Quantity of heat energy required for change of phase = (mass) x (heat of fusion or heat of vaporization), or in equation form, Q = mL. Quantity of heat energy responsible for a temperature change = (mass) x (specific heat) x (change in temperature), or in equation form,
Q=mcΔT
For water, heat of fusion = 80 cal/g; heat of vaporization = 540 cal/g. Calculate the energy needed to melt 50 grams of $0^circ C$ ice.