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12.7Chapter 12: Energy Transfer

Chapter 12 Review: Energy Transfer — Alhussan Physics - Stage 9 Revision Notes & Topical Questions

5 min read 8 parts Lesson 7 of 7 1 quiz

📚 Alhussan Physics - Stage 9 Hub / Topical Revision
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Lesson summary

Physics 12.7 Chapter 12 Review: Energy Transfer — Alhussan International Academy — Physics (Stages 7–9) notes: Summarise Chapter 12 on temperature, energy stores and transfers, conduction, convection, radiation, evaporation and the energy needed to raise temperature.Burning coal …

  • Conservation
  • Reducing losses
  • Demonstration
  • Explanation
  • Without heating
  • Temperature rise

Part 1 of 6Energy stores and transfers

Burning coal
  • Energy is transferred from a chemical store to a thermal store, with some as light.
Conservation
  • Energy is not made or destroyed, only moved between stores by heating, light, sound, electrical current or forces.

Part 2 of 6Three methods of energy transfer

MethodTravels throughExample
ConductionA solid in contactHeat along a metal spoon
ConvectionA liquid or gas that can flowConvection currents in water and air
RadiationEmpty space or transparent air; no particles neededInfrared from the Sun
Together
  • A hot cup of tea loses energy by conduction through the cup, by convection and evaporation from the surface and by infrared radiation.
Reducing losses
  • Lids, double walls and shiny surfaces reduce these losses.

Part 3 of 6A drink left in the Sun

Radiation
  • Infrared from the Sun is absorbed by the container and the liquid, transferring energy to its thermal store.
Convection
  • Energy is spread through the liquid as warm liquid rises and cooler liquid sinks.
Conduction
  • Energy passes through the container walls.
Losses
  • The warm drink also loses energy by radiation, by convection to the air and by evaporation from the surface.

Part 4 of 6Convection currents and the purple crystal

Demonstration
  • Heating a beaker gently under a crystal of potassium manganate(VII) makes a purple stream rise.
Explanation
  • Warm water carries the dissolved colour upwards before it cools and sinks, a convection current.
Without heating
  • The colour spreads slowly by diffusion.
Conduction
  • A hot cup of tea transfers energy through the cup to the surroundings, or to a cold spoon, until they reach the same temperature.

Part 5 of 6Energy needed to raise temperature

Mass
  • More mass needs more energy for the same temperature rise.
Temperature rise
  • A bigger rise needs more energy.
Material
  • Water needs more energy per kilogram than most substances.

Part 6 of 6Evaporation and temperature

1Thermal energy and temperature
  • Temperature measures hotness, whereas thermal energy depends on the amount of material.
2Evaporation
  • Fast particles escape, so the liquid left behind cools.

Key terms

TermMeaning
ConductionEnergy transfer through a solid by vibrating particles and electrons.
ConvectionEnergy transfer by the movement of a heated fluid.
RadiationEnergy transfer by waves, which can travel through a vacuum.
Thermal storeThe store of energy in the motion of particles of an object.
EvaporationA liquid changing to vapour at its surface.

Avoid these mistakes

1
Thinking energy is used up when it transfers — it is conserved.
2
Confusing conduction and convection — convection needs a fluid that flows.
3
Thinking radiation needs particles — it travels through a vacuum.
4
Thinking a lid only stops conduction — it also reduces convection and evaporation.

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