Thermal Conductivity & Heat Transfer by Conduction (MYP Physics)
Touch a metal spoon and a wooden spoon that have both been in hot soup and the metal feels far hotter. Same temperature, different materials — the difference is thermal conductivity. Understanding conduction explains why pans are metal with plastic handles, why houses have insulation, and why a winter jacket works by trapping air.
Try it yourself: choose a material, customise the specimen and watch how heat moves through it.
How conduction works
In a solid, particles vibrate around fixed positions. When one end is heated its particles vibrate more strongly and pass that energy to their neighbours through collisions, so thermal energy spreads along the object without the material itself moving.
Why metals conduct best
Metals contain free (delocalised) electrons that carry energy quickly through the material in addition to the vibrating particles, which is why metals are good thermal conductors. Materials like wood, plastic and air have no free electrons and transfer energy slowly, making them insulators.
What controls the rate of heat transfer
For a solid bar, the rate at which heat flows increases with:
- •a larger temperature difference between the two ends,
- •a bigger cross-sectional area,
- •a material with a higher thermal conductivity,
- •and decreases as the bar gets longer (a thicker barrier).
Using it in design
Good design matches the material to the job: high-conductivity metals where heat should move quickly (cooking pans, heat sinks), and insulators where it should not (oven gloves, cavity walls). Trapped air is an excellent insulator because gases conduct poorly, which is why fleece, double glazing and foam work.
Frequently asked questions
Metal conducts heat away from your hand faster, so it feels colder, even though both are at room temperature.
A material that conducts heat poorly, such as wood, plastic or trapped air.
A longer rod transfers heat more slowly, because the energy must be passed along more particles.