How Do You Calculate Thermal Equilibrium and Ice Formation Times?

  • Thread starter Thread starter Goalcard
  • Start date Start date
  • Tags Tags
    Stuck
Click For Summary

Homework Help Overview

The discussion revolves around calculating thermal equilibrium in heat transfer scenarios and determining ice formation times through radiation. The problems involve a copper slug in water, ice formation under specific conditions, and the application of the ideal gas law.

Discussion Character

  • Mixed

Approaches and Questions Raised

  • Participants explore the heat transfer between a heated copper slug and water, questioning the setup for thermal equilibrium. Others express confusion about starting points for calculating ice formation and seek guidance on the ideal gas law application.

Discussion Status

Some participants provide partial guidance on the ideal gas law problem, suggesting the use of the formula relating initial and final states. However, there is a lack of consensus on the first two problems, with participants seeking further clarification and formulas.

Contextual Notes

Participants mention deadlines for homework submission, indicating urgency in finding solutions. There is also a reference to reviewing material on heat transfer and black body radiation, suggesting a need for foundational understanding in these areas.

Goalcard
Messages
6
Reaction score
0
1. Heat Transfer
A copper slug whose mass mc is 75g is heated in a laboratory oven to a temperature T of 3120C. The slug is then dropped into a glass beaker containing a mass mw =220g of water. The heat capacity Cb of the beaker is 45 cal/K. The initial temperature Ti of the water and the beaker is 120C. What is the final temperature Tf of the slug, the beaker, and the water when thermal equilibrium is reached?

Would this look about right?
mc(water)+mc(copper calorimeter) +mc (beaker) = 0.

2. How to Make Ice Without a Refrigerator
On a clear moonless night, the sky acts like a blackbody radiator at a temperature Ts=
-230 C. You thermally insulate a container from the ground (by placing a poorly conducting layer of straw beneath it). Then you pour water into the container, forming a thin, uniform layer with mass m=4.5 g, with surface area A = 9.0 cm2 and depth= 5.0 mm. The emissivity is .9, and initial temperature 6.00C. Find the time required for the water to freeze via radiation.

On this one I am super lost, no idea from where to start.

3. The Ideal Gas Law
A cylinder contains 12 L of oxygen at 200C and 15 atm. The temperature is raised to 350C, and the volume is reduced to 8.5 L. What is the final pressure of the gas in atmospheres?

Same as the other one, if you guys/gals can point me to the right direction formula wise that would be great.
 
Physics news on Phys.org
I didn't have time to read 1 and 2 but for 3 you should be able to use

intial PV/T = final PV/T
 
Hermite said:
I didn't have time to read 1 and 2 but for 3 you should be able to use
intial PV/T = final PV/T
Does this look about right?
P(12)/200=P(8.5)/350
 
Goalcard said:
Does this look about right?
P(12)/200=P(8.5)/350

yes no maybe so? :biggrin:
 
you're on the right track.. How about including your initial pressure [itex]P_i[/itex] and solving for final pressure [itex]P_f[/itex]
 
Ouabache said:
you're on the right track.. How about including your initial pressure [itex]P_i[/itex] and solving for final pressure [itex]P_f[/itex]
final pressure would be 37.059?
 
Goalcard said:
final pressure would be 37.059?
Yeah? any tips on the first two?
 
Goalcard said:
Yeah? any tips on the first two?
Maybe throw me a formula, that would help me a lot, it's due tomorrow(Wednesday)
 
Goalcard said:
final pressure would be 37.059?
Looks good to me..

On the first two, if I were assigned these questions, instead of guessing which formula to use, I would review material on heat transfer and black body radiation. Here is a starting point ref
 

Similar threads

  • · Replies 6 ·
Replies
6
Views
1K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 4 ·
Replies
4
Views
4K
  • · Replies 1 ·
Replies
1
Views
4K
Replies
6
Views
1K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 1 ·
Replies
1
Views
6K
  • · Replies 3 ·
Replies
3
Views
10K
  • · Replies 10 ·
Replies
10
Views
9K
  • · Replies 6 ·
Replies
6
Views
3K