Does Gas Density Influence Expansion When Heated?

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SUMMARY

The discussion clarifies that gas density does not influence the extent of gas expansion when heated. For ideal gases, only pressure and temperature are significant factors. In real gases, additional considerations include molecular size and Van der Waals forces, which affect expansion. The densities of Xenon (5.894 g/L) and Helium (0.1786 g/L) do not determine their expansion under identical conditions; rather, their molecular characteristics and energy distribution play crucial roles.

PREREQUISITES
  • Understanding of ideal gas laws, specifically PV = nRT
  • Familiarity with real gas behavior and Van der Waals forces
  • Knowledge of kinetic molecular theory and energy distribution in gases
  • Concept of mass density vs. number density in gases
NEXT STEPS
  • Research the implications of Van der Waals forces on gas behavior
  • Study the kinetic molecular theory in detail
  • Explore the differences between ideal and real gases
  • Learn about energy distribution in monoatomic versus polyatomic gases
USEFUL FOR

Students of chemistry, physicists, and engineers interested in thermodynamics and gas behavior will benefit from this discussion.

s.p.q.r
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Hi,

Apart from heat and number of moles, what dictates how much a gas will expand when exposed to heat.
Is it density?

The density of Xenon is 5.894 g/L and the density of Helium is 0.1786 g/L does this mean that if they were both in the same conditions of volume of container, number of moles and both exposed to 100 degress C. , that Xenon would expand more because it has larger density?

Cheers
 
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For an ideal gas only pressure and temperature.
Even for a real gas density doesn't have an effect.
There are two extra terms to account for the actual size of the molecules, which stop the gas going to zero volume at zero temperature.
And the Van de Waals forces which stick molecules together reducing the amount they expand with temperature.
 
With gases, it is important to distinguish
MASS density = mass/Volume
NUMBER density = N/Volume .
Temperature is proportional to Energy/N/3 dimensions of translation,
but Added Energy (that is, Heat) spreads out among
(into?) these 3d, plus EXTRA modes of motion for most molecules.
Xenon and Helium have no extra modes of motion (being single atoms)
but H2, N2, O2, CO2, etc have 2 rotation axes that hold Energy,
and H2O, NH3, CH4, etc have 3 extra motions to store Energy in.

A thermometer only samples 3/3, or 3/5, or 3/6 of the molecule Energy
(from mon-atomic, linear, or 3-d gas molecules) ...
A Pressure-meter only samples 2/3, or 2/5, or 2/6 of their Energy.

That's why PV = 2/2 nRT ...
but KE_translation = 1/2 mv^2 = 3/2 nRT
 

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