M_i = 2kg T_i = -20^oC M_w = 5kg T_w = 20^oC Assume all ice and water come in thermal equilibrium at 0^oC ice. H = -H_{(ice - 20 to 0)} + Water_{(20\ o 0)} + Water_{(0^o ice)} =-m_is_i \\Delta T + M_wS_w \\Delta T + M_w L =-2\ imes 5\ imes 20 + .5 \ imes 1 \ imes 20 + 5 \ imes 80 = -20 + 100 + 400 H = +480 Heat come positive, so this heat will melt the ice from 0^o ice to 0^oC waterNow, total mass of ice = 2+5=7kg .Must that convert into water from given heat H = 480 H = M'L M' = \\dfrac{H}{L} = \\dfrac{480}{80} M' =6kg Mass of water =6kg ice =1kg