Quick answer: An energy transfer is the movement of energy from one store to another or its change from one form to another. This grade 7 science test on energy transfers has 8 questions worth 20 marks, to do in 45 minutes: conservation of energy, radio chain and water pump Sankey. The mark scheme is on a separate page; free printable PDF.
This test checks energy chains, conservation of energy, wasted energy and efficiency. Show your working, give units and use complete sentences for the explanations.
Level: Grade 7 science (Year 8 · Class 7) · Curriculum: MS-PS3-5
Question 1 Conservation of energy (2 marks)
State the law of conservation of energy and give one example of a wasted energy transfer.Question 2 Radio chain (3 marks)
A battery radio plays music.- Write the energy chain from the battery to the sound. (2 marks)
- Name one wasted output. (1 mark)
Question 3 Water pump Sankey (3 marks)
The Sankey diagram shows a small water pump.- State the useful energy output. (1 mark)
- State the wasted energy. (1 mark)
- Calculate the efficiency of the pump. (1 mark)
Question 4 Gas ring (3 marks)
A gas ring gives out 3000 J of thermal energy every second. Of this, 1800 J heats the pan and the rest heats the room.- Write the formula for efficiency. (1 mark)
- Calculate the efficiency of the ring. (2 marks)
Question 5 Hard to reuse (2 marks)
Explain why wasted thermal energy from a laptop cannot be collected and used again.Question 6 Compare two devices (3 marks)
Device A takes in 50 J and gives 40 J of useful energy. Device B takes in 40 J and gives 36 J of useful energy.- Calculate the efficiency of each device. (2 marks)
- State which device wastes less energy. (1 mark)
Question 7 Impossible claim (2 marks)
An inventor says a machine takes in 200 J and always gives out 250 J of useful energy. Explain why this cannot be true.Question 8 Insulating a kettle (2 marks)
Suggest how adding a layer of insulation to the outside of a kettle changes its efficiency, and explain why.
