Unit 9I Energy and electricity
About the unit Where the unit fits in
In this unit pupils: This unit builds on work on electricity and energy in units 7I ‘Energy resources’, 7J • explore a range of useful energy transfers and transformations ‘Electrical circuits’ and 8I ‘Heating and cooling’. It relates to work on the reactivity of metals • discuss the use of electricity as a convenient way to transfer energy to do useful things in unit 9F ‘Patterns of reactivity’ and work on fuels in unit 9G ‘Environmental chemistry’. It • associate the concept of voltage with the transfer of energy in a circuit relates to unit 9D ‘Using control for electronic monitoring’ in the design and technology • investigate the voltage of cells scheme of work, and to unit 18 ‘Twentieth-century conflicts’ and unit 20 ‘Twentieth-century
• study how electricity is generated, with reference to environmental impacts medicine’ in the history scheme of work.
• use the principle of conservation of energy to identify ways in which energy is dissipated
during transfers Expectations In scientific enquiry pupils: At the end of this unit • use models to explain observations relating to electric currents in terms of scientific enquiry • use scientific knowledge to frame a question for investigation most pupils will: identify patterns in measurements of voltage and use these to draw • measure voltage in circuits conclusions about circuits; identify and control key factors in investigating simple cells • identify patterns in the measurements of voltage in series circuits and use these to draw and identify patterns in their results, including observations that do not fit the main trends conclusions some pupils will not have made so much progress and will: measure the voltage of a Note on the teaching of energy range of cells; present data as charts or tables
This unit presents a range of useful changes and helps pupils to use the language of energy some pupils will have progressed further and will: relate energy transfer devices in the
transfer and transformation in describing them. The word ‘transfer’ is used to describe laboratory to everyday appliances; synthesise information from secondary sources about
the development of the electricity supply industry and communicate it clearly; consider energy’s change of place; the word ‘transform’ is used to describe a change in the way
whether data is sufficient, and account for anomalies energy shows itself, eg from electrical energy to light.
in terms of physical processes The unit focuses on how transfers and/or transformations of energy by electricity are
most pupils will: describe some energy transfers and transformations in familiar situations, important in everyday life. It explains these simply and looks at some of the consequences
including dissipated energy, and devices; recognise that the voltage change across a of the electricity supply industry. The unit covers the ideas of dissipation or ‘wasted’ energy circuit component is a measure of its energy transfer; describe how voltage originates and the conservation of energy. In extending the concept to these contexts, simplifications from a chemical cell; give examples of the hazards of high-voltage circuits; compare the appropriate to year 9 pupils have been made. energy consumption of common electrical appliances; describe how electricity is Pupils need labels they can use when they come across energy, eg electrical energy, light generated by energy from fuels, and recognise possible environmental effects of this and heat. This is a first step in developing understanding. Teachers should help pupils some pupils will not have made so much progress and will: describe some useful recognise that they need to go further in some contexts, eg that ‘spring energy’ is the result energy transfer devices; recognise that any functioning circuit needs a power supply to of the elastic properties of the metal the spring is made of, and so could be called ‘potential provide a voltage and that high voltages are hazardous; recognise that electricity is a energy’ because of its compressed position. It would be inappropriate, at this stage, to convenient way of ‘delivering’ energy, but that it must be paid for and that its generation develop this further and associate the energy with the electric bonding forces between the can cause environmental problems; give examples of how energy goes to waste atoms of the spring. Formal definitions of work, kinetic energy and potential energy are also some pupils will have progressed further and will: apply a model of voltage and energy best left until key stage 4 for most pupils. changes to a circuit; recognise that although the total energy in a system is conserved,
energy can be dissipated; use ‘power ratings’ in comparing the costs of using different This unit is expected to take approximately 8 hours.
electrical appliances; link the function of an electric generator to magnetic effects
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Prior learning Out-of-school learning It is helpful if pupils: Pupils could:
• know how to connect simple series and parallel circuits • survey the power rating of various devices in the home or observe their electricity meter
• recall that fossil fuels and wind, waves and the Sun are all energy resources when different appliances are running
• check their own electricity bill
• keep a diary of energy experiences, eg Today I used my personal stereo with new Health and safety batteries Risk assessments are required for any hazardous activity. In this unit pupils: • use mains electrical equipment in their investigations
Pupils must not experiment with mains electricity.
