MOL-011 · Real gases, liquids and solids Sample material

Real gases. The van der Waals equation

Intermolecular interaction and real gases: the van der Waals equation, van der Waals and Andrews isotherms, the critical state, the internal energy of a real gas, the Joule–Thomson effect, liquefaction of gases, refrigerators and heat pumps.

Estimated time: 3 h 3 activities

Learning objective

Explain the difference between a real and an ideal gas in terms of intermolecular forces.
Study the van der Waals equation and the physical meaning of the corrections $a$ and $b$.
Analyse the critical state, Andrews isotherms and metastable states.
Study the Joule–Thomson effect, gas liquefaction and the operating principle of refrigerating machines.

Expected outcomes

Calculates the pressure of a real gas from the van der Waals equation and compares it with the ideal-gas result.
Finds the critical parameters ($T_c$, $p_c$, $V_c$) from the constants $a$, $b$.
Explains the volume dependence of a real gas's internal energy and the sign of the Joule–Thomson effect.
Calculates the coefficient of performance of a refrigerator and of a heat pump.

Interactive modelVan der Waals isotherms

Activities

Lecture
Lecture · 1 h 20 min · required
Problem solving on the topic "Real gases. The van der Waals equation"
Practice · 1 h 20 min · required
Final test
Test · 20 min · required · pass ≥ 70%

Completion conditions

  • Lecture
  • Problem solving on the topic "Real gases. The van der Waals equation"
  • Final test — at least 70%