels vast distances from the sun before it is pulled back and returns to orbit at a much closer distance every 76 years. (b) Some students believe that gravity must be stronger if it is to pull distant planets into an orbit. Emphasise that gravity is considerably weaker for distance planets but it is still there and does still have an effect. (c) Swing a bung on a string around in a circular orbit and discuss the forces on the bung. Draw situation diagrams of the planets and the Sun, showing that there is only one force on the planets and that is towards the the Sun. Consider why the plants continue in a circular orbit and do not move closer to the Sun.
9k Speeding up QCA objective
Know that if you travel faster you travel a fixed distance quicker
(a) Working in small groups the students compete to see who can come up with the most words or phrases that describe 'speed' eg 'lightning quick' or 'fast as a bullet'. Discuss how their answers could be ranked - which has the highest speed? Then introduce the idea of speed as a measure of the distance travelled over time. State that speed doesn't necaessarily mean fast. (b) In groups, the students sort cards of pictures of animals into groups of fast, medium and slow. They then have to identify cards that they found difficult to place or justify their groups. (c) Students match pictures of moving objects with cards with values of distances travelled each second and compare work with others.
Know that that speed is distance/time
(a) Focus the students attention on the idea of speed, where it occurs in everyday life and what units it is measured in by showing pictures of different examples examples of speed limit signs. (b) Consider speed cameras that measure the time it takes for a vehicle to travel between lines marked on the road. Ask if the students have noticed these lines and discuss how the speed of the vehicle could be calculated. (c) Watch video clips of fast moving action eg athletics, car racing. Discuss how the speed of the moving object could be measured. What measurements would they take? Use the clips to measure the time, estimate the distance and calulate the speed, considering the units.
Knows the units of speed (a) Estimate the speed at which a caterpillar walks, fingernails grow, jet planes move at etc. Listing as m/s the various units and emphasise that in each case the speed is quoted as a distance divided by a time. Think of other possible combinations of distance and time and ask what these units could be used to measure! Introduce metres per second as the unit of speed that is used most commonly in science. Pay attention to the word 'per' and consider what it means. (b) There are different notations for the units of speed (eg mps, m/s, ms-1) which can often confuse students. Find out what units they have been used to seeing in mathematics. Confront the problem with the students and agree which one makes the most sense. Show the relationship between distance/time and metres/second (c) Many students think that a bigger number means faster eg 60km/h is faster than 40mph. It is important to emphasise to students the importance of units. Illustrate this by looking at different units in the context of another quantity eg height.
Know that average speed is the total distance divided by the total journey time
(a) Draw a large equilateral triangle. In the bottom left-hand corner write 'average speed', in the top corner write 'total distance travelled', and in the right-hand corner write 'total journey time'. Students to make their own copy on card and use it as a reminder of how to calculate average speed by placing their thumb over the top of 'average speed'. (b) In threes students measure the time for a student to run 20m and then a further 20m. Two of the students have stopclocks that they both start when the third student starts to run. The 'timers' are positioned at the "0m and 40m marks and stop their clocks as the runner passes. They are then to discuss if the student run the first 20m faster than the second by comparing times. Inform them that average speed is total distance divided by total time. (c) Taking it turns students compete to blow a marble around a race track. Tabulate and calculate ave speed on a spreadsheet. Ask the students where they lost time and relate to how that effected their average speed.
Know that average speed takes into account variations in speed that occur over the course of a journey
(a) Refer to a speedometer and ask what it is actually measuring. The answer is the speed of the wheels and it is an instaneous speed. Compare the expression 'instaneous speed' with 'average speed'. Elicit what the students believe the difference is and ask them to give examples. Agree a contract with the students that you (the teacher) will also say either 'average speed' or 'instaneous speed' rather than just 'speed' when teaching. (b) The idea of average speed can be highlighted by first asking the question: 'if Pedro travels 40 miles in an hour, how fast is he going?'. Students will probable reply 40 miles per hour. Then relate to a real journey, where the car stopped at lights etc. Say this journey also took an hour to travel 40 miles - how come? Elicit from them the idea that speeds are often not steady but the average speed includes periods when the car was moving faster and slower than the average. (c) Compare distance-time graphs for walkers and runners.
