Conduction revision notes

Edexcel International GCSE Physics (4PH1), chapter 15: Thermal energy, specification point 4.6. Free lesson.

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Conduction transfers thermal energy through a solid from a hotter place to a colder one. Understanding how particles and free electrons transfer energy helps explain why some materials conduct well and others insulate.

How conduction transfers energy through a solid

Particles in a solid vibrate about fixed positions. Heating one end makes its particles vibrate more. They bump into neighbouring particles and pass on some energy, so those neighbours vibrate more too. This continues along the solid until the far end gets hotter. The particles stay in place. Energy moves, not the particles. Energy transfers from the hot end to the cold end.

Why metals conduct better than other solids

In both metals and non-metals, vibrating particles pass energy to their neighbours. Metals also contain free electrons, which can move throughout the metal. They gain energy at the hot end and carry it quickly towards the cold end. Free electrons transfer energy much faster than vibrations do, so metals are good conductors. Non-metals such as wood and plastic are poor conductors, also called insulators.

Choosing conductors and insulators

A material is chosen according to whether energy should move through it. A saucepan has a metal base so energy can reach the food, but a plastic handle so little energy reaches your hand. Wood is also a poor conductor, which is why a wooden spoon does not transfer heat to your hand quickly. Air is a very poor conductor because its particles are far apart. When air is trapped in fibres or foam, it makes a good insulator. Good conductors: metals, such as the base of a saucepan. Poor conductors: plastic and wood, used for handles and spoons. Trapped air: found in materials such as…

Why a metal bench feels colder

A metal bench and a wooden bench left outside are both at the temperature of the air. The metal is not colder. It feels colder because it conducts energy away from your hand faster than the wood does.

Explaining insulation in exam answers

For an explain question, link a material's properties to what happens to energy. Give the point and then its reason or consequence. For a woolly jumper, trapped air limits energy transfer from your body because air is a very poor conductor and cannot move around while trapped in the wool.