Strengthening teaching and learning of energy
Strengthening teaching and learning of energy Quantitative model of energy transfer
The Coalition Government took office on 11 May 2010. This publication was published prior to that date and may not reflect current government policy. You may choose to use these materials, however you should also consult the Department for Education website www.education.gov.uk for updated policy and resources.
The National Strategies | Secondary Science Framework study guides: Strengthening teaching and learning of energy
1
Strengthening teaching and learning of energy: Quantitative model of energy transfer It is useful to consider conservation of energy as if it were a financial accounting system (showing the transfer of money or wealth, particularly online, where no physical cash is involved) because it helps move pupils away from energy as a causal agent. Energy does not make things happen – it merely makes things possible. In the same way, money does not actually cause things to happen, it merely makes them possible. Using conservation of energy as an accounting system helps to reinforce a correct understanding that energy is not stuff or material and therefore does not physically flow from one place to another. It also helps to reinforce the idea of energy transfer, which means the same energy can be located in different places.
© Crown copyright 2009
01035-2009PDF-EN-05
2
The National Strategies | Secondary Science Framework study guides: Strengthening teaching and learning of energy
Energy transfer – yearly learning objectives Year 7
Year 8
Year 9
Year 10
Year 11
Year 12
describe how energy can be stored, e.g. electrical cells
use a simple model of energy transfer to describe common observations
develop more complex models of energy transfer mechanisms (incorporating ideas about particles or waves)
apply the concept of conservation of energy to energy efficiency calculations in living and non-living systems
apply broader or deeper knowledge and understanding of energy in explanations of observations and phenomena
use energyaccounting systems, including Sankey diagrams, to track energy transfers
develop the idea of energy dissipation in a variety of contexts
use quantitative measures and the concept of energy conservation to evaluate a range of strategies to conserve limited energy resources
describe how energy is transferred in simple contexts such as heating and cooling, food chains and simple circuits recognise that quantitative measures of energy transfer are needed to inform decisions, e.g. about lifestyles describe how energy stored in a range of energy resources can be usefully transferred
explain why quantitative measures of energy transfer should also be considered when making informed decisions, e.g. building wind farms explain how electricity is generated using a variety of energy resources
use quantitative measures of energy transfer to support informed decisionmaking
evaluate the economic costs and environmental effects of energy use through the measurement of energy transfers and efficiency calculations
apply the idea of energy conservation and dissipation to simple biological, chemical and physical systems
describe the effects of energy transfer to living systems by electromagnetic and nuclear radiation
use and apply complex models of energy transfer to a wide range of phenomena
use valid and rational argument to offer solutions to problems arising from the applications and implications of energy
explain a wide range of complex phenomena using the principle of conservation of energy and appropriate wave or particle models
Source: Renewed science Framework, 4 Energy, electricity and forces, 4.1 Energy transfer and electricity
Quantitative measures of energy transfer are drawn on when pupils are working at levels 5 and above. For most pupils this would correspond with Year 8 onwards in terms of the yearly learning objectives set out in the table above. The developments in pupils’ understanding of the quantitative aspects of energy transfer have been included.
01035-2009PDF-EN-05
© Crown copyright 2009
The National Strategies | Secondary Science Framework study guides: Strengthening teaching and learning of energy
3
Task 8: Explaining conservation of energy Read the two accounts below that describe: 1. a scenario for explaining conservation of energy using blocks 2. a Sankey diagram for a light bulb.
1. Imagine Dennis who has blocks that are absolutely indestructible and cannot be divided into pieces. Each is the same as the other. Let us suppose he has 28. His mother puts him with his 28 blocks into a room at the beginning of the day. At the end of each day, being curious, Dennis’ mother counts the blocks and discovers a phenomenal law. No matter what he does with the blocks, there are always 28 remaining. This continues for some time until, one day, she only counts 27, but with a little searching she finds one under a rug. She realises that she must be careful to look everywhere. One day later, she can only find 26. She looks everywhere in the room, but cannot find the missing blocks. Then she realises the window is open and the two blocks are outside in the garden. Another day, careful counts show there are 33 blocks. This causes considerable dismay until it is realised that Bruce came to visit, bringing his blocks with him and left a few. Dennis’ mother removes the five extra blocks and gives them back to Bruce and all returns to normal. We can think of energy like this, except there are no blocks. We can use this idea to track energy transfers during changes. We need to be careful to look everywhere to ensure that we can account for all the energy. Adapted from Feynman, R.P. (1998), Six Easy Pieces, Basic Books. Reprinted by kind permission of Basic Books, a member of Perseus Book Group.