Calculate speed from distance & time
(a) A circus of events such as trolleys on an incline; bubbles rising in a water column, paper helicopters. Students have to calculate the speed of objects. Students could then rank in order, appreciating that speeds can be compared even if distances are different. (b) From a suitable viewpoint, students to calculate the speed of vehicles passing along a road. Discuss the measurements that need to be made and devise a strategy for surveying average speeds along the road. A series of video clips of cars can be found in the Institute of Physics' Supporting Physics Teachers CDs. (c) It is often fruitful to approach the mathematics department of a school and see what overlap there is with teaching this subject. Also, the mathematics textbooks have a large number of repetitive practise questions.
Calculate distance from speed & time
(a) Algebraic manipulation of formulas is recognised as a major problem for many students. Display the word equation speed=distance/time and then issue the students with a series of true or false statements such as: 'A man walking at 8m/s will travel 16m in 2 seconds', 'A car travelling at 100m/s will travel 1000m in a minute'. Discuss if any of the students used a form of the equation to derive their answers, and if so what was it? Take students through simple comparative relationships eg 20metres in 2seconds is the same as 10 metres each second. Establish the equation distance=speed xtime. (b) Try to avoid teaching using symbols instead of the words. In many textbooks, distance can be represented as an 's', or 'x' and speed as 'v'. Also when rearranging equations it is good to keep track of the real quantities involved with early learners. (c) Estimate the speeds of aircraft, ships and cars and convert to metres/second using a conversion chart. set questions such as if the car had enough fuel to continue at that speed for 5000seconds, how far would it travel in this time?
Interprets distance/time graphs
(a) Visit http://phet.colorado.edu/web-pages/simulations-base.html and download the Moving Man for an interactive animation that plots graphs simultaneously as a man moves. (b) Arrange the members of the class at equal distances around a playing field and issue each with a stop clock. A volunteer runs passed each student and they record the time from the start to the time that they pass. Tabulate all results on a class board and then ask students to graph the results. Inspect the graphs and ask the students to draw lines of best fit asking what their line of best fit shows. Repeat with another volunteer and compare the graphs. (c) Race a woodlouse or a maggot down a race track made between two rulers. Record the times to pass each 10cm and plot these times on a distance-time graph.
Interprets speed-time graphs
(a) 'Multimedia Motion', CDrom by Cambridge Science Media, has many clips of various motions that can be paused and various graphs can be plotted. It is possible to compare distance-time, speedtime, and acceleration-time graphs for the same motion (b) A team of students to measure the time taken for a trolley to pass various points on a ramp. Speeds are calculated and the results are plotted on a speed-time graph. Repeat with differnt angles of the ramp and compare graphs. (c) Introduce the term 'accelerate' ask students what they understand by the term. Show a speed-time graph for a falling object reaching terminal velocity and discuss which parts show acceleration.
Know that an applied force can cause a change in speed
(a) It is counter-intuitive to think of friction-free environments. If a force is applied to a heavy box, it doesnt always move! This applet, http://phet.colorado.edu/web-pages/simulations-base.html. Forces in 1 dimension, shows a gradually increasing force eventually overcoming friction and then accelerating the body. (b) Demonstrate a trolley with srings attached to either end and to equal weights hanging either end of the bench. The trolley will stay put until one of the strings is cut. Before this, ask the students if there will be a resultant applied force and what will be its effect. (c) Imagine riding a bicycle and lifting your feet off the pedals. Describe the motion. Does the bicycle stay at a steady speed forever? If it changing speed, what is slowing it down? Relate to a sdiagram of the situation and draw on a force arrow representing resistive force (friction + drag)
Know that an object continues at a steady speed unless a force acts on it.
