How much heat is released from water into ice.

[ScienceGeek24]

Homework Statement

How much heat is released when 250 g of water at 10 degrees celcius freezes into ice and cools to -10 degrees celcius?

Homework Equations

Q=mcΔt

The Attempt at a Solution

q= (250g)(4186)(283-273)=1.046*10^4 J

than q=(250g)(2090)(263-283)=-1.045*10^4 J

when i subtract the two i get 1*10^4

The answer is -9.86*10^4 what am i doing wrong?

 

[gneill]

Three stages:
1. Cool to freezing point
2. Freeze
3. Cool to final temp

Each stage is governed by a different heat constant.

 

[ScienceGeek24]

OK this is what I'm doing

1. cool to freezing point

q=(.250kg)(4186J/kgK)(273K-283K)=-1.046*10^4J

2.Freeze

MLf=(.250)(3.33*10^5)=8.32*10^4 J

3.Cool to final temp

Q= (.250kg)(2090j/kgK)(-283K-273K)=-2.90510*10^5

so when i sum up Q1+mLf+Q2= -2.177*10^5 J
Like seriously what am i doing wrong?

 

[ScienceGeek24]

got it! i found the mistakes ! thanks! :D