The heat needed to raise the temperature of a substance by [tex]\Delta T[/tex] is given by
[tex]Q= m C_s \Delta T[/tex]
where
m is the mass of the substance
[tex]C_s[/tex] is its specific heat capacity
[tex]\Delta T[/tex] is the increase in temperature.
In our problem, the mass of the ice is [tex]m=150 g [/tex], the specific heat capacity of ice is [tex]C_s = 2.108 J/(g ^{\circ} C)[/tex] while the increase in temperature is [tex]\Delta T = -15 ^{\circ}C- (-30 ^{\circ})=15 ^{\circ}[/tex], so the amount of heat needed is
[tex]Q=(150 g)(2.108 J/(g^{\circ}C)(15^{\circ}C)=4748 J[/tex]