© Crown copyright 2009
01035-2009PDF-EN-05
4
The National Strategies | Secondary Science Framework study guides: Strengthening teaching and learning of energy
2. A way of representing energy transfers from a light bulb is to use a quantitative approach called a Sankey diagram. This quantitative approach for representing energy transfer in a bulb uses a concrete method to explain an abstract idea.
electric current
Cell
light
Filament bulb heating
heating
Energy in surroundings
The numbers of blocks transferred to each place suggest the relative amounts of energy transferred by each process. For example, relatively little of the energy transferred from a conventional filament bulb (in the middle of the diagram above) is transferred by light (represented by one block) – most is transferred by heating (represented by four blocks). In contrast, almost all of the energy on the left-hand side of the diagram is transferred from the cell to the bulb, when the electric current flows in the circuit (represented by five blocks). Relatively little is transferred from the cell to the surroundings by heating (represented by one block). In fact, the amount of energy represented by one block is much too high here (energy transferred from the cell to the surroundings by heating). Using more blocks for the energy stored in the cell could help develop accuracy in the model, but this version may be ‘good enough’ for the first stages of understanding it.
01035-2009PDF-EN-05
© Crown copyright 2009
The National Strategies | Secondary Science Framework study guides: Strengthening teaching and learning of energy
5
Conservation of energy as a useful accounting system during energy transfers Using a system of counters to represent energy can be a useful way to develop an accounting system for energy. You can try out the method yourself and then with pupils during the next two tasks. Below are five energy stories that provide good scenarios for using an accounting system and developing an understanding of energy conservation, dissipation and efficiency. 1. A firelighter stores 200kJ of energy. When it burns, 190kJ is transferred to the surroundings by heating and 10kJ by light. 2. Jay eats a chocolate bar at breaktime. The label says there is 1000kJ of energy stored in the chocolate. As he runs around, he transfers 600kJ to the surroundings by heating and 5kJ by sound (that’s a lot of shouting!). How much of the energy from the chocolate bar is left to be stored by Jay’s body at the end of break? 3. A ‘low energy’ light bulb typically transfers about 80 per cent of its energy to its surroundings by light and the rest by heating. 4. Of every 1000J of energy transferred to a hairdryer by the electric current, the hairdryer typically transfers about 800J to the warm air by heating and moving it, about 190J through the case to the person’s hands by heating and movement (vibration) and about 10J to the surroundings by sound. 5. For every 50J of energy transferred to the surroundings by sound, a portable CD player transfers another 300J by heating.
© Crown copyright 2009
01035-2009PDF-EN-05
6
The National Strategies | Secondary Science Framework study guides: Strengthening teaching and learning of energy
Task 9: Using a physical model of an energy accounting system Try this task to develop your confidence in the methodology.
• • •
You will need to print a copy of Appendix 9 to give you the materials for the paper tokens and presentation grid. Cut up the tokens ready for use. Select one of the five energy stories given above. Use the cut-out energy tokens and grid to account for one of these stories.
Remember that this is an accounting system; no tokens should be lost or destroyed during the transfer.
Conservation of energy Sankey diagrams are similar in principle to the tokens model and are a widely recognised way to demonstrate the energy transfer teaching model. Many teachers introduce pupils to Sankey diagrams in Year 9. The diagram below shows how a Sankey diagram can be used to illustrate the energy transfers in an electric torch. You may find that using actual blocks or tokens enhances the effectiveness of these Sankey diagrams in the teaching of conservation of energy as an accounting system. Pupils’ understanding of efficiency and dissipation of energy can also be developed by the effective use of Sankey diagrams.
