First order phase transition (van der waals gas)

In summary, a first order phase transition is a sudden, discontinuous change in properties of a substance. The van der Waals equation of state is a mathematical expression that takes into account attractive forces and finite volume of gas molecules. A van der Waals gas differs from an ideal gas by considering these factors. This type of gas undergoes a first order phase transition when temperature and pressure are within a certain range and the gas is in a supersaturated state. Near this transition, the gas exhibits non-ideal behavior, while at other temperatures and pressures it behaves more like an ideal gas.
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jasony
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Homework Statement


Give the physical explanation of the graphs (Fig 4(a) and 4(b)) on Page 4
http://www.pma.caltech.edu/~mcc/Ph127/b/Lecture3.pdf"


Homework Equations



1) Why [tex]V_{g}[/tex] decreases with temperature but [tex]V_{l}[/tex] increases with temperature
2) Why must phase transition happen at constant pressure (Maxwell construction)

The Attempt at a Solution



4(a) As temperature increases, greater proportion of molecules acquire sufficient energy to escape from liquid and consequently a higher pressure is needed to establish equilibrium between liquid and vapour

4(b) don't really know how to explain

 
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Anyone who can help? please...
 

1. What is a first order phase transition?

A first order phase transition is a physical change that occurs in a substance when there is a sudden, discontinuous change in one or more of its properties, such as volume, density, or energy.

2. What is the van der Waals equation of state?

The van der Waals equation of state is a mathematical expression that describes the behavior of real gases, taking into account the attractive forces between gas molecules and the finite volume of the molecules themselves.

3. How does a van der Waals gas differ from an ideal gas?

A van der Waals gas differs from an ideal gas in that it takes into account the volume occupied by gas molecules and the attractive forces between them, while an ideal gas assumes no volume or intermolecular forces.

4. What are the conditions for a first order phase transition to occur in a van der Waals gas?

A first order phase transition in a van der Waals gas occurs when the temperature and pressure are within a certain range, known as the coexistence curve, and the gas is in a supersaturated state.

5. How does the behavior of a van der Waals gas near a first order phase transition differ from its behavior at other temperatures and pressures?

Near a first order phase transition, a van der Waals gas exhibits non-ideal behavior, such as a discontinuous change in volume or heat capacity, as well as the coexistence of two phases. At other temperatures and pressures, the gas behaves more like an ideal gas.

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