Thermo Chemistry: Explaining Cp vs Cv

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SUMMARY

The discussion clarifies the concepts of heat capacity at constant pressure (Cp) and constant volume (Cv) in thermodynamics. It establishes that Cp is greater than Cv because, at constant pressure, some heat is utilized for work during expansion, while at constant volume, all heat increases the temperature without allowing for expansion. The participants also address the misconception regarding the behavior of gases under constant volume conditions, emphasizing that pressure increases when a gas is heated without allowing for expansion.

PREREQUISITES
  • Understanding of thermodynamic principles, specifically heat capacity.
  • Familiarity with the concepts of pressure, volume, and temperature in gases.
  • Knowledge of the first law of thermodynamics and work done by gases.
  • Basic grasp of the ideal gas law and its implications.
NEXT STEPS
  • Study the differences between Cp and Cv in detail, including mathematical formulations.
  • Explore the first law of thermodynamics and its application to heat transfer in gases.
  • Investigate real gas behavior versus ideal gas behavior under varying temperature and pressure conditions.
  • Learn about the implications of heat capacity in practical applications, such as engine efficiency and refrigeration cycles.
USEFUL FOR

This discussion is beneficial for students of thermodynamics, chemical engineers, and anyone involved in the study of heat transfer and gas behavior in physical chemistry.

zorro
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This is a statement in my book 'The heat capacity at constant pressure Cp is generally larger than that at constant volume Cv because at constant pressure, a part of heat added to the substance may be used in work of expanding whereas at constant volume all the added heat produces a rise in temperature'. I did not understand these two things-

At constant pressure, how can heat added be used for expanding (since expanding leads to change in pressure).

At constant volume what if the added heat expands the gas?
 
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If you heat something it usually inflates, to keep the pressure constant it has to expand.

In constant volume heated gas WANTS to expand - but as the volume is kept constant, it is impossible, so instead the pressure goes up.

--
 
what is the difference between expansion and inflation of gas?
 
None as far as I am concerned, sorry if it sounded as there is a difference.
 

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