(a) It is common sense, though not correct, to think to keep an object moving at a steady speed you need a driving force. It is important to separate the initial force that started the motion, from any subsequent forces which might be present during motion. Consider firing a gun. Does the bullet speed up after leaving the muzzle? No, it achieves a speed during the explosion. Consider throwing a book along a desk. Does the book carry the throwing force with it? In this way, the initial event that got an object up to speed can be shown to be different to the subsequent motion. Ask the students to think of similar examples (b) Video clips of the sport of curling are useful to show motion in a low friction environment. Look at the clips, deciding where force arrows could be drawn during motion. Discuss the motion and the arrows if curling was played on grass. (c) Imagine maintaining a spaceship and throwing a spanner into space. Describe the motion. Would it speed up or come to rest? What forces are acting on it after the spanner as it leaves your hand?
Know that a greater force will cause a greater change in speed to a moving object
(a) A trolley with string attached to one end and to a weight hanging over the edge of the bench, could be used to demonstrate the effect of more force on speed. Agree with the students that if the trolley, starts from rest, and then travels the same distance in a shorter time then it must be change speed more quickly. Also agree that changing the weight will effect the driving force, and ask the students to investigate the effect of greater force on change in speed. (b) Relate vehicle engine sizes to publicised 0-60 mph values. Tabulate results and conclude that a larger driving force results in a shorter time to get to 60 mph. (c) Some students will find it confusing that a car has to exert a greater force to get up a hill but the speed doesnt increase, or that the same force can be applied to different masses and result in different changes in speed. It is important to stress that in everyday world there are often other forces that complicate the picture and the mass of an object is important. Issac Newton was so clever because he managed to work it out despite all the confusion of everyday experience.
Know that friction opposes motion.
(a) Some pupils believe that friction is only associated with moving objects and some that it is only associated with stationary objects. Ask the students if you are experiencing friction when you stand and when you walk. Secure a sandpaper strip onto a ramp and place on top a sandpaper block. Gradually increase the angle of the ramp amd discuss why it doesnt move at first. Elicit ideas that the grains of sand lock together up to a point, and that there is a force resisting motion. It is important for students to realise that friction is not a phenomenon, just the name given to the resisting force. (b) Inform the students that even apparently smooth objects have rough surfaces when looked at under a microscope and ask them to draw two rough surfaces in contact. Demonstrate gradually increasing the force to a sandpaper block on a flat sandpaper surface. Discuss the size and direction of the friction force before and after the block starts to move. Compare ideas with pushing a smoother block over a smother surface. (c) Ask the students to write a story 'the day in the life without friction'.
Know the factors that increase or decrease friction.
(a) An elastic band catapult can be used to slide a 100g mass along a table top. A class competition could find the group that could slide their coin the furthest. Discuss the reasons why they won (more force, smoother surfaces). To make it a fair test, keep the force the same and investigate the effect of putting some olive oil of the table. Ask what effect theoil had on friction. (b) Before a curling match water is sprayed on the rink. Why is this? The answer is that the little bobbles of ice that are formed reduce the contact area between the ice and stone and so the stone has even less friction. In fact, to slow down the stone as it approaches the target these bobbles are swepped away to increase the friction. Use this information to deduce that contact area is important factor in the amount of friction. Reinforce by showing a worn brake pad from a bicycle and ask why its no good in terms of friction and its function. (c) Demonstrate increasing the angle of a ramp until a block starts to move. Ask the students to predict what would be the result if a heavier block was used? Students investigate their predictions.
