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2.3.1Thermal Physics

Conduction — Cambridge IGCSE Physics 0625 Revision Notes & Topical Questions

5 min read 9 parts Lesson 27 of 45 1 quiz

📚 Cambridge IGCSE Physics 0625 Hub / Topical Revision
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Lesson summary

2.3.1 Conduction — IGCSE PHYSICS notes: Describe thermal conduction in terms of particles and compare good and bad conductors.Good conductors — transfer thermal energy quickly, for example an aluminium pan or copper wireBad conductors — also called thermal insulators, transfer th…

  • Definition
  • Main method
  • Equilibrium
  • Lattice vibrations
  • Free electrons
  • Non-metals

Part 1 of 7Conductors and insulators

Good conductors
  • Good conductors transfer thermal energy quickly, for example an aluminium pan or copper wire
Bad conductors
  • Bad conductors also called thermal insulators, transfer thermal energy poorly, for example wool or paper
Metals
  • Metals the best thermal conductors

Part 2 of 7Conduction in solids

Definition
  • Definition transfer of thermal energy through lattice vibrations and, in metals, free electrons
Main method
  • Main method conduction is the main method of energy transfer in solids
Equilibrium
  • Equilibrium collisions pass energy on until the whole substance is at the same temperature

Part 3 of 7Mechanisms

Lattice vibrations
  • Lattice vibrations atoms at the hot end vibrate more and bump into neighbours, passing energy along
  • Happens in all solids, metals and non-metals
Free electrons
  • Free electrons in a metal the vibrating atoms also transfer energy to free (delocalised) electrons
  • The electrons travel far and collide with distant atoms
  • This is much faster than lattice vibrations alone

Part 4 of 7Liquids and gases

Liquids
  • Liquids most are poor conductors because particles slide past one another rather than vibrating in a lattice
Gases
  • Gases widely separated particles collide less often, so conduction is very poor
Exception
  • Exception liquid metals conduct well because they still have free electrons

Part 5 of 7Relative conductivity

Range
  • Range solids vary widely in how well they conduct
Free electrons
  • Free electrons materials with free electrons are better conductors
Non-metals
  • Non-metals conduct less well because they lack free electrons
Comparisons
  • Copper is a better conductor than iron
  • Rubber is a better insulator than glass

Part 6 of 7Everyday uses

Conductors
  • Conductors metal pans and radiators transfer energy quickly
Insulators
  • Insulators plastic saucepan handles slow energy to the hands
  • Air gaps in walls or windows retain energy because air is a poor conductor

Part 7 of 7More from the specification

1Conduction
  • Conduction thermal energy passes through a solid as vibrating particles pass on energy to neighbours, and in metals also by free electrons.
2Convection
  • Convection heat transfer in fluids where warmer, less dense fluid rises and cooler fluid sinks, forming currents.
3Radiation
  • Radiation infrared waves emitted by every hot object that need no medium;
    • the Earth receives the Sun's energy this way.
4Surface effects
  • Surface effects dull black surfaces absorb and emit infrared best, while shiny light surfaces reflect it.
5Greenhouse effect
  • Greenhouse effect gases in the atmosphere absorb infrared emitted by the warmed Earth and re-emit it, raising temperature.
6Conduction
  • Conduction thermal energy passes through a solid as vibrating particles pass on energy to neighbours, and in metals also by free electrons.
7Convection
  • Convection heat transfer in fluids where warmer, less dense fluid rises and cooler fluid sinks, forming currents.
8Radiation
  • Radiation infrared waves emitted by every hot object that need no medium;
    • the Earth receives the Sun's energy this way.
9Surface effects
  • Surface effects dull black surfaces absorb and emit infrared best, while shiny light surfaces reflect it.
10Greenhouse effect
  • Greenhouse effect gases in the atmosphere absorb infrared emitted by the warmed Earth and re-emit it, raising temperature.
11Greenhouse effect
  • Warming of the Earth because gases absorb and re-emit its infrared radiation
12Convection current
  • Circulating flow of fluid caused by density differences
13Potassium permanganate
  • A purple compound used to show convection currents in water.
14Convection
  • Transfer of thermal energy by the movement of a heated fluid
15Infrared
  • The part of the electromagnetic spectrum emitted by warm objects.
16Absorbed
  • Taken in by an object, with light energy transferred to thermal energy.

Key terms

TermMeaning
ConductionTransfer of thermal energy by lattice vibrations and free electrons
Thermal conductorMaterial that transfers thermal energy quickly
Thermal insulatorMaterial that transfers thermal energy poorly
Free electronsDelocalised electrons in a metal that carry energy

Avoid these mistakes

Avoid these mistakes
Saying energy is carried by atoms moving along the solid — atoms vibrate in place and pass energy on.
Saying all solids use free electrons — only metals do.
Saying cold flows in — thermal energy flows from hot to cold.

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