The heat transferred by the steam to the skin is given by
[tex]Q=m L_v[/tex]
where
m is the mass of the steam
[tex]L_v[/tex] is the latent heat of vaporization.
In our problem, the mass of the steam is (converting into kg)
[tex]m=25.0 g=0.025 kg[/tex]
while the latent heat of vaporization of the steam is
[tex]L_v = 2.256 \cdot 10^6 J/kg[/tex]
Substituting into the previous formula, we find the heat transferred to the skin:
[tex]Q=m L_v = (0.025 kg)(2.256 \cdot 10^6 J/kg)=56400 J = 2.56 \cdot 10^4 J[/tex]
