# Homework Help: Thermodynamics with styrofoam cooler

1. Feb 13, 2012

### physikx

1. The problem statement, all variables and given/known data
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

2. Relevant equations
H=-KA (ΔT/ΔX)
(conductive heat flow)

3. 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!

2. Feb 14, 2012

### ehild

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

ehild

3. Feb 16, 2012

### 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

4. Feb 17, 2012

### ehild

Congratulation!

ehild