01035-2009PDF-EN-05
© Crown copyright 2009
The National Strategies | Secondary Science Framework study guides: Strengthening teaching and learning of energy
7
A Sankey diagram showing energy transfers in an electric torch.
Cell
Bulb
Surroundings Light
Electric current
Heating
Heating
Surroundings
Task 10: Pupils construct Sankey diagrams
• • • • •
Select an appropriate class or small group of pupils to try this with. Sankey diagrams are often introduced in Year 9. Use one (or more) of the five energy stories as the transfers to be illustrated. Prepare the tokens and the grids given in Appendix 9. Prepare your language to ensure that you emphasise the transfer model, rather than the transformation model, when you explain the diagrams to the pupils. Record any of the advantages or disadvantages of this method of introducing Sankey diagrams to your group of pupils.
Some of the advantages of this method often noted are that:
• • • • •
moving the tokens across the diagram reinforces the idea of a transfer from one place to another having to account for all the tokens encourages pupils to look for where the energy has gone and challenges the misconception that it simply disappears (you are not allowed to throw any tokens away) a lot of energy in one place at the start is gradually broken down into smaller and smaller amounts with each successive transfer efficiency can be calculated by comparing the number of tokens (or the value of those tokens in joules) that end up in the desired location with the total number transferred dissipation can be introduced by looking at the smaller amounts of energy located in a number of different places at the end of the transfer process compared with the concentrated store of energy in one place at the start.
© Crown copyright 2009
01035-2009PDF-EN-05
8
The National Strategies | Secondary Science Framework study guides: Strengthening teaching and learning of energy
Some of the limitations noted are that:
• • • •
sticking down tokens at each stage results in a proliferation of tokens, which may reinforce the misconception about creating and destroying energy energy is not a real thing like a token, so the model may encourage pupils to think of energy as a substance, which is particularly problematic when dealing with heating energy does not come in finite packets – it may be quantified into packets in some circumstances, but there is no standard-sized energy packet energy is not red (or any other colour) paper.
Dissipation of energy and energy efficiency This method of using tokens to build Sankey diagrams can also be used to teach about dissipation of energy and energy efficiency. You can try this out with some of the energy stories above.
Dissipation of energy The fourth energy story provides an opportunity to exemplify dissipation. In the story, the concentrated energy transferred to the hairdryer by the electric current is ‘spread out’ into several smaller, and therefore less useful, quantities in other places.
Energy efficiency This is a challenging idea and one you can try it with any of the energy stories. You will need to use the formula: efficiency =
useful energy transferred total energy transferred
You can try calculating the efficiency either using the number of tokens or the number of joules quoted in the energy stories. The answers given by both methods should agree. You may find the amplified objectives of the new science Framework helpful here, as you can see the progression in ideas about energy transfer, conservation, dissipation and energy efficiency (see appendix 10).
Reflection Look back at the true and false answers you gave for Task 3 in Energy: Misconceptions and teaching models. Have any of your responses changed now? Why have they changed?
01035-2009PDF-EN-05
© Crown copyright 2009
The National Strategies | Secondary Science Framework study guides: Strengthening teaching and learning of energy
Statement
True
False
9
Comment
1. Energy is a kind of stuff that is transferred from place to place when something happens. 2. Energy causes events to happen. 3. Heat and temperature are the same thing. 4. Heat is a form of energy. 5. Heating is a process of energy transfer. 6. Electricity is an energy source. 7. An electric current transfers energy. 8. Energy is dissipated but not lost when appliances are used. 9. Sound energy is transferred to the surroundings by vibrations. 10. Lighting is a process of energy transfer. 11. Respiration uses energy. 12. Photosynthesis makes energy. 13. Energy is a fuel. 14. The world is facing an energy crisis. 15. Chemical reactions cause energy to be transferred. 16. A car transfers all of the energy from the petrol to heating the surroundings.
Acknowledgements Dennis the Menace Model adapted from Feynman, R.P. (1998), Six Easy Pieces, Basic Books. Reprinted by kind permission of Basic Books, a member of Perseus Book Group.