Interpret information (a) This applet http://phet.colorado.edu/web-pages/simulations-base.html. Forces in 1 dimension, can about friction from motion be used to record limiting friction values on a number of different objects. (b) Students to perform experiments. investigations into the frictional force associated with pulling a shoe with a forcemeter. Find the force to just make a shoe move and investigate the effect of putting weight into the shoe. Compare with different shoes and discuss why some shoes are disgned to have high friction. (b) Consider the force arrows on a block of wood that is being pushed along a table. Gradually increase the force and ask what the value and direction of friction would be before it moves, as it is moving with a steady speed, and as it is being made to speed up. Ask students to draw force arrow diagrams for each of the three situations and closely inspect their work. (c) Roll a trolley down a ramp and measure its stopping distance. Students to investigate the stopping distances on different surfaces eg paper, carpet.
Know that air & water (a) For many students air is nothing. Remind them of a really windy day and imagine what it would be resistance increases with like to stick your head out of a sunroof of a moving car. 'Why do you think that we call air resistance?' increasing speed and, as a class, summarise its properties eg. it gets bigger as the car moves faster, it slows you down, it depends how big your head is. (b) Ask students to suggest why streamlining is important for fast-moving fish. Why does streamlining help an athlete to run or swim faster. Write a radio advertisement for a streamlined car, explaining the advantages that streamlining brings. (c) Imagine cycling home in cold rain. The particles of rain hit more often the faster the cyclist travels. In this way, relate to air and water being made of molecules that hit an object more often the faster it goes. Know how to draw & label two forces acting on an object.
(a) Take the students out for a tug-o-war competition. Establish two even teams and then unbalance the teams by asking one or two students to join the other team. Draw the situation diagrams so that the students can see and ask them to stick the correct sized carboard arrow onto the diagram. Conclude that the correct force arrows could even help us predict the outcome of a tug-o-war event (b) Many students are sloppy when it comes to drawing force arrows and, of course, the teacher should always give a good example. They should be straight, proportional in length to the size of the force, and acting from the object. If students are finding drawing arrows difficult, then card stencils of arrows of different lengths could be used. (c) Show to the students that forces are there all the time but they can only be seen with Force Spectacles.Remind them that the force of gravity is there all the time. When the sunglasses are worn then force arrows can be seen on objects. While a volunteer is putting them on, add cardboard arrows to everyday objects. Joke with the class that there isnt enough arrows for everything so we'll have to be selective when we use them.
Knows that a change in speed is the result of unbalanced forces.
(a) To many students it is counter-intuitive to think of friction-free environments. This applet, http://phet.colorado.edu/web-pages/simulations-base.html. Friction in 1 dimension, shows a gradually increasing force eventually overcoming friction and then accelerating the body. The animation shows force arrows cancelling out up to a point and then, when motion occurs, the resultant force is greater than zero. (b) Some students persist with the idea that for steady motion to be achieved that the driving force must be slightly bigger than the drag/friction forces. Pursue the idea that a even a small inbalance will cause the object to change speed but it may be while before that change in speed is noticed eg a comet has a small force acting on it but eventually it picks up speed as its passes the Sun. (c) Draw a situation diagram of a tractor pulling a load. Discuss what would happen to the speed of the tractor if the load fell off. Students to draw a wall display explaining the situation without using any written words.
Know about the effect of (a) Inform the students that objects are either moving at a steady speed or at a changing speed. Pose balanced forces acting the question: 'well, what if I have no speed?' and inform them that it is important to realise that if on objects objects are still then they are said to have a steady speed of zero. (b) Imagine you are travelling in along a motorway in a car. Does the driver need to have their foot on the accelerator all the time? When you are travelling at 50 mph, does the driver need their foot on the floor all the time? If the car ran out of petrol would it suddenly stop? Why does it say the most economical speed for my car is 56 mph?. Use these questions to elicit student ideas about motion, leading them to conclude that for steady motion all that the engine need to do is overcome friction. (c) Consider the forces on the curling stone in a vertical direction -its not rising or sinking even in motion, so what can be said about the resultant vertical forces? The resultant force in the vertical direction must be zero (i.e. weight is equal and opposite to the reaction force)
Intrepret acceleration and (a) The students in groups, consider a choice of pre-drawn graph shapes. Ask them to pick the correct deceleration from a graph shape for a falling object, and then ask them what their graph axis represented. 'What would be speed/time graph. the graph shape if the axis were speed against time and what would its general shape look like if the axis were acceleration and time?'. (b) An applet show graphs being simultaneously constructed at the same time as motion can be found at http://www.walter-fendt.de/ph14e/acceleration.htm. (c) Consider a speed/time graph for a car journey. Use the graph to answer questions such as: 'At what times did the car speed up and slow down?' Understand the various stages of a parachute descent.
