Calculating Heat Release: Freezing a 8.5 km^2 Lake to 1.0m Depth

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Discussion Overview

The discussion revolves around calculating the heat released when a lake with a surface area of 8.5 km² freezes to a depth of 1.0 m, assuming the water starts at 0 degrees Celsius. The context includes mathematical reasoning and conceptual understanding of heat transfer and phase changes.

Discussion Character

  • Mathematical reasoning
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant requests help with calculating the heat released, providing a specific answer of 6.2 x 10^11 Kcal.
  • Another participant suggests using Newton's law of cooling as a potential approach to the problem.
  • A different participant argues that the problem is simpler than using Newton's law, emphasizing that since the water is at 0°C, there is no temperature change, and the calculation involves the volume of ice and the heat of fusion of ice.
  • A chemist participant proposes calculating the number of moles of water frozen and using the heat of fusion in kJ/mol, implying a different perspective from a physics approach.
  • The original poster expresses confusion about the supplied answer being incorrect, indicating uncertainty in the provided information.

Areas of Agreement / Disagreement

Participants present differing approaches to the problem, with no consensus on the method or the correctness of the supplied answer. The discussion remains unresolved regarding the accuracy of the initial answer and the best approach to the calculation.

Contextual Notes

Participants mention various methods for calculating heat release, including the heat of fusion and the number of moles, but do not clarify specific assumptions or definitions that may affect the calculations.

jimmyche
Can anyone help me with the following question.

How much heat is released when a lake of surface area 8.5 km^2 freezes to a depth of 1.0m? assume the water is initially at 0 degree C. The answer is 6.2 X10^11 Kcal.

Thanks.

any help is approciated.
 
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Look up Newton's law of cooling, it should help you to figure that one out.
 
It is really much simpler then Newtons law of cooling. Since the water is at 0C already there is no temperature change involved. You know the volumn of Ice forming (area x thickness) and you should know about the heat of fusion of Ice, this is given as some number of Kcals per mole of water, simple multiplication.

If I told you any more I would be doing the problem for you.
 
Since I'm a chemist, i would find out the number of mol's of water you have frozen and then use the kj/mol of fusion. Thus giving it to you. but you physics people might have an easier way :-)

Pete
 
got it.
thanks everyone.

is just that the supplied answer is somehow wrong which confuse me.
 

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