# Homework Help: Phase Change Question

1. Nov 28, 2007

### danield

1. The problem statement, all variables and given/known data
Some ceramic materials will become superconducting if immersed in liquid nitrogent. In an experiment, a 0.150kg block piece of such material at 20C is placed in liquid nitrogent at its boiling poitn to cool in a perfectly insulated flask, whcih allows the gaseous N2 immeadiately to escape. How many liters of liquid nitrogen will be boiled away in doing this operation? (Take the specific headt of the ceramic material to be the same as that of glass, and take the density of liquid nitrogen to be 800kb/m3)

2. Relevant equations
Q=mc#T
L=Q/m
density=mass/volume

3. The attempt at a solution
well right now i have the data but i dont know where to go from here
I have
Mass of ceramic =.15kg
Tinitiail of ceramic= 20 C
Tinitial of Nitrogen = -196C
C for ceramic= 840
C for N= 20.8
Latent Heat of nitrogen = 2x10^5

I tried using Sum of Q=0
meaning that
MCTf - MCTi + MCTf - MCTi
But i dont hace nitrogens mass, so i am stuck
any help is appreciated