Conduction · Year 7
In Year 7 you learn: conduction and insulators.
Conduction is how energy passes through a solid. Particles at the hot end vibrate more and pass energy to their neighbours, and in metals free electrons carry it quickly too, so metals are good conductors. Materials that trap air, such as wool, foam and double glazing, are good insulators and slow the energy down.
Key facts
- Conduction: vibrating particles pass energy to their neighbours; metals conduct best (free electrons).
- Insulators (trapped air, wool, foam) slow conduction and convection.
- Liquids and gases are poor conductors: their particles are further apart.
Worked examples
Example 1
A metal spoon and a wooden spoon stand in a bowl of hot soup. Why does the metal handle get hot much more quickly?
Answer: metal is a good thermal conductor; wood is an insulator, so heat travels along it very slowly
Example 2
Is steel a good thermal conductor or a good thermal insulator?
Answer: good conductor
Example 3
How is energy mainly transferred by heating in your hand warming up a cold metal railing?
Answer: conduction
Example 4
Why does a woolly hat keep your head warm?
Answer: it traps air, reducing heat loss by conduction and convection
Example 5
Why do birds fluff up their feathers on a cold day?
Answer: fluffed-up feathers trap more air, and air is a good insulator, so the bird loses heat more slowly
Example 6
How does double glazing reduce heat loss through a window?
Answer: the trapped gas between the panes is a poor conductor