Can anyone explain why the change of entropy of free adiabetic expansion is not zero?i mean since there is no heat entering the system ,the entropy does not change,right?

Question

anonymous · Answer

Sorry, but you are not right. Actually, when the gas expands its molecules get more separated from each other and that's why randomness increases and hence the entropy.
 
That's what I think about it, it might not be exact, but it can't be completely wrong.

shamim · Answer

here, change of entropy is$$dS$$

shamim · Answer

change of heat$$dQ$$ is

shamim · Answer

the formula is$$dS=\frac{ dQ }{ T }$$

shamim · Answer

$$T$$is temperature in kelvin scale

shamim · Answer

in adiabatic process $$dQ=0$$

shamim · Answer

so$$dS=\frac{ 0 }{ T }=0$$

shamim · Answer

so in adiabatic process change of entropy is      0

anonymous · Answer

Thanks for your replies 
That is actually what I think ,but in most physics text books they said the entropy has increased ,so which one is right?(the second law of thermodynamics says that any irreversible process has a change of entropy bigger than zero)