Types of Processes

The method of bringing about a change in state is called process.

Isothermal Process

When the temperature of the system remains constant during various operations, then the process is said to be isothermal. This is attained either by removing heat from the system or by supplying heat to the system.

For example, ice melts at 273 K and 1 atm pressure. The temperature does not change as long as the process of melting goes on.

Adiabatic Process

In an adiabatic process there is no exchange of heat between the system and the surroundings. Thus, in adiabatic processes there is always a change in temperature.

For example, if an acid is mixed with a base in a closed thermos flask, the heat evolved is retained by the system.

Reversible Process

In a reversible process, the initial and the final states are connected through a succession of equilibrium states. All changes occurring in any part of the process are exactly reversed when it is carried out in the opposite direction. Thus, both the systems and its surroundings must be restored exactly to their original state, when the process has been performed and then reversed.

Reversible processes are those processes in which the changes are carried out so slowly that the system and surroundings are always in equilibrium.

Irreversible Process

A process that is not reversible is called irreversible.