Thermodynamics with styrofoam cooler

[physikx]

Homework Statement

A cubical styrofoam cooler 80cm on a side and 2.0 cm thick contains 2.0kg of ice at 0C. If it takes four hours for the ice to melt what is the outside temperature? K(st)=.02 w/m*K

Homework Equations

H=-KA (ΔT/ΔX)
(conductive heat flow)

The Attempt at a Solution

Area: 6(a)^2= 6(.8)^2= 3.8m^2
Δx=.02m
K(st)=.02 w/m*K

H=-.02 w/m*K(3.8m^2) (ΔT/.02m)So I used the formula for the conductive heat flow, but I still have two unknowns. I know H is ΔQ/Δt, but I am asked for the time. I had two questions in regards to this problem:
1. for the area do I find the total surface area or just one side?
2. what temperature change ΔT should I set the ΔQ formula if I am assuming the ice is melting?

Thanks for the help!

 

[ehild]

So I used the formula for the conductive heat flow, but I still have two unknowns. I know H is ΔQ/Δt, but I am asked for the time. I had two questions in regards to this problem:
1. for the area do I find the total surface area or just one side?
2. what temperature change ΔT should I set the ΔQ formula if I am assuming the ice is melting?

Thanks for the help!

First of all, what do the symbols in the formula for the conductive heat flow mean?
Can you derive that formula?


ehild

 

[physikx]

ehild, thank you for your reply and I apologize for this far too late of response. I figured out the answer to this problem after grinding the problem for a while. I am done with my final for the first part of physics! I can not wait for the second part in a week :) Thanks again and talk to you soon.

physikx

 

[ehild]

Congratulation!

ehild