A metal stirring spoon and a plastic stirring spoon are placed into a saucepan containing hot soup. After a short time, the handle of the metal spoon becomes very hot, while the handle of the plastic spoon remains relatively cool.
Explain how delocalised electrons transfer thermal energy through the metal spoon from the hot soup to the handle.
Explain why the plastic spoon conducts thermal energy much less effectively than the metal spoon.
Explain, in terms of the arrangement and motion of particles, why gases (such as air) are poor thermal conductors compared to solid non-metals (such as plastic).
301 exam-style questions on CIE IGCSE Physics 2.3 Transfer of thermal energy, covering 2.3.1a Thermal conductors and thermal insulators, 2.3.1b Explaining thermal conduction, 2.3.2 Convection, 2.3.3a Thermal radiation, 2.3.3b Surface colour and texture, 2.3.3c Rate of emission and absorption of radiation, and 2.3.4 Consequences of thermal energy transfer. Each one has a worked solution and a mark scheme showing where the marks go.