1. Q = 112.8 kJ
2. Q = 5.01 kJ
The heat to change the phase can be formulated :
Q = mLf (melting/freezing)
Q = mLv (vaporization/condensation)
Lf=latent heat of fusion
Lv=latent heat of vaporization
1. m=50 g=0.05 kg
Lv for water = 2256 kJ/kg
[tex]\tt Q=m.L_v\\\\Q=0.05\times 2256\\\\Q=\boxed{\bold{112.8~kJ}}[/tex]
2. m=15 g=0.015 kg
Lf for water = 334 kj/kg
[tex]\tt Q=m.L_f\\\\Q=0.015\times 334\\\\Q=\boxed{\bold{5.01~kJ}}[/tex]