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abcdefg10645
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Why entropy is an extensive quantity ?
sweet springs said:Hi.
Entropy increase by volume. Gas of 2 m^3 have double entropy than gas of 1 m^3 in the same temperature and pressure.
Regards.
sweet springs said:Hi.
First law of thermodynamics, about the conservation of energy: δQ=dU - dW =dU - pdV
δQ is extensive because dU and pdV are extenxive. δQ/T and ∫δQ/T are also extensive.
Regards.
abcdefg10645 said:But for different systems , their temperature T may not be the same !
First Law sates that deltaQ=dU+deltaW
We can only infer that deltaQ is additive !
sweet springs said:Hi.
Thanks for correcting my sign mistake of deltaW.
You are right. Additive is the essence of extensive quantity. For isolated two different systems
S1 = ∫dQ1/T1, S2 = ∫dQ2/T2 and the entropy of total system is S = S1 + S2.
Regards.
sweet springs said:Hi.
Definition ∫ δQ/T is already addition of δQ/T , isn't it ?
Why not additive you think?
Regards.
Entropy is considered an extensive quantity because it depends on the size or amount of the system. This means that as the system grows, the entropy also increases.
The extensive property of entropy is related to its definition because it is a measure of the disorder or randomness of a system. As the size of the system increases, the number of possible arrangements or microstates also increases, resulting in a higher level of disorder and therefore a higher entropy.
An example of an extensive quantity other than entropy is mass. The mass of a system increases as more matter is added to it, just as the entropy of a system increases as it becomes larger.
The extensive property of entropy in thermodynamics is significant because it allows for the calculation of the total entropy of a system by adding the individual entropies of its components. This is important in understanding the overall behavior of a system and predicting changes in entropy during processes.
The extensive property of entropy is directly related to the second law of thermodynamics, which states that the total entropy of an isolated system always increases over time. This is because as the system grows, the number of possible microstates also increases, leading to a higher overall entropy. Therefore, the extensive property of entropy supports the second law of thermodynamics.