Energy transfers – peer assessment
Task
A GCSE student called Donald was given a test about energy transfer. Below are his answers. Read the questions and his answers carefully.
Mark Donald’s answers and annotate the paper to show where and why you have awarded marks. Add notes to show how Donald could improve his answers.
Energy transfer test
1.
Light is a type of energy. Name two other types of energy. (1)
Thermal energy
2.
Tick any type of energy that is a useful ‘energy out’ for each appliance. (5)
Appliance
Hair straighteners
Washing machine
Dishwasher
Mobile phone
Light
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

Thermal



Sound


Kinetic


Light bulb    
3.
Draw a labelled Sankey diagram to show the energy transfers in a very efficient electric heater. (3)
Examiner’s notes
4.
Describe the energy transfers in a petrol lawn mower. You may use a diagram if you wish. (6)
Electrical energy is converted into a few other types of energy, including movement energy, sound energy and heat energy. All of the energy that goes in is changed into other types of energy. The sound energy is annoying, and there is no point in the heat energy but not all of the energy can become movement energy.
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Energy transfers – peer assessment
5.
Explain what is meant by efficiency. (2)
It’s when you do something really quickly but still do it well. For example, I am answering this question efficiently – I haven’t written much, but it’s correct and to the point.
6.
Describe how to calculate the efficiency of a light bulb. (3)
Find out how much energy becomes heat energy and how much becomes light energy. Divide the light energy by the total energy in
(electrical energy) and you have your answer.
7.
Harry wants to reduce his electricity bills. Advise him by using examples about energy transfers, how to choose appliances that will reduce his electricity bills.
You will be assessed on using good English, organising information clearly and using specialist terms where appropriate. ( 6)
It would be best to choose expesnive cheaper apliances so that they cost less and so you will spend less money. Try to get apliances that have a low eficiency so that less energy is wasted and your bills will be lower. A lot of apliances such as hoovers, washing machines, irons and computers waste energy as heat – try not to choose these.
Choose apliances that don’t waste energy.
Total mark ____/26
Positive comments
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Targets for improvement
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Energy transfers – peer assessment
This ‘peer-assessment’ task was designed to be used by students after they had studied the basics of energy transfers (e.g. Sankey diagrams, idea of efficiency). Resources to support this prior learning include ‘efficiency of machines’ and ‘energy transfers’. It should be used to consolidate learning. Too often, students don’t gain enough from peer-assessment, so creating answers to address specific misconceptions, errors, omissions helps avoid this problem.
If you wish to give students a resource to read prior to the task or to refer to during the task, the following website links have appropriate material http://www.bbc.co.uk/schools/gcsebitesize/science/edexcel/energy_future/energy_tra nsfer_efficiencyrev1.shtml http://www.bbc.co.uk/education/guides/z99jq6f/revision
Students of GCSE age are notoriously critical. They take delight in noticing Donald’s errors, misconceptions and lack of exam technique. Sometimes however, Donald surprises the students with a great answer!
Donald’s work was designed to review energy transfers in the Edexcel Core Science specification Topic P1. However, specification content for these concepts varies little between exam boards.
To stimulate discussion, Donald’s work can be used in pair or small group work, followed by targeted whole class questioning.
The following marks and comments are expected from students:
1.
Donald would score 1 mark on this question.
Donald should have taken note of the ‘2’ marks and this should have prompted him to realise that one response will not be enough! Thermal energy is a good answer though (better than heat).
2.
Donald would likely score 4 marks in this question.
Appliance hair straighteners washing machine dishwasher mobile phone light bulb
© www.teachitscience.co.uk 2014 light



 thermal


23332 sound

  kinetic

 
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Energy transfers – peer assessment
On the first line, Donald has correctly selected thermal energy. Some hair straighteners probably do have a light on them too, so this answer is fine and would score a mark. Light probably wouldn’t be needed for the mark though.
On the second line, he scores a mark because washing machines do transfer energy to thermal and kinetic energy (these are useful), but sound is definitely a type of
‘energy out’ as well. Washing machines, just like most other appliances also have indicator lights on them or timers which light up.
The third line scores no mark. Maybe Donald doesn’t know what a dishwasher is, but he could have guessed – and this might have got him a mark! All the boxes should have been ticked here.
The fourth line scores a mark, although Donald clearly got himself a bit confused, he has made his answer very clear. Don’t forget that mobile phones vibrate – hence kinetic energy is an output too.
The fifth line scores a mark – the useful energy output from a light bulb is light.
3.
Donald would probably score all 3 marks.
Donald’s diagram is messy, but there was no request for anything like a scale drawing. His labels are correct, and it is clear that he wants the heat energy part to be by far the largest part.
4.
Although Donald’s answer is brief, he may score 5 marks.
Donald has correctly described the energy transfer. He would have been better to use the term ‘thermal’ rather than ‘heat’. He has correctly stated that not all energy can become useful types, implying a lack of efficiency. His answer would probably have been made clearer with a diagram, but this was not essential. Using the words thermal and kinetic instead of heat and movement may have gained him the full marks, particularly if the concept of efficiency was mentioned.
5.
Donald has not thought about what he has learnt in Science! He would score 0 marks.
Donald should have remembered that efficiency is a measure of the % of energy that is usefully transferred. He could give a general example such as the more energy that is usefully transferred, the higher the efficiency to get the second mark.
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Energy transfers – peer assessment
6.
Donald’s answer is mostly correct, and he would likely score 2 marks.
He has correctly recognised all the energy types and the initial calculation is correct. However, Donald has omitted to say to multiply the answer by 100 to get the % efficiency.
He is still using heat instead of thermal.
7.
Donald has mostly missed the point of the question and would probably score 2 marks.
The marks would be awarded for some recognition of the role of efficiency in choosing appliances. However, cheap appliances won’t save money on the electricity bill, just on the initial purchase. It’s often actually more expensive appliances that are more efficient, although this is not always true. What Donald should be including is the idea of choosing appliances with a high efficiency. He should then give examples, such as a lightbulb with a higher efficiency will transfer more of its electrical energy into light energy and hence less energy will be wasted. His spelling needs improving as he is forgetting that appliance has a double ‘p’ and that efficiency has a double ‘f’.
Overall, Donald would score (about) seventeen marks.
Positive comments
 His spelling is generally good
 He has good grasp of energy transfers and Sankey diagrams
Targets for improvement
 ensure that his answers match the question given
 complete all questions (e.g. the missing row in the table) and re-reading questions such as q7 to check that his answer matches the question
 in some questions (e.g. calculating efficiency), a small addition (x 100) could have gained him an extra mark
 re-reading his answers would likely help.
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