Model risk assessments used by most employers for normal science activities can be found in the publications listed in the Teacher’s guide. Teachers need to follow these as indicated
in the guidance notes for the activities, and consider what modifications are needed for classroom situations.
Language for learning
Through the activities in this unit pupils will be able to understand, use and spell correctly: • words and phrases relating to scientific enquiry, eg independent and dependent variable,
control
• words and phrases describing energy transfers and transformations,
eg movement as kinetic energy, position as potential energy, chemical energy, electrical energy, sound, heat and light
• words and phrases relating to energy supply and waste, eg conservation, dissipation,
electric generator, dynamo, power station
Through the activities pupils could:
• use secondary sources to assess conflicting evidence and arrive at a considered viewpoint
• write coherent text to communicate information effectively
Resources
Resources include:
• a selection of electrical toys and devices to show energy transfers and transformations • samples of fruit and vegetables or dilute acid solutions
• a selection of samples of metals to make electrodes, eg copper, zinc, iron, aluminium,
magnesium
• secondary source material on generating electricity and associated environmental issues, electric cars and other ‘energy-saving’ appliances
• small motors or materials to build generators
• a bicycle dynamo
• a joulemeter (and datalogger)
• ammeters and voltmeters or digital multimeters
• a household electricity meter or picture of one
• domestic appliances, including low-energy bulbs, or pictures of and energy information about these
? QCA 2000 Browse, save, edit or print Schemes of Work from the Standards Site at www.standards.dfee.gov.uk Science - Unit 9I Energy and electricity 2
LEARNING OBJECTIVES POSSIBLE TEACHING ACTIVITIES LEARNING OUTCOMES POINTS TO NOTE
PUPILS SHOULD LEARN PUPILS
How is energy involved in doing useful things?
• that useful changes usually • Remind pupils of their experience of energy transfers and transformations • recognise that energy is • The energy ‘transfers’ met in involve energy transfers and in years 7 and 8 with demonstrations of ‘useful changes’, eg working a routinely converted from one conduction in unit 8I ‘Heating and transformations model steam engine, a spring-driven clock, eating food. Help pupils form to another in order to cooling’ can be contrasted with • that the terms ‘kinetic’, associate the presence of energy with the different situations in the be useful energy ‘transformations’ in these ‘potential’, ‘radiation’ and demonstrations, eg steam-engine fuel, flame, hot water, movement, and to • categorise devices on the devices. Energy should, however, be ‘chemical’ are useful when use the terms ‘kinetic’, ‘potential’, ‘chemical energy’, ‘heat’, ‘light’ and basis of type of energy input associated with the situations rather describing energy ‘sound’ as ways of describing energy in such situations. or output than being described as different
• Ask pupils to explore a circus of toys and devices that work by transferring • explain why electricity is ‘types of stuff’. See the note on
and/or transforming energy. Ask pupils to identify the source of energy and used widely as a source of teaching energy in the Teacher’s the use to which it is put. Include a range of electrical toys and devices, eg energy guide. – battery-operated and clockwork/spring-operated vehicles • describe energy transfers in • Potential energy is used to refer to – yo-yo (if possible one that lights up at maximum speed) everyday changes energy associated with an object’s – battery-operated and manually operated fans position, eg a stretched spring or a – electromagnet for lifting raised mass. – electric bell or buzzer
– solar-powered calculator or motor
– low-voltage heater that is set to get warm, not hot, to the touch
– toys that feature light-emitting diodes (LEDs)
– simple control circuit, eg one that sounds a buzzer when a light sensor
is covered
• that electrical circuits are • Elicit from pupils’ observations the conclusion that electrical energy is a • describe the energy transfers used to perform a variety of convenient way to do many useful things. Recall pupils’ year 7 work on and/or transformations in
useful tasks fuels as energy stores and elicit other ways that energy can be stored, eg several toys or devices
• that electrical energy is compressed spring – potential; flywheel – kinetic; battery – chemical. • recognise that electricity is a transferred around circuits Contrast this with electricity, which cannot be stored. useful means of
and can be transformed in transforming energy
components, eg to produce • give examples of ways in
light, sound, movement and which energy can be stored
heat
• to identify devices and
situations that act as energy
stores
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LEARNING OBJECTIVES POSSIBLE TEACHING ACTIVITIES LEARNING OUTCOMES POINTS TO NOTE
PUPILS SHOULD LEARN PUPILS
How does electricity transfer energy?
