Heat required to raise the temperature of water is given as
[tex]Q = ms\Delta T[/tex]
here we have
m = 100 g = 0.100 kg
s = 4183 J/kg C
[tex]\Delta T = 50 ^0 C[/tex]
now we can use the above equation
[tex]Q = 0.100 * 4184 * 50[/tex]
[tex]Q = 20920 J[/tex]
so here it requires 20920 J heat to raise the temperature of 100 g water by 50 degree C