# Change of entropy in irreverisle adiabatic expansion

For an irreversible and adiabatic expansion, I understood how calculate the entropy change to the system by using hypothetical path(reversible adiabatic process and isobaric process) But, I don't know why the entropy change to the surroundings is zero . In my textbook, 'it is because that heat transfer to the surroundings is zero. ' but I think that the process must be reversible to explain that like above statement.

• Let us say that the surroundings did not noted any changes, because nothing came from the inside. Then, why should its entropy change? – user126422 Mar 25 '17 at 5:00