Newcomer Asks: What is the Final Temperature?

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Discussion Overview

The discussion revolves around a problem involving the final temperature of a mixture of two bodies of water at different initial temperatures. Participants explore the application of heat transfer principles, specifically focusing on the conservation of energy in the context of mixing water. The scope includes conceptual understanding and mathematical reasoning related to thermodynamics.

Discussion Character

  • Homework-related
  • Conceptual clarification
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant suggests using the equation deltaT=deltaQ/cm for solving the problem.
  • Another participant confirms that the equation is appropriate for the scenario.
  • A participant expresses confusion over their calculations, arriving at an unexpected result of 15C/175,000.
  • One participant emphasizes the principle that the heat lost by the hotter water equals the heat gained by the cooler water as a starting point for solving the problem.
  • Another participant questions the impact of the added mass of water on the final temperature and seeks clarification on the specific heat capacity of water.
  • A participant provides the specific heat capacity of water as 4.19 kJ/kg*K and suggests thinking in terms of conservation of energy.
  • One participant asks whether to average the temperatures or consider the temperature difference directly, indicating confusion about the energy conservation concept.
  • A later reply clarifies that at thermal equilibrium, both parts of the water will share the same final temperature and encourages calculating the heat gained by each part.
  • Another participant speculates that one part of the water gains 15 degrees while the other gains nothing, questioning if the final temperature would be 40 degrees.
  • A participant expresses frustration with the complexity of the problem and indicates a need to revisit their textbook for further understanding.
  • One participant suggests a method of thinking about the problem in terms of heat transfer calculations involving the total mass and temperature change.

Areas of Agreement / Disagreement

Participants express various viewpoints on the approach to solving the problem, with some agreeing on the principles of heat transfer while others remain confused about the calculations and concepts involved. The discussion does not reach a consensus on the final temperature or the method of calculation.

Contextual Notes

Participants exhibit uncertainty regarding the application of heat transfer principles, the role of mass in the calculations, and the specifics of the temperature change. There are unresolved mathematical steps and assumptions about energy conservation that are not fully clarified.

Msnyder
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First time here so be easy please!

Problem: What would final temp. be when 100g of 25C water is mixed with 75g of 40c water?

Do I use deltaT=deltaQ/cm?

If there is a more basic forum, please let me know, I do not want to offend anyone.
 
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Yep, that's the equation to use.
 
any help would be appreciated, I am getting confused with the problem

somehow I am getting 15C/175,000?

By the way, if there is a more basic forum, let me know...I do not want to offend anyone!
 
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what did you do to get that answer?

the heat released by the hotter portion is the heat gained by the cooler portion. that's where I'd start solving the problem from.

addition: maybe this should be in some of the homework forums? otherwise it's in the right place. if this is in the wrong place don't start a new thread but wait for a moderator to move it to the right place.
 
I understand that heat lost is = to heat gained,but what about the added water?

I guess the better question would be, what is the c of water?

**I feel like a 10 yr old boy in this class!
 
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c is 4.19kJ/kg*K.

Think in terms of conservation of energy. If no energy is lost then the Q of the final state (175 grams of water at some temperature T) must be equal to... You fill the blank.
 
Quick questions, do I average the temps or do I subtract 40 -25 which is 15C. Are you saying that the water conserves it's energy, so the addition of mass does not matter, it's just 15C?
 
Don't be confused by the fact that you're mixing water with water. In the end (at thermal equilibrium) both 'parts' share the same temperature. Call it T.
Using this T, what is the amount of heat 1 part of the water gained, what is the amount of heat the other one gained? What should T be such that the total amount of heat gained is zero?
 
wow...I guess one gained 15 degrees and the other gained nothing, so together they gain 15, because the transfer of heat is from the hotter to the cooler?

So, from the original problem, the water ends up at 40 degrees?
 
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  • #10
Thanks for your help everyone, but I am not getting anywhere. This is just extra hard for me at this point. I will try my text again and see if I can come up with something. Thanks again,
Mike
 
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  • #11
Msnyder said:
Thanks for your help everyone, but I am not getting anywhere. This is just extra hard for me at this point. I will try my text again and see if I can come up with something. Thanks again,
Mike
Think of the problem this way:

Begin with 175 g of water at 25 deg. C and add heat that is sufficient to warm 75g of water to 40 degrees (ie. 75 g x 15 deg = 1125 Cal). What is the temperature raised by? (ie. 1125 Cal into 175 g = ? deg).

AM
 

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