It is defined as there is no heat transfer in the system. It does not contain heat or loss heat in the system.
It is thermodynamic system and does not exchange heat in system. The system work as adiabtc has insulated walls of container and Work done in an Adiabatic Process has no chance for transferring energy or heat because it done for short period of time.Due to short period of time energy is not transferred and entropy is constant in the system.
The temperature may be changes in adiabtc system and due to variation pressure also varies in the system. Adiabtc has two process and they are adiabatic cooling and adiabtc heating. Adiabtc cooling has low pressure and temperature also decreased into system.Adiabtc heating has high pressure and temperature also increased into system.
Isentropic process is also called Irreversible Adiabatic Process where energy is transferred into other form as heating or cooling. In this process some part of energy may be lost and converted into other form. Heat or energy is transferred into or exit from the system and temperature remains constant in this system.This process takes long time so energy can easily transferred from the system.
Adiabtc compression and adiabtc expansion are two processes and in this system energy is not transferred into system. The Work from an Adiabatic Expansion has insulated wall system and gas filled into system and evaporates without absorbing energy at constant temperature.The external pressure is not used in the system and total work done is depends on internal energy and the work done in the system is remains zero.
Adiabatic Expansion of an Ideal Gas has constant temperature and work done is zero. In reversible process if we add energy into system at constant volume then gas does not expand into system but if gas expands into system then temperature also constant. The other method of adiabtc compression has gas compressed into system and pressure decrease into system at constant volume.
The temperature decreases but work done remains zero because it neither absorbs energy nor release energy into system. Internal energy of an Ideal gas depends on temperature if temperature increases then internal energy decreases and if temperature decreases then internal energy increases. Work done in adiabtc process depends on temperature at constant pressure and internal energy also depends on temperature.