Energy Transfer in a Water and Aluminum Pan System

  • Thread starter Thread starter rkjul
  • Start date Start date
  • Tags Tags
    Heat
Click For Summary

Homework Help Overview

The problem involves energy transfer in a system consisting of boiling water and an aluminum pan. It requires calculating the temperature of the water after pouring it into the pan and determining the energy transfer from a stove to the system after additional work is done on the water.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the application of the energy equations, particularly the use of heat capacity and mass in calculating energy transfer. There are questions about the correct values for heat capacity and mass used in the calculations. Some participants attempt to derive a weighted average for heat capacity and total mass.

Discussion Status

There is an ongoing exploration of the calculations needed for part B, with participants sharing their attempts and questioning the values used in their equations. Some guidance is offered regarding the combination of heat capacities and masses, but no consensus has been reached on the correct approach or values.

Contextual Notes

Participants note potential confusion regarding the system's definition and the implications of the work done on the water. There is also mention of the need to clarify the values used in calculations, which may be contributing to incorrect results.

rkjul
Messages
7
Reaction score
0

Homework Statement



100 grams of boiling water (temperature 100° C, heat capacity 4.2 J/gram/K) are poured into an aluminum pan whose mass is 375 grams and initial temperature 24° C (the heat capacity of aluminum is 0.9 J/gram/K).
(a) After a short time, what is the temperature of the water?

(b) Next you place the pan on a hot electric stove. While the stove is heating the pan, you use a beater to stir the water, doing 1400 J of work, and the temperature of the water and pan increases to 74.6° C. How much energy transfer due to a temperature difference was there from the stove into the system consisting of the water plus the pan?


Homework Equations



deltaE=mC*deltaT
deltaE=Q+W

The Attempt at a Solution



Ok I got part A with no trouble but I'm struggling with part B. I tried using the mC*delta T equation for the water and the aluminum pan...adding those values and setting it equal to Q+W. I used 8.6 for delta T (74.6-66) since I got 66 degrees for my answer in part A. I then subtracted W to find Q in the second equation but it's not the correct answer. I think what might be throwing me is that the system consists of the water and pan. Any suggestions?
 
Physics news on Phys.org
You didn't say what value of C you used in the second calculation. But C' should be the weighted average of the mass of the water and the aluminium ( British spelling), and M' the sum of the masses.

C' = (C1*M1 + C2*M2)/(M1+M2)
M' = M1 + M2.

I think this will work, but I could be wrong.
 
Mentz114 said:
You didn't say what value of C you used in the second calculation. But C' should be the weighted average of the mass of the water and the aluminium ( British spelling), and M' the sum of the masses.

C' = (C1*M1 + C2*M2)/(M1+M2)
M' = M1 + M2.

I think this will work, but I could be wrong.

I calculated two values of mC*delta T, one for the water (100*4.2*8.6) and one for aluminum (375*0.9*8.6) and added those together and set that equal to Q+1400. I got Q=5115 (same answer as you) and it's incorrect.
 
how did u get a?
 

Similar threads

Heat Energy and Power -- Heating ice in a copper pan
  • · Replies 5 ·
Replies
5
Views
2K
I try to solve a thermodynamics problem on heat transfer
  • · Replies 3 ·
Replies
3
Views
2K
Ice cube in water: entropy calculation (Calorimetry)
  • · Replies 6 ·
Replies
6
Views
1K
Change in temperature for a system with entropy change
  • · Replies 4 ·
Replies
4
Views
2K
Find the final Celsius temperature of the aluminum and water
  • · Replies 2 ·
Replies
2
Views
3K
Finding Initial Temperature Entropy and Heat Exchange
  • · Replies 1 ·
Replies
1
Views
2K
How to Calculate Final Temperature in a Water and Aluminum System?
  • · Replies 2 ·
Replies
2
Views
2K
Do you need to account for the water heating up to the boiling point?
  • · Replies 23 ·
Replies
23
Views
3K
Thermal energy in boiling water
  • · Replies 7 ·
Replies
7
Views
25K
Calorimetry - finding the final temperature of a system of ice and water
  • · Replies 7 ·
Replies
7
Views
2K