© Crown copyright 2009
01035-2009PDF-EN-05
The Coalition Government took office on 11 May 2010. This publication was published prior to that date and may not reflect current government policy. You may choose to use these materials, however you should also consult the Department for Education website www.education.gov.uk for updated policy and resources.
The National Strategies | Secondary Science Framework study guides: Strengthening teaching and learning of energy
1
Strengthening teaching and learning of energy: Quantitative model of energy transfer It is useful to consider conservation of energy as if it were a financial accounting system (showing the transfer of money or wealth, particularly online, where no physical cash is involved) because it helps move pupils away from energy as a causal agent. Energy does not make things happen – it merely makes things possible. In the same way, money does not actually cause things to happen, it merely makes them possible. Using conservation of energy as an accounting system helps to reinforce a correct understanding that energy is not stuff or material and therefore does not physically flow from one place to another. It also helps to reinforce the idea of energy transfer, which means the same energy can be located in different places.
© Crown copyright 2009
01035-2009PDF-EN-05
2
The National Strategies | Secondary Science Framework study guides: Strengthening teaching and learning of energy
Energy transfer – yearly learning objectives Year 7
Year 8
Year 9
Year 10
Year 11
Year 12
describe how energy can be stored, e.g. electrical cells
use a simple model of energy transfer to describe common observations
develop more complex models of energy transfer mechanisms (incorporating ideas about particles or waves)
apply the concept of conservation of energy to energy efficiency calculations in living and non-living systems
apply broader or deeper knowledge and understanding of energy in explanations of observations and phenomena
use energyaccounting systems, including Sankey diagrams, to track energy transfers
develop the idea of energy dissipation in a variety of contexts
use quantitative measures and the concept of energy conservation to evaluate a range of strategies to conserve limited energy resources
describe how energy is transferred in simple contexts such as heating and cooling, food chains and simple circuits recognise that quantitative measures of energy transfer are needed to inform decisions, e.g. about lifestyles describe how energy stored in a range of energy resources can be usefully transferred
explain why quantitative measures of energy transfer should also be considered when making informed decisions, e.g. building wind farms explain how electricity is generated using a variety of energy resources
use quantitative measures of energy transfer to support informed decisionmaking
evaluate the economic costs and environmental effects of energy use through the measurement of energy transfers and efficiency calculations
apply the idea of energy conservation and dissipation to simple biological, chemical and physical systems
describe the effects of energy transfer to living systems by electromagnetic and nuclear radiation
use and apply complex models of energy transfer to a wide range of phenomena
use valid and rational argument to offer solutions to problems arising from the applications and implications of energy
explain a wide range of complex phenomena using the principle of conservation of energy and appropriate wave or particle models
Source: Renewed science Framework, 4 Energy, electricity and forces, 4.1 Energy transfer and electricity
Quantitative measures of energy transfer are drawn on when pupils are working at levels 5 and above. For most pupils this would correspond with Year 8 onwards in terms of the yearly learning objectives set out in the table above. The developments in pupils’ understanding of the quantitative aspects of energy transfer have been included.
01035-2009PDF-EN-05
© Crown copyright 2009
The National Strategies | Secondary Science Framework study guides: Strengthening teaching and learning of energy
3
Task 8: Explaining conservation of energy Read the two accounts below that describe: 1. a scenario for explaining conservation of energy using blocks 2. a Sankey diagram for a light bulb.
1. Imagine Dennis who has blocks that are absolutely indestructible and cannot be divided into pieces. Each is the same as the other. Let us suppose he has 28. His mother puts him with his 28 blocks into a room at the beginning of the day. At the end of each day, being curious, Dennis’ mother counts the blocks and discovers a phenomenal law. No matter what he does with the blocks, there are always 28 remaining. This continues for some time until, one day, she only counts 27, but with a little searching she finds one under a rug. She realises that she must be careful to look everywhere. One day later, she can only find 26. She looks everywhere in the room, but cannot find the missing blocks. Then she realises the window is open and the two blocks are outside in the garden. Another day, careful counts show there are 33 blocks. This causes considerable dismay until it is realised that Bruce came to visit, bringing his blocks with him and left a few. Dennis’ mother removes the five extra blocks and gives them back to Bruce and all returns to normal. We can think of energy like this, except there are no blocks. We can use this idea to track energy transfers during changes. We need to be careful to look everywhere to ensure that we can account for all the energy. Adapted from Feynman, R.P. (1998), Six Easy Pieces, Basic Books. Reprinted by kind permission of Basic Books, a member of Perseus Book Group.