• how current behaves in • Review pupils’ understanding of simple circuits – the requirements for • describe current as not being
electrical circuits current to flow, and the effect of the number of cells or components in used up in a circuit and as
series and parallel circuits (unit 7J ‘Electrical circuits’) – by using quiz dividing along the different
cards that describe real circuits with faults and by measuring currents in branches in a parallel circuit
circuits. • identify that an ammeter
measures flow of current
• how to measure voltage in a • Ask pupils to construct simple series circuits incorporating several • use a voltmeter correctly • Emphasise that ammeters measure circuit components and batteries or power supplies of different voltages. Help • draw from trends in flow ‘through’, so are inserted in a
them to connect the voltmeter across each component in turn, without numerical data conclusions circuit; voltmeters measure a
breaking the circuit. Individual readings can be seen to add to the total about the way voltage varies ‘difference’, so are connected across
voltage. Encourage pupils to associate large voltage changes with large around a circuit a circuit, without breaking it.
energy transfers by the components, eg bright bulbs.
• a simple model of energy • Introduce a model to associate energy transfer with voltage, eg the ‘almost • use a simple model to • With some pupils, the term ‘potential transfer from batteries to Monopoly’ or ‘pocket money’ analogy, where pupils are given money that describe the link between difference’ could be substituted for components in circuits has to be spent around the circuit before they can return. Pupils are the voltage and energy in a ‘voltage’ and linked with other uses • a simple model of potential current, the cell is the source of the money (‘GO’), which is the energy. circuit of the word ‘potential’.
difference making a current The cells or voltage permit them to move. If they go through more cells, • learn how to identify faults in • Other models use ideas of water flow in a circuit they pick up more money; and as they go round the circuit, they have to equipment pressure and gravitational potential • to work with others to pay out equal amounts per device (assuming identical devices). As an • choose a suitable method for energy. Encourage pupils to devise simulate energy transfer analogy of resistance, money could be paid out in proportion to ‘number of presenting results their own models to explain features around a circuit hotels’, or use a similar rule from Monopoly. Note the shortcoming in the of their observations, eg an energy
analogy – in Monopoly circuits all the money does not have to be spent. carrier/supplier, continuity of circuit.
• An alternative model is the ‘up-and-down’ ski-lift. Chairs are the • A particle model of electricity is not
‘current/charge’ which the ‘voltage’ of the motor causes to move (flow). required (electrons can be left until
Skiers are the ‘energy’, climbing on at the motor-house and getting off at key stage 4), but the idea of static
suitable places (‘devices’) around the ski-lift circuit. charge could be used here.
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LEARNING OBJECTIVES POSSIBLE TEACHING ACTIVITIES LEARNING OUTCOMES POINTS TO NOTE PUPILS SHOULD LEARN PUPILS
How does electricity transfer energy? (Cont.)
• that a cell has chemical • Show the inside of a dry cell. Establish that there is a chemical change • describe energy • Reactivity of metals is covered in
energy, which is transformed when a battery/cell produces a current. Associate the energy of the transformation from a unit 9F ‘Patterns of reactivity’. to electrical energy in a chemical change with input to a circuit. cell/battery to a circuit Safety circuit • Ask pupils to plan an investigation into how to make a cell from a fruit or • identify and describe – a dry cell contains hazardous • to consider which factors are vegetable to produce the highest voltage, eg the performance of a patterns in data chemicals. The use of solutions important and how to vary particular fruit with a range of electrode sizes, separations or metal • draw conclusions from their such as vinegar or lemon juice them combinations, the relative effectiveness of different fruit. If appropriate, link data provides a cheaper alternative to a • to choose appropriate to work on the relative reactivity of different metals. • describe how to improve range of fruits. The size of the techniques and equipment their work, eg by identifying voltage depends mainly on the • to explain results that do not strengths in the work of difference in reactivity of the fit a pattern that arises others metals used as electrodes, eg the • to compare their best will probably be copper and investigative method and magnesium, giving about 1.5V results with those of others – pupils’ plans should be checked and evaluate the work in the for health and safety before light of comparisons practical work begins
• to apply scientific knowledge • Use the Electricity Council video Electric graffiti, or other secondary • give a reasoned report to explain the use and sources, to identify the hazards of high voltages and associate these with associating the use/hazard occurrence of high voltages the transfer of large amounts of energy, eg lightning, overhead and power of high voltage with energy
lines on railway tracks. transfer
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LEARNING OBJECTIVES POSSIBLE TEACHING ACTIVITIES LEARNING OUTCOMES POINTS TO NOTE
PUPILS SHOULD LEARN PUPILS
What are we paying for when we use electricity?
