Approximately how long should it take 9.6 kg of ice at 0?C to melt when it is placed in a carefully sealed Styrofoam ice chest of dimensions 25 cm × 35 cm × 55 cm whose walls are 1.8 cm thick? Assume that the conductivity of Styrofoam is double that of air and that the outside temperature is 36 ?C. Express your answer to two significant figures and include the appropriate units. Solution rate of heat transfer H = k*A*dT/t H = 0.048*2*((0.25*0.35)+(0.35*0.55)+(0.25*0.55))*(36-0)/(1.8*10^-2) H = 80.16 J heat required to melt the ice Q = m*Lf m = mass of ice = 9.6 kg Lf = 334*10^3 J time to melt = Q/H = 9.6*334*10^3/80.16 = 40000 s = 11 hours .

1. Approximately how long should it take 9.6 kg of ice at 0?C to melt when it is placed in a
carefully sealed Styrofoam ice chest of dimensions 25 cm × 35 cm × 55 cm whose walls
are 1.8 cm thick? Assume that the conductivity of Styrofoam is double that of air and that the
outside temperature is 36 ?C.
Express your answer to two significant figures and include the appropriate units.
Solution
rate of heat transfer
H = k*A*dT/t
H = 0.048*2*((0.25*0.35)+(0.35*0.55)+(0.25*0.55))*(36-0)/(1.8*10^-2)
H = 80.16 J
heat required to melt the ice Q = m*Lf
m = mass of ice = 9.6 kg
Lf = 334*10^3 J
time to melt = Q/H = 9.6*334*10^3/80.16 = 40000 s = 11 hours