(a) Students have to appreciate that objects accelerate as they fall under gravity, but also to recognise that they may achieve a terminal speed due to drag forces. Imagine the experiences of a skydiver. First they speed up, gravity pulling them down with a constant force, but as they fall, the wind in their face gets stronger and stronger. They may reach a velocity when the downward weight is equal but opposite to the drag force. At this point ask the students what the resultant force is and what would happen to their motion. Some will argue that they should stop if there is no force - but clearly this doesn't happen! When the parachute is opened, suddenly the drag that such a large canopy produces unbalances the forces, the resultant is upward and the skydiver's descent slows down. Note there are two possible periods when the velocity is constant, the second as a skydiver slows to a point when the drag again is equal and opposite to the weight. (b) Investigate terminal velocity by timing ball bearings to descend in a tube of wallpaper paste. Mark the tube at regular intervals and challenge the students to find when the ball bearins started to fall at a constant speed..
Interpret graphs of parachute descent.
(a) Provide the students with data of speeds at various stages of a parachute descent, including speeds before the opening of the parachute. Students to construct their own graph and label stages. Writing an account of the descent as if they were giving commentary they are to describe what if feels like at the various stages of the descent (c) Students drop model parachutes and toy people and observe the descent closely. Time how long to takes and compare with different size parachutes or weights. Students to draw graphs for each descent and present their work.
Unit 9L Pressure and moments sobj
Recognises that pressure (a) Relate to the students that as part of their training as scientist thay have to realise that, in science, = force/area some keywords have a particular meaning. Ask the students to write as many expressions as they can that include the word 'pressure'. Use their answers to form groups. State that in science, the word pressure only means one thing and that is force divide by area. (b) Ask the students to push themselves in the chest with a flat hand and then a pointed finger. The force was about the same, but why did the poking finger hurt more? Elicit ideas about the force being 'concentrated' to a point, and write sentences that explain the experience using the words: pressure, force and area. (c) Deflated bike tyres have more area in contact with the floor. It is worth associating the pressure of air and the pressure that the tyre makes with the floor. 'If I remove air from the tyre and decrease the pressure inside, what happens to the tyre?' Elicit ideas that it flattens out because of the weight of the bike and associate increasing area and decreasing pressure.
Able to apply qualitative assessment to pressure situation
(a) It aids understanding to emphasise that pressure is a scalar quantity ie it should not have an arrow associated with it. Forces act on objects in particular directions, pressure is just a useful measured quantity. (b) Show a brick to the students and challenge them to position the brick so the pressure is at its lowest value and at its highest value ie. balanced on its end. Explain why they have chosen those positions. Emphasise that the weight of the brick has not altered. (c) Ask how students could survive if they walked into quicksand. Many will know the advice to spread out but ask them why, challenge them to use the expression 'force on each unit of area'. Draw two situation diagrams showing a person lying down and standing up. On each diagram position 5 cardboard arrows, each representing 10N. In the case of the person lying down they are spaced out but in the case of the person standing the arrows overlap to act only at the feet.
