Question

How much energy is needed to change 1.5 kg of water at 20oC to steam at 100oC?

Answer 1

Given  

water initial temperature T1 = 20 0C , mass is m = 1.5 kg

final temperature is T2 = 100 0C ( steam)

here the energy required is first to heat the water from 20 0C to 100 0C ( liquid) form and converting it in to steam

we know that the heat energy required is Q = m*C*dT + m*L

where C , L are specific heat capacity of water and latent heat of vapourisation of water

C = 4184 J/kg.k, L = 2.26*10^6 J/kg

substituting the values  

Q = 1.5*4184(100-20)+1.5*2.26*10^6 J

Q = 3892080 J

so the energy required to convert to change 1.5 kg of water at 20oC to steam at 100oC is 3892080 J = 389.208 kJ