A piece of copper of mass 200 g is heated from 30°C to 80°C. If the specific heat capacity of copper is 400 J kg⁻¹ K⁻¹, calculate the quantity of heat absorbed by the copper.

Using the formula Q = mcΔT, where m = 0.2 kg, c = 400 J kg⁻¹ K⁻¹, and ΔT = (80 − 30) = 50 K: Q = 0.2 × 400 × 50 = 4 000 J. Option A results from using ΔT = 25 (half the correct value), option C from using the full temperature of 80°C instead of the change, and option D from using m = 0.4 kg.