MYP Physics sample question: Specific heat capacity and conduction

A 0.50 kg aluminium block is heated from 20 °C to 60 °C. The specific heat capacity of aluminium is 900 J/kg °C.

1. (a)Calculate the thermal energy supplied to the block.[3]
   Show the mark scheme for (a)

   • • Q = mcΔT (1)
   • • Q = 0.50 × 900 × 40 (1)
   • • Q = 18 000 J (18 kJ) (1)
2. (b)Explain, in terms of particles, why metals are good conductors of thermal energy.[2]
   Show the mark scheme for (b)

   • • Metals contain free (delocalised) electrons that gain kinetic energy when heated (1)
   • • These electrons move through the metal and transfer energy by collisions with other particles (1)

In part b, the marks are for the mechanism. Saying that metals conduct heat well because they are metals scores nothing.