© Crown copyright 2009
01035-2009PDF-EN-05
4
The National Strategies | Secondary Science Framework study guides: Strengthening teaching and learning of energy
2. A way of representing energy transfers from a light bulb is to use a quantitative approach called a Sankey diagram. This quantitative approach for representing energy transfer in a bulb uses a concrete method to explain an abstract idea.
electric current
Cell
light
Filament bulb heating
heating
Energy in surroundings
The numbers of blocks transferred to each place suggest the relative amounts of energy transferred by each process. For example, relatively little of the energy transferred from a conventional filament bulb (in the middle of the diagram above) is transferred by light (represented by one block) – most is transferred by heating (represented by four blocks). In contrast, almost all of the energy on the left-hand side of the diagram is transferred from the cell to the bulb, when the electric current flows in the circuit (represented by five blocks). Relatively little is transferred from the cell to the surroundings by heating (represented by one block). In fact, the amount of energy represented by one block is much too high here (energy transferred from the cell to the surroundings by heating). Using more blocks for the energy stored in the cell could help develop accuracy in the model, but this version may be ‘good enough’ for the first stages of understanding it.
01035-2009PDF-EN-05
© Crown copyright 2009
The National Strategies | Secondary Science Framework study guides: Strengthening teaching and learning of energy
5
Conservation of energy as a useful accounting system during energy transfers Using a system of counters to represent energy can be a useful way to develop an accounting system for energy. You can try out the method yourself and then with pupils during the next two tasks. Below are five energy stories that provide good scenarios for using an accounting system and developing an understanding of energy conservation, dissipation and efficiency. 1. A firelighter stores 200kJ of energy. When it burns, 190kJ is transferred to the surroundings by heating and 10kJ by light. 2. Jay eats a chocolate bar at breaktime. The label says there is 1000kJ of energy stored in the chocolate. As he runs around, he transfers 600kJ to the surroundings by heating and 5kJ by sound (that’s a lot of shouting!). How much of the energy from the chocolate bar is left to be stored by Jay’s body at the end of break? 3. A ‘low energy’ light bulb typically transfers about 80 per cent of its energy to its surroundings by light and the rest by heating. 4. Of every 1000J of energy transferred to a hairdryer by the electric current, the hairdryer typically transfers about 800J to the warm air by heating and moving it, about 190J through the case to the person’s hands by heating and movement (vibration) and about 10J to the surroundings by sound. 5. For every 50J of energy transferred to the surroundings by sound, a portable CD player transfers another 300J by heating.
© Crown copyright 2009
01035-2009PDF-EN-05
6
The National Strategies | Secondary Science Framework study guides: Strengthening teaching and learning of energy
Task 9: Using a physical model of an energy accounting system Try this task to develop your confidence in the methodology.
• • •
You will need to print a copy of Appendix 9 to give you the materials for the paper tokens and presentation grid. Cut up the tokens ready for use. Select one of the five energy stories given above. Use the cut-out energy tokens and grid to account for one of these stories.
Remember that this is an accounting system; no tokens should be lost or destroyed during the transfer.
Conservation of energy Sankey diagrams are similar in principle to the tokens model and are a widely recognised way to demonstrate the energy transfer teaching model. Many teachers introduce pupils to Sankey diagrams in Year 9. The diagram below shows how a Sankey diagram can be used to illustrate the energy transfers in an electric torch. You may find that using actual blocks or tokens enhances the effectiveness of these Sankey diagrams in the teaching of conservation of energy as an accounting system. Pupils’ understanding of efficiency and dissipation of energy can also be developed by the effective use of Sankey diagrams.
