entropy is an extensive property that can be transferred across system boundaries

unlike mass energy, entropy is not conserved but is produced within systems whenever internal irreversibilities are present

when a closed system undergoing an internally reversible process receives energy by heat transfer, the system experiences an increase in entropy

• an entropy transfer accompanies heat transfer

entropy balances are expressions of the second law that account for the entropy of systems in terms of entropy transfers and entropy production

entropy reflects the microscopic disorder of a system

Key Terms and Concepts

• isentropic process - a constant entropy process (when adiabatic and internally reversible)

• increase of entropy principle - entropy is produced in all actual processes, therefore the only processes that can occur are those for which entropy of the isolated system increases

• reversibility - a characteristic of certain processes that can be restored to its initial state without effects on the system