WAEC Physics 2010 Paper

Concept:The total heat required is the sum of the heat needed to raise the solid from $50^\circ\mathrm{C}$ to its melting point and the latent heat needed to melt it completely at $60^\circ\mathrm{C}$.Explanation:Given: $m = 0.5\ \mathrm{kg}$, $\Delta\theta = 60 - 50 = 10\ \mathrm{K}$Specific heat capacity, $c = 2.0\ \mathrm{kJ\ kg^{-1}K^{-1}}$Specific latent heat of fusion, $L = 1.0\ \mathrm{kJ\ kg^{-1}}$Heat to raise the solid to melting point:$Q_1 = mc\Delta\theta = 0.5 \times 2.0 \times 10 = 10\ \mathrm{kJ}$Heat to melt the solid completely:$Q_2 = mL = 0.5 \times 1.0 = 0.5\ \mathrm{kJ}$Total heat:$Q = Q_1 + Q_2 = 10 + 0.5 = 10.5\ \mathrm{kJ}$$Q = 10.5 \times 1000 = 10500\ \mathrm{J}$Answer:The quantity of heat required is $10500\ \mathrm{J}$, so the correct option is C.