How much heat raises 2 kg of water by 5 °C if c = 4.2 kJ/(kg·°C)? Assume no phase change.

A) 63 kJ

B) 42 kJ

C) 21 kJ

D) 84 kJ

Answer: B

Explanation: Use heat = mass × specific heat capacity × temperature rise for the stated idealized conditions. Substitution gives 2 × 4.2 × 5 = 42 kJ.