understanding the units for pressure
(a) There are several units for pressure such as, 'bar' and 'pounds per square inch'. Show pictures of different pressure readings such as weather maps and footpumps. Agree that it will be easier if we only use one unit in science. Refer to the equation, pressure=force/area and recall the units for force as 'Newtons' and the unit for area being 'square meters'. Challenge the students to derive the standard unit of pressure as Newtons / square metre. (b) It is a common confusion amongst learners to mix the 'number of square metres' and the 'number of metres squared' eg a 2x2 metre square board has an area of 4 square metres but to state 4 metres square implies 4x4. (c) The standard unit for pressure can be represented as N/m2; Nm-2 or Pascals (Pa). It is a source of confusion for many students and so it is advised that in teaching, you use the full words whenever possible ie. Newtons on each square metre, to give a feel of the use of pressure as a quantity.
doubling or halving force (a) Display the equation pressure=force/area and input some figures. Keep the area value constant over constant area (but not equal to 1) and calculate the pressure values for different forces. For each case try to get a picture of the physical situation by saying pressure has a value the same as 'so many Newtons per square metre'. (b) Use a tray of sand and a square of chipboard. Students investigate the depth of indent against load on the board. Discuss results and conclude as a group. Elicit ideas that the value of pressure has doubled when double load is added and as a consequence the indent is deeper. (c) Describe a scenario where an indian tracker can tell whether a horse carries two passengers or none at all by looking at the hoof prints. Discuss how the tracker could know and relate to a scientific experession relating weight and the resulting pressure value. pressure = force/area
(a) Some students will understand an equation better by inputting numbers rather than letters. Display the equation pressure = force/area and input some numbers. Keep force value constant, say 10N, and calculate the new pressure when the area is altered (b) Use a mnemonic to help remember then equation pressure=force/area such as 'pantomime equals food over the areana' (c) As a homework, research the science meaning of the word 'stress' related to materials. Ask students to identify the difference between the word 'stress' and 'pressure'. It difference is that stress has a direction associated with it but pressure is a scalar quantity
describe some effects (a) Some students believe that gases are too 'thin' to have a pressure value. Show the Gas Properties and uses of gases under applet found at http://phet.colorado.edu/web-pages/simulations-base.html to visualise why gases pressure exert a force on the walls of the container (b) Introduce the word 'pneumatics'; ask about experiences of gases under pressure, eg bicycle tyre ('pneu' is french for 'tyre'). (c) Demonstrate a model steam engine and show how useful machines can be made by increasing the pressure of the gas. Ask students to explain why the steam has more pressure when heated using ideas of particle motion.
describe an effect of atmospheric pressure
(a) Heat an opened drinks can and then submerse in water. The can should collapse. Ask the students to explain, paying particular attention to answers such as: 'the can collapsed because the vacuum sucked the walls in'. Students need to appreciate that the can collapsed because there is an imbalance between the force exerted by particles outside the can and the force exerted by particles inside the can. (b) Show the students of flat fish that live on the bottom of the sea eg skate, and tell them that we are at the bottom of a sea as well - a sea of air! Discuss what the effects of living at the bottom of the sea would be for the fish. 'It doesn't notice it because its used to it' and explain that we dont notice the effects of 'air pressure' because we are used to it, but on an average table there is a force equivalent to the weight of 5 cars on it! Students could draw a poster to display this interesting fact. (c) Demonstrate the use of sink plunger or dent removers that can lift smooth boards. Draw a cartoon strip showing the forces on the plunger due to air before and after its use.
describe some effects (a) Offer the students syringes connected by rubber tubing. Fill one of the syringes with water and and uses of liquids under and the push the plunger to move the water into the other chamber. Consider what use this could be pressure, and ask the students to invent something that could use this effect. (b) Ask a volunteer to lightly hold a balloon between flat hands. Fill the balloon with water from a tap and ask if the balloon is trying to push the hands apart. Show pictures of hydraulic machines like big yellow bulldozers and state these work on a similar principle. Discuss how bulldozers can lift heavy loads (c) Discuss how remarkable brake systems are on a car - how they can stop a car travelling fast. Explain that they work by moving brake fluid around and challenge the students, working in groups to explain how brakes might work. Discuss the properties of the brake fluid - it is runny, non-compressible and doesnt freeze at normal temperatures - why are these properties important?
