Energy Transformations in Everyday Devices — Answers
Answer sheet with model answers and success criteria for the Year 7 energy, light, sound & electricity worksheet.
Success TutoringWorksheetsAnswer sheetYear 7 · Science · Energy, Light, Sound & ElectricityEnergy Transformations in Everyday Devices — Answers
Part A: Forms of energy
Read the passage, then answer the questions.
Energy is what makes things happen. It comes in different forms. Kinetic energy is the energy of anything that moves. Thermal energy is heat. Light, sound and electrical energy are other forms we use every day.
Some energy is stored. Food, fuels and batteries store chemical energy. An object high up has gravitational energy, and a stretched spring or rubber band has elastic energy.
Energy is never used up or made from nothing. Instead, it is transformed (changed) from one form to another.
- kinetic (movement) energy
- chemical energy
- sound energy
- thermal (heat) energy
- gravitational energy
- a hot cup of soup
- a book resting on a high shelf
- a ringing bell
- a rolling ball
- the energy stored in food and batteries
Answer: kinetic (movement) energy → a rolling ball; chemical energy → the energy stored in food and batteries; sound energy → a ringing bell; thermal (heat) energy → a hot cup of soup; gravitational energy → a book resting on a high shelf
Answer: changed
Also accept: transformed, transferred.
Answer: elastic
Also accept: elastic potential, stored.
Part B: Energy transformations in devices
Circle the best answer or write your answer.
We can show an energy transformation with an energy flow diagram. For a toaster: electrical energy → heat energy (and a little light energy).
Many devices change energy more than once. A battery-powered lamp: chemical energy → electrical energy → light energy (and some heat).
- Aelectrical → kinetic
- Bchemical → light
- Clight → electrical
- Dkinetic → chemical
Answer: electrical → kinetic
The fan uses electrical energy to spin its blades, which is kinetic energy.
- Asound energy into light energy
- Blight energy into electrical energy
- Cheat energy into chemical energy
- Dkinetic energy into sound energy
Answer: light energy into electrical energy
Its small solar cell turns light into the electrical energy that runs the calculator.
- Aelectrical energy in the bike
- Bchemical energy from the food you ate
- Clight energy from the Sun hitting the wheels
- Dsound energy from the road
Answer: chemical energy from the food you ate
Your muscles use chemical energy from food to make kinetic energy.
- Akinetic energy
- Bchemical energy
- Celectrical energy
- Dlight energy
Answer: kinetic energy
As it falls it loses height and speeds up, so gravitational energy becomes kinetic energy.
Answer: electrical
- The battery's chemical energy becomes electrical energy, which the speaker turns into sound.
Answer: chemical energy (in the wood) → heat (thermal) energy + light energy (also some sound)
Part C: Useful and wasted energy
Write True or False.
Useful energy is the form we want from a device, such as light from a lamp. Wasted energy is energy changed into forms we do not want, usually heat or sound, which spreads out into the surroundings.
An efficient device turns a large share of its energy into the useful form.
Answer: False
Most devices produce some energy we do not want, such as heat or sound, as well as the useful form.
Answer: True
The useful output is electrical energy for the laptop; the heat is not useful and is wasted.
Answer: True
Filament bulbs turn most of their energy into heat. LEDs waste much less, so they are more efficient.
Answer: False
Energy is never destroyed. Wasted energy usually spreads out into the surroundings as heat or sound.
Part D: Explain it
Model answer: Electrical energy → heat energy + kinetic energy (moving air) + sound energy. The heat and the moving air are useful because they dry the hair. The sound is wasted energy. Dryer B is likely to be more efficient because it dries hair just as quickly but wastes less energy as sound, so more of its electrical energy becomes useful heat and moving air.
Success criteria:
- Correct energy flow diagram starting with electrical energy
- Identifies heat and moving air as useful
- Identifies sound as wasted
- Chooses Dryer B with a reason linked to wasted energy
Marking tips
- Give credit for correct method even when the final answer slips — the working shows where the thinking went right.
- For open-ended tasks, use the success criteria as a checklist rather than looking for one "right" answer.
- Celebrate what went well first, then pick one thing to work on next.