• that electric current is • Discuss the household mains supply at 230V and how appliances, eg • give examples of some • This is best not done as a class conducted from ‘the mains’ television, computer, run from this, using pupils’ experiences. Show an devices that use energy at a experiment as the joulemeter may to components in electrical electricity bill and ask pupils What are the units used? Remind them that greater rate than others, eg be confused with the ammeter. Here circuits current is not used, but energy is. Show (pictures of) a household heating appliances transfer it is simply required to gather data • that energy is transmitted via electricity meter. more energy than others for comparison purposes.
electricity to an appliance, • Demonstrate the energy used by a range of electrical devices, eg for • give an example of their own • The concept of power as rate of where it is converted to heating, lighting, (over a fixed period of time for comparison purposes) use of an electrical appliance energy transformed could be another form of energy using a joulemeter/datalogger. Show how these comparisons relate to the that has to be paid for introduced to some pupils. Here it is • that some appliances power ratings on devices. • contribute to planning and used to support the simple transfer more energy than • Ask pupils if they think people are aware of these differences, eg Do carrying out a survey of comparisons, eg heaters use a lot of others (in a given time) parents talk about the waste of money of ‘leaving the TV on all evening’? energy use of household energy, other devices less.
• to identify the power rating of Ask how they could find evidence to check such comments, and then devices • Spreadsheets could help pupils common household devise a parents’ guide entitled ‘How to get your children to save energy • communicate data effectively make quantitative comparisons.
electrical devices by switching the right things off’. This could be supported by putting through writing a coherent • Extension: some pupils could be told • to present advice based on examples of household appliances on cards and asking pupils to arrange text that the unit charged for is a kilowatt scientific understanding as a them in order of energy consumption. Compare the amount of energy hour, and be asked to find out about coherent text used by a range of devices in the home or school, as shown by the power the costs of using devices for typical
rating noted on the devices, eg light bulbs, fridges, microwaves, heaters, times per day, eg TV for 6 hours,
cookers, computers, televisions. fridge for 24 hours. This could be
compiled and presented as a bar
chart.
Safety
– mains appliances must have been
tested using a portable appliance
tester. Any brought from home
must be carefully checked
Checking progress
• to review their understanding • Ask pupils to summarise ways in which electricity can transfer and • relate use of electricity to • Use an internet search engine to of energy and electricity transform energy to provide people with useful facilities – as a list or a energy supply in everyday look for information.
concept map. situations/devices
? QCA 2000 Browse, save, edit or print Schemes of Work from the Standards Site at www.standards.dfee.gov.uk Science - Unit 9I Energy and electricity 6
LEARNING OBJECTIVES POSSIBLE TEACHING ACTIVITIES LEARNING OUTCOMES POINTS TO NOTE
PUPILS SHOULD LEARN PUPILS
Where do we get electricity from?
• that electricity can be made • Elicit ideas about where mains electricity comes from. Trace the story • identify a range of energy • Details of how a generator works are to flow by causing back to a power station. resources used to generate not required at this stage. Some movement in an electrical • Demonstrate a bicycle dynamo or simple generator. Show how increasing electricity pupils, however, might like to generator (energy) input will increase (energy) output. • describe a simple electrical compare the device with the electric • that fossil fuels, nuclear • Use a small motor as an electrical generator, or make one from a kit, and generator motor. It has the same structure, but fuels and renewable energy test its output using a sensitive meter. Possibly drive it using a windmill to with input and outputs reversed.
sources can be used to drive simulate wind turbines. Plan a visit, show a video or use information • The role of Michael Faraday in electrical generators resources such as a CD-ROM to introduce pupils to the generation of laying the foundations for electricity • to follow instructions electricity in power stations. Contrast the scale of the operation with generation could link with the history carefully to construct and/or laboratory generators, and consider the fuels used. area of study ‘Britain 1750–1900’.
test a generator • Pupils are often surprised to realise • that electrical energy cannot that electricity is generated ‘on be stored demand’ and that commercial
breaks on TV can increase demand,
so that workers at power stations
have to increase the supply to
provide for the nation’s electric
kettles.
