Density of water at 4°C and 20°C are 1000 kg/m3 and 998 kg/m3 respectively. The increase in internal energy of 4 kg of water when it is heated from 4°C to 20°C is ________ J.
(Specific heat capacity of water = 4.2 J/kg, and 1 atmospheric pressure = 105 Pa) [2026]
(4)
Q=msΔT=4×4200×16 J=268800 J
W=PΔV
ΔV=(mρf-mρi)=4[1998-11000]
P=105 Pa
∴ W=105×4[1998-11000]=8×105103×998≈0.8 J
ΔU=Q-W=268799.2 J