Under what conditions will the entropy of a gas decrease as the gas expands? Why doesn’t this violate the second law of
Under what conditions will the entropy of a gas decrease as it expands?
Answer to Problem 1CQ
When the gas is allowed to expand adiabatically, then the entropy decreases.
Explanation of Solution
Expansion of gas usually results in increase of entropy. But if certain conditions are applied, we can decrease the entropy with the expansion.
If the gas is allowed to expand in an adiabatic environment, then there will be decrease in entropy. It should be ensured that no heat flows in and out of the system. Also any chance of friction also should be avoided. If a gas expands by pushing of a piston, work is done by gas to expand. Thus due to this energy is lost from the gas. And this leads to decrease the random motion or entropy of gas.
Conclusion
When the gas is allowed to expand adiabatically, then the entropy decreases.
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