1. The problem statement, all variables and given/known data For your cabin in the wilderness, you decide to build a primitive refrigerator out of Styrofoam, planning to keep the interior cool with a block of ice that has an initial mass of 24.0 kg. The box has dimensions of 0.5 m x 0.8 m x 0.5 m. Water from melting ice collects in the bottom of the box. Suppose the ice block is at 0 °C and the outside temperature is 21 °C. If the top of the empty box is never opened and you want the interior of the box to remain at 5 °C for exactly one week, until all the ice melts, what must be the thickness of the Styrofoam? 2. Relevant equations no equations especified 3. The attempt at a solution heat required for melting the ice: 80.16 x 105 J time in seconds during one week: 6.048 x 105 s If I wish to mantain the temp at 5 °C until all the ice melts, then the rate at wich thermal energy enters in the box must be 80.16 x 105 J / 6.048 x 105 s = 13.25 W. Using the expression for the heat current I found the thickness of the styrofoam to be equal to 0.428 cm, but the correct answer is 2.5 cm.