# Homework Help: Block of ice melts - entropy of ice?

1. Jul 26, 2008

### ally1h

1. The problem statement, all variables and given/known data
A 2.00 kg block of ice at 0.0˚C melts. What is the change in entropy of the ice as a result of this process?

2. Relevant equations
Q = mcΔT
ΔS = Q/T

3. The attempt at a solution
Q = (2.00 kg)(2.1 kJ/kg*K)(273 K)
Q = 1092 J

ΔS = 1092 J / 273 K
ΔS = 4 J/K

Any good?

2. Jul 26, 2008

### Mapes

Re: entropy

Not good. Why would you calculate Q using an equation with ΔT? The temperature change is zero, not 273 K. I like your second equation, though, which assumes constant temperature.

How about getting the energy from the phase change?

3. Jul 26, 2008

### ally1h

Re: entropy

Then I'm not sure how to do the problem, the first part anyway, because then Q = 0 and if Q = 0 then ΔS = 0 as well...

4. Jul 26, 2008

### Mapes

Re: entropy

How about looking up the energy associated with the phase change?

5. Jul 26, 2008

### ally1h

Re: entropy

Ahhh... so I'm looking at latent heat then?
Q = mass x latent heat of fusion
Q = (2.00 kg)(333.7 kJ/kg)
Q = 667.4 kJ

Better? And then plug that into the second equation?

6. Jul 26, 2008

Re: entropy

Better.