100 g of water is heated from 30 °C to 50 °C. Ignoring the slight expansion of
the water, the change in its internal energy is (specific heat of water is 4184 J kg–
1 K–1)
(a) 4.2 kJ
(b) 8.4 kJ
(c) 84 kJ
(d) 2.1 kJ