Question
- State first law of thermodynamics.
- Heat (q) and work function (w) individually are not state functions but their sum is always a state function. Why?
- Define extensive property with example.
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Answer
- First law of thermodynamics: It states energy can neither be created, nor be destroyed. It can change from one from to another. The total energy of universe remains constant.
$\Delta\text{U}=\text{q}+\text{w}$
- 'q' and 'w' depend upon path, therefore, these are path function.
$\text{q}+\text{w}=\Delta\text{U}$
$\Delta\text{U}$ is internal energy change which is state function because it depends upon initial and final state of the system and not on path, therefore, 'q + w' is state function.
- Extensive property: The property which depends upon amount of substance is called extensive property, e.g., mass, volume are extensive properties.
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