Converting Calories to Joules: Uncovering the Correct Conversion Formula

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SUMMARY

The correct conversion of calories to joules is established as 1 calorie equals 4.2 joules. In the discussion, a conversion of 2000 kcal results in 8,400,000 joules, which is correctly expressed as 8,400,000 kg·m²/s² when using the appropriate units. The confusion arose from mixing specific heat in grams with the standard joule conversion, which should utilize 4200 J/(kg·°C) for clarity. This distinction is crucial for accurate calculations in thermodynamics.

PREREQUISITES
  • Understanding of calorie and joule units
  • Knowledge of specific heat capacity
  • Familiarity with thermodynamic equations such as Q=mcT and W=mgh
  • Basic unit conversion principles
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  • Study the concept of specific heat capacity in detail, focusing on J/(kg·°C)
  • Learn about thermodynamic equations and their applications in physics
  • Explore unit conversion techniques between calories and joules
  • Investigate the implications of using different mass units in thermodynamic calculations
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Students in physics or chemistry, educators teaching thermodynamics, and professionals involved in energy calculations will benefit from this discussion.

Quarlep
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Lets suppose we have 2000 kcal and we want to translate it joule.
1 calorie is 4,2 J/gC isn't it so I think it will be 8400000 g m^2/s^2 But my teacher says its 8400000 kg m^2/s^2
Which one is true
Thanks
 
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Note: Here (4,2 J/gC) J is joule g is grams and C is celsius
 
Quarlep said:
1 calorie is 4,2 J/gC isn't it

No, 1 cal = 4.2 J (to one decimal place).

You're thinking of the specific heat of water, which is 4.2 J/(g·°C) = 1 cal/(g·°C).
 
Then let me clear Q=mcT and W=mgh so If we takes m we get Q/cT=W/gh If we write the unit form cal cal^-1 g C^-1 C we get g which it grams
and the other side kg m^2 s^-2 s^2 m^-1 m^-1 then we get kg.It does not match.and I think its a problem
 
You're getting grams for the m from the first equation because you're using the specific heat per gram. Use the specific heat per kilogram instead: 4200 J/(kg·°C).
 
Thanks I understan it
 

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