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Question
Write a note on free expansion.
Solution
- Free expansions are adiabatic expansions thus there is no exchange of heat between a system and its environment.
- Also, there is no work done on the system or by the system. Q = W = 0, and according to the first law of thermodynamics, ΔU = 0.
- For example, when a balloon is ruptured suddenly, or a tire is suddenly punctured, the air inside rushes out rapidly but there is no displacement of a piston or any other surface.
- A free expansion is different than other thermodynamic processes because it is an uncontrolled change. It is an instantaneous change and the system is not in thermodynamic equilibrium.
- A free expansion cannot be plotted on a p-V diagram. Only it's initial and the final state can be plotted.
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