describe an effect of underwater pressure
(a) The pressure in a liquid or gas is the same in all directions. Distinguish between force which acts in a particluar direction. Remind students of the last time they had their head underwater. They were not pushed to any direction - the force due to water was the same from every direction. (b) Elicit sudents' ideas as to why special submarines have to be used to explore the very deep oceans. What would be the effect of going too deep? (c) Refer to a diver who said: 'The pressure of the water pushes directly on my ear drums' and ask if this statement is scientifically correct. It is important to distinguish between the words 'force' and 'pressure'. The pressure causes a force, pressure has not direction associated on it and a force is exerted by one thing acting on another. Ask the students to rewrite the statement correctly, by substituting the word 'pressure' for 'force'.
apply the concept of transmission of pressure to predict the resulting force
(a) Some students develop a picture of forces being carried, by the fluid, from cylinder to cylinder. Care is needed not to suggest the force 'slides around the bends' from one piston to another. Instead make the connection by pressure values. Consider that the pressure throughout the fluid increases by the same amount when a force is applied to one cylinder and then the system equilibrates back to its original level and a force can be felt at the other cylinder. (b) Show students a set up were two syringes of different cross-sectional area are connected via a rubber tube. Fill one of the chambers with water and push in the plunger so the water is transferred to the other chamber - this is a simple hydraulic system. Hold both syringes vertically downwards and add a weight to the small plunger so that the larger plunger goes up. Vote on how much weight has to be put on the large plunger to push the small plunger back up. Is it less, more or equal to the weight on the other side. It is counterintuitive to many but the large piston will need considerably more weight to push the small piston back up.
apply the model of the particle theory of matter to explain the behaviour of gases under pressure
(a) Agitate a tray of marbles and ask the students to listen for the collisions the marbles have with each other and wall. Distinguish that there are two distinct sounds and try to count the number of collisions with the walls of the tray only. Discuss how this helps to explain gas pressure. Repeat with a smaller tray or move one of the slides in, this time there should be move collisions with the walls in a certain time. Conclude that pressure is increased as volume is decreased. (b) Use the Gas Properties applet at http://phet.colorado.edu/web-pages/simulations-base.html. to demonstrate the effect on gas pressure as volume is varied (c) Role play gas particles in an enclosed room. The particles must obey the rules of travelling in a straight line, not speeding up and bouncing off each other at a sensible angle. Discuss the effect of giving energy to the system - the individual particles all speed up. Try to observe that there are now more collisions in a certain time i.e. the pressure has gone up!
apply the particle model of matter to explain why liquids are incompressible and gases are compressible
(a) Ask groups of students to draw on a flipchart how particles are arranged in liquids and gases. Discuss answers and ask them why it is easier to compress liquids than gases. (b) Push two sealed syringes, one filled with air and the other with water. Ask why it the air syringe has a little 'give' in it before it resists the push. (c) Refer to the braking system in a car, showing brake fluid being pushed from one cylinder to another. Inform the students that brake fluid is a liquid not a gas - ask why it would be dangerous to use gas in a brake system.
