First Law of Thermodynamics and temperature

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SUMMARY

The forum discussion centers on calculating the change in internal energy (ΔU) of a gas in a toy balloon using the First Law of Thermodynamics. The balloon's initial temperature is 20°C, and it is heated to 52.23°C, with a volume of 0.0042 m³ and atmospheric pressure of 101.3 kPa. Participants utilize the equation ΔU = (5/2)nRΔT, where n is the number of moles derived from the ideal gas law PV = nRT. The correct calculation leads to a change in internal energy of approximately 0.117 Joules after resolving unit discrepancies and ensuring proper conversions.

PREREQUISITES
  • Understanding of the Ideal Gas Law (PV = nRT)
  • Familiarity with the concept of internal energy in thermodynamics
  • Knowledge of unit conversions between liters and cubic meters
  • Basic proficiency in using constants such as R = 8.31 J/(K·mol)
NEXT STEPS
  • Study the derivation and application of the First Law of Thermodynamics
  • Learn about the specific heat capacities of diatomic gases
  • Explore advanced thermodynamic equations and their applications
  • Investigate common pitfalls in unit conversions in physics problems
USEFUL FOR

Students studying thermodynamics, physics educators, and anyone involved in gas law calculations or internal energy assessments in scientific contexts.

  • #31
Why do you not use SI units? And you do not need to evaluate n or N.

PV=nRT. ΔU=5/2 (nR) ΔT. -->

nR=PV/T , ΔU=2.5 PV ΔT/T.

P=101.3 kPa=1.013 e5 Pa. V=4.2 e-3 m3. T=293 K, ΔT=32.23 K.

The result is in joules.
 

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