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/K)

- 2.1 kJ
- 4.2 kJ
- 8.4 kJ
- 84 kJ

**Answer**

ΔQ = MSΔT = 100 x 10^{-3} x 4.184 x 20 = 8.4 X 10^{3}

ΔQ = 84 kJ, ΔW = 0

ΔQ = ΔV + ΔW

V = 8.4 kJ

**The correct option is C.**