• present a considered • to use secondary sources • Ask pupils to use secondary sources to compare the impact on the • This builds on unit 7I ‘Energy viewpoint based on about an environmental environment of various forms of electrical generation. This may be done in resources’ and links to unit 9G information from secondary aspect of the generation of groups, with each group reporting back its findings. This may include both ‘Environmental chemistry’. sources, eg identify the electricity and contribute to a renewable and non-renewable resources as well as the more complex problems of pollution presentation issue of nuclear waste. associated with electricity • to examine conflicting generation by fossil fuels and evidence and arrive at a the environmental impact of
considered viewpoint renewable and nuclear
energy sources
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LEARNING OBJECTIVES POSSIBLE TEACHING ACTIVITIES LEARNING OUTCOMES POINTS TO NOTE
PUPILS SHOULD LEARN PUPILS
How can we reduce the waste of energy?
• that in energy transfers, • Recall earlier work on energy devices and on burning fuels. Review the • distinguish between useful • Power stations dissipate about 70% energy may go to waste paradox that although electricity is clean and safe to use, its generation energy and wasted or of their energy input as waste – an
can have a big environmental impact. Introduce the idea of dissipation of dissipated energy inevitable consequence of their
waste energy as an inevitable consequence of many energy transfers; • make comparisons between processes, not simply inefficient
refer to cooling towers at power stations. appliances and devices working practices.
• Broaden the issue to looking at use of energy in different ways, eg ask concerning their efficient use Safety pupils to consider how environmentally friendly electric cars really are. of energy – if using school-produced holders (Although electric motors are three times as efficient as internal for lamps, these must have been combustion engines, the electricity has to be generated first.) Compare checked with a portable appliance battery-powered cars (recharged at the mains) with fuel-cell powered tester 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?
• Use questions to discuss with pupils the difference between tungsten-
filament light bulbs and ‘energy-saver’ bulbs, eg a 20W energy-saver lamp
is said to be equivalent to a 100W filament lamp. Can this be supported?
What happens to the other 80W from the filament lamp? (Feel the heat –
carefully.)
• Provide information about these lamps, eg advertising material, and ask
pupils to work out whether the purchase of energy-saver bulbs is cost
effective.
• that when energy is • Introduce the principle of the conservation of energy, using a range of • use flow diagrams as a • Energy flow diagrams need not be transferred the total amount examples to make the distinction between energy that is useful and energy simple means of energy quantitative at this stage; simply of energy remains constant that is dissipated and not useful. Ask pupils to draw flow diagrams, eg accounting show where all the energy is • to use flow diagrams to Sankey-type, to show energy transfers in everyday situations, eg home transferred. show qualitatively how heating, transport, use of insulation. energy is
transferred/transformed in
devices
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LEARNING OBJECTIVES POSSIBLE TEACHING ACTIVITIES LEARNING OUTCOMES POINTS TO NOTE
PUPILS SHOULD LEARN PUPILS
Reviewing work
• to summarise and make • Draw flow diagrams identifying energy transfers and transformations in a • identify key points • The domino game is similar to chain connections between the key wider range of situations, eg the devices studied earlier in the unit, home • contribute to a summary or loop games used in the numeracy ideas in this unit, and those insulation. sheet of key ideas strategy.
preceding it • Encourage pupils to use games to review connections, eg • Relates to work done in unit 8I
– chain games from the numeracy strategy ‘Heating and cooling’ on house
– ‘energy consequences’ (first line – describe an event, second line – insulation to reduce heat loss.
describe an energy transformation. When the text is revealed pupils have
to explain whether the consequences are possible or not)
– ‘energy dominoes’ (prepare a set of cards with a question about an
aspect of energy on one half and an unrelated answer on the other. One
pupil asks a question and the pupil who has the answer reads it aloud,
then asks his/her question)
• The opportunity could be taken to revise related topics from previous
years, eg conduction and convection, covered in unit 8I ‘Heating and
cooling’.
? QCA 2000 Browse, save, edit or print Schemes of Work from the Standards Site at www.standards.dfee.gov.uk Science - Unit 9I Energy and electricity 9