describe how to make a task easier by increasing the distance between the effort and the pivot
(a) A large demonstration see-saw made from a plank of wood and a log can be used to lift a volunteer with one hand! The volunteer sits at one end of the see saw and the teacher at a much larger distance from the pivot can lift themin the air. Many students will have experiences of this in playgrounds. (b) Close a door with one finger. repeat at distances nearer and nearer to the hinges. Notice that it is harder to close the door at a smaller distance. Agree on a conclusion to record in their books (c) Challenge students to hold a retort stand out in a clenched fist. Add a bag of weights to the end of the rod and ask them to hold the rod level at for as long as possible. Then, do the same yourself but this time push the bag nearer the fist ie nearer the pivot, and you will be able to beat anybody! Explain to the students that there is a trick involved and they have to guess what it is
identify levers in a number of household devices
(a) Students are invited to label photographs of levers so that they can get better at finding the lines of action, the forces acting, and the pivots. The images could include door handles, spanner in use, screwdriver opening a paint tin. (b) Encourage students to go on a 'lever hunt' at the school or at home, identifying where the pivot is in each case with a small sticker (c) Consider a wheel-barrow and why it makes lifting heavy objects easier. On a drawing of a wheel-barrow, identify the pivot, the effort force and the load. Discuss whether a wheel-barrow is a kind of lever.
describe how an object can be kept in balance
(a) Ask students to stand with their heels touching a wall and try picking up a coin placed 0.5 m away. It is impossible to pick up the coin without loosing balance. Discuss what what have to be done to keep balance and show pictures of a crane with a heavy counterbalance. (b) Ask a volunteer to lift an object with their arm only so that their bicep bulges. Show a diagram of the bones and muscles in the are. Indentify the pivot, the effort and load (c) It is important to insist on accurate drawings of distances and forces when teaching turning forces. The distance is as important as th size of the force and care should be taken to draw force arrows straight, in proportion to the size of the force, and acting from the correct point. Other arrows indicating motion may at some point be drawn on the diagrams so the force arrows should be distinguished.
apply the idea of the turning effect of a force to everyday situations
(a) Some students may think that levers just magnify a force i.e. that they get something for nothing in a lever. Emphasise that to get a larger force out of a lever, the effort needs to be further away (b) Look at pictures of steering wheels, large and small. In each, indentify the pivot as being in the middle. Consider where the forces would be if both hands were on the wheel. There would be two turning forces, one clockwise and the other anticlockwise. Now discuss why sports cars have a small steering wheel - it is not just to look good, it is also because it is more responsive but harder to turn. Relate to experiences driving bumper cars at the fayre. (c) Relate to experiences of windsurfing, especially trying to bring a sail to the vertical position. When the surfer is balanced there are two turning forces balanced - can the students identify them?
Describe the turning effect of a force as its moment
(a) Inform the students that in science the word 'moment' does not refer to time but is a word used instead of 'turning force'. (b) Make a mobile for a child's bedroom. Write notes about the construction using the terms 'pivot', 'balance' and 'moment' . (c) Challenge students to deduce the unit of a moment. Use the equation moment=perpendicular force x distance from the pivot to establish the unit is Newton metres (Nm)
Identfy the direction & magnitude of a turning force
(a) Working in pairs, students investigate for themselves the relationship between force and distance to balance a see-saw. After a period of investigation, students can write their relationship on a mini whiteboard and compare with others .(b) Relate to experiences of windsurfing, especially trying to bring a sail to the vertical position. The centre of gravity of the sail is a set distance from the pivot but the force needed to correct the sail is greater at first because the force is not perpendicular to the sail (c) Consider a loft trapdoor. The door swings open and comes to rest in a vertical position. The force that is causing the turning effect is weight but why no turning effect when the loft hatch is hanging vertically? Elicit answers that the weight is not in the correct direction to cause turning when vertical.
Simple calculation of moments
(a) The applet found at http://www.walter-fendt.de/ph14e/lever.htm is a simulation of a see-saw which may enable students to establish the relationship between forces and distance. (b) Calculate the weight of a retort stand by first marking its centre of gravity (or balancing point), then make it pivot about another point, adding weights to an end to make it balance. The distance of the centre of gravity to pivot multiplied by the weight of clampstand = to the weight added multiplied by its distance to the pivot. (c) Tabulate correct distance and weight values for a balanced see-saw. Erase some of the readings and challenge the students to work out the missing numbers