01035-2009PDF-EN-05
© Crown copyright 2009
The National Strategies | Secondary Science Framework study guides: Strengthening teaching and learning of energy
7
A Sankey diagram showing energy transfers in an electric torch.
Cell
Bulb
Surroundings Light
Electric current
Heating
Heating
Surroundings
Task 10: Pupils construct Sankey diagrams
• • • • •
Select an appropriate class or small group of pupils to try this with. Sankey diagrams are often introduced in Year 9. Use one (or more) of the five energy stories as the transfers to be illustrated. Prepare the tokens and the grids given in Appendix 9. Prepare your language to ensure that you emphasise the transfer model, rather than the transformation model, when you explain the diagrams to the pupils. Record any of the advantages or disadvantages of this method of introducing Sankey diagrams to your group of pupils.
Some of the advantages of this method often noted are that:
• • • • •
moving the tokens across the diagram reinforces the idea of a transfer from one place to another having to account for all the tokens encourages pupils to look for where the energy has gone and challenges the misconception that it simply disappears (you are not allowed to throw any tokens away) a lot of energy in one place at the start is gradually broken down into smaller and smaller amounts with each successive transfer efficiency can be calculated by comparing the number of tokens (or the value of those tokens in joules) that end up in the desired location with the total number transferred dissipation can be introduced by looking at the smaller amounts of energy located in a number of different places at the end of the transfer process compared with the concentrated store of energy in one place at the start.
© Crown copyright 2009
01035-2009PDF-EN-05
8
The National Strategies | Secondary Science Framework study guides: Strengthening teaching and learning of energy
Some of the limitations noted are that:
• • • •
sticking down tokens at each stage results in a proliferation of tokens, which may reinforce the misconception about creating and destroying energy energy is not a real thing like a token, so the model may encourage pupils to think of energy as a substance, which is particularly problematic when dealing with heating energy does not come in finite packets – it may be quantified into packets in some circumstances, but there is no standard-sized energy packet energy is not red (or any other colour) paper.
Dissipation of energy and energy efficiency This method of using tokens to build Sankey diagrams can also be used to teach about dissipation of energy and energy efficiency. You can try this out with some of the energy stories above.
Dissipation of energy The fourth energy story provides an opportunity to exemplify dissipation. In the story, the concentrated energy transferred to the hairdryer by the electric current is ‘spread out’ into several smaller, and therefore less useful, quantities in other places.
Energy efficiency This is a challenging idea and one you can try it with any of the energy stories. You will need to use the formula: efficiency =
useful energy transferred total energy transferred
You can try calculating the efficiency either using the number of tokens or the number of joules quoted in the energy stories. The answers given by both methods should agree. You may find the amplified objectives of the new science Framework helpful here, as you can see the progression in ideas about energy transfer, conservation, dissipation and energy efficiency (see appendix 10).
Reflection Look back at the true and false answers you gave for Task 3 in Energy: Misconceptions and teaching models. Have any of your responses changed now? Why have they changed?
01035-2009PDF-EN-05
© Crown copyright 2009
The National Strategies | Secondary Science Framework study guides: Strengthening teaching and learning of energy
Statement
True
False
9
Comment
1. Energy is a kind of stuff that is transferred from place to place when something happens. 2. Energy causes events to happen. 3. Heat and temperature are the same thing. 4. Heat is a form of energy. 5. Heating is a process of energy transfer. 6. Electricity is an energy source. 7. An electric current transfers energy. 8. Energy is dissipated but not lost when appliances are used. 9. Sound energy is transferred to the surroundings by vibrations. 10. Lighting is a process of energy transfer. 11. Respiration uses energy. 12. Photosynthesis makes energy. 13. Energy is a fuel. 14. The world is facing an energy crisis. 15. Chemical reactions cause energy to be transferred. 16. A car transfers all of the energy from the petrol to heating the surroundings.
Acknowledgements Dennis the Menace Model adapted from Feynman, R.P. (1998), Six Easy Pieces, Basic Books. Reprinted by kind permission of Basic Books, a member of Perseus Book Group.
© Crown copyright 2009
01035-2009PDF-EN-05
