Energy = msT joules, where
s = specific heat capacity
T = temperature difference
Here, m = 1g, s = 4.184 joules / deg. Celsius, , T = 100 deg. Celsius
so Energy = 418.4 joules... Answer
Please note water is in liquid state both at 100 and 0 deg Celsius, For steam and ice, we